hash
stringlengths 32
32
| doc_id
stringlengths 7
13
| section
stringlengths 3
121
| content
stringlengths 0
3.82M
|
|---|---|---|---|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
3.7.7.2 Conditional IE errors
|
When the MS upon receipt of a message diagnoses a "missing conditional IE" error, or an "unexpected conditional IE error", or when it receives a message containing at least one syntactically incorrect conditional IE (other than Facility), it shall send a RELEASE COMPLETE message with cause #100 "conditional IE error". The network may follow the same procedure. ETSI TS 100 941 V6.0.1 (1998-07) 22 GSM 04.10 version 6.0.1 Release 1997
|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
4 Password management
|
The password management procedures consist of two independent procedures: - password check; - password registration.
|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
4.1 Password check
| |
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
4.1.1 Successful procedure
|
When the password check procedure is invoked by a parent procedure (e.g. for service activation, service deactivation, password registration), the network sends to the MS an invoke component of the operation "get password" with "password" as the value of the mandatory GuidanceInfo information element. This invoke component is embedded in a FACILITY message, since the password check procedure is always invoked during an existing transaction. The MS will return to the network the required password in the return result component of the operation. This return result component is embedded in a FACILITY message, see figure 4.1. If the provided password is right the password check procedure returns to the parent procedure an indication of successful password check. MS Network REGISTER (note) ===========================================================================> Facility FACILITY <------------------------------------------------------------------------------------------------------------------------------------ Facility (Invoke = GetPassword (GuidanceInfo = "password")) FACILITY ------------------------------------------------------------------------------------------------------------------------------------> Facility (Return result = GetPassword (Password)) RELEASE COMPLETE (note) <=========================================================================== NOTE: This message is part of the initiating SS operation. Figure 4.1: Password check: successful procedure
|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
4.1.2 Error cases
|
If no result is returned by the MS for the "Get password" operation invoked by the network, the password check procedure is terminated. If the password value which is returned by the MS does not match the password value registered in the network, the network increments a counter and sends to the MS a Return Error component indicating "Negative Password Check". The counter is reset as soon as the right password is returned. If the served mobile subscriber enters a wrong call barring "password" three consecutive times, the subscription option "control of services" is set to "by the service provider" in the network: thus the network makes the use of password impossible for any subscriber operation. The password check procedure returns to the parent procedure an indication of Password Attempts Violation. The password can be made valid by the service provider only. ETSI TS 100 941 V6.0.1 (1998-07) 23 GSM 04.10 version 6.0.1 Release 1997
|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
4.2 Password registration
|
If the served mobile subscriber is given the possibility to control the service by the use of a password, the service provider has to register a password at provision time. Furthermore, the served mobile subscriber can change the call barring password at any time. The password registration procedure is as follows: When the mobile subscriber wants to register a new password the old password, the new password and the repeat of the new password shall be entered into the MS. Then the MS sends to the network an invoke component of the operation "register password". The common SS-code for call restriction services shall be used, but if the service code is not entered by the user the MS shall include the SS-code referring to all supplementary services.
|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
4.2.1 Successful procedure
|
The successful procedure consists of three steps: - the password registration procedure invokes first the password check procedure as it is described above; - if the password check procedure has returned an indication of successful password check, the network sends secondly to the MS, in an invoke component of the operation "get password" with "new password?" as the value of the mandatory GuidanceInfo information element. This invoke component is embedded in a FACILITY message. The MS will return to the network the required new password in the return result component of the operation. This return result component is embedded in a FACILITY message; - the network sends thirdly to the MS an invoke component of the operation "get password" with "new password again?" as the value of the mandatory GuidanceInfo information element. This invoke component is embedded in a FACILITY message. The MS will return again to the network the required new password in the return result component of the operation. This return result component is embedded in a FACILITY message. If the two values of the provided passwords are identical, the network confirms the registration of the new password by sending to the MS the return result component of the operation "register password", with the new password as a mandatory information element, see figure 4.2.
|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
4.2.2 Error cases
|
If the subscription option "control of services" is set to "by the service provider" or if the WPA is greater than 3 an attempt to register a password will be denied by the network (see GSM 03.11). If the counter for wrong password attempts is smaller than four, the network will return to the MS an error component with the error value "SS_SubscriptionViolation". If the counter is larger than three, the error value "Password Attempts Violation" is returned. If the password check procedure returns an indication of negative password check, the network will send to the MS a return error component of the operation "register password" with the error value "negativePasswordCheck". If the new password is not repeated twice identically by the mobile subscriber, the network returns to the MS an error component of the "register password" operation with the error value "passwordRegistrationFailure". The diagnostic "newPasswordsMismatch" may be passed as an error parameter. The old password remains registered. If no result is returned by the MS for the "Get password" operation invoked by the network the "register password" procedure is terminated, and the old password remains registered. ETSI TS 100 941 V6.0.1 (1998-07) 24 GSM 04.10 version 6.0.1 Release 1997 If the format of a new password which is returned by the MS is invalid (e.g. the value does not belong to the [0000-9999] range), the network sends to the MS an error component of the "register password" operation with the error value "passwordRegistrationFailure". The diagnostic "invalidFormat" may be passed as an error parameter. The old password remains registered. MS Network REGISTER ------------------------------------------------------------------------------------------------------------------------------------> Facility (Invoke = Register Password (SS-Code)) FACILITY <------------------------------------------------------------------------------------------------------------------------------------ Facility (Invoke = GetPassword (GuidanceInfo = "password")) FACILITY ------------------------------------------------------------------------------------------------------------------------------------> Facility (Return result = GetPassword (Password)) FACILITY <------------------------------------------------------------------------------------------------------------------------------------ Facility (Invoke = GetPassword (GuidanceInfo = "new password")) FACILITY ------------------------------------------------------------------------------------------------------------------------------------> Facility (Return result = GetPassword (Password)) FACILITY <------------------------------------------------------------------------------------------------------------------------------------ Facility (Invoke = GetPassword (GuidanceInfo = "new password again")) FACILITY ------------------------------------------------------------------------------------------------------------------------------------> Facility (Return result = GetPassword (Password)) RELEASE COMPLETE <------------------------------------------------------------------------------------------------------------------------------------ Facility(Return result = Register Password (Password)) RELEASE COMPLETE <- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Facility (Return error (Error)) RELEASE COMPLETE <- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Facility (Reject (Invoke_problem)) NOTE: The figure illustrates successful outcome only. In case of input errors by the mobile subscriber, the information flow may be interrupted as defined in GSM 03.11. Figure 4.2: Password registration procedure ETSI TS 100 941 V6.0.1 (1998-07) 25 GSM 04.10 version 6.0.1 Release 1997
|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
4.3 Cross phase compatibility
|
When password procedures are initiated by an MS which does not provide an SS version indicator and where errors occur in password procedures, the network shall not send the protocol error values "DataMissing", "CallBarred" or "NumberOfPWAttemptsViolation". When an MS that supports version 2 of the SS-protocol receives the guidance values "badPW-TryAgain" or "badPW-FormatTryAgain" it shall release the transaction and notify the mobile user in the same way as if the error value "negativePasswordCheck" has been returned by the network in reply to the parent operation.
|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
5 Supplementary service cross phase compatibility
| |
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
5.1 Cross phase, or cross protocol version, interworking
|
Due to the phased approach to GSM standardization it is possible for a service to be changed, or new services to be added, between different versions of the standard. Since GSM supports the features "terminal mobility" and "roaming" and is a system of open interfaces, it is possible for entities supporting different versions of the standards to have to interwork. This clause describes the supplementary service procedures which provide this interworking. This clause describes compatibility procedures for radio interface SS operations. In this clause the term "SS operation" refers to one of the operations sent in the Facility IE as defined in GSM 04.80 and GSM 09.02. An "MS initiated operation" is an SS operation where the MS sends the invoke component. A corresponding definition applies to network initiated operations.
|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
5.2 Objectives
|
The objectives of these procedures are as follows: - to allow flexibility of implementation, i.e. allow different combinations of services to be supported at different versions within a single entity; - to allow SSs to evolve from version to version of the standards; - to decouple SS protocol from other protocols; - to guarantee the best quality of service in situations where different entities support different versions of that service.
|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
5.3 Supplementary service compatibility philosophy
|
The purpose of the SS compatibility procedures is to ensure that when a service is invoked the highest common version of the service protocol is used in the entities supporting that service. The highest protocol version gives the best level of service to the subscriber. The commonality of versions between entities provides compatibility. The basic philosophy is that the MS shall provide the network with information about its capabilities in order that the network may adjust to the capabilities of the MS. This ensures that compatible information is sent to the MS. This process is not required in the other direction, i.e. the network does not provide the MS with capability information. The network is expected to be able to cope with unexpected information cleanly and due to network evolution will generally be more advanced than operating MSs. In this description the terms "phase" and "version" are used with respect to supplementary services. In this context "phase" means a particular collection of GSM standards or an implementation according to that phase of standards. In each phase of GSM standards "versions" of a service or protocol are described. Therefore it is sometimes applicable to refer to which version of a service is supported. ETSI TS 100 941 V6.0.1 (1998-07) 26 GSM 04.10 version 6.0.1 Release 1997
|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
5.4 Compatibility mechanisms
|
Two signalling indicators are used in the MS to network direction to provide information on the general capabilities of the MS and on specific SS protocol versions. A protocol extension mechanism is also used for protocol evolution. NOTE: These compatibility mechanisms are flexible, and could be applied in ways outside the scope of this standard. In general, MSs and networks should support complete implementations of supplementary services (e.g. mobile initiated USSD) including all elements that are not explicitly indicated as manufacturer or operator options. Complete support for a service also implies that the necessary compatibility indicators are set to appropriate values. If the MS or network does not implement all the elements necessary to support a service then the user may receive only a subset of the complete service. Such a MS or network is outside the scope of this standard and may: - provide a version of the service that is unpredictable or inconsistent; - fail to meet important service requirements; - be incompatible with other entities.
|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
5.4.1 SS screening indicator
|
The SS screening indicator is sent by the MS at the beginning of the radio connection to allow the network to assess the capabilities of the MS and hence determine, - whether a particular network initiated SS operation may be invoked; or - what version of a network initiated SS operation should be invoked. The SS screening indicator is only relevant to network initiated SS operation and is valid for the duration of a radio connection. The coding of the SS screening indicator is described in GSM 04.08 and GSM 04.80.
|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
5.4.2 SS version indicator
|
The SS version indicator is sent by the MS and is associated with one or more related SS operations. It indicates to the network the correct version of radio interface protocol and procedures to use for those SS operations. For call related SSs the version indicator is valid for the invocation period of the SS operation to which it was attached (i.e. the validity of the invoke ID). For call independent SSs the indicator is valid for the duration of the call independent transaction. The SS version indicator takes precedence over the screening indicator during its period of validity. The coding of the SS version indicator is described in GSM 04.08 and GSM 04.80.
|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
5.4.3 Protocol extension mechanism
|
A protocol extension mechanism is used in the common information element category supplementary service protocol to allow controlled evolution of the protocol. The purpose of this mechanism is to allow optional information to be introduced into operations without causing receiving entities, who do not recognize this information, to reject the entire operation. ETSI TS 100 941 V6.0.1 (1998-07) 27 GSM 04.10 version 6.0.1 Release 1997
|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
5.5 SS compatibility procedures
| |
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
5.5.1 Screening indicator procedures
| |
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
5.5.1.1 MS procedure
|
If a MS supports Phase 2 GSM 04.10 error handling and the Phase 2 GSM 04.80 extension mechanism it shall send the screening indicator to the network during layer 3 connection establishment. The value of the indicator shall indicate Phase 2. The sending of the screening indicator does not depend upon the invocation of any supplementary service.
|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
5.5.1.2 Network procedure
|
At layer 3 connection establishment with the MS, the network shall check for the SS screening indicator and note, for the duration of the connection, whether the indicator was sent, and if sent, the value of the indicator. On invocation of any network initiated SS operation (unless an SS version indicator has taken precedence over the screening indicator) the network shall check the screening indicator status. If the screening indicator was not sent, the network shall screen information sent to the MS, i.e. invoke the Phase 1 version of the operation or abort the invocation if only a Phase 2 version is available. If the screening indicator was received, indicating that Phase 2 error handling and extension mechanisms are supported at the MS, the network shall invoke the highest supported version of the operation toward the MS. According to this version of the standards the highest version is Phase 2. However when the next version of standards is available, new services may also be invoked. If the MS does not support the service the error handling or extension mechanism will handle unrecognised information cleanly. If in the future a new value is assigned to the screening indicator, new screening procedures may also be defined for networks of similar or higher capability. These procedures cannot be predicted and no definition is required in this version of the standards. If the value of the screening indicator is unrecognised the network shall attempt to handle network initiated SS operations as if the MS had indicated the highest values supported by the network. The indicator has been defined in such a way that it is ignored when received by a Phase 1 network therefore no Phase 1 procedures are described.
|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
5.5.2 SS version indicator procedures
| |
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
5.5.2.1 MS procedure
|
If an SS operation has been initiated at the MS, and the MS supports Phase 2 GSM 04.10 error handling and the Phase 2 GSM 04.80 extension mechanism and the operations used by the mobile initiated procedure are implemented according to the Phase 2 GSM standards, then: - in the case of call independent activity, the MS shall send the SS version indicator at the beginning of the transaction indicating the version of the SS operation being invoked. No further indication shall be sent by the MS during the transaction. No operations shall be sent within the same transaction which are not compliant with the SS version indicated. - in the case of call related activity, the MS shall send the SS version indicator in the GSM 04.08 message containing the invoke component of the related operation. The version of the service being invoked is indicated. This procedure applies on a per operation basis and shall be repeated for each call related operation. ETSI TS 100 941 V6.0.1 (1998-07) 28 GSM 04.10 version 6.0.1 Release 1997
|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
5.5.2.1.1 MS procedure for version 3 or higher operations
|
The relevant stage 3 specification for each service shall state if the operation requires the use of SS version indicator 3 or higher for MS initiated operations. The SS version indicator is used within the network to define the MAP Application Context used for a specific operation (see GSM 09.02). An MS initiating an SS version 3 or higher operation must be able to decode all of the possible returned information from the MAP Version 3 Application Context of the operation invoked. If an SS version 3 or higher operation has been initiated at the MS, then: - in the case of call independent activity, the MS shall send the SS version 3 or higher indicator at the beginning of the transaction indicating the version of the SS operation being invoked. No further indication shall be sent by the MS during the transaction. No operations shall be sent within the same transaction which are not compliant with the SS version indicated. - in the case of call related activity, the MS shall send the SS version 3 or higher indicator in the GSM 04.08 message containing the invoke component of the related operation. The version of the service being invoked is indicated. This procedure applies on a per operation basis and shall be repeated for each call related operation. ETSI TS 100 941 V6.0.1 (1998-07) 29 GSM 04.10 version 6.0.1 Release 1997
|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
5.5.2.2 Network procedure
| |
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
5.5.2.2.1 Call independent SS activity
|
When a new transaction is set up for call independent SS activity the network shall check for the SS version indicator and note, for the duration of the transaction, whether the indicator was present, and if present, the value of the indicator. The network shall use this indication to establish the correct MAP application context in the network for the processing of all operations made on that transaction. The network shall discard this information at the end of the transaction. If the indicator was not present the network shall operate according to Phase 1. If the indicator was present and indicates Phase 2 the network shall operate according to the Phase 2 standards. If the value of the indicator is unrecognised the network shall attempt to handle the communication at its highest possible version. The detailed interworking for this situation is described in subclause 5.5.4. The screening indicator shall not be taken into account for processing transactions that start with MS initiated operations. Special procedures concerning SS version indicator values other than Phase 2 will be described in future standards if required.
|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
5.5.2.2.2 Call related SS activity
|
When a call related common information element SS operation is received by the network, the network shall check the GSM 04.08 carrier message for the SS version indicator. The network shall note whether the indicator was present, and if present, what value was provided. The network shall use this information to operate in a compatible way and set up compatible contexts in the fixed network. If the indicator was not present the network shall operate according to Phase 1. If the indicator was present and indicates Phase 2 the network shall operate according to the Phase 2 standards. If the value of the indicator is unrecognised the network shall attempt to handle the communication at its highest possible version. The network shall discard the indicated information when the operation has been completed, i.e. when a result, error or reject is provided. If no response is expected to an operation the indicator is discarded immediately after the operation has been processed. The screening indicator shall not be taken into account for processing MS initiated operations. If the version indicator is received but no supplementary service information is supplied the network shall ignore the indicator. Special procedures concerning SS version indicator values other than Phase 2 will be described in future versions of the standards if required.
|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
5.5.3 Extension mechanism procedures
|
The handling of the extension mechanism (ellipsis) is a detailed protocol matter and is described in the MAP version 2, GSM 09.02. ETSI TS 100 941 V6.0.1 (1998-07) 30 GSM 04.10 version 6.0.1 Release 1997
|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
5.5.4 SS version indicator - MAP context interworking
| |
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
5.5.4.1 Call independent interworking
|
The compatibility mechanisms described in these subclauses concern the radio interface. The fixed network protocol MAP also specifies compatibility mechanisms. The interworking between these mechanisms occurs at the MSC/VLR. The MSC shall operate and set up contexts according to the version indicated by the MS wherever possible. If the MS signals a higher version than the MSC/VLR is capable of supporting, the MSC/VLR shall attempt to support service at the highest version which is supported. If this is not possible then the communication is rejected. Detailed interworking is described in GSM 09.11.
|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
5.5.4.2 Call related interworking
|
No interworking identified.
|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
5.6 Development of future protocol versions
|
As a general rule all future versions of protocol should be designed such that they are a superset of the previous protocol. This provides backward compatibility. Optional information shall be introduced, where appropriate, in the extensible parts of operations. Non-compatible protocol changes, i.e. the introduction of mandatory protocol elements or new operations shall cause an increment in the protocol version. This shall be reflected in the use of the SS version indicator. Amendments to the Phase 2 services shall specify in the relevant stage 3 specification which value of the SS version indicator to use for MS initiated operations. The extension mechanism shall be introduced wherever possible in new operations or new constructed data types of the common information element SS protocol. Care should also be taken that functional service changes are made in a backwards compatible manner. ETSI TS 100 941 V6.0.1 (1998-07) 31 GSM 04.10 version 6.0.1 Release 1997
|
09d74d05684eb66f6a6137f7ddbe7123
|
100 941
|
6 Forward Check SS Indication
|
The forward check SS indication procedure is used when supplementary services data in the HLR may have become corrupted. The procedure is initiated by the network to inform the user to verify his supplementary services data. The procedure consists of the network sending the ForwardCheckSSIndication operation on a call independent SS transaction. The procedure shall create a new network initiated transaction. The new transaction may be used on its own, or in parallel with other call independent SS transactions. The message flow is shown in figure 6.1. MS Network REGISTER <------------------------------------------------------------------------------------------------------------------------------------ Facility (Invoke = ForwardCheckSSIndication) RELEASE COMPLETE ------------------------------------------------------------------------------------------------------------------------------------> Figure 6.1: ForwardCheckSSIndication sent on new transaction ETSI TS 100 941 V6.0.1 (1998-07) 32 GSM 04.10 version 6.0.1 Release 1997 Annex A (normative): Notation used for stage 3 description of supplementary services The structure of the signalling used for supplementary services on the Um Interface is defined using diagrams in GSM 04.10 and the GSM 04.8x and 04.9x-series of technical specifications. These SS stage 3 diagrams show example message flows between the MS and the network. Separate diagrams specify how supplementary services signalling shall be used to perform each defined supplementary service function. For signalling that uses the common information element approach, these diagrams are the normative definition of a number of important aspects of the supplementary services signalling: - the diagrams normatively define the allowed responses to each supplementary service operation shown; - the diagrams normatively define which GSM 04.08 or GSM 04.80 message is to be used to transport the supplementary services operations in the Facility IE; - The diagrams normatively define which parameters are allowed and required in the invocation and response of each operation. A.1 General structure of the SS stage 3 diagrams In the SS stage 3 diagrams the messages that correspond to the normal case with successful outcome are shown using solid arrows. Messages for exceptional, or unsuccessful cases are shown using dashed arrows. In general, the diagrams show the initiating operation together with all possible outcomes. Obviously, in practice only one of the possible outcomes shown in the diagrams will occur when the operation is used. An example is given in figure A.1. MS Network Initiating Operation ------------------------------------------------------------------------------------------------------------------------------------> Normal, Successful Outcome <------------------------------------------------------------------------------------------------------------------------------------ Unsuccessful Outcome 1 <- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Unsuccessful Outcome 2 <- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Figure A.1: Example of the general structure of the SS stage 3 diagrams ETSI TS 100 941 V6.0.1 (1998-07) 33 GSM 04.10 version 6.0.1 Release 1997 A.1.1 Exceptional release procedures To prevent transactions being kept open following exceptional cases, either side of the transaction may release it by sending a RELEASE COMPETE message without a Facility IE. This procedure can be used to release any call independent SS procedure, at any time while supplementary service support is established. For clarity this is not shown on the specific diagrams in the GSM 04.8x and 04.9x series, though it is still available. MS Network RELEASE COMPLETE <- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - or - RELEASE COMPLETE - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -> Figure A.2: Exceptional release procedures A.2 Messages used to transport operations The message used to transport the supplementary service operation is shown above the arrow. If a single message or a list of messages is specified then only these messages shall be used to transport the operation shown in the context shown. If the letters "e.g." are included before the message name or a list of messages then the messages shown are only suggested examples. If "e.g." is used then any message that carries the Facility information element which is consistent with the transaction state may be used for the SS operation. ETSI TS 100 941 V6.0.1 (1998-07) 34 GSM 04.10 version 6.0.1 Release 1997 A.3 Contents of messages The contents of messages is specified below the arrow. The diagrams do not show the SS version indicator, or other parts of the message contents unless they are directly related to the service shown. The names of relevant information elements are shown, and the associated contents is shown in brackets. If the information element is the Facility IE then the contents information includes: - the type of component that shall be used for the operation (e.g. invoke, return result, return error, reject); - the name of the operation to be used (for the invoke and return result components only); - the parameters that shall be included in the operation. For the function described by the diagram, only those parameters shown in the diagram are allowed. Unless stated otherwise all the parameters shown in the diagram shall be present when the operation is used for the function described by the diagram. The detailed encoding of the operations and parameters shown in the diagrams is defined in GSM 04.80 and GSM 09.02. Appropriate ASN.1 structures from these specifications shall be used to align with the diagrams. The examples in figure A.2 illustrate the encoding. The first example shows a common information element operation where the operation name is shown. The second example shows a common information element operation where the operation name is not shown. Items in italics would be substituted with the appropriate identifiers. MESSAGE NAME ------------------------------------------------------------------------------------------------------------------------------------> Facility (Component Type = OperationName (parameters)) MESSAGE NAME ------------------------------------------------------------------------------------------------------------------------------------> Facility (Component Type (parameters)) Figure A.2: Examples of the contents of messages ETSI TS 100 941 V6.0.1 (1998-07) 35 GSM 04.10 version 6.0.1 Release 1997 Annex B (informative): Status of Technical Specification GSM 04.10 Status of Technical Specification GSM 04.10 Date Version Remarks Release 92 3.2.3 Last common Phase 1/Phase 2 version June 1991 4.0.0 CR 04.10-13 rev 2 (category D) / CR 04.10-14 rev 1 (category D) CR 04.10-18 (category C) / CR 04.10-19 rev 1 (category B); all approved by GSM#31 April 1992 4.1.0 CR 04.10-22 (category C) / CR 04.10-24 rev 1 (category D) CR 04.10-25 (category D) / CR 04.10-27 (category D; all approved by SMG#02 January 1993 4.2.0 CR 04.10-31 (category D) / CR 04.10-32 rev 2 (category C) CR 04.10-33 rev 1 (category C); all approved by SMG#05 April 1993 4.3.0 CR 04.10-28 rev 3 (category B) / CR 04.10-29 rev 2 (category B) CR 04.10-36 rev 1 (category B) / CR 04.10-37 rev 1 (category C) CR 04.10-38 rev 1 (category C) / CR 04.10-39 (category D) CR 04.10-40 rev 1 (category C); all approved by SMG#06 June 1993 4.4.0 CR 04.10-43 rev 3 (category D) / CR 04.10-45 (category B) CR 04.10-46 (category B); all approved by SMG#07 TS frozen for Phase 2 by SMG#07 October 1993 4.5.0 CR 04.10-47 rev 1 (category F) approved by SMG#08 TS changed to draft prETS 300 558 January 1994 4.6.0 CR 04.10-48 rev 2 (category F) CR 04.10-49 (category F)approved by SMG#09 April 1994 4.7.0 CR 04.10-51 (category F) CR 04.10-52 rev 1 (category F)approved by SMG#10 July 1994 4.8.0 CR 04.10-54 rev 1 (category F) approved by SMG#11 October 1994 4.8.1 TS changed to final draft prETS 300 558 January 1995 4.8.2 TS changed to ETS 300 558 First edition January 1995 Amend ment 1 AR 04.10-A001 rev 1 (category 2) approved by SMG#13 AR 04.10-A002 rev 1 (category 2) ----->Version 4.9.0 February 1996 4.10.0 CR 04.10-A004 rev 1 (category F) approved by SMG#17 August 1996 4.10.1 TS changed to ETS 300 558 Second edition December 1996 5.0.0 TS changed to draft prETS 300 941 (Release 96) May 1997 5.0.1 TS changed to ETS 300 941 first edition March 1998 6.0.0 CR 04.10-A005r3 (CCBS and TEI R97) CR 04.10-A006 (TEI R97); all approved SMG#25 Specification converted to version 6.0.0 for Release 97 July 1998 6.0.1 Specification published as TS 100 941 Text and figures: WinWord 7.0 Stylesheet: etsiw_70.dot Rapporteur: Ian Sharp (Nortel) ETSI TS 100 941 V6.0.1 (1998-07) 36 GSM 04.10 version 6.0.1 Release 1997 History Document history V6.0.1 July 1998 Publication ISBN 2-7437-2417-X Dépôt légal : Juillet 1998
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
1 Scope
|
The present document defines the service offered by the physical layer (GSM 05-series of Technical Specifications) of the MS-BS interface (GSM 05- and 04-series of Technical Specifications). Its main objective is to be a guidance for the interface between the GSM Technical Specifications in the 05-series and the 04-series. It also specifies the format of signalling channels and the order of bit transmission. As far as possible, the present document makes use of the layering principles of the Reference Model for Open System Interconnection (OSI) as contained in CCITT Recommendations X.200 and X.210.
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
1.1 References
|
The following documents contain provisions which, through reference in this text, constitute provisions of the present document. • References are either specific (identified by date of publication, edition number, version number, etc.) or non-specific. • For a specific reference, subsequent revisions do not apply. • For a non-specific reference, the latest version applies. • A non-specific reference to an ETS shall also be taken to refer to later versions published as an EN with the same number. • For this Release 1998 document, references to GSM documents are for Release 1998 versions (version 7.x.y). [1] GSM 01.04: "Digital cellular telecommunications system (Phase 2+); Abbreviations and acronyms". [2] GSM 02.11: "Digital cellular telecommunications system (Phase 2+); Service accessibility". [3] GSM 03.13: "Digital cellular telecommunications system (Phase 2+); Discontinuous Reception (DRX) in the GSM system". [4] GSM 03.20: "Digital cellular telecommunications system (Phase 2+); Security related network functions". [5] GSM 04.01: "Digital cellular telecommunications system (Phase 2+); Mobile Station - Base Station System (MS - BSS) interface; General aspects and principles". [6] GSM 04.02: "Digital cellular telecommunications system (Phase 2+); GSM Public Land Mobile Network (PLMN) access reference configuration". [7] GSM 04.03: "Digital cellular telecommunications system (Phase 2+); Mobile Station - Base Station System (MS - BSS) interface Channel structures and access capabilities". [8] GSM 04.05: "Digital cellular telecommunications system (Phase 2+); Data Link (DL) layer General aspects". [9] GSM 04.06: "Digital cellular telecommunications system (Phase 2+); Mobile Station - Base Station System (MS - BSS) interface; Data Link (DL) layer specification". [10] GSM 04.07: "Digital cellular telecommunications system (Phase 2+); Mobile radio interface signalling layer 3; General aspects". [11] GSM 04.08: "Digital cellular telecommunications system (Phase 2+); Mobile radio interface layer 3 specification". [12] GSM 04.10: "Digital cellular telecommunications system (Phase 2+); Mobile radio interface layer 3 Supplementary services specification; General aspects". ETSI ETSI TS 100 936 V7.0.0 (1999-08) 6 (GSM 04.04 version 7.0.0 Release 1998) [13] GSM 04.11: "Digital cellular telecommunications system (Phase 2+); Point-to-Point (PP) Short Message Service (SMS) support on mobile radio interface". [14] GSM 04.12: "Digital cellular telecommunications system (Phase 2+); Short Message Service Cell Broadcast (SMSCB) support on the mobile radio interface". [15] GSM 04.13: "Digital cellular telecommunications system (Phase 2+); Performance requirements on mobile radio interface". [16] GSM 04.21: "Digital cellular telecommunications system (Phase 2+); Rate adaption on the Mobile Station - Base Station System (MS - BSS) Interface". [17] GSM 04.22: "Digital cellular telecommunications system (Phase 2+); Radio Link Protocol (RLP) for data and telematic services on the Mobile Station - Base Station System (MS - BSS) interface and the Base Station System - Mobile-services Switching Centre (BSS - MSC) interface". [17a] GSM 04.60: "Digital cellular telecommunications system (Phase 2+); General Packet Radio Service (GPRS); Mobile Station - Base Station System (MS-BSS) interface; Radio Link Control and Medium Access Control (RLC/MAC) layer specification". [18] GSM 04.80: "Digital cellular telecommunications system (Phase 2+); Mobile radio interface layer 3 supplementary services specification; Formats and coding". [19] GSM 04.81: "Digital cellular telecommunications system (Phase 2+); Line identification supplementary services - Stage 3". [20] GSM 04.82: "Digital cellular telecommunications system (Phase 2+); Call Forwarding (CF) supplementary services - Stage 3". [21] GSM 04.83: "Digital cellular telecommunications system; Call Waiting (CW) and Call Hold (HOLD) supplementary services - Stage 3". [22] GSM 04.84: "Digital cellular telecommunications system (Phase 2+); MultiParty (MPTY) supplementary services - Stage 3". [23] GSM 04.85: "Digital cellular telecommunications system (Phase 2+); Closed User Group (CUG) supplementary services - Stage 3". [24] GSM 04.86: "Digital cellular telecommunications system (Phase 2+); Advice of Charge (AoC) supplementary services - Stage 3". [25] GSM 04.88: "Digital cellular telecommunications system (Phase 2+); Call Barring (CB) supplementary services - Stage 3". [26] GSM 04.90: "Digital cellular telecommunications system (Phase 2+); Unstructured Supplementary Services Data (USSD) - Stage 3". [27] GSM 05.01: "Digital cellular telecommunications system (Phase 2+); Physical layer on the radio path; General description". [28] GSM 05.02: "Digital cellular telecommunications system (Phase 2+); Multiplexing and multiple access on the radio path". [29] GSM 05.03: "Digital cellular telecommunications system (Phase 2+); Channel coding". [30] GSM 05.04: "Digital cellular telecommunications system (Phase 2+); Modulation". [31] GSM 05.05: "Digital cellular telecommunications system (Phase 2+); Radio transmission and reception". [32] GSM 05.08: "Digital cellular telecommunications system (Phase 2+); Radio subsystem link control". [33] GSM 05.10: "Digital cellular telecommunications system (Phase 2+); Radio subsystem synchronization". ETSI ETSI TS 100 936 V7.0.0 (1999-08) 7 (GSM 04.04 version 7.0.0 Release 1998) [34] GSM 05.90: "Digital cellular telecommunications system; GSM Electro Magnetic Compatibility (EMC) considerations". [35] CCITT Recommendation X.200: "Reference Model of open systems interconnection for CCITT applications". [36] CCITT Recommendation X.210: "Open systems interconnection layer service definition conventions".
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
1.2 Definitions and abbreviations
|
Abbreviations used in the present document are listed in GSM 01.04.
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
2 Interfaces to the physical layer
|
The physical layer (layer 1) is the lowest layer in the OSI Reference Model and it supports all functions required for the transmission of bit streams on the physical medium. These bit streams are transferred on traffic channels, packet data traffic channels and control channels as defined in GSM 04.03. NOTE: For GSM application the physical layer may also be referred to as the radio subsystem. However, the radio subsystem supports functions additional to those described in the present document. The physical layer interfaces the Data Link Layer, the Radio Link Control and Medium Access Control layer and the supported functional units of the application (figure 2.1). Physical Layer Data Link Layer RLC/MAC layer Radio Resource management (layer 3) to other functional units to upper layers MPH- primitives PH- primitives PH- primitives TCH Figure 2.1: Interfaces with the Physical Layer
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
2.1 Interface to the Data Link Layer
|
The physical layer interfaces the data link layer. On this interface control channels are supported. The data link layer is specified in GSM 04.05 and 04.06. Communication between the Physical Layer and the Data Link Layer is in an abstract way performed by means of PH-primitives. They do not constrain implementations. NOTE: The terms physical layer and layer 1, and data link layer and layer 2, will be used synonymously in the present document. The PH-primitives exchanged between the physical layer and the data link layer are used for the transfer of layer 2 frames. They are also used to indicate the establishment of channels to layer 2. ETSI ETSI TS 100 936 V7.0.0 (1999-08) 8 (GSM 04.04 version 7.0.0 Release 1998) 2.1a Interface to the Radio Link Control and Medium Access Control layer The physical layer interfaces the Radio Link Control and Medium Access Control (RLC/MAC) layer. On this interface packet data control channels and packet data traffic channels are supported. The RLC/MAC layer is specified in GSM 04.60. Communication between the Physical Layer and the RLC/MAC layer is in an abstract way performed by means of PH-primitives. They do not constrain implementations. The PH-primitives exchanged between the physical layer and the RLC/MAC layer are used for the transfer of RLC/MAC blocks. They are also used to indicate the establishment of packet data physical channels to the RLC/MAC layer.
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
2.2 Interface to radio resource management
|
The physical layer interfaces the radio resource management (RR-management) entity of layer 3 in the MS and in the network. Communication is performed in an abstract way by means of MPH-primitives. They do not constrain implementations. The primitives exchanged with the RR-management entity are related to the assignment of channels, physical layer system information (including measurement results), etc.
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
2.3 Interface to other functional units
|
The physical layer interfaces other functional units in the MS and in the network for supporting traffic channels. These interfaces are described in the 06 and 07 series of Technical Specifications.
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
3 Service of the physical layer
|
The physical layer supports transfer of bit streams on the radio medium according to the Technical Specifications of the 05-series. The scope of the 05-series of Technical Specifications is the definition of a framework for operation on the radio medium. The application of this framework on the radio medium results in a transmission service. General characteristics of the service obtained by applying the framework of the 05-series at the operation on the radio medium are described in this clause.
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
3.1 Service Access Point
|
In the Reference Model for Open System Interconnection, Service Access Points (SAPs) of a layer are defined as gates through which services are offered to an adjacent higher layer (figure 3.1). Through a SAP the physical layer offers a service to the data link layer. The SAP is used both for the control of the service providing entity (in case this is the physical layer; commands related to the establishment and release of channels) and the transfer of data (in case of the physical layer; the transfer of bits). The physical layer service access points defined in the present document differ from the OSI physical layer Service Access Points; the layer 3 RR-management instead of the data link layer controls the SAPs (establishment and release of channels). ETSI ETSI TS 100 936 V7.0.0 (1999-08) 9 (GSM 04.04 version 7.0.0 Release 1998) transm ission m edium adjacent higher layer adjacent higher layer SAP SAP Figure 3.1: Service Access Point principle On the physical layer of the GSM system a SAP is defined between the physical layer and the data link layer for each control channel (figure 3.2). The characteristics of SAPs (channels) are listed in GSM 04.03. Physical layer BCCH PCH+AGCH RACH SDCCH SACCH FACCH Data Link Layer Figure 3.2: SAPs between the physical layer and the data link layer in the MS Moreover, on the physical layer of the GSM system a SAP is defined between the physical layer and the RLC/MAC layer for the packet data control channels and the packet data traffic channel (figure 3.2a). Multiplexing of these channels is controlled by the RLC/MAC layer, see GSM 04.60. The characteristics of channels are listed in GSM 04.03. Physical layer RLC/MAC layer PBCCH + PPCH + PAGCH + PRACH + PACCH + PDTCH Figure 3.2a: SAP between the physical layer and the RLC/MAC layer in the MS
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
3.2 Service of the physical layer
|
* Access capabilities: The physical layer offers a transmission service on a limited set of logical channels. The BS and MS access capabilities and the characteristics of logical channels (SAPs) are defined in GSM 04.03. NOTE: Between GSM 04.03 and the GSM 05-series there is a slight difference in terminology. The "channels" mentioned in GSM 04.03 are "logical channels" according to the GSM 05-series (especially GSM 05.02). The "CCCH", a channel name commonly used in the 04-series, covers the logical channels of the type RACH, PCH and AGCH. Similarly, the “PCCCH” covers the logical channels of the type PPCH, PAGCH and PRACH . ETSI ETSI TS 100 936 V7.0.0 (1999-08) 10 (GSM 04.04 version 7.0.0 Release 1998) Logical channels are multiplexed on physical channels. Physical channels are the units scheduled on the radio medium. Some are reserved by the network for common use (e.g. a combination of CCCH and BCCH), others are assigned to dedicated connections with MSs (dedicated physical channels), or are assigned to a shared usage between MSs for packet switched data traffic (packet data physical channels). In time, the combination of logical channels used on an assigned physical channel may change. Allowed combinations of logical channels on a physical channel are defined in GSM 04.03. Data on SAPs of control channels is exchanged in discrete blocks with a size of 23 or 21 (SACCH) octets. Data on a SAP of packet data traffic channels is exchanged in discrete blocks with a size of 184, 271, 315 or 431 bits. Synchronization between layer 1 and layer 2 (data link layer) is provided for piggy-backing of RR (receive ready) frames, and the starting of timers (T200). See also GSM 04.06. Synchronization between the physical layer and the RLC/MAC layer is provided for the handling of timers, and the multiplexing of logical channels. See also GSM 04.60 . * Error detection: The physical layer offers an error protected transmission service, it includes error detection functions and to a lower level, error correction functions. Erroneous received frames are not offered to the data link layer or the RLC/MAC layer. The probability of one or more errors in a physical block transferred by the physical layer is defined in GSM 05.05. Due to not specified methods of quality detection, the probability of residual errors in transferred blocks may vary between implementations. * Encryption: Security related functions implemented at the physical layer are described in GSM 03.20. An overview of the functions specified in the 05-series which create the service of the physical layer can be found in GSM 05.01.
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
3.2.1 Specific services of the physical layer in the MS
|
The access capability service of the physical layer in the MS differs depending on the nature of the channel (traffic, packet data traffic or broadcast/common channels). - Establishment of dedicated physical channels: Establishment of dedicated physical channels on the physical layer is controlled by the radio resources management of layer 3 (GSM 04.08). During operation on a dedicated physical channel, the physical layer measures the signals of neighbouring base stations and the signal quality of the used dedicated physical channel. Measurements are transferred to layer 3, measurement control information is offered by layer 3. - Establishment of packet data physical channels : Establishment of packet data physical channels on the physical layer is controlled by the radio resource management of layer 3. Packet access and the reservation of radio resource on packet data physical channels is controlled by the RLC/MAC layer in co-operation with layer 3 (GSM 04.60 and GSM 04.08). During operation on packet data physical channels, the physical layer measures the signals of neighbouring base stations and the signal quality of the used packet data physical channel. Measurements are transferred to layer 3, measurement control information is offered by layer 3. - cell/PLMN selection in idle mode or in packet mode: In idle mode or in packet mode, the physical layer selects the best cell with its BCCH/CCCH in close co-operation with layer 3, meeting requirements for PLMN selection specified in GSM 02.11. The idle mode procedures are not modelled within the present document. Examples of procedures for cell selection are described in GSM 05.08. The physical layer performs automatic crossover.
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
4 Primitives of the physical layer
|
The Physical layer interacts with other entities as illustrated in figure 2.1. The interactions with the data link layer of Dm channels and the interactions with the RLC/MAC layer of packet data physical channels are shown in terms of primitives where the primitives represent the logical exchange of information and control between the physical layer and adjacent layers. They do not specify or constrain implementations. The interactions between the physical layer and layer 1 entities for Bm/Lm channels are for further study. For the physical layer two sets of primitives are defined: ETSI ETSI TS 100 936 V7.0.0 (1999-08) 11 (GSM 04.04 version 7.0.0 Release 1998) - Primitives between physical layer and data link layer and RLC/MAC layer respectively: PH - Generic name - Type: Parameters. - Primitives between layer 1 and the RR-management layer 3 entity: MPH - Generic name - Type: Parameters. 4.1 Generic names of primitives between layers 1 and 2 for the transfer of layer 2 frames and RLC/MAC blocks The following primitive generic names are defined on the SAPs between the physical layer and the data link layer: a) PH-DATA: The PH-DATA primitives are used on a SAP to pass message units containing frames used for data link layer and RLC/MAC layer respective peer-to-peer communications to and from the physical layer. b) PH-RANDOM ACCESS: The PH-RANDOM ACCESS (PH-RA) primitives are used on the SAP of the RACH and the PRACH to request and confirm (in the MS) the sending of a random access frame and to indicate (in the network) the arrival of a random access frame. The random access protocols are specified in GSM 04.08 and GSM 04.60 respectively. c) PH-CONNECT: The PH-CONNECT primitive is used on a SAP to indicate that the physical connection on the corresponding control channel or packet data physical channel has been established. d) PH-READY-TO-SEND: The PH-READY-TO-SEND primitive is used by the physical layer to trigger, if applicable, piggy backing, the start of timer for the data link layer or the RLC/MAC layer and the forwarding a data unit to the physical layer. It is passed to the upper layer just before a new physical block is transmitted. e) PH-EMPTY-FRAME: The PH-EMPTY-FRAME primitive can be used by the data link layer and the RLC/MAC layer to indicate that no frame has to be transmitted after receiving the PH-READY-TO-SEND primitive. It enables polling of several upper layer entities by the physical layer and support DTX. 4.2 Generic names of primitives between layer 1 and the RR- management entity of layer 3 The following primitive generic name is defined between layer 1 and the RR-management entity of layer 3: - MPH-INFORMATION: MPH-INFORMATION (MPH-INFO) primitives are used for the control of the physical layer by the RR-management of layer 3. This information activates and deactivates, configures and deconfigures, through connects and disconnects physical and logical channels. It is also used for the transfer of measurements and measurement control information from layer 1 to layer 3.
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
4.3 Primitive types
|
The primitive types defined in the present document are: a) REQUEST: The REQUEST primitive type is used when a higher layer is requesting a service from a lower layer. ETSI ETSI TS 100 936 V7.0.0 (1999-08) 12 (GSM 04.04 version 7.0.0 Release 1998) b) INDICATION: The INDICATION primitive type is used by a layer providing a service to notify the next higher layer of activities in the layer. This activities are directly related to the occurrence of a REQUEST primitive on the peer-protocol side. c) RESPONSE: The RESPONSE primitive type is used by a layer to acknowledge receipt from the INDICATION primitive type. d) CONFIRM: The CONFIRM primitive type is used by the layer providing the requested service to confirm that the activity has been completed.
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
4.4 Parameter definition
|
Primitives contain a variable amount of parameters. The primitives with included parameters are listed in table 4.1. Table 4.1: Primitives of the physical layer message unit channel control parameters system information absolute frame No. primitive entity direction measurement MPH-INFO-REQ MS/BS RR(L3) PH(L1) x x MPH-INFO-CON MS/BS PH(L1) RR(L3) x x MPH-INFO-IND MS/BS PH(L1) RR(L3) x x x PH-CONNECT-IND MS/BS PH(L1) DL(L2) RLC/MAC x PH-READY-TO- SEND MS/BS PH(L1) DL(L2) RLC/MAC x x PH-EMPTY-FRAME MS/BS DL(L2) RLC/MAC PH(L1) x PH-DATA-REQ MS/BS DL(L2) RLC/MAC PH(L1) x x PH-DATA-IND MS/BS PH(L1) DL(L2) RLC/MAC x x x PH-RA-REQ MS DL(L2) RLC/MAC PH(L1) x PH-RA-IND BS PH(L1) DL(L2) RLC/MAC x x PH-RA-CON MS PH(L1) DL(L2) RLC/MAC x x Parameters involved in the primitive exchange with the physical layer are: a) Message unit: The message unit contains peer-to-peer information of a layer. It is transferred by the physical layer to the peer layer. ETSI ETSI TS 100 936 V7.0.0 (1999-08) 13 (GSM 04.04 version 7.0.0 Release 1998) b) Channel control parameters: These parameters contain information for channel control, specified in GSM 04.08 and GSM 04.60. c) System information: This information is exchanged in the cell/PLMN selection procedures. It may also contain control information for DRX (sleep mode, see GSM 03.13). d) Absolute Frame Number: The absolute frame number is used (in combination with a random access identifier) to uniquely identify a random access. e) Measurements: This parameter is used to report the quality of a dedicated physical channel (MS and network) and to report the quality of surrounding BCCH carriers (MS only).
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
5 Physical layer procedures
|
The main body of physical layer procedures is specified in GSM 04.08, GSM 04.60 and 05.08.
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
5.1 States of the physical layer
|
In the physical layer of the MS the following states are defined: NULL: the equipment is switched off; SEARCHING BCH: the physical layer tracks the best BCCH; BCH: the physical layer listens to a BCCH/CCCH or PBCCH/PCCCH and is able to do random access; TUNING DCH: the physical layer seizes on a respective dedicated physical channel or packet data physical channel; DCH: the physical layer has seized a respective dedicated physical channel or packet data physical channel and may establish and through connect logical channels. NOTE: BCH = Bcch/ccch physical CHannel or pbcch/pccch physical channel; DCH = Dedicated physical CHannel or packet data physical channel. Figure 5.1 gives a general state diagram of the physical layer. All state transitions of the physical layer are controlled by MPH-INFORMATION primitives. ETSI ETSI TS 100 936 V7.0.0 (1999-08) 14 (GSM 04.04 version 7.0.0 Release 1998) NULL BCH SEARCHING BCH TUNING DCH DCH idle mode packet wait state dedicated mode packet transfer state Figure 5.1: States of the physical layer in the MS The states of the physical layer in the network are not specified. The states in the network will reflect the other characteristics of operation on channels.
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
5.2 Control procedures
|
Requirements and examples of procedures for idle mode and for packet mode operation of the MS are specified in GSM 02.11 and 05.08. In the idle mode and packet mode procedures the physical layer tracks the best cell and may tune on their BCCH/PBCCH in order to enable layer 3 to read the system information of the BCCH/PBCCH. This system information of the BCCH/PBCCH is used in the selection process.
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
5.3 Physical layer interface procedures
|
Three types of primitives are defined for the communication between the physical layer and the data link layer both in the MS and the network. When a control channel or a packet data physical channel is being established, a PH-CONNECT-INDICATION is offered to the data link layer or the RLC/MAC layer, the one which is applicable, on the corresponding SAP. On an established full duplex control channel (DCCHs) in both MS and network, on an established packet data physical channel or on the established BCCH/CCCH in the MS, physical blocks received correctly are offered on the corresponding SAP in PH-DATA-INDICATION primitives. On a full duplex control channel (DCCHs) or on the BCCH/CCCH in the network, the data link layer will offer physical blocks to be transmitted in PH-DATA-REQUEST primitives. On a packet data physical channel, the RLC/MAC layer will offer physical blocks to be transmitted in PH-DATA-REQUEST primitives. In the MS in idle mode or in packet wait state, random accesses on RACH or on PRACH can be offered in PH-RANDOM ACCESS-REQUEST primitives. The physical layer of the MS will perform a random access as soon as possible. The physical layer of the MS will confirm the data link layer or the RLC/MAC layer, the one which is applicable, the transmission of the random access attempt in a PH-RANDOM ACCESS-CONFIRM. This confirmation contains the absolute frame number in which the random access is transmitted. The physical layer of the BS offers correctly received random accesses to the data link layer or the RLC/MAC layer, the one which is applicable, in a PH-RANDOM ACCESS-INDICATION. This indication contains the absolute frame number in which the random access is received. ETSI ETSI TS 100 936 V7.0.0 (1999-08) 15 (GSM 04.04 version 7.0.0 Release 1998)
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
6 Physical layer protocol header
|
The physical layer implements a peer-to-peer protocol for the control of timing advance and power control at the operation on dedicated physical channels, and further, for the control of timing advance at the operation on packet data physical channels. For this purpose a two octet physical header is defined on all blocks transferred via the SACCH, a logical channel always present on a dedicated physical channel. Further more, a 16 octet information field is defined on downlink blocks transferred via the PTCCH, a logical channel present on a packet data physical channel .
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
6.1 Physical layer protocol fields and procedures
|
Procedures for handling the ordered and actual power level fields are specified in GSM 05.05 and 05.08. The ordered MS power level field and the actual MS power level field are coded as the binary representation of the "power control level", see GSM 05.05. Procedures for handling the ordered and actual timing advance fields are specified in GSM 05.10. The numbers corresponding to the timing advance steps in GSM 05.10 are included binary coded in the 7 bit ordered and actual timing advance fields of the physical layer header. The bit pattern "1111111" indicates that the field does not contain a timing advance value. All other bit combinations (64 to 126 decimal) are reserved. A MS in packet transfer state which is assigned a TAI shall, when receiving a PTCCH downlink block on the packet data physical channel containing PACCH, read the corresponding ordered timing advance field in that PTCCH block. The ordered timing advance fields corresponding to other TAIs than the assigned one shall be ignored .
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
7 Block transmission
| |
1542eafea182f455171d0fbe295d1ced
|
100 936
|
7.1 SACCH downlink block format
|
The originally 23 octets of SACCH blocks are used downlink in the following way: bit numbering <---------------------------------------------------------------------------------- 8 7 6 5 4 3 2 1 Spare Ordered MS power level octet 1 Spare Ordered timing advance octet 2 octet octet 3 numbering 21 octets V : : : : : : layer 2 frame octet 23 NOTE: The numbering convention specified in GSM 04.06 applies. Figure 7.1: SACCH downlink block format
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
7.2 SACCH uplink block format
|
The originally 23 octets of SACCH blocks are used uplink in the following way: ETSI ETSI TS 100 936 V7.0.0 (1999-08) 16 (GSM 04.04 version 7.0.0 Release 1998) bit numbering <---------------------------------------------------------------------------------- 8 7 6 5 4 3 2 1 Spare Actual MS power level octet 1 Spare Actual timing advance octet 2 octet octet 3 numbering 21 octets V : : : : : : layer 2 frame octet 23 NOTE: The numbering convention specified in GSM 04.06 applies. Figure 7.2: SACCH uplink block format
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
7.3 FACCH/SDCCH/CCCH/BCCH/CBCH downlink block format
|
The originally 23 octets blocks are used downlink in the following way: <---------------------------------------------------------------------------------- 8 7 6 5 4 3 2 1 octet 1 23 octets : : : : : : layer 2 frame octet 23 NOTE: The numbering convention specified in GSM 04.06 and 04.12 applies. Figure 7.3: FACCH/SDCCH/BCCH/CCCH/CBCH downlink block format
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
7.4 FACCH/SDCCH uplink block format
|
The originally 23 octets blocks are used uplink in the following way: <---------------------------------------------------------------------------------- 8 7 6 5 4 3 2 1 octet 1 23 octets : : : : : : layer 2 frame octet 23 NOTE: The numbering convention specified in GSM 04.06 applies. Figure 7.4: FACCH/SDCCH uplink block format ETSI ETSI TS 100 936 V7.0.0 (1999-08) 17 (GSM 04.04 version 7.0.0 Release 1998) 7.5 PBCCH/PCCCH downlink/PACCH/PDTCH block type 1 (CS-1) format The originally 184 bit (23 octets) blocks are used in the following way: <---------------------------------------------------------------------------------- 8 7 6 5 4 3 2 1 octet 1 184 bit : : : : : : RLC/MAC block octet 23 NOTE: The numbering convention specified in GSM 04.60 applies. Figure 7.5: PBCCH/PCCCH downlink/PACCH/PDTCH block type 1 (CS-1) format
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
7.6 PDTCH block type 2 (CS-2) format
|
The originally 271 bit blocks are used in the following way: <---------------------------------------------------------------------------------- 8 7 6 5 4 3 2 1 octet 1 271 bit : : : : : : RLC/MAC block octet 34 NOTE: The numbering convention specified in GSM 04.60 applies. Figure 7.6: PDTCH block type 2 (CS-2) format ETSI ETSI TS 100 936 V7.0.0 (1999-08) 18 (GSM 04.04 version 7.0.0 Release 1998)
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
7.7 PDTCH block type 3 (CS-3) format
|
The originally 315 bit blocks are used in the following way: <---------------------------------------------------------------------------------- 8 7 6 5 4 3 2 1 octet 1 315 bit : : : : : : RLC/MAC block octet 39 octet 40 NOTE: The numbering convention specified in GSM 04.60 applies. Figure 7.7: PDTCH block type 3 (CS-3) format
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
7.8 PDTCH block type 4 (CS-4) format
|
The originally 431 bit blocks are used in the following way: <---------------------------------------------------------------------------------- 8 7 6 5 4 3 2 1 octet 1 431 bit : : : : : : RLC/MAC block octet 54 NOTE: The numbering convention specified in GSM 04.60 applies. Figure 7.8: PDTCH block type 4 (CS-4) format 7.9 PRACH uplink/PACCH uplink short acknowledgement block formats Two alternative PRACH uplink/PACCH uplink short acknowledgement block formats are specified. The originally 8 bit (1 octet) blocks are used uplink in the following way: <---------------------------------------------------------------------------------- 8 7 6 5 4 3 2 1 8 bit RLC/MAC block octet 1 NOTE: The numbering convention specified in GSM 04.60 applies. Figure 7.9 (sheet 1 of 2): PRACH uplink/PACCH uplink short acknowledgement block format ETSI ETSI TS 100 936 V7.0.0 (1999-08) 19 (GSM 04.04 version 7.0.0 Release 1998) The originally 11 bit blocks are used uplink in the following way: <---------------------------------------------------------------------------------- 8 7 6 5 4 3 2 1 11 bit RLC/MAC block octet 1 octet 2 NOTE: The numbering convention specified in GSM 04.60 applies. Figure 7.9 (sheet 2 of 2): PRACH uplink/PACCH uplink short acknowledgement block format
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
7.10 PTCCH downlink block format
|
The originally 184 bit (23 octets) blocks are used downlink in the following way: <---------------------------------------------------------------------------------- 8 7 6 5 4 3 2 1 Spare Ordered timing advance for MS assigned TAI = 0 octet 1 Spare Ordered timing advance for MS assigned TAI = 1 octet 2 : : : : : : Spare Ordered timing advance for MS assigned TAI = 15 octet 16 7 octet 17 octets : : : : : : fill octets: "00101011" octet 23 Figure 7.10: PTCCH downlink block format The field mapping convention in this sub-clause is that when a field is contained within a single octet, the highest bit number of the field represents the highest order value and lowest bit number of the field represents the lowest order value. Spare bits are encoded with the binary value "0". Fill octets are encoded with the binary value "00101011". ETSI ETSI TS 100 936 V7.0.0 (1999-08) 20 (GSM 04.04 version 7.0.0 Release 1998)
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
7.11 PTCCH uplink block formats
|
Two alternative PTCCH uplink block formats are specified. The originally 8 bit (1 octet) blocks are used uplink in the following way: <---------------------------------------------------------------------------------- 8 7 6 5 4 3 2 1 8 fixed bits: "01111111" octet 1 Figure 7.11 (sheet 1 of 2): PTCCH uplink block format The originally 11 bit blocks are used uplink in the following way: <---------------------------------------------------------------------------------- 8 7 6 5 4 3 2 1 11 fixed bits: "11111111111" octet 1 octet 2 Figure 7.11 (sheet 2 of 2): PTCCH uplink block format The field mapping convention of sub-clause 7.10 applies. In the addition, when a field spans more than one octet, the order of bit values within each octet progressively decreases as the octet number increases. In that part of a field contained in a given octet the lowest bit number represents the lowest order value.
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
7.12 Order of bit transmission
|
On channels for normal burst transmission having a block format with an integer N number of octets, the N octets are mapped onto 8N bits, d(0) to d(8N-1), defined in GSM 05.03 clause 4 and 5 as follows: Bit m of octet n shall be transmitted as bit d((n-1)*8+m-1) with m=(1..8) and n=(1..N). On channels for normal burst transmission having a block format with a non-integer number of octets, or for transmission having a defined block format but which does not follow the normal burst transmission, the octets are mapped onto M bits, d(0) to d(M-1), defined in GSM 05.03 clause 5 as follows: Bit m of octet n shall be transmitted as bit d(8(n-1) + m-1) with n = (1 .. ((M-1) DIV 8) + 1)) and m = (1 .. min (8, (M - 8(n-1))), and where 'DIV' is the integer division operator.
|
1542eafea182f455171d0fbe295d1ced
|
100 936
|
8 Vocabulary
|
The terminology used in the present document is as follows: - Idle mode: In this mode the MS is not allocated any dedicated physical channel; it listens to the CCCH and the BCCH. - Dedicated mode: In this mode the MS is allocated a dedicated physical channel, at least containing two logical channels, only one of them being a SACCH. - Packet mode : In this mode the MS is ready to access and operate on a packet data physical channel. The packet mode includes two sub-states: packet wait state and packet transfer state (see GSM 04.60). ETSI ETSI TS 100 936 V7.0.0 (1999-08) 21 (GSM 04.04 version 7.0.0 Release 1998) - Physical block: The physical block is the minimal unit which can be transferred by the physical layer. - Dedicated physical channel: The physical blocks scheduled on the radio medium assigned to a dedicated connection with a MS. - Packet data physical channel : The physical blocks scheduled on the radio medium assigned to a shared usage between MSs for packet switched data traffic. ETSI ETSI TS 100 936 V7.0.0 (1999-08) 22 (GSM 04.04 version 7.0.0 Release 1998) Annex A (informative): Document change history SPEC SMG# CR PHASE VERS NEW_VERS SUBJECT 04.04 s24 A001 R97 5.0.1 6.0.0 Introduction of GPRS 04.04 s29 R98 7.0.0 Specification version upgrade to Release 1998 version 7.0.0 ETSI ETSI TS 100 936 V7.0.0 (1999-08) 23 (GSM 04.04 version 7.0.0 Release 1998) History Document history V7.0.0 August 1999 Publication ISBN 2-7437-3344-6 Dépôt légal : Août 1999
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
0 Scope
|
The present document specifies the network functions needed to provide the security related service and functions specified in GSM 02.09. The present document does not address the cryptological algorithms that are needed to provide different security related features. This topic is addressed in annex C. Wherever a cryptological algorithm or mechanism is needed, this is signalled with a reference to annex C. The references refers only to functionalities, and some algorithms may be identical or use common hardware.
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
0.1 References
|
The following documents contain provisions which, through reference in this text, constitute provisions of the present document. • References are either specific (identified by date of publication, edition number, version number, etc.) or non-specific. • For a specific reference, subsequent revisions do not apply. • For a non-specific reference, the latest version applies. • A non-specific reference to an ETS shall also be taken to refer to later versions published as an EN with the same number. • For this Release 1998 document, references to GSM documents are for Release 1998 versions (version 7.x.y). [1] GSM 01.04: "Digital cellular telecommunications system (Phase 2+); Abbreviations and acronyms". [2] GSM 01.61: "Digital cellular telecommunications system (Phase 2+); General Packet Radio Service (GPRS); GPRS ciphering algorithm requirements". [3] GSM 02.07: "Digital cellular telecommunications system (Phase 2+); Mobile Station (MS) features". [4] GSM 02.09: "Digital cellular telecommunications system (Phase 2+); Security aspects". [5] GSM 02.17: "Digital cellular telecommunications system (Phase 2+); Subscriber Identity Modules (SIM) Functional characteristics". [6] GSM 02.56: "Digital cellular telecommunications system (Phase 2+); GSM Cordless Telephone System (CTS) Phase 1; Service Description; Stage 1". [7] GSM 02.60: " Digital cellular telecommunications system (Phase 2+); General Packet Radio Service (GPRS); Service description; Stage 1". [8] GSM 03.03: "Digital cellular telecommunications system (Phase 2+); Numbering, addressing and identification". [9] GSM 03.56: "Digital cellular telecommunications system (Phase 2+); GSM Cordless Telephone System (CTS), Phase 1; CTS Architecture Description; Stage 2". [10] GSM 03.60: " Digital cellular telecommunications system (Phase 2+); General Packet Radio Service (GPRS); Service description; Stage 2" [11] GSM 04.08: "Digital cellular telecommunications system (Phase 2+); Mobile radio interface layer 3 specification". [12] GSM 04.64: " Digital cellular telecommunications system (Phase 2+), General Packet Radio Service (GPRS); Logical Link Control (LLC)". ETSI ETSI TS 100 929 V7.2.0 (1999-11) 10 (GSM 03.20 version 7.2.0 Release 1998) [13] GSM 05.01: "Digital cellular telecommunication system (Phase 2+); Physical layer on the radio path; General description". [14] GSM 05.02: "Digital cellular telecommunications system (Phase 2+); Multiplexing and multiple access on the radio path". [15] GSM 05.03: "Digital cellular telecommunications system (Phase 2+); Channel coding". [16] GSM 09.02: "Digital cellular telecommunications system (Phase 2+); Mobile Application Part (MAP) specification". [17] GSM 11.11: "Digital cellular telecommunications system (Phase 2+); Specification of the Subscriber Identity Module- Mobile Equipment (SIM-ME) interface".
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
0.2 Abbreviations
|
Abbreviations used in the present document are listed in GSM 01.04. Specific abbreviations used in annex A are listed in clause A.3. Specific CTS related abbreviations used in annex E are listed in clause E.1.3. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 11 (GSM 03.20 version 7.2.0 Release 1998)
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
1 General
|
The different security related services and functions that are listed in GSM 02.09 are grouped as follows: - Subscriber identity confidentiality; - Subscriber identity authentication; - Signalling information element and connectionless user data confidentiality and data confidentiality for physical connections (ciphering). It shall be possible to introduce new authentication and ciphering algorithms during the systems lifetime. The fixed network may support more than one authentication and ciphering algorithm. The security procedures include mechanisms to enable recovery in event of signalling failures. These recovery procedures are designed to minimize the risk of a breach in the security of the system. General on figures in the present document: - In the figures below, signalling exchanges are referred to by functional names. The exact messages and message types are specified in GSM 04.08 and GSM 09.02. - No assumptions are made for function splitting between MSC (Mobile Switching Centre), VLR (Visitor Location Register) and BSS (Base Station System). Signalling is described directly between MS and the local network (i.e. BSS, MSC and VLR denoted in the figures by BSS/MSC/VLR). The splitting in annex A is given only for illustrative purposes. - Addressing fields are not given; all information relates to the signalling layer. The TMSI allows addressing schemes without IMSI, but the actual implementation is specified in the GSM 04-series. - The term HPLMN in the figures below is used as a general term which should be understood as HLR (Home Location Register) or AuC (Authentication Centre). - What is put in a box is not part of the described procedure but it is relevant to the understanding of the figure. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 12 (GSM 03.20 version 7.2.0 Release 1998)
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
2 Subscriber identity confidentiality
| |
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
2.1 Generality
|
The purpose of this function is to avoid the possibility for an intruder to identify which subscriber is using a given resource on the radio path (e.g. TCH (Traffic Channel) or signalling resources) by listening to the signalling exchanges on the radio path. This allows both a high level of confidentiality for user data and signalling and protection against the tracing of a user's location. The provision of this function implies that the IMSI (International Mobile Subscriber Identity), or any information allowing a listener to derive the IMSI easily, should not normally be transmitted in clear text in any signalling message on the radio path. Consequently, to obtain the required level of protection, it is necessary that: - a protected identifying method is normally used instead of the IMSI on the radio path; and - the IMSI is not normally used as addressing means on the radio path (see GSM 02.09); - when the signalling procedures permit it, signalling information elements that convey information about the mobile subscriber identity must be ciphered for transmission on the radio path. The identifying method is specified in the following subclause. The ciphering of communication over the radio path is specified in clause 4.
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
2.2 Identifying method
|
The means used to identify a mobile subscriber on the radio path consists of a TMSI (Temporary Mobile Subscriber Identity). This TMSI is a local number, having a meaning only in a given location area; the TMSI must be accompanied by the LAI (Location Area Identification) to avoid ambiguities. The maximum length and guidance for defining the format of a TMSI are specified in GSM 03.03. The network (e.g. a VLR) manages suitable data bases to keep the relation between TMSIs and IMSIs. When a TMSI is received with an LAI that does not correspond to the current VLR, the IMSI of the MS must be requested from the VLR in charge of the indicated location area if its address is known; otherwise the IMSI is requested from the MS. A new TMSI must be allocated at least in each location updating procedure. The allocation of a new TMSI corresponds implicitly for the MS to the de-allocation of the previous one. In the fixed part of the network, the cancellation of the record for an MS in a VLR implies the de-allocation of the corresponding TMSI. To cope with some malfunctioning, e.g. arising from a software failure, the fixed part of the network can require the identification of the MS in clear. This procedure is a breach in the provision of the service, and should be used only when necessary. When a new TMSI is allocated to an MS, it is transmitted to the MS in a ciphered mode. This ciphered mode is the same as defined in clause 4. The MS must store its current TMSI in a non volatile memory, together with the LAI, so that these data are not lost when the MS is switched off. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 13 (GSM 03.20 version 7.2.0 Release 1998)
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
2.3 Procedures
|
This subclause presents the procedures, or elements of procedures, pertaining to the management of TMSIs.
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
2.3.1 Location updating in the same MSC area
|
This procedure is part of the location updating procedure which takes place when the original location area and the new location area depend on the same MSC. The part of this procedure relative to TMSI management is reduced to a TMSI re-allocation (from TMSIo with "o" for "old" to TMSIn with "n" for "new"). The MS sends TMSIo as an identifying field at the beginning of the location updating procedure. The procedure is schematized in figure 2.1. !"! #"! $# % !&' !% ($!!') *$!+, )) ' # !%( , - '. &)! ! /!0 )) ' # Figure 2.1: Location updating in the same MSC area Signalling Functionalities: Management of means for new ciphering: The MS and BSS/MSC/VLR agree on means for ciphering signalling information elements, in particular to transmit TMSIn. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 14 (GSM 03.20 version 7.2.0 Release 1998)
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
2.3.2 Location updating in a new MSCs area, within the same VLR area
|
This procedure is part of the location updating procedure which takes place when the original location area and the new location area depend on different MSCs, but on the same VLR. The procedure is schematized on figure 2.2. ! " #$%$" &%$ "'& ("$) * $( "#+'$$*, -'$./ ,, * " & " +" $/ $(+ "/+" $/ *01 "# 2! ! +" $/ *3" ),$ #$+" $/*3" ),$ #$ ! 2! 4$5 ,, * " & NOTE: From a security point of view, the order of the procedures is irrelevant. Figure 2.2: Location updating in a new MSCs area, within the same VLR area Signalling functionalities: Loc.Updating: stands for Location Updating The BSS/MSC/VLR indicates that the location of the MS must be updated. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 15 (GSM 03.20 version 7.2.0 Release 1998)
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
2.3.3 Location updating in a new VLR; old VLR reachable
|
This procedure is part of the normal location updating procedure, using TMSI and LAI, when the original location area and the new location area depend on different VLRs. The MS is still registered in VLRo ("o" for old or original) and requests registration in VLRn ("n" for new). LAI and TMSIo are sent by MS as identifying fields during the location updating procedure. The procedure is schematized in figure 2.3. 123 - !'4!)4 # !"! #"! $# % !& ' !% ($!!') *$!+, )) ' # !%( ,( !, '45 ( !, - '. &)! !( !,'. &)! !( !, - '!)) - /!0 )) ' # NOTE: From a security point of view, the order of the procedures is irrelevant. Figure 2.3: Location updating in a new VLR; old VLR reachable Signalling functionalities: Sec.Rel.Info.: Stands for Security Related information The MSC/VLRn needs some information for authentication and ciphering; this information is obtained from MSC/VLRo. Cancellation: The HLR indicates to VLRo that the MS is now under control of another VLR. The "old" TMSI is free for allocation. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 16 (GSM 03.20 version 7.2.0 Release 1998)
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
2.3.4 Location Updating in a new VLR; old VLR not reachable
|
This variant of the procedure in subclause 2.3.3 arises when the VLR receiving the LAI and TMSIo cannot identify the VLRo. In that case the relation between TMSIo and IMSI is lost, and the identification of the MS in clear is necessary. The procedure is schematized in figure 2.4. " ! , " ($ * 6,$ $" 7$8-$' 2! ! " #$%$" &%$ "'& ("$) * $( "#+'$$*, -'$./ ,, * " & " $(+ "/+" $/ * "1 "#+" $/ 2! ! *3" ),$ #$+" $/*3" ),$ #$+" $/ ! 2! "*$,, " 2! 4$5 ,, * " & NOTE: From a security point of view, the order of the procedures is irrelevant. Figure 2.4: Location Updating in a new VLR; old VLR not reachable ETSI ETSI TS 100 929 V7.2.0 (1999-11) 17 (GSM 03.20 version 7.2.0 Release 1998)
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
2.3.5 Reallocation of a new TMSI
|
This function can be initiated by the network whenever a radio connection exists. The procedure can be included in other procedures, e.g. through the means of optional parameters. The execution of this function is left to the network operator. When a new TMSI is allocated to an MS the network must prevent the old TMSI from being allocated again until the MS has acknowledged the allocation of the new TMSI. If an IMSI record is deleted in the VLR by O&M action, the network must prevent any TMSI associated with the deleted IMSI record from being allocated again until a new TMSI is successfully allocated to that IMSI. If an IMSI record is deleted in the HLR by O&M action, it is not possible to prevent any TMSI associated with the IMSI record from being allocated again. However, if the MS whose IMSI record was deleted should attempt to access the network using the TMSI after the TMSI has been allocated to a different IMSI, then authentication or ciphering of the MS whose IMSI was deleted will almost certainly fail, which will cause the TMSI to be deleted from the MS. The case where allocation of a new TMSI is unsuccessful is described in subclause 2.3.8. This procedure is schematized in figure 2.5. ,, * " & " $(+ "/ 2! *3" ),$ #$ ! 4$5 ,, * " & Figure 2.5: Reallocation of a new TMSI ETSI ETSI TS 100 929 V7.2.0 (1999-11) 18 (GSM 03.20 version 7.2.0 Release 1998)
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
2.3.6 Local TMSI unknown
|
This procedure is a variant of the procedure described in subclauses 2.3.1 and 2.3.2, and happens when a data loss has occurred in a VLR and when a MS uses an unknown TMSI, e.g. for a communication request or for a location updating request in a location area managed by the same VLR. This procedure is schematized in figure 2.6. 123 ( !, $ * . & ! 6!7*!$ - !"! #"! $# % !& ' !% ($!!') *$!+, )) ' # !%( , - '. &)! ! NOTE: Any message in which TMSIo is used as an identifying means in a location area managed by the same VLR. Figure 2.6: Location updating in the same MSC area; local TMSI unknown ETSI ETSI TS 100 929 V7.2.0 (1999-11) 19 (GSM 03.20 version 7.2.0 Release 1998)
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
2.3.7 Location updating in a new VLR in case of a loss of information
|
This variant of the procedure described in 2.3.3 arises when the VLR in charge of the MS has suffered a loss of data. In that case the relation between TMSIo and IMSI is lost, and the identification of the MS in clear is necessary. The procedure is schematized in figure 2.7. " ! ! 1"3" )" $" 7$8-$' 2! 2! ! " #$%$" &%$ "'& ("$) * $( "#+'$$*, -'$./ ,, * " & " $(+ "/+" $/ * "1 "#+" $/ 2! ! *3" ),$ #$+" $/*3" ),$ #$+" $/ ! 2! "*$,, " 2! 4$5 ,, * " & NOTE: From a security point of view, the order of the procedures is irrelevant. Figure 2.7: Location updating in a new VLR in case of a loss of information
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
2.3.8 Unsuccessful TMSI allocation
|
If the MS does not acknowledge the allocation of a new TMSI, the network shall maintain the association between the old TMSI and the IMSI and between the new TMSI and the IMSI. For an MS-originated transaction, the network shall allow the MS to identify itself by either the old TMSI or the new TMSI. This will allow the network to determine the TMSI stored in the MS; the association between the other TMSI and the IMSI shall then be deleted, to allow the unused TMSI to be allocated to another MS. For a network-originated transaction, the network shall identify the MS by its IMSI. When radio contact has been established, the network shall instruct the MS to delete any stored TMSI. When the MS has acknowledged this instruction, the network shall delete the association between the IMSI of the MS and any TMSI; this will allow the released TMSIs to be allocated to another MS. In either of the cases above, the network may initiate the normal TMSI reallocation procedure. Repeated failure of TMSI reallocation (passing a limit set by the operator) may be reported for O&M action. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 20 (GSM 03.20 version 7.2.0 Release 1998)
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
2.3.9 Combined location area updating with the routing area updating
|
This subclause is only applicable if GPRS is supported. This procedure is part of the location updating of a General Packet Radio Service (GPRS) class A or B mobile when the Gs-interface (SGSN MSC/VLR signalling interface) is implemented. This procedure is not relevant if the Gs-interface is not implemented. The location area updating procedure and the routing area updating procedure are combined to one MS Serving GPRS Support Node (SGSN) procedure. The MS includes a Location Area Update (LAU) indication in the Routing Area Update Request message. The SGSN performs the location updating towards the VLR on behalf of the MS. The procedure described in figure 2.8 shows only the interaction between the SGSN and the VLR. The full procedure including the update to other network element (e.g. HLR, old MSC/VLR) is described in GSM 03.60 . ┌─────┐┌─────────────┐┌────────────┐ ┌────────┐ │MS ││ BSS ││ SGSN │ │ VLR │ └──┬──┘└─────────────┘└──────┬┬────┘ └────┬───┘á │ ││ │ á │RAI, TLLI, LAU indication ││ │ ├──────────────────────────>┤│ │ │ (note 1) ││ │ │ ┌────────────┐ │ │ │ Security │á │ │ │ functions │ │ │ └────────────┘ │ á │ ││ │ │ ││IMSI,LAI (note 2) │ │ │├──────────────────>┤ │ ││ ┌────────────┐ │ ││ │Allocation │ │ ││ │ of TMSIn │ │ ││ └────────────┘ │ ││ │ │ ││ TMSIn (note 3) │ │ │├<──────────────────┤ │ ││ │ á │ ││ │ │ Cipher(TMSIn)(note 4) ││ │ ├<──────────────────────────┤│ │á │ ││ │ á │ ││ │ á │ Acknowledge (note 5) ││Acknowledge(note 6)│ á ├──────────────────────────>┤├─────────────────>─┤ á │ ┌────────────┐ │ │Deallocation│á │ │of TMSIo │ │ └────────────┘ NOTE 1: The Routeing Area Update Request message including the old Routing Area Identifier (RAI), the Temporary Logical Link Identifier (TLLI), and an indication that a combined Location Area Update (LAU) is performed. NOTE 2: Location Updating message. NOTE 3: Location Updating Accept message including the new TMSI. NOTE 4: Routing Area Update Accept message including the new TMSI and the new TLLI (if any). NOTE 5: Routing Area Update Complete message including the TLLI and TMSI. NOTE 6: TMSI Reallocation Complete message including the TMSI. Figure 2.8: Combined routing area and location updating in the same VLR ETSI ETSI TS 100 929 V7.2.0 (1999-11) 21 (GSM 03.20 version 7.2.0 Release 1998) When the VLR does not change the TMSI, the old TMSI will stay in use and there is no need to send any TMSI to the MS. In case of combined routing area update and inter-VLR location area updating procedure, the old TMSI will be cancelled and the HLR is updated as described in GSM 03.60. If the Location Updating message indicates a reject (if for example the MS try to enter a forbidden location area), then this should be indicated to the MS and the MS shall not access non-GPRS service until a successful Location Update is performed. For the combined location and routing area update and the combined GPRS Attach and IMSI Attach for GPRS class A and B mobiles, the authentication is performed by the SGSN. The authentication procedure for GPRS is described in annex D. The MSC/VLR relies on the SGSN authentication. This authentication procedure generates no ciphering key for circuit switched ciphering. The ciphering key for circuit switched operation is allocated through an authentication by MSC/VLR when the circuit switched service is requested. Also, the MSC/VLR may use the old ciphering key if existing. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 22 (GSM 03.20 version 7.2.0 Release 1998)
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
3 Subscriber identity authentication
| |
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
3.1 Generality
|
The definition and operational requirements of subscriber identity authentication are given in GSM 02.09. The authentication procedure will also be used to set the ciphering key (see clause 4). Therefore, it is performed after the subscriber identity (TMSI/IMSI) is known by the network and before the channel is encrypted. Two network functions are necessary: the authentication procedure itself, and the key management inside the fixed subsystem.
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
3.2 The authentication procedure
|
The authentication procedure consists of the following exchange between the fixed subsystem and the MS. - The fixed subsystem transmits a non-predictable number RAND to the MS. - The MS computes the signature of RAND, say SRES, using algorithm A3 and some secret information: the Individual Subscriber Authentication Key, denoted below by Ki. - The MS transmits the signature SRES to the fixed subsystem. - The fixed subsystem tests SRES for validity. The general procedure is schematized in figure 3.1. 3!& %.$ ! 3/ 8 3/( !, 8 9 9 : ; 6!$ NOTE: IMSI is used to retrieve Ki in the network. Figure 3.1: The authentication procedure Authentication algorithm A3 is specified in annex C. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 23 (GSM 03.20 version 7.2.0 Release 1998)
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
3.3 Subscriber Authentication Key management
|
The Subscriber Authentication Key Ki is allocated, together with the IMSI, at subscription time. Ki is stored on the network side in the Home Public Land Mobile Network (HPLMN), in an Authentication Centre (AuC). A PLMN may contain one or more AuC. An AuC can be physically integrated with other functions, e.g. in a Home Location Register (HLR).
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
3.3.1 General authentication procedure
|
When needed for each MS, the BSS/MSC/VLR requests security related information from the HLR/AuC corresponding to the MS. This includes an array of pairs of corresponding RAND and SRES. These pairs are obtained by applying Algorithm A3 to each RAND and the key Ki as shown in figure 3.1. The pairs are stored in the VLR as part of the security related information. The procedure used for updating the vectors RAND/SRES is schematized in figure 3.2. NOTE: The Authentication Vector Response contains also Kc(1..n) which is not shown in this and the following figures. For discussion of Kc see clause 4. 1* !'*% 6!) ! # %" !7*!$ ! !% !8 3/(<44 , 9 *! ' !' %!$ $! - (:(<44 ,3/(<44 ,, %!3/: =!' %$ Figure 3.2: Procedure for updating the vectors RAND/SRES ETSI ETSI TS 100 929 V7.2.0 (1999-11) 24 (GSM 03.20 version 7.2.0 Release 1998) When an MSC/VLR performs an authentication, including the case of a location updating within the same VLR area, it chooses a RAND value in the array corresponding to the MS. It then tests the answer from the MS by comparing it with the corresponding SRES, as schematized in figure 3.3. 4+9/:+9/ 2! ; 4+9/ < :+9/ :+9/ ! = 7$'" Figure 3.3: General authentication procedure
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
3.3.2 Authentication at location updating in a new VLR, using TMSI
|
During location updating in a new VLR (VLRn), the procedure to get pairs for subsequent authentication may differ from that described in the previous subclause. In the case when identification is done using TMSI, pairs for authentication as part of security related information are given by the old VLR (VLRo). The old VLR shall send to the new VLR only those pairs which have not been used. The procedure is schematized in figure 3.4. " ! ! ; 4+>00"/ :+>00"/ 4 2! 2! < : ! = 7$'" * "1 "# Figure 3.4: Authentication at location updating in a new VLR, using TMSI ETSI ETSI TS 100 929 V7.2.0 (1999-11) 25 (GSM 03.20 version 7.2.0 Release 1998)
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
3.3.3 Authentication at location updating in a new VLR, using IMSI
|
When the IMSI is used for identification, or more generally when the old VLR is not reachable, the procedure described in subclause 3.3.2 cannot be used. Instead, pairs of RAND/SRES contained in the security related information are requested directly from the HPLMN. The procedure is schematized in figure 3.5. " $*0$,0 "& $80 ! ! ; 4+> 00"/ 4 2! 2!:+>00"/ < : ! = 7$'" * "1 "# Figure 3.5: Authentication at location updating in a new VLR, using IMSI ETSI ETSI TS 100 929 V7.2.0 (1999-11) 26 (GSM 03.20 version 7.2.0 Release 1998) 3.3.4 Authentication at location updating in a new VLR, using TMSI, TMSI unknown in "old" VLR This case is an abnormal one, when a data loss has occurred in the "old" VLR. The procedure is schematized in figure 3.6. " ! ! 1"3" )" $" 7$8-$' 2! 2! !$*0$,0 "& $80 ! 4+>00"/:+>00"/ 2! ; 4 2! < : ! = 7$'" * "1 "# Figure 3.6: Authentication at location updating in a new VLR, using TMSI, TMSI unknown in "old" VLR ETSI ETSI TS 100 929 V7.2.0 (1999-11) 27 (GSM 03.20 version 7.2.0 Release 1998) 3.3.5 Authentication at location updating in a new VLR, using TMSI, old VLR not reachable The case occurs when an old VLR cannot be reached by the new VLR. The procedure is schematized in figure 3.7 123 %! ' >)! ! 6!7*!$ - !'4!)4 # !74 3/(<44 ,:(<44 , - 8 3/ - 9 : ; 6!$ ' 5 Figure 3.7: Authentication at location updating in a new VLR, using TMSI, old VLR not reachable
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
3.3.6 Authentication with IMSI if authentication with TMSI fails
|
If authentication of an MS which identifies itself with a TMSI is unsuccessful, the network requests the IMSI from the MS, and repeats the authentication using the IMSI. Optionally, if authentication using the TMSI fails the network may reject the access request or location registration request which triggered the authentication. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 28 (GSM 03.20 version 7.2.0 Release 1998)
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
3.3.7 Re-use of security related information in failure situations
|
Security related information consisting of sets of RAND, SRES and Kc is stored in the VLR and in the HLR. When a VLR has used a set of security related information to authenticate an MS, it shall delete the set of security related information or mark it as used. When a VLR needs to use security related information, it shall use a set which is not marked as used in preference to a set which is marked as used; if there are no sets which are not marked as used then the VLR shall request fresh security related information from the HLR. If a set of fresh security related information cannot be obtained in this case because of a system failure, the VLR may re-use a set which is marked as used. "System failure" in this context means that the VLR was unable to establish contact with the HLR, or the HLR returned a positive acknowledgement containing no sets of security related information, or the HLR returned an error indicating that there was a system failure or that the request was badly formatted. If the HLR responds to a request for security related information with an indication that the subscriber is unknown or barred in the HLR, the VLR shall not re-use security information which has been marked as used. It is an operator option to define how many times a set of security related information may be re-used in the VLR; when a set of security related information has been re-used as many times as is permitted by the operator, it shall be deleted. If a VLR successfully requests security related information from the HLR, it shall discard any security related information which is marked as used in the VLR. If a VLR receives from another VLR a request for security related information, it shall send only the sets which are not marked as used. If an HLR receives a request for security related information, it shall send any sets which are not marked as used; those sets shall then be deleted or marked as used. If there are no sets which are not marked as used, the HLR may as an operator option send sets which are marked as used. It is an operator option to define how many times a set of security related information may be re-sent by the HLR; when a set of security related information has been sent as many times as is permitted by the operator, it shall be deleted. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 29 (GSM 03.20 version 7.2.0 Release 1998) 4 Confidentiality of signalling information elements, connectionless data and user information elements on physical connections
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
4.1 Generality
|
In GSM 02.09, some signalling information elements are considered sensitive and must be protected. To ensure identity confidentiality (see clause 2), the Temporary Subscriber Identity must be transferred in a protected mode at allocation time and at other times when the signalling procedures permit it. The confidentiality of connection less user data requires at least the protection of the message part pertaining to OSI layers 4 and above. The user information confidentiality of user information on physical connections concerns the information transmitted on a traffic channel on the MS-BSS interface (e.g. for speech). It is not an end-to-end confidentiality service. These needs for a protected mode of transmission are fulfilled with the same mechanism where the confidentiality function is a OSI layer 1 function. The scheme described below assumes that the main part of the signalling information elements is transmitted on DCCH (Dedicated Control Channel), and that the CCCH (Common Control Channel) is only used for the allocation of a DCCH. Four points have to be specified: - the ciphering method; - the key setting; - the starting of the enciphering and deciphering processes; - the synchronization.
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
4.2 The ciphering method
|
The layer 1 data flow (transmitted on DCCH or TCH) is ciphered by a bit per bit or stream cipher, i.e. the data flow on the radio path is obtained by the bit per bit binary addition of the user data flow and a ciphering bit stream, generated by algorithm A5 using a key determined as specified in subclause 4.3. The key is denoted below by Kc, and is called "Ciphering Key". For multislot configurations (e.g. HSCSD) different ciphering bit streams are used on the different timeslots. On timeslot "n" a ciphering bit stream, generated by algorithm A5, using a key Kcn is used. Kcn is derived from Kc as follows: - Let BN denote a binary encoding onto 64 bits of the timeslot number "n" (range 0-7). Bit "i" of Kcn, Kcn(i), is then calculated as Kc(i) xor (BN<<32(i)) ("xor" indicates: "bit per bit binary addition" and "<<32" indicates: "32 bit circular shift"), the number convention being such that the lsb of Kc is xored with the lsb of the shifted BN. Deciphering is performed by exactly the same method. Algorithm A5 is specified in annex C. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 30 (GSM 03.20 version 7.2.0 Release 1998)
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
4.3 Key setting
|
Mutual key setting is the procedure that allows the mobile station and the network to agree on the key Kc to use in the ciphering and deciphering algorithms A5. A key setting is triggered by the authentication procedure. Key setting may be initiated by the network as often as the network operator wishes. Key setting must occur on a DCCH not yet encrypted and as soon as the identity of the mobile subscriber (i.e. TMSI or IMSI) is known by the network. The transmission of Kc to the MS is indirect and uses the authentication RAND value; Kc is derived from RAND by using algorithm A8 and the Subscriber Authentication key Ki, as defined in annex C. As a consequence, the procedures for the management of Kc are the authentication procedures described in subclause 3.3. The values Kc are computed together with the SRES values. The security related information (see subclause 3.3.1) consists of RAND, SRES and Kc. The key Kc is stored by the mobile station until it is updated at the next authentication. Key setting is schematized in figure 4.1. 3!& %.$ ! 3/ % - 8 3/3/8 ?? 8'8' %!8' %!8' Figure 4.1: Key setting ETSI ETSI TS 100 929 V7.2.0 (1999-11) 31 (GSM 03.20 version 7.2.0 Release 1998)
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
4.4 Ciphering key sequence number
|
The ciphering key sequence number is a number which is associated with the ciphering key Kc and they are stored together in the mobile station and in the network. However since it is not directly involved in any security mechanism, it is not addressed in the present document but in GSM 04.08 instead.
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
4.5 Starting of the ciphering and deciphering processes
|
The MS and the BSS must co-ordinate the instants at which the enciphering and deciphering processes start on DCCH and TCH. On DCCH, this procedure takes place under the control of the network some time after the completion of the authentication procedure (if any), or after the key Kc has been made available at the BSS. No information elements for which protection is needed must be sent before the ciphering and deciphering processes are operating. The transition from clear text mode to ciphered mode proceeds as follows: deciphering starts in the BSS, which sends in clear text to the MS a specific message, here called "Start cipher". Both the enciphering and deciphering start on the MS side after the message "Start cipher" has been correctly received by the MS. Finally, enciphering on the BSS side starts as soon as a frame or a message from the MS has been correctly deciphered at the BSS. The starting of enciphering and deciphering processes is schematized in figure 4.2. ( $* $( "# ? (* $(? 2! ( $* $( "# " ($"* $( "# "7* (($*,7 $* $($ %$'' #$ ! ($"* $( "# Figure 4.2: Starting of the enciphering and deciphering processes When a TCH is allocated for user data transmission, the key used is the one set during the preceding DCCH session (Call Set-up). The enciphering and deciphering processes start immediately.
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
4.6 Synchronization
|
The enciphering stream at one end and the deciphering stream at the other end must be synchronized, for the enciphering bit stream and the deciphering bit streams to coincide. The underlying Synchronization scheme is described in annex C. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 32 (GSM 03.20 version 7.2.0 Release 1998)
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
4.7 Handover
|
When a handover occurs, the necessary information (e.g. key Kc, initialization data) is transmitted within the system infrastructure to enable the communication to proceed from the old BSS to the new one, and the Synchronization procedure is resumed. The key Kc remains unchanged at handover.
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
4.8 Negotiation of A5 algorithm
|
Not more then seven versions of the A5 algorithm will be defined. When an MS wishes to establish a connection with the network, the MS shall indicate to the network which of the seven versions of the A5 algorithm it supports. The network shall not provide service to an MS which indicates that it does not support the ciphering algorithm(s) required by GSM 02.07. The network shall compare its ciphering capabilities and preferences, and any special requirements of the subscription of the MS, with those indicated by the MS and act according to the following rules: 1) If the MS and the network have no versions of the A5 algorithm in common and the network is not prepared to use an unciphered connection, then the connection shall be released. 2) If the MS and the network have at least one version of the A5 algorithm in common, then the network shall select one of the mutually acceptable versions of the A5 algorithm for use on that connection. 3) If the MS and the network have no versions of the A5 algorithm in common and the network is willing to use an unciphered connection, then an unciphered connection shall be used. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 33 (GSM 03.20 version 7.2.0 Release 1998)
|
c26f502af59545c0bddf8ce8e94c7b28
|
100 929
|
5 Synthetic summary
|
Figure 5.1 shows in a synopsis a normal location updating procedure with all elements pertaining to security functions, i.e. to TMSI management, authentication and Kc management. " ! ! * "1 "# 4+>00"/ :+>00"/ ;*+>00"/ ; 4 2! 2! <@A : ! ;*= 7$'" * "1 "# ! *3" ),$ #$ (* $( "# *3 2! 2! ! ,, * " & " * "1 "# % ,$$ 2! *3" ),$ #$ ! "*$,, " 2! 4$5 ,, * " & Figure 5.1: Normal location updating procedure ETSI ETSI TS 100 929 V7.2.0 (1999-11) 34 (GSM 03.20 version 7.2.0 Release 1998) Annex A (informative): Security issues related to signalling schemes and key management A.1 Introduction The diagrams in this annex indicate the security items related to signalling functions and to some of the key management functions. The purpose of the diagrams is to give a general overview of signalling, both on the radio path and in the fixed network. The diagrams indicate how and where keys are generated, distributed, stored and used. The security functions are split between VLR and BSS/MSC. A.2 Short description of the schemes Scheme 1:Location registration - no TMSI available. The situation occurs where an MS requests registration and for some reason e.g. TMSI is lost or this is the first registration, there is no TMSI available. In this case the IMSI is used for identification. The IMSI is sent in clear text via the radio path as part of the location updating. Scheme 2:Location updating - MS registered in VLR; - TMSI is still available. The mobile station stays within the area controlled by the VLR. The mobile station is already registered in this VLR. All information belonging to the mobile station is stored in the VLR, so no connection with the HLR is necessary. Identification is done by the CKSN, LAI and TMSI. For authentication a new set of RAND, SRES and Kc is already available in the VLR. Scheme 3:Location updating - MS not yet registered in VLR; - TMSI is still available. The MS has roamed to an area controlled by another VLR. The LAI is used to address the "old" VLR. The TMSI is used for identification. The "old" VLR informs the "new" VLR about this MS. The security related information is sent by the "old" VLR to the "new" VLR. Scheme 4:Location updating - MS not yet registered in VLR and no old LAI. The VLR cannot identify the VLR where the MS was last registered. Identification is therefore done by using the IMSI. The VLR cannot request authentication information from the previous VLR (LAI not available), so the HLR has to send the authentication information to the VLR. Scheme 5:Call set-up - mobile originated; - early assignment. The users of the registered MS wants to set-up a call. Identification is done by using the TMSI. All signalling information elements in all messages on the radio path are encrypted with ciphering key Kc. The PLMN is setting up calls with "early assignment". ETSI ETSI TS 100 929 V7.2.0 (1999-11) 35 (GSM 03.20 version 7.2.0 Release 1998) Scheme 6:Call set-up - mobile originated; - off air call set-up. As in scheme 5 the user of the registered MS wants to set-up a call. Identification is done by using the TMSI. All signalling information elements in all messages on the radio path are encrypted with ciphering key Kc after the cipher mode command message. The PLMN is setting up calls with "off air call set-up" Scheme 7:Call set-up - mobile terminated; - early assignment. A paging request is sent to the registered MS, addressed by the TMSI. All signalling information elements in all messages on the radio path are encrypted with ciphering key Kc after the cipher mode command message. The PLMN is setting up calls with "early assignment". A.3 List of abbreviations In addition to the abbreviations listed in GSM 01.04, the following abbreviations are used in the schemes: A3 authentication algorithm A5 signalling data and user data encryption algorithm A8 ciphering key generating algorithm BSS Base Station System HLR Home Location Register IMSI International Mobile Subscriber Identity Kc ciphering key Kc[M] message encrypted with ciphering key Kc Kc[TMSI] TMSI encrypted with ciphering key Kc Ki individual subscriber authentication key LAI Location Area Identity MS Mobile Station MSC Mobile services Switching Centre R Random number (RAND) S Signed response (SRES) TMSI o/n Temporary Mobile Subscriber Identity old/new VLR o/n Visitor Location Register old/new ETSI ETSI TS 100 929 V7.2.0 (1999-11) 36 (GSM 03.20 version 7.2.0 Release 1998) Scheme 1 Location registration - no TMSI available. ! "# $%& '(() * +!, - "# .!,.. !, / 01'#222 * 0")!, 3 , 3 , 1 !, 4. 4. * , +3/* , 1 !,.. --- * ! 4. 4. "# .!,.. / "# !, $%&'#222 '(()")!, !, !, * '#2225 +/ "# %4/ - "# / ,6 .!,.. / 7- !,.4 '() 3 , ') .8 * "# 9 : -9 9 ') ETSI ETSI TS 100 929 V7.2.0 (1999-11) 37 (GSM 03.20 version 7.2.0 Release 1998) Scheme 1 (concluded) "# / 9 . 4 ') ;/ ; , : - !, 0//:3 , !,, 0 ,0"# ,,3 , ,, -/ -- "#!, < , ') '(), 0 , 0!,!,=> !,=> !,=> "#"# < , 9 !,"# ,13 , ,,'()'#222 !, -")!,'#222 !,=.9 > 9 !,/ 0")!, "#'#222* 0 !, / 9 ,1 %4/ 1 '#222 9 . 3, 09 , ') !,=> 1 - .!,.. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 38 (GSM 03.20 version 7.2.0 Release 1998) Scheme 2 Location updating - MS registered in VLR; - TMSI is still available. "#"# .9 9 !, !.!,. '#222 4")!, ') 9 !, 3 , 3 , '#222 %4/ 9 . . 9 . . 4 4 "# !, , '#222 --")!, ! 4. 4. !, "#'#222 $%&"# '(() / ,6 !, 7- '() 3 , "# / .8 !,.4 ')"# : 9 * ') 9 - 9 ETSI ETSI TS 100 929 V7.2.0 (1999-11) 39 (GSM 03.20 version 7.2.0 Release 1998) Scheme 2 (concluded) "# / 9 . 4 ') ;/ ; , : - !, 3 , , 0 ,0 ,,3 , ,, --- "# !,/ !, "#') < , '(), 0 , 0!,!,=> !,=> !,=> "# < , ,1'() / 0 3 , ,, ,1* 0 - 1 !,=.9 > "# * , +3/ / 9 ?/ 1 * 0 9 . 3, 09 ,"#- ') 0 + .!,.. !,=> 9 ') ETSI ETSI TS 100 929 V7.2.0 (1999-11) 40 (GSM 03.20 version 7.2.0 Release 1998) Scheme 3 Location updating - MS not yet registered in VLR; - TMSI is still available. ! "### $% "%& ' ( ) & *) + ("### ,,,-.$'/"### - ! - ! - ! /% $/$/ ' "### 0 & *& - 00 / -$ /-$ / !1.!2"### "33%% "### -.$'/ & '& 4 ' ,,50 $-/-/"3%& ) "%, - 6/ 7 "% + 0 - / ETSI ETSI TS 100 929 V7.2.0 (1999-11) 41 (GSM 03.20 version 7.2.0 Release 1998) Scheme 3 (concluded) "# / 9 . 4 ') ;/ ; , : - !, , 0 ,03 , ,,3 , :,, --- !,"# / ,,3 "#!,3 , < , ')- '(), 0 , 0!,!,=> !,=> !,=> "# ?/3 ,,,3 < , ,, ,1'() / 0* 0 1 3 , ,, ,1@ * , - +3/ "# !,=.9 > ?/* 0 / 9 . 9 ')3, 09 ,"#-" 0 + .!,.. !,=> 9 ') ETSI ETSI TS 100 929 V7.2.0 (1999-11) 42 (GSM 03.20 version 7.2.0 Release 1998) Scheme 4 Location updating - MS not yet registered in VLR; no old LAI. !!! "# " $ # %$ & '( ' ))*# + , !!! *- ,*- ,)( .$#& * ,( '/# # %# # 000 *- ,*- ,* , /12/3 !!! 44"" !!! *2-&, # &# 5 & ))60 -*,*, 4"# $ ") 7& 7* 8, 9 0 * , $ ' '# $ # 9 000 * , & $ $ "0 /:* ,* , 4" ' ' ;<# ;<) =&$ $ * ;<, /:* ,) + 4"& '( '* , *# + , >)( $ # +# * ,.$#& 0 =&( '/# * ;<,# 0 * , ETSI ETSI TS 100 929 V7.2.0 (1999-11) 43 (GSM 03.20 version 7.2.0 Release 1998) Scheme 5 Call set-up - Mobile originated; - early assignment. ! "### $% "% & '( ( '### ) *+$&, * $,) * $, - ( .( // *$ ,* $ , !0+!1 "22% ( &( 3 ))4 *,*,"2% & $5& 5 "% 6 6 7 // * , & & ! $ !8* ,"%"% "2% 6 6 9: 9:) * 9:,"### !8* ,% ;"2% "### *+$&, ETSI ETSI TS 100 929 V7.2.0 (1999-11) 44 (GSM 03.20 version 7.2.0 Release 1998) Scheme 5 (concluded) / 0 /* * 0 * : 1 / A ,1,33/ A * , !,=.?A> ?/+3/* 0 ,33 , -* , 1 * :- //:,0,33/ A .!,.. -- !,=> !, "# < , '()//:, 0!,=>!, !,=> !,=> "# < , ,1'() ,1 - 3 -8 - , , - , , , !,!, "#"# <, <, ')!,= >') !,!, "#"# -<,-B<,- ')!,= >') ETSI ETSI TS 100 929 V7.2.0 (1999-11) 45 (GSM 03.20 version 7.2.0 Release 1998) Scheme 6 Call set-up - Mobile originated; - Off air call set-up. "#"# .9 9 !, !.!,. '#222 4")!, ') !, / A A'222 , %4/ 9 .4 9 .4 * , !,.. , -- ! 4. 9 .. "#4 $%& '(()"# !, / ,6 7- '() "# / !,.4;/ ; '), 0 ,0, : -- "# !, "# !,/ / 4. !, "#')') < , '(), 0 , 0!,!,=> !,=> !,=> "# < , ,1'() ,1 ETSI ETSI TS 100 929 V7.2.0 (1999-11) 46 (GSM 03.20 version 7.2.0 Release 1998) Scheme 6 (concluded) !"#$% & '(( ' & '(( ) '(( '*+ ) ( + )) +, &'-) ) - '!$% - ./ 0 % 1*"+* **% ' 23 4( - # 0 + ) **" '""% &' - ' ' ) ' ' ' ' ' ././ +5' +5' 23 '! $23 ' ' ././ )+5')6+5') 23 '! $23 ETSI ETSI TS 100 929 V7.2.0 (1999-11) 47 (GSM 03.20 version 7.2.0 Release 1998) Scheme 7 Call set-up - Mobile terminated; - Early assignment. C "#"# .9 9 !, !.!,. '#222 4")!, ')9 !, 222 - /* * %4/ ,,33/ A 8 * , 9 . . !,.. , : - - 9 , 3 9 00//: - 9 :/ 9 .4 - ! 4. "# $%& '(()"# !, / / 6 7- '() "# / * !,.4,* , '), 0 ,0,33/ A -- "# !, "# / !,/ 4. ')') ETSI ETSI TS 100 929 V7.2.0 (1999-11) 48 (GSM 03.20 version 7.2.0 Release 1998) Scheme 7 (concluded) !, "# < , '(), 0 , 0!,!,=> !,=> !,=> "# < , ,1'() "# / A !, - ,1'#222 !,=> ")!, !, ,33, *'#222 !,=> "# 9 !, '#222 //:,0")!, -9 !,/ 0 !,=> '#222* 0 %4/ 1 //:, 0 * , +3/ !,=> 1 * 0 - 3 ?/ .!,.. , , 8 !,=> , , , - !,!, "#"# <, <, ')!,= >') !,!, "#"# -<,-B<,- ')!,= >') ETSI ETSI TS 100 929 V7.2.0 (1999-11) 49 (GSM 03.20 version 7.2.0 Release 1998) Annex B (informative): Security information to be stored in the entities of the GSM system B.1 Introduction This annex gives an overview of the security related information and the places where this information is stored in the GSM network. The entities of the GSM network where security information is stored are: - home location register; - visitor location register; - mobile services switching centre; - base station system; - mobile station; - authentication centre. B.2 Entities and security information B.2.1 Home Location Register (HLR) If required, sets of Kc, RAND and SRES coupled to each IMSI are stored in the HLR. B.2.2 Visitor Location Register (VLR) Sets of Kc, RAND and SRES coupled to each IMSI are stored in the VLR. In addition the CKSN, LAI and TMSI are stored together with the presumed valid Kc. After a new TMSI is generated, both the old and the new TMSI are stored. When the old TMSI is no longer valid, it is removed from the database. B.2.3 Mobile services Switching Centre (MSC)/Base Station System (BSS) Encryption algorithm A5 is stored in the MSC/BSS. Call related information stored in the MSC includes the ciphering key Kc and CKSN associated with the identity of the mobile engaged in this call. After a new TMSI is generated, both the old and the new TMSI are stored. When the old TMSI is no longer valid, it is removed from the database. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 50 (GSM 03.20 version 7.2.0 Release 1998) B.2.4 Mobile Station (MS) The mobile station stores permanently: - authentication algorithm A3; - encryption algorithm A5; - ciphering key generating algorithm A8; - individual subscriber authentication key Ki; - ciphering key Kc; - ciphering key sequence number; - TMSI. The mobile station generates and stores: - ciphering key Kc. The mobile station receives and stores: - ciphering key sequence number; - TMSI; - LAI. B.2.5 Authentication Centre (AuC) In the authentication centre are implemented: - authentication algorithm(s) A3; - ciphering key generating algorithm(s) A8. The secret individual authentication keys Ki of each subscriber are stored in an authentication centre. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 51 (GSM 03.20 version 7.2.0 Release 1998) Annex C (normative): External specifications of security related algorithms C.0 Scope This annex specifies the cryptological algorithms which are needed to provide the various security features and mechanisms defined in, respectively, GSM 02.09 and GSM 03.20. The following three algorithms are considered in GSM 03.20: - Algorithm A3: Authentication algorithm; - Algorithm A5: Ciphering/deciphering algorithm; - Algorithm A8: Ciphering key generator. Algorithm A5 must be common to all GSM PLMNs and all mobile stations (in particular, to allow roaming). The external specifications of Algorithm A5 are defined in subclause C.1.3. The internal specifications of Algorithm A5 are managed under the responsibility of GSM/MoU; they will be made available in response to an appropriate request. Algorithms A3 and A8 are at each PLMN operator discretion. Only the formats of their inputs and outputs must be specified. It is also desirable that the processing times of these algorithms remain below a maximum value. Proposals for Algorithm A3 and A8 are managed by GSM/MoU and available, for those PLMN operators who wish to use them, in response to an appropriate request. C.1 Specifications for Algorithm A5 C.1.1 Purpose As defined in GSM 03.20, Algorithm A5 realizes the protection of both user data and signalling information elements at the physical layer on the dedicated channels (TCH or DCCH). Synchronization of both the enciphering and deciphering (especially at hand-over) must be guarantied. C.1.2 Implementation indications Algorithm A5 is implemented into both the MS and the BSS. On the BSS side description below assumes that one algorithm A5 is implemented for each physical channel (TCH or DCCH). The ciphering takes place before modulation and after interleaving (see GSM 05.01); the deciphering takes place after demodulation symmetrically. Both enciphering and deciphering need Algorithm A5 and start at different times (see clause 4). As an indication, recall that, due to the TDMA techniques used in the system, the useful data (also called the plain text in the sequel) are organized into blocks of 114 bits. Then, each block is incorporated into a normal burst (see GSM 05.02) and transmitted during a time slot. According to GSM 05.03, the useful information bits into a block are numbered e0 to e56 and e59 to e115 (the flag bits e57 and e58 are ignored). Successive slots for a given physical channel are separated at least by a frame duration, approximately 4.615 ms (see GSM 05.01). ETSI ETSI TS 100 929 V7.2.0 (1999-11) 52 (GSM 03.20 version 7.2.0 Release 1998) For ciphering, Algorithm A5 produces, each 4.615 ms, a sequence of 114 encipher/decipher bits (here called BLOCK) which is combined by a bit-wise modulo 2 addition with the 114-bit plain text block. The first encipher/decipher bit produced by A5 is added to e0, the second to e1 and so on. As an indication, the resulting 114-bit block is then applied to the burst builder (see GSM 05.01). For each slot, deciphering is performed on the MS side with the first block (BLOCK1) of 114 bits produced by A5, and enciphering is performed with the second block (BLOCK2). As a consequence, on the network side BLOCK1 is used for enciphering and BLOCK2 for deciphering. Therefore Algorithm A5 must produce two blocks of 114 bits (i.e. BLOCK1 and BLOCK2) each 4.615 ms. Synchronization is guarantied by driving Algorithm A5 by an explicit time variable, COUNT, derived from the TDMA frame number. Therefore each 114-bit block produced by A5 depends only on the TDMA frame numbering and the ciphering key Kc. COUNT is expressed in 22 bits as the concatenation of the binary representation of T1, T3 and T2. It is an input parameter of Algorithm A5. The coding of COUNT is shown in figure C.1. 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 Figure C.1: The coding of COUNT Binary representation of COUNT. Bit 22 is the most significant bit (msb) and bit 1 the least significant bit (lsb) of COUNT. T1, T3 and T2 are represented in binary. (For definition of T1, T3 and T2, see GSM 05.02). Figure C.2 summarizes the implementation indications listed above, with only one enciphering/deciphering procedure represented (the second one for deciphering/enciphering is symmetrical). ! " ## $%$&$%$& '('( )) *+$,,,-! *+$,,,-! &./ !0 & &./ !0 & ## ! &/ 0! '! %1'! %1' ,,-! ,,-! .0 2.0 2 Figure C.2: Deciphering on the MS side ETSI ETSI TS 100 929 V7.2.0 (1999-11) 53 (GSM 03.20 version 7.2.0 Release 1998) C.1.3 External specifications of Algorithm A5 The two input parameters (COUNT and Kc) and the output parameters (BLOCK1 and BLOCK2) of Algorithm A5 shall use the following formats: - length of Kc: 64 bits; - length of COUNT: 22 bits; - length of BLOCK1: 114 bits; - length of BLOCK2: 114 bits. Algorithm A5 shall produce BLOCK1 and BLOCK2 in less than a TDMA frame duration, i.e. 4.615 ms. NOTE: If the actual length of the ciphering key is less than 64 bits, then it is assumed that the actual ciphering key corresponds to the most significant bits of Kc, and that the remaining and less significant bits are set to zero. It must be clear that for signalling and testing purposes the ciphering key Kc is considered to be 64 unstructured bits. C.1.4 Internal specification of Algorithm A5 The internal specification of Algorithm A5 is managed under the responsibility of GSM/MoU; it will be made available to in response to an appropriate request. C.2 Algorithm A3 Algorithm A3 is considered as a matter for GSM PLMN operators. Therefore, only external specifications are given. However a proposal for a possible Algorithm A3 is managed by GSM/MoU and available upon appropriate request. C.2.1 Purpose As defined in GSM 03.20, the purpose of Algorithm A3 is to allow authentication of a mobile subscriber's identity. To this end, Algorithm A3 must compute an expected response SRES from a random challenge RAND sent by the network. For this computation, Algorithm A3 makes use of the secret authentication key Ki. C.2.2 Implementation and operational requirements On the MS side, Algorithm A3 is contained in a Subscriber Identity Module, as specified in GSM 02.17. On the network side, it is implemented in the HLR or the AuC. The two input parameters (RAND and Ki) and the output parameter (SRES) of Algorithm A3 shall use the following formats: - length of Ki: 128 bits; - length of RAND: 128 bits; - length of SRES: 32 bits. The run-time of Algorithm A3 shall be less than 500 ms. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 54 (GSM 03.20 version 7.2.0 Release 1998) C.3 Algorithm A8 Algorithm A8 is considered as a matter for GSM PLMN operators as is Algorithm A3. A proposal for a possible Algorithm A8 is managed by GSM/MoU and available upon appropriate request. C.3.1 Purpose As defined in GSM 03.20, Algorithm A8 must compute the ciphering key Kc from the random challenge RAND sent during the authentication procedure, using the authentication key Ki. C.3.2 Implementation and operational requirements On the MS side, Algorithm A8 is contained in the SIM, as specified in GSM 02.17. On the network side, Algorithm A8 is co-located with Algorithm A3. The two input parameters (RAND and Ki) and the output parameter (Kc) of Algorithm A8 shall follow the following formats: - length of Ki: 128 bits; - length of RAND: 128 bits; - length of Kc: 64 bits. Since the maximum length of the actual ciphering key is fixed by GSM/MoU, Algorithm A8 shall produce this actual ciphering key and extend it (if necessary) into a 64 bit word where the non-significant bits are forced to zero. It is assumed that any non-significant bits are the least significant bits and that, the actual ciphering key is contained in the most significant bits. For signalling and testing purposes the ciphering key Kc has to considered to be 64 unstructured bits. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 55 (GSM 03.20 version 7.2.0 Release 1998) Annex D (normative): Security related network functions for General Packet Radio Service This annex is only applicable if GPRS is supported. D.1 General This annex gives an overview of the different security related services and functions for General Packet Radio Service (GPRS) which is described in GSM 02.60 and GSM 03.60. They are grouped as follows: - Subscriber identity confidentiality; - Subscriber identity authentication; - Confidentiality of user information and signalling between MS and SGSN; - Security of the GPRS backbone. It shall be possible to introduce new authentication and ciphering algorithms during the systems lifetime. The fixed part of the network may support more than one authentication and ciphering algorithm. The security procedures include mechanisms to enable recovery in the event of signalling failures. These recovery procedures are designed to minimise the risk of a breach in the security of the system. In this annex, the terms GPRS-Kc and GPRS-CKSN are introduced to provide a clear distinction from the ciphering parameters (Kc and CKSN) used for circuit switched. The GPRS-Kc is the ciphering key used for GPRS, and GPRS- CKSN is the corresponding Ciphering Key Sequence Number used for GPRS. The use of these parameters is described in clause D.4. D.2 Subscriber identity confidentiality D.2.1 Generality The purpose of this function is to avoid the possibility for an intruder to identify which subscriber is using a given resource on the radio path by listening to the signalling exchanges or the user traffic on the radio path. This allows both a high level of confidentiality for user data and signalling and protection against the tracing of users location. The provision of this function implies that the IMSI (International Mobile Subscriber Identity), or any information allowing a listener to derive the IMSI easily, should not normally be transmitted in clear text in any signalling message on the radio path. Consequently, to obtain the required level of protection, it is necessary that: - a protected identifying method is normally used instead of the IMSI on the radio path; - the IMSI is not normally used as addressing means on the radio path (see GSM 02.09); - when the signalling procedures permit it, signalling information elements that convey information about the mobile subscriber identity must be ciphered for transmission on the radio path. The identifying method is specified in the following subclause. The ciphering of communication over the radio path is specified in clause D.4. Furthermore, Anonymous Access allows a user to access the network without a subscriber identity (see GSM 03.60). Therefore, Anonymous Access always guarantees by its nature subscriber identity confidentiality. The following parts of the clause D.2 are not applicable for Anonymous Access. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 56 (GSM 03.20 version 7.2.0 Release 1998) D.2.2 Identifying method The means used to identify a mobile subscriber on the radio path consists of a Temporary Logical Link Identity (TLLI). This TLLI is a local number, having a meaning only in a given RA (Routing Area); the TLLI must be accompanied by the Routing Area Identity (RAI) to avoid ambiguities. The maximum length and guidance for defining the format of a TLLI are specified in GSM 03.03. The SGSN manages suitable data bases to keep the relation between TLLIs and IMSIs. When a TLLI is received with an RAI that does not correspond to the current SGSN, the IMSI of the MS must be requested from the SGSN in charge of the indicated routing area if its address is known; otherwise the IMSI is requested from the MS. A new TLLI may be allocated in each routing area updating procedure. The allocation of a new TLLI corresponds implicitly for the MS to the de-allocation of the previous one. In the fixed part of the network, the cancellation of the record for an MS in a SGSN implies the de-allocation of the corresponding TLLI. To cope with some malfunctioning, e.g. arising from a software failure, the fixed part of the network can require the identification of the MS in clear. This procedure is a breach in the provision of the service, and should be used only when necessary. When a new TLLI is allocated to an MS, it is transmitted to the MS in a ciphered mode. This ciphered mode is the same as defined in clause D.4. The MS must store its current TLLI in a non volatile memory, together with the RAI, so that these data are not lost when the MS is switched off. D.2.3 Procedures This subclause presents the procedures, or elements of procedures, pertaining to the management of TLLIs. These security procedures may also be applied between two PLMNs of different operators for seamless service when the PLMN is changed. D.2.3.1 Routing area updating in the same SGSN area This procedure is part of the routing area updating procedure which takes place when the original routing area and the new routing area depend on the same SGSN. The part of this procedure relative to TLLI management is reduced to a TLLI re-allocation (from TLLIo with "o" for "old" to TLLIn with "n" for "new"). The MS sends TLLIo as an identifying field at the beginning of the routing area updating procedure. The procedure is schematised in figure D.2.1. ┌─────┐ ┌────────────┐á │MS │ │ SGSN │á └──┬──┘ └──────┬─────┘á │ │ á │ RAI, TLLIo │ á ├───────────────────────────────────────────>┤ á │ │ á á │ │ á │ ┌────────────┐á │ │Allocation │á │ │ of TLLIn │á │ └────────────┘á │ Ciphered(TLLIn) │ á ├<───────────────────────────────────────────┤ á │ │ á │ Acknowledge │ á ├───────────────────────────────────────────>┤ á │ │ á ┌─────────────┐ │De-allocation│ │ of TLLIo │ └─────────────┘ Figure D.2.1: Routing area updating in the same SGSN area ETSI ETSI TS 100 929 V7.2.0 (1999-11) 57 (GSM 03.20 version 7.2.0 Release 1998) D.2.3.2 Routing area updating in a new SGSN; old SGSN reachable This procedure is part of the routing area updating procedure, using TLLI and RAI, when the original routing area and the new routing area depend on different SGSNs. The MS is still registered in SGSNo ("o" for old or original) and requests registration in SGSNn ("n" for new). RAI and TLLIo are sent by the MS as identifying fields during the routing area updating procedure. The Routing Area Update Request is not ciphered to allow the new SGSN to read RAI and TLLIo. The procedure is schematised in figure D.2.2. ┌─────┐ ┌────────────┐┌────────┐┌─────┐á │MS │ │ SGSNn ││SGSNo ││HPLMN│á └──┬──┘ └──────┬┬────┘└────┬───┘└───┬─┘á │ ││ │ │áá │ RAI, TLLIo ││RAI,TLLIo │ │áá ├──────────────────────────>┤├──────────>┤ │áá │ ││ │ │ á │ ││ IMSI │ │ á │ │├<──────────┤ │ á │ ││Sec.Rel.Inf│ │ á │ ┌────────────┐ │ │ á │ │Allocation │ │ │ á │ │of TLLIn │ │ │ á │ └────────────┘ │ á │ ││ │ á │ ││ │ á │ Ciphered(TLLIn) (note) ││Update Loc. (note) │ á ├<──────────────────────────┤├───────────────────>┤ á │ ││ │ á │ ││ │ á │ Acknowledge (note) ││Acknowledge (note) │ á ├──────────────────────────>┤├<───────────────────┤ á │ │ á │Cancellation ├<───────┤ á ┌─────────────┐ á │De-allocation│ á │of TLLIo │ á └─────────────┘ á NOTE: From a security point of view, the order of the procedures is irrelevant. Figure D.2.2: Routing area updating in a new SGSN; old SGSN reachable Signalling functionalities: Update Loc. stands for Update Location The new SGSN informs the HLR that it is now handling the MS. Sec.Rel.Info.: Stands for Security Related information The SGSNn needs some information for authentication and ciphering; this information is obtained from SGSNo. Cancellation: The HLR indicates to SGSNo that the MS is now under control of another SGSN. The "old" TLLI is free for allocation. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 58 (GSM 03.20 version 7.2.0 Release 1998) D.2.3.3 Routing area updating in a new SGSN; old SGSN not reachable This variant of the procedure in subclause D.2.3.2 arises when the SGSN receiving the RAI and TLLIo cannot identify the SGSNo. In that case the relation between TLLIo and IMSI is lost, and the identification of the MS in clear is necessary. The procedure is schematised in figure D.2.3. ┌────┐ ┌────────────┐ ┌────────┐ ┌─────┐á │MS │ │ SGSNn │ │SGSNo │ │HPLMN│á └─┬──┘ └──────┬─────┘ └────────┘ └───┬─┘á │ │ │ á │ RAI, TLLIo │ │ á ├───────────────────────────>┤ │ á │ ┌────────────┐ │ á │ │old SGSN not│ │ á │ │ reachable │ │ á │TLLI unknown (note 1)└────────────┘ │ á ├<───────────────────────────┤ │ á │ │ │ á │ IMSI (note 1) │ │ á ├───────────────────────────>┤ │ á │ │ │ á ┌──────────────────────────────────────────────────────┐ á │ Management of means for new │ á │ ciphering (see clause D4) │ á └──────────────────────────────────────────────────────┘ á │ ┌────────────┐ │ á │ │Allocation │ │ á │ │ of TLLIn │ │ á │ └────────────┘ │ á │ ││ │ á │ ││ │ á │ Ciphered(TLLIn) (note 2)││Update Loc. (note 2) │ á ├<───────────────────────────┤├───────────────────────>┤ á │ ││ │ á │ Acknowledge (note 2) ││ Acknowledge (note 2) │ á ├───────────────────────────>┤├<───────────────────────┤ á │ │ á │Cancellation│ á ├<───────────┤ á ┌─────────────┐ á │De-allocation│ á │ of TLLIo │ á └─────────────┘ á NOTE 1: From a security point of view, the exact signalling messages (described in GSM 03.60) used to indicate that the TLLI is unknown, or to send the IMSI are irrelevant. NOTE 2: From a security point of view, the order of the procedures is irrelevant. Figure D.2.3: Routing area updating in a new SGSN; old SGSN not reachable ETSI ETSI TS 100 929 V7.2.0 (1999-11) 59 (GSM 03.20 version 7.2.0 Release 1998) D.2.3.4 Reallocation of a TLLI This function may be initiated by the network at any time for a GPRS attached MS. The procedure can be included in other procedures, e.g. through the means of optional parameters. The execution of this function is left to the network operator. When a new TLLI is allocated to an MS the network must prevent the old TLLI from being allocated again until the MS has acknowledged the allocation of the new TLLI. If an MM context of an MS is deleted in the SGSN by O&M action, the network must prevent any TLLI associated with the deleted MM context from being allocated again until a new TLLI is successfully allocated to that IMSI. If an IMSI record is deleted in the HLR by O&M action, it is not possible to prevent any TLLI associated with the IMSI record from being allocated again. However, if the MS whose IMSI record was deleted should attempt to access the network using the TLLI after the TLLI has been allocated to a different IMSI, then authentication or ciphering of the MS whose IMSI was deleted will fail, which will cause the TLLI to be deleted from the MS. The case where allocation of a new TLLI is unsuccessful is described in subclause D.2.3.7. This procedure is schematised in figure D.2.4. ┌─────┐ ┌────────────┐á │MS │ │ SGSN │á └─────┘ └────────────┘á │ ┌────────────┐á │ │Allocation │á │ │ of TLLIn │á │ └────────────┘á │ Ciphered(TLLIn) │ á ├<──────────────────────────────────────────┤ á │ │ á │ Acknowledge │ á ├──────────────────────────────────────────>┤ á │ │ á ┌─────────────┐ │De-allocation│ │ of TLLIo │ └─────────────┘ Figure D.2.4: Reallocation of a new TLLI ETSI ETSI TS 100 929 V7.2.0 (1999-11) 60 (GSM 03.20 version 7.2.0 Release 1998) D.2.3.5 Local TLLI unknown This procedure is a variant of the procedure described in subclauses D.2.3.1 and happens when a data loss has occurred in a SGSN and when a MS uses an unknown TLLI, e.g. for a communication request or for a routing area updating request in a routing area managed by the same SGSN. The SGSN indicates to the MS that the TLLI is unknown and and the identification of the MS in clear is necessary. This procedure is schematised in figure D.2.5. ┌─────┐ ┌────────────┐ ┌───────┐á │MS │ │ SGSN │ │HPLMN │á └──┬──┘ └──────┬─────┘ └────┬──┘á │ │ │ á │ RAI, TLLIo (note 1) │ │ á ├────────────────────────────────>┤ │ á │ ┌────────────┐ │ á │ │ TLLIo is │ │ á │ │ unknown │ │ á │ TLLI unknown (note 2)└────────────┘ │ á ├<────────────────────────────────┤ │ á │ │ │ á │ IMSI (note 2) │ │ á ├────────────────────────────────>┤ │ á │ │ │ á ┌───────────────────────────────────────────────┐ á │ Management of means for new │ á │ ciphering (see clause D4) │ á └───────────────────────────────────────────────┘ á │ ┌────────────┐ á │ │Allocation │ á │ │ of TLLIn │ á │ Ciphered(TLLIn) └────────────┘ á ├<────────────────────────────────┤ á │ │ á │ Acknowledge │ á ├────────────────────────────────>┤ á │ │ á NOTE 1: Any message in which TLLIo is used as an identifying means in a routing area managed by the same SGSN. NOTE 2: From a security point of view, the exact signalling messages (described in GSM 03.60) used to indicate that the TLLI is unknown, or to send the IMSI are irrelevant. Figure D.2.5: Routing area updating in the same SGSN area; local TLLI unknown ETSI ETSI TS 100 929 V7.2.0 (1999-11) 61 (GSM 03.20 version 7.2.0 Release 1998) D.2.3.6 Routing area updating in a new SGSN in case of a loss of information This variant of the procedure described in D.2.3.2 arises when the SGSN in charge of the MS has suffered a loss of data. In that case the relation between TLLIo and IMSI is lost, and the identification of the MS in clear is necessary. The procedure is schematised in figure D.2.6. ┌────┐ ┌────────────┐ ┌────────┐ ┌─────┐á │MS │ │SGSNn │ │SGSNo │ │HPLMN│á └─┬──┘ └──────┬┬────┘ └───┬────┘ └───┬─┘á │ ││ │ │ á │ RAI, TLLIo ││RAI,TLLIo │ │ á ├───────────────────────────>┤├──────────>┤ │ á │ ││ │ │ á │ ││ Unknown │ │ á │ TLLI Unknown(note 1) │├<──────────┤ │ á ├<───────────────────────────┤│ │ │ á │ │ │ á │ IMSI(note 1) │ │ á ├───────────────────────────>┤ │ á │ │ │ á ┌──────────────────────────────────────────────────────┐ á │ Management of means for new │ á │ ciphering (see clause D4) │ á └──────────────────────────────────────────────────────┘ á │ ┌────────────┐ │ á │ │Allocation │ │ á │ │of TLLIn │ │ á │ └────────────┘ │ á │ ││ │ á │ Ciphered(TLLIn) (note 2) ││Update location (note 2)│ á ├<───────────────────────────┤├───────────────────────>┤ á │ ││ │ á │ Acknowledge (note 2) ││ Acknowledge (note 2)│ á ├───────────────────────────>┤├<───────────────────────┤ á │ │ á │Cancellation│áá ├<───────────┤ á ┌─────────────┐ á │De-allocation│ á │ of TLLIo │ á └─────────────┘ á NOTE 1: From a security point of view, the exact signalling messages (described in GSM 03.60) used to indicate that the TLLI is unknown, or to send the IMSI are irrelevant. NOTE 2: From a security point of view, the order of the procedures is irrelevant. Figure D.2.6: Routing area updating in a new SGSN in case of a loss of information D.2.3.7 Unsuccessful TLLI allocation If the MS does not acknowledge the allocation of a new TLLI, the network shall maintain the association between the old TLLI and the IMSI and between the new TLLI and the IMSI. For an MS-originated transaction, the network shall allow the MS to identify itself by either the old TLLI or the new TLLI. This will allow the network to determine the TLLI stored in the MS; the association between the other TLLI and the IMSI shall then be deleted. For a network-originated transaction, the network shall identify the MS by its IMSI. When radio contact has been established, the network shall instruct the MS to delete any stored TLLI. When the MS has acknowledged this instruction, the network shall delete the association between the IMSI of the MS and any TLLI. In either of the cases above, the network may initiate the normal TLLI reallocation procedure. Repeated failure of TLLI reallocation (passing a limit set by the operator) may be reported for O&M action. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 62 (GSM 03.20 version 7.2.0 Release 1998) D.3 Subscriber identity authentication D.3.1 Generality The definition and operational requirements of subscriber identity authentication are given in GSM 02.09. The authentication procedure may be performed at any time by the network. The authentication procedure will also be used to set the ciphering key (see clause D.4). Therefore, it is performed after the subscriber identity (TLLI/IMSI) is known by the network for the management of new ciphering. Two network functions are necessary: the authentication procedure itself, and the key management. D.3.2 The authentication procedure The authentication procedure is described in subclause 3.2. D.3.3 Subscriber Authentication Key management The management of Subscriber Authentication Key (Ki) is described in subclause 3.3. D.3.3.1 General authentication procedure When needed, the SGSN requests security related information for a MS from the HLR/AuC corresponding to the IMSI of the MS. This includes an array of pairs of corresponding RAND and SRES. These pairs are obtained by applying Algorithm A3 to each RAND and the key Ki as shown in figure 3.1. The pairs are stored in the SGSN as part of the security related information. The procedure used for updating the vectors RAND/SRES is schematised in figure D.3.2. NOTE: The Authentication Vector Response contains also GPRS-Kc(1..n) which is not shown in this and the following figures. For discussion of GPRS-Kc see clause D.4. ┌──────────────┐ ┌──────────────┐ │ SGSN │ │ HLR/AuC │ └────┬─────────┘ └───────┬──────┘ │ │ á │Security Related Information Req(IMSI)│ á ├─────────────────────────────────────>┤ á │ │ á │ ┌───────────┐ á │ │generate │ Ki á │ │RAND(1..n)│ │ á │ └─────┬─────┘ │ á │ │ │ á │ V V á │ ┌─────────────┐á │ │ A3 │á │ └───────┬─────┘á │ Authentication Vector Response │ á ├<─────────────────────────────────────┘ á │ (SRES(1..n), RAND(1..n)) á │ á ┌───────────────┐ á │Store RAND/SRES│ á │ vectors │ á └───────────────┘ á Figure D.3.2: Procedure for updating the vectors RAND/SRES ETSI ETSI TS 100 929 V7.2.0 (1999-11) 63 (GSM 03.20 version 7.2.0 Release 1998) When an SGSN performs an authentication, including the case of a routing area updating within the same SGSN area, it chooses a RAND value in the array corresponding to the MS. It then tests the answer from the MS by comparing it with the corresponding SRES, as schematised in figure D.3.3. ┌───────────┐ ┌──────────────┐á │ MS │ │ SGSN │á └───────────┘ └──────┬───────┘á │ │ á │ RAND(j) │ SRES(j)á ├<─────────────────────────────────┤ á │ │ á │Ki │RAND(j) │ │ á V V │ │ á ┌─────────────┐ │ │ á │ A3 │ │ │ á └────────┬────┘ │ │ á │SRES(j) │ │ á │ │ │ á V │ │ á │ │ á │ SRES(j) │ │ á ├─────────────────────────────────>┤──┐ │ á │ │ │ │ á │ │ V V á ┌─────┐á │ = │á └──┬──┘á V á yes/no á Figure D.3.3: General authentication procedure D.3.3.2 Authentication at routing area updating in a new SGSN, using TLLI During routing area updating in a new SGSN (SGSNn), the procedure to get pairs for subsequent authentication may differ from that described in the previous subclause. In the case when identification is done using TLLI, pairs for authentication as part of security related information are given by the old SGSN (SGSNo). The old SGSN shall send to the new SGSN only those pairs which have not been used. SGSNn may also request the triplets directly from HLR. The procedure is schematised in figure D.3.4. ┌────┐ ┌────────────┐┌────────┐┌─────┐á │MS │ │ SGSNn ││SGSNo ││HPLMN│á └─┬──┘ └──────┬┬────┘└────┬───┘└───┬─┘á │ ││ │ │ á │ RAI, TLLIo ││TLLIo, RAI│ │ á ├───────────────────────────>┤├──────────>┤ │ á │ ││ │ │ á │ ││IMSI │ │ á Ki│ ││RAND(1..n)│ │ á ││ ││SRES(1..n)│ │ á ││ RAND │├<──────────┤ │ á │├<───────────────────────────┤ │ á ││ │ │ á V V │ │ á ┌─────┐ │ │ á │A3 │ │ │ á └─────┘ │ │ á │ SRES │ │ á ├───────────────────────────>┤ │ á │ ┌─────┐ │ á │ │ = │ │ á │ └──┬──┘ │ á V │ á yes/no │ á ┌──────────────────────┐ á │ Update Location │ á └──────────────────────┘ á Figure D.3.4: Authentication at routing area updating in a new SGSN, using TLLI ETSI ETSI TS 100 929 V7.2.0 (1999-11) 64 (GSM 03.20 version 7.2.0 Release 1998) D.3.3.3 Authentication at routing area updating in a new SGSN, using IMSI When the IMSI is used for identification, or more generally when the old SGSN is not reachable, the procedure described in subclause D.3.3.2 cannot be used. Instead, pairs of RAND/SRES contained in the security related information are requested directly from the HPLMN. The procedure is schematised in figure D.3.5. ┌────┐ ┌────────────┐ ┌─────┐á │MS │ │ SGSNn │ │HPLMN│á └─┬──┘ └──────┬┬────┘ └───┬─┘á │ IMSI ││Sec. Rel. Info Req. │ á ├───────────────────────────>┤├───────────────────>┤ á │ ││ (IMSI) │ á │ ││ │ á Ki│ ││ RAND(1,..n) │ á ││ RAND │├<───────────────────┤ á │├<───────────────────────────┤ SRES(1..n) │ á V V │ │ á ┌─────┐ │ │ á │A3 │ │ │ á └─────┘ │ │ á │ SRES │ │ á ├───────────────────────────>┤ │ á │ ┌─────┐ │ á │ │ = │ │ á └──┬──┘ │ á V │ á yes/no │ á ┌─────────────────────┐ á │ Update Location │ á └─────────────────────┘ á Figure D.3.5: Authentication at routing area updating in a new SGSN, using IMSI ETSI ETSI TS 100 929 V7.2.0 (1999-11) 65 (GSM 03.20 version 7.2.0 Release 1998) D.3.3.4 Authentication at routing area updating in a new SGSN, using TLLI, TLLI unknown in 'old' SGSN This case is an abnormal one, when a data loss has occurred in the 'old' SGSN. The procedure is schematised in figure D.3.6. ┌────┐ ┌────────────┐┌────────┐┌─────┐á │MS │ │ SGSNn ││SGSNo ││HPLMN│á └─┬──┘ └──────┬┬────┘└────┬───┘└───┬─┘á │ ││ │ │ á │ RAI, TLLIo ││RAI, TLLIo │ │ á ├───────────────────────────>┤├──────────>┤ │ á │ ││ │ │ á │ ││ Unknown │ │ á │ TLLI Unknown │├<──────────┤ │ á ├<───────────────────────────┤ │ á │ │ │ á │ IMSI │ │ á ├───────────────────────────>┤│Sec. Rel. Info Req. │ á │ │├────────────────────>┤ á │ ││ (IMSI) │ á │ ││ │ á │ ││RAND(1..n) SRES(1..n)│ á │ │├<────────────────────┤ á Ki│ RAND │ │ á │├<───────────────────────────┤ │ á V V │ │ á ┌─────┐ │ │ á │A3 │ │ │ á └─────┘ │ │ á │ SRES │ │ á ├───────────────────────────>┤ │ á │ ┌─────┐ │ á │ │ = │ │ á └──┬──┘ │ á V │ á yes/no │ á ┌──────────────────────┐ á │ Update Location │ á └──────────────────────┘ á Figure D.3.6: Authentication at routing area updating in a new SGSN, using TLLI, TLLI unknown in 'old' SGSN ETSI ETSI TS 100 929 V7.2.0 (1999-11) 66 (GSM 03.20 version 7.2.0 Release 1998) D.3.3.5 Authentication at routing area updating in a new SGSN, using TLLI, old SGSN not reachable The case occurs when an old SGSN cannot be reached by the new SGSN. The procedure is schematised in figure D.3.7 ┌────┐ ┌────────────┐┌────────┐┌─────┐á │MS │ │ SGSNn ││SGSNo ││HPLMN│á └─┬──┘ └──────┬─────┘└────────┘└───┬─┘á │ │ │ á │ RAI, TLLIo │ │ á ├───────────────────────────>┤ │ á │ │ │ á │ ┌────────────┐ │ á │ │SGSNo not │ │ á │ │reachable │ │ á │ └────────────┘ │ á │ TLLI Unknown │ │ á ├<───────────────────────────┤ │ á │ │ │ á │ IMSI │ │ á ├───────────────────────────>┤│Sec. Rel. Info Req. │ á │ │├────────────────────>┤ á │ ││ (IMSI) │ á │ ││ │ á │ ││RAND(1..n) SRES(1..n)│ á │ │├<────────────────────┤ á Ki│ RAND │ │ á │├<───────────────────────────┤ │ á V V │ │ á ┌─────┐ │ │ á │A3 │ │ │ á └─────┘ │ │ á │ SRES │ │ á ├───────────────────────────>┤ │ á │ ┌─────┐ │ á │ │ = │ │ á └──┬──┘ │ á V │ á yes/no │ á ┌──────────────────────┐ á │ Update Location │ á └──────────────────────┘ á Figure D.3.7: Authentication at routing area updating in a new SGSN, using TLLI, old SGSN not reachable D.3.3.6 Authentication with IMSI if authentication with TLLI fails If authentication of an MS which identifies itself with a TLLI is unsuccessful, the network requests the IMSI from the MS, and repeats the authentication using the IMSI. Optionally, if authentication using the TLLI fails the network may reject the access request or location registration request which triggered the authentication. D.3.3.7 Re-use of security related information in failure situations Security related information consisting of sets of RAND, SRES and a ciphering key (GPRS-Kc) is stored in the SGSN and in the HLR. When a SGSN has used a set of security related information to authenticate an MS, it shall delete the set of security related information or mark it as used. When a SGSN needs to use security related information, it shall use a set which is not marked as used in preference to a set which is marked as used; if there are no sets which are not marked as used then the SGSN shall request fresh security related information from the HLR. If a set of fresh security related information cannot be obtained in this case because of a system failure, the SGSN may re-use a set which is marked as used. "System failure" in this context means that the SGSN was unable to establish contact with the HLR, or the HLR returned a positive acknowledgement containing no sets of security related information, or the HLR returned an error indicating that there was a system failure or that the request was badly formatted. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 67 (GSM 03.20 version 7.2.0 Release 1998) If the HLR responds to a request for security related information with an indication that the subscriber is unknown or barred in the HLR, the SGSN shall not re-use security information which has been marked as used. It is an operator option to define how many times a set of security related information may be re-used in the SGSN; when a set of security related information has been re-used as many times as is permitted by the operator, it shall be deleted. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 68 (GSM 03.20 version 7.2.0 Release 1998) If a SGSN successfully requests security related information from the HLR, it shall discard any security related information which is marked as used in the SGSN. If a SGSN receives from another SGSN a request for security related information, it shall send only the sets which are not marked as used. If an HLR receives a request for security related information, it shall send any sets which are not marked as used; those sets shall then be deleted or marked as used. If there are no sets which are not marked as used, the HLR may as an operator option send sets which are marked as used. It is an operator option to define how many times a set of security related information may be re-sent by the HLR; when a set of security related information has been sent as many times as is permitted by the operator, it shall be deleted. D.4 Confidentiality of user information and signalling between MS and SGSN D.4.1 Generality In GSM 02.09, some signalling information elements are considered sensitive and must be protected. To ensure identity confidentiality (see clause 2), the new TLLI must be transferred in a protected mode at allocation time. The confidentiality of user information concerns the information transmitted on the logical connection between MS and SGSN. These needs for a protected mode of transmission are fulfilled by a ciphering function in the LLC layer. It is not an end- to-end confidentiality service. Four points have to be specified: - the ciphering method; - the key setting; - the starting of the enciphering and deciphering processes; - the synchronisation. D.4.2 The ciphering method The LLC layer information flow is ciphered by the algorithm GPRS-A5 as described in GSM 01.61. D.4.3 Key setting Mutual key setting is the procedure that allows the mobile station and the network to agree on the key GPRS-Kc to use in the ciphering and deciphering algorithms GPRS-A5. This procedure corresponds to the procedure described in subclause 4.3 besides the different confidential subscriber identity. The GPRS-Kc is handled by the SGSN independently from the MSC. If a MS is using both circuit switched and packet switched, two different ciphering keys will be used independently, one (Kc) in the MSC and one (GPRS-Kc) in the SGSN. A key setting is triggered by the authentication procedure. Key setting may be initiated by the network as often as the network operator wishes. If an authentication procedure is performed during a data transfer, the new ciphering parameters shall be taken in use immediately at the end of the authentication procedure in both SGSN and MS. Key setting may not be encrypted and shall be performed as soon as the identity of the mobile subscriber (i.e. TLLI or IMSI) is known by the network. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 69 (GSM 03.20 version 7.2.0 Release 1998) The transmission of GPRS-Kc to the MS is indirect and uses the authentication RAND value; GPRS-Kc is derived from RAND by using algorithm A8 and the Subscriber Authentication key Ki, in the same way as defined in annex C for Kc. As a consequence, the procedures for the management of GPRS-Kc are the authentication procedures described in subclause D.3.3. The values GPRS-Kc are computed together with the SRES values. The security related information (see subclause D.3.3.1) consists of RAND, SRES and GPRS-Kc. The key GPRS-Kc is stored by the mobile station until it is updated at the next authentication. Key setting is schematised in figure D.4.1. ┌───────────┐ ┌──────────────┐á │ MS │ │Network side │á └────────┬──┘ └──────┬───────┘á │ │ á │ RAI and TLLI or IMSI │ á ├─────────────────────────────────>┤ á │ │ á │ RAND │ á ├<─────────────────────────────────┤ á │ │ á │Ki │RAND │RAND │Kiá V V V V á ┌─────────────┐ ┌─────────────┐á │ A8 │ │ A8 │á └──────┬──────┘ └──────┬──────┘á │GPRS-Kc │GPRS-Kc V V á ┌─────────────┐ ┌─────────────┐á │Store GPRS-Kc│ │Store GPRS-Kc│á └─────────────┘ └─────────────┘á Figure D.4.1: Key setting D.4.4 Ciphering key sequence number The GPRS-CKSN (Ciphering Key Sequence Number) is a number which is associated with each ciphering key GPRS-Kc. The GPRS-CKSN and GPRS-Kc are stored together in the mobile station and in the network. It permits the consistency check of the keys stored in the MS and in the network. Two independent pairs, Kc and CKSN (for circuit switched), and GPRS-Kc and GPRS-CKSN (for packet switched) may be stored in the MS simultaneously. However since it is not directly involved in any security mechanism, it is not addressed in the present document but in [GSM 04.08] instead. D.4.5 Starting of the ciphering and deciphering processes The MS and the SGSN must co-ordinate the instants at which the ciphering and deciphering processes start. The authentication procedure governs the start of ciphering. The SGSN indicates if ciphering shall be used or not in the Authentication and Ciphering Request message. If ciphering is used, the MS starts ciphering after sending the Authentication and Ciphering Response message. The SGSN starts ciphering when a valid Authentication and Ciphering Response message is received from the MS. Upon GPRS Attach, if ciphering is to be used, an Authentication and Ciphering Request message shall be sent to the MS to start ciphering. If the GPRS-CKSN stored in the network does not match the GPRS-CKSN received from the MS in the Attach Request message, then the network should authenticate the MS. As an option, the network may decide to continue ciphering without authentication after receiving a Routing Area Update Request message with a valid GPRS-CKSN. Both the MS and the network shall use the latest ciphering parameters. The MS starts ciphering after a receiving a valid ciphered Routing Area Update Accept message from the network. The SGSN starts ciphering when sending the ciphered Routing Area Update Accept message to the MS. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 70 (GSM 03.20 version 7.2.0 Release 1998) Upon delivery of the Authentication and Ciphering Response message or the Routing Area Update Accept message, the GPRS Mobility and Management entity in both SGSN and MS shall be aware if ciphering has started or not. LLC provides the capability to send both ciphered and unciphered PDUs. The synchronisation of ciphering at LLC frames level is done by a bit in the LLC header indicating if the frame is ciphered or not. Only a few identified signalling messages (e.g., Routing Area Update Request message) described in GSM 04.08 may be sent unciphered, any other frames sent unciphered shall be deleted. Once the encryption has been started, neither the MS nor the network shall go to an unciphered session. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 71 (GSM 03.20 version 7.2.0 Release 1998) D.4.6 Synchronisation The enciphering stream at one end and the deciphering stream at the other end must be synchronised, for the enciphering bit stream and the deciphering bit streams to coincide. Synchronisation is guaranteed by driving Algorithm GPRS-A5 by an explicit variable INPUT per established LLC and direction. These initial INPUT values shall not be identical for the different LLC link. The initial INPUT value shall be determined by the network. It may be identical for uplink and downlink value because the direction is given to the ciphering algorithm as described in GSM 01.61 and illustrated on the figure D.4.2. In a given direction, the INPUT value shall be unique for each frame. The calculation of the INPUT value is described in GSM. The use of the INPUT value is described in GSM 01.61 and illustrated on the figure D.4.2. INPUT DIRECTION Kc CIPHER ALGORITHM Kc CIPHER ALGORITHM PLAIN TEXT PLAIN TEXT CIPHERED TEXT CIPHERED TEXT SGSN/MS MS/SGSN OUTPUT OUTPUT INPUT DIRECTION Figure D.4.2: Use of the INPUT parameter D.4.7 Inter SGSN routing area update When an Inter SGSN routing area update occurs, the necessary information (e.g. key Kc, INPUT parameters) is transmitted within the system infrastructure to enable the communication to proceed from the old SGSN to the new one, and the Synchronisation procedure is resumed. The key Kc may remains unchanged at Inter SGSN routing area update. D.4.8 Negotiation of GPRS-A5 algorithm When an MS wishes to establish a connection with the network, the MS shall indicate to the network which version(s) of the GPRS-A5 algorithm it supports. The negotiation of GPRS-A5 algorithm happens during the authentication procedure. The network may renegotiate the version of the GPRS-A5 algorithm in use at inter SGSN routing area update by performing an authentication procedure. The network shall compare its ciphering capabilities and preferences, and any special requirements of the subscription of the MS, with those indicated by the MS and may take one of the following decisions: 1) The network decides to release the connection because no common version of the GPRS-A5 algorithm is available or because the MS indicated an illegal combination of supported algorithms. 2) The network selects one of the mutually acceptable versions of GPRS-A5 to be used. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 72 (GSM 03.20 version 7.2.0 Release 1998) D. Figure D.5.1 shows in a synopsis a routing area updating procedure with all elements pertaining to security functions, i.e. to TLLI management, authentication and GPRS-Kc management. ┌────┐ ┌────────────┐┌──────────┐ ┌─────┐á │MS │ │ SGSNn ││ SGSNo │ │HPLMN│á └─┬──┘ └──────┬┬────┘└────┬─────┘ └───┬─┘á │ ││ │ │ á │ RAI, TLLIo ││RAI, TLLIo│ │ á ├───────────────────────────>┤├──────────>┤ │ á │ Routing area updating ││ │ │ á │ ││IMSI │ │ á │ ││RAND │ │ á │ ││SRES │ │ á │ ││GPRS-Kc │ │ á Ki│ RAND │├<──────────┤ │ á │├<───────────────────────────┤│ │ │ á V V ││ │ │ á ┌─────┐ ││ │ │ á │A3&A8│ ││ │ │ á └─────┘ SRES ││ │ │ á │├───────────────────────────>┤│ │ │ á V │ ┌─────┐ │ │ á GPRS-Kc│ │ = │ │ │ á │ └──┬──┘ │ │ á │ V │ á │ yes │ á │ ┌───────────────────┐ │ á │ │start of ciphering │ │ á │ └───────────────────┘ │ á │ ││ Update location │ á │ │├───────────────────────>┤ á │ ││ │ á │ ││ Acknowledge │ á │ │├<───────────────────────┤ á │ ┌─────────────┐ │ │ á │ │Allocation │ │ │ á │ │of TLLIn │ │ │ á │ └─────────────┘ │ │ á │ ││ │ │ á │ Routing area update Accept││ │ │ á ├<───────────────────────────┤│ │ │ á │ ││ │ │ á │ ││ │ │ á │ TLLI acknowledge ││ │ │ á ├───────────────────────────>┤│ │ │ á │Cancellation│ á │<───────────┤ á ┌─────────────┐ á │De-allocation│ á │ of TLLIo │ á └─────────────┘ á Figure D.5.1: Routing area updating procedure ETSI ETSI TS 100 929 V7.2.0 (1999-11) 73 (GSM 03.20 version 7.2.0 Release 1998) D.6 Security of the GPRS backbone The operator is responsible for the security of its own Intra-PLMN backbone which includes all network elements and physical connections. The operator shall prevent unauthorised access to its Intra-PLMN backbone. A secure Intra- PLMN backbone guarantees that no intruder can eavesdrop or modify user information and signalling in the Intra- PLMN backbone. The GPRS architecture utilises GPRS tunnelling and private IP addressing within the backbone to restrict unauthorised access to the backbone. User traffic addressed to a network element shall be discarded. Firewall functionality may provide these means at the access points (Gi reference point and Gp interface) of the Intra-PLMN backbone. The Inter-PLMN links shall be negotiated between operators as part of the roaming agreement. They shall ensure that the Inter-PLMN links are secure providing integrity and confidentiality. For example, secure links can be achieved by point to point links, private Inter-PLMN backbones or encrypted tunnels over the public Internet. Operators shall be able to determine the origin of packets coming from the inter-PLMN backbone. One example is to use a Frame Relay PVC between two operators. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 74 (GSM 03.20 version 7.2.0 Release 1998) Annex E (normative): GSM Cordless Telephony System (CTS), (Phase 1); Security related network functions; Stage 2 This annex is defining the security related service and functions for the GSM Cordless Telephone System (CTS). This annex is only applicable if CTS is supported. E.1 Introduction E.1.1 Scope This annex specifies the functions needed to provide the security related services and functions specified in GSM 02.56. E.1.2 References [1] GSM 01.04: "Digital cellular telecommunications system (Phase 2+); Abbreviations and Acronyms". [2] GSM 02.56: "Digital cellular telecommunications system (Phase 2+); GSM Cordless Telephone System (CTS) Phase 1; Service Description; Stage 1". [3] GSM 02.09: "Digital cellular telecommunications system(Phase 2+); Security Aspects". [4] GSM 03.56: "Digital cellular telecommunications system (Phase 2+); GSM Cordless Telephone System (CTS), Phase 1; CTS Architecture Description; Stage 2". [5] GSM 11.11: "Digital cellular telecommunications system (Phase 2+); Specification of the Subscriber Identity Module- Mobile Equipment (SIM-ME) interface". [6] CCITT Recommendation T.50: "International Alphabet No. 5". (ISO 646: 1983, Information processing - ISO 7-bits coded characters set for information interchange). [7] GSM 03.20: "Digital cellular telecommunications system (Phase 2+); Security related network functions"; [8] GSM 04.57: "Digital cellular telecommunications system (Phase 2+); CTS supervising system layer 3 specification ". E.1.3 Definitions and Abbreviations E.1.3.1 Definitions The following list gives definitions which are used in this annex. For additional definitions related to CTS refer to the CTS stage 1 specification GSM 02.56. Attachment: Attachment is the procedure where a CTS-MS accesses a CTS-FP either for local or over the fixed network communication or signalling. This procedure applies to CTS-MSs that have already been enrolled onto the CTS-FP. CTS license exempt band: A frequency band that may be allocated by national regulator to CTS usage outside of a GSM license allocated to a GSM operator. CTS licensed band: A frequency band that can be reserved by the operator for GSM-CTS usage or can be shared with the cellular system. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 75 (GSM 03.20 version 7.2.0 Release 1998) CTS Local security system: The term CTS local security system is used to describe all security aspects of a CTS- MS/CTS-FP pair. CTS Operator: This term is used in this annex for any operator performing supervising security tasks in the CTS e.g. control of the CTS subscription or control of the CTS frequency usage. It is not considered here if this is one and the same PLMN operator for all supervising security tasks. However the security functions introduced here shall not restrict the system to be controlled by one specific PLMN operator. CTS Supervising security system: The term CTS supervising security system is used to describe all security aspects of operation control of the local CTS from the GSM PLMN. CTS-FP: The CTS Fixed Part consisting of the CTS-FPE and the FP-SIM. CTS-MS: The CTS Mobile Station consisting of the CTS-ME and the MS-SIM. Enrolment: The enrolment of a CTS-MS onto a CTS-FP is the procedure where a CTS-MS/CTS-FP pair is established locally and under the control of the CTS operator if license exempt band is used. A CTS-MS can only enrol onto a CTS- FP that has already been initialised. FP-SIM: The SIM_FP is a GSM Phase 2+ SIM with additional data stored to allow CTS operation. This card is inserted in the CTS-FPE. The FP-SIM is only used in case of licensed band. IFPSI: The IFPSI is a CTS specific subscriber identity stored in the FP-SIM card. Initialisation: The initialisation of a CTS-FP is the procedure where the CTS-FP receives the necessary data to provide CTS service. Local CTS: This term is used to describe all aspects of a CTS-MS/CTS-FP pair as seen from outside (from the GSM PLMN) MS-SIM: The SIM_MS is a normal GSM Phase 2+ SIM according to GSM 11.11 with additional data stored to allow CTS operation. This card is inserted in the CTS-ME. Operation data: This term is used as a place holder for any kind of data which is used to control CTS. The definition of this data, if it is not directly related to the CTS security aspects, is defined in other parts of the CTS specifications. E.1.3.2 Abbreviations The following list describes the abbreviations and acronyms used in this annex. The GSM abbreviations defined in GSM 01.04 and in the CTS stage 1 specification GSM 02.56 are not included below. B1 CTS ciphering key generation algorithm B2 CTS authentication key generation algorithm B3 CTS authentication algorithm (calculating the signed response of the CTS-FP challenge CH1) B4 CTS authentication algorithm (calculating the signed response of the CTS-MS challenge CH2) B5 CTS message authentication algorithm (for the authentication of the CTS-FP by the CTS-SN) B6 CTS message authentication algorithm (for the authentication of the signature issued by the CTS-SN) CH1 CTS random Challenge value of the CTS-FP CH2 CTS random Challenge value of the CTS-MS CTS HLR CTS Home Location Register Functional Entity CTS-FP CTS-Fixed Part CTS-FPE CTS-Fixed Part Equipment CTS-ME CTS-Mobile Equipment CTSMSI CTS Mobile Subscriber Identity related to the x-th CTS-MS enrolled on a CTS-FP CTS-PIN CTS-Personal Identification Number CTS-SN FPAC Fixed part authorisation code (derived from the CTS-PIN) FP-SIM Fixed Part CTS-Subscriber Identity Module IFPEI International Fixed Part Equipment Identity IFPSI International Fixed Part Subscription Identity Ka CTS authentication key related to the x-th CTS-MS enrolled on a CTS-FP Kc CTS ciphering key related to the CTS-MS enrolled on a CTS-FP ETSI ETSI TS 100 929 V7.2.0 (1999-11) 76 (GSM 03.20 version 7.2.0 Release 1998) KiFP CTS subscription authentication key (used for authentication of the CTS-FP by the CTS operator) KOP Secret key used to validate tokens signed by the operator MS-SIM Mobile CTS-Subscriber Identity Module RIFP CTS Random Initial value sent from the CTS-MS to the CTS-FP RIMS CTS Random Initial value sent from the CTS-FP to the CTS-MS SRES1 CTS Signed RESponse of the CTS-FP's CH1 and the Ka of the CTS-MS SRES2 CTS Signed RESponse of the CTS-MS's CH2 and the Ka of the CTS-FP Tval XSRES1 CTS Signed RESponse of the CTS-FP's CH1 and the Ka of the CTS-FP (to be compared with SRES1) XSRES2 CTS Signed RESponse of the CTS-MS's CH2 and the Ka of the CTS-MS (to be compared with SRES2) E.2 General In GSM 02.56 the CTS service is introduced and security service requirements are listed. Based on this, the CTS security system can be seen as a set of two subsystems, the CTS local security system and the CTS supervising security system. The local security system deals with aspects of CTS-MS/CTS-FP pairs. It is related to security aspects of the CTS user. The different CTS local security services, functions and procedures that are listed in GSM 02.56 are grouped as follows: - MS subscriber identity confidentiality; - identity authentication (including the MS subscriber identity - and the FP subscriber identity authentication); - confidentiality of user and signalling information between CTS-MS and CTS-FP. These functions are part of the following procedures: - local part of the CTS enrolment/de-enrolment procedures; - access procedure of a CTS-MS/CTS-FP pair. When licensed band is used, the supervising security system deals with aspects of network security. It is related to security aspects of the CTS operator. The different CTS supervising security services, functions and procedures that are listed in GSM 02.56 are grouped as follow: - identity authentication with the CTS operator (including the FP subscriber authentication and if required the MS subscriber authentication with the GSM operator); - secure operation control; - subscription Control; - equipment checking (IMEI, IFPEI). These functions are part of the following procedures: - CTS system initialisation/de-initialisation procedures; - CTS supervising security part of the CTS enrolment procedure; - CTS-FP/CTS-SN Access procedure; General comments on the figures in this annex: - in the figures below, signalling exchanges are referred by functional names; - signalling refers to exchange of information. This shall not imply any implementation of information elements and messages at this stage of the CTS specification. - addressing fields are not given; all information relates to the signalling layer. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 77 (GSM 03.20 version 7.2.0 Release 1998) E.3 CTS local security system The subclauses below are described under normal operation. Abnormal operation is described in document [4]. The CTS local security applies for licensed band or license exempt band. In the following sub-clauses the functions and procedures related to the CTS local security are defined. The following system elements and interfaces according to GSM 03.56 are involved: - The CTS-FP (consisting of the CTS-FPE and the FP-SIM); - The CTS-MS (consisting of the CTS-ME and the MS-SIM); - The CTS radio interface between the CTS-MS and the CTS-FP. E.3.1 Mobile Subscriber identity confidentiality The purpose of this function is to avoid the possibility of an intruder identifying which subscriber is present on the CTS radio interface by listening to signalling exchanges or the user traffic. This allows both a high level of confidentiality for user data and signalling against the tracing of users. The provision of this function implies that the mobile subscriber identity (IMSI), or any information allowing a listener to derive the identity easily, should not normally be transmitted in clear text in any signalling message on the CTS radio interface. Consequently, to obtain the required level of protection, it is necessary that: - the subscriber identity (IMSI) is not normally used as an addressing method on the CTS radio interface (see GSM 02.09); - when the signalling procedures and operating conditions (see GSM 03.56) permit it; signalling information elements that convey information about the mobile subscriber identity shall be ciphered for transmission on the CTS radio interface. E.3.1.1 Identifying method The means used to identify a mobile subscriber on the CTS radio interface consists of a CTSMSI (CTS Mobile Subscriber Identity). This CTSMSI is a local number, having a meaning only for a given CTS-MS/CTS-FP pair. The CTSMSI is assigned by the CTS-FP to the CTS-MS by signalling procedures at enrolment and is valid until updated by the CTS-FP. During normal operation, this CTSMSI identifies a CTS-MS uniquely among all CTS-MSs enrolled onto one CTS-FP. See also GSM 03.56. The CTS-MS shall store the CTSMSI in the MS-SIM, together with the IFPEI. The CTS-FP shall store the CTSMSI in the CTS-FPE, together with the IMEI and the IMSI. The IMEI is stored in order to allow tracking of mobile equipment as required in GSM 02.56. The storage requirements are given in clause E.9. E.3.1.2 Procedures This subclause presents the procedures, or elements of procedures, pertaining to the management of the CTSMSI with respect to the local security. E.3.1.2.1 CTSMSI assignment This procedure is part of the enrolment procedure of a CTS-MS onto a CTS-FP (see subclause E.3.4.1). The CTS-FP generates randomly a CTSMSI not equal to any of the existing CTSMSIs stored in the CTS-FP. The resulting CTSMSI is sent encrypted to the CTS-MS. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 78 (GSM 03.20 version 7.2.0 Release 1998) E.3.1.2.2 CTSMSI update This procedure is part of general access procedure of a CTS-MS/CTS-FP pair. The CTSMSI shall be updated by the CTS-FP as part of each MS/FP signalling exchange in order to preserve identity confidentiality. The CTS-FP generates randomly a CTSMSI not equal to any of the existing CTSMSIs stored in the CTS-FP. The resulting CTSMSI is the new CTSMSI for the CTS-MS/CTS-FP pair and is sent encrypted to the accessing CTS-MS. The CTS-MS stores the new CTSMSI on the MS-SIM. After successful storage, it acknowledges the update of the CTSMSI to the CTS-FP. Upon reception of the acknowledgement from the CTS-MS, the CTS-FP stores the new CTSMSI and deletes the old CTSMSI. See also GSM 03.56. E.3.1.2.3 CTS local identification This procedure is part of general access procedures of a CTS-MS/CTS-FP pair. The CTS-MS transmits the CTSMSI to the CTS-FP in the initial message in order to give its identity. If the CTS-MS announces a CTSMSI which is unknown at the CTS-FP, then the CTS-FP requires the IMSI; if the IMSI is unknown, the CTS-FP shall deny access to that CTS-MS. The CTS-FP may consider that the CTS-MS is not enrolled into it. The reason that the CTSMSI is unknown is generally not a matter of security and not considered here. See also GSM 03.56. E.3.2 Identity authentication According to the definitions given in GSM 02.56, a local mutual authentication is required, containing both, the authentication of the mobile subscriber identity at the CTS-FP and the authentication of the CTS-FP identity at the CTS-MS. It can be noted that the IMSI is not tied to the equipment identity (IMEI) as the security related data derived from the enrolment procedure are stored on the MS-SIM; therefore a subscriber can remove his MS-SIM card and insert it in another CTS-ME without locally re-enrolling onto the CTS-FP. The authentication procedure will also be used to set the ciphering key (see subclause E.3.3). E.3.2.1 The mutual authentication procedure A pre-condition of the procedure described below is, that both involved parties, the CTS-MS and the CTS-FP share the knowledge of the authentication key Ka. The authentication procedure consists of the following exchange between the CTS-FP and the CTS-MS: - The CTS-FP transmits an unpredictable number CH1 to the CTS-MS; - The CTS-MS transmits an unpredictable number CH2 to the CTS-FP; - The CTS-MS computes the response SRES1 from CH1 and the individual authentication key Ka using the algorithm B3; - The CTS-FP computes the expected response XSRES1 from CH1 and the individual authentication key Ka using the algorithm B3; - The CTS-MS transmits SRES1 to the CTS-FP; - The CTS-FP tests SRES1 for validity, i.e. it compares SRES1 and XSRES1; - The CTS-FP computes the response SRES2 from CH2 and the individual authentication key Ka using the algorithm B4; ETSI ETSI TS 100 929 V7.2.0 (1999-11) 79 (GSM 03.20 version 7.2.0 Release 1998) - The CTS-MS computes the expected response XSRES2 from CH2 and the individual authentication key Ka using the algorithm B4; - The CTS-FP transmits SRES2 to the CTS-MS; - The CTS-MS tests SRES2 for validity, i.e. it compares SRES2 and XSRES2. Note that the order of transmission of information as mentioned above and as shown in the figure shall not imply any implementation. Protocols to exchange the information shall be implemented with respect to efficiency of calculation time and effective messaging. CTS-M S sharing the know ledge of the K a w ith the CTS-FP C TS R adio Interface B 4 B 3 B 4 B3 = Y es/N o Y es/N o C H 1 C H 2 SRES1 = SR ES2 K a K a C H 2 CH 1 K a K a X SR ES2 X SR ES1 C TS-FP sharing the know ledge of the K a w ith the CTS-M S Figure E1: General mutual authentication procedure E.3.2.1.1 Authentication failure An authentication failure (from security point of view) occurs, if: - The CTS-MS and the CTS-FP have different Ka; - The algorithm B3 or B4 are not implemented as specified (i.e. non type approved equipment). In this case the side which has detected the failure shall indicate "authentication failure" to the other side and cancel the connection with the other side. E.3.2.2 Authentication Key management. The Ka associated with a CTS-MS/CTS-FP pair is generated randomly during enrolment procedure as described in subclause E.3.4.1. As defined in GSM 02.56, keys of the CTS shall be controlled by the PLMN operator. In order to fulfil this requirement, all relevant information to reproduce Ka is transmitted to the PLMN operator as described in subclause E.3.4.1 and in subclause E.4. E.3.3 Confidentiality of user information and signalling between CTS-MS and CTS-FP In GSM 02.56 some signalling information is considered sensitive and must be protected. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 80 (GSM 03.20 version 7.2.0 Release 1998) The needs for a protected mode of transmission are fulfilled with an OSI layer 1 confidentiality function. The scheme described below assumes that the signalling information is transmitted on a dedicated channel. Four points have to be specified: - the ciphering method; - the key setting; - the starting of the enciphering and deciphering algorithms; - the synchronisation. E.3.3.1 The ciphering method The OSI layer 1 data flow (transmitted on a dedicated channel) is ciphered on a bit by bit basis or stream cipher; i.e.; the data flow on the CTS radio interface is obtained by the bit per bit binary addition of the user data flow and the ciphering bit stream generated by the algorithm A5/2 using a key determined as specified in subclause E.10.1. The key is denoted below by Kc and is called the CTS Ciphering Key. The Kc is specific to one CTS-MS/CTS-FP pair. Deciphering is performed by exactly the same method. Algorithm A5/2 is one of the A5 algorithms specified in GSM 03.20, Annex C. Only A5/2 algorithm is supported on the CTS-FP to enable local ciphering. The CTS-MS supports at least the A5/2 algorithm. E.3.3.2 Key setting Mutual key setting is the procedure that allows the CTS-MS and the CTS-FP to agree on the key Kc to use in the ciphering and deciphering algorithm A5/2. A key setting is triggered by the mutual authentication procedure. Key setting must occur on a channel not yet encrypted and as soon as the CTSMSI is known by the CTS-FP. Kc is generated using CH1, the algorithm B1 and the CTS Authentication key Ka, as defined in subclause E.10.1. Kc is stored in the CTS-ME and the CTS-FPE as described in subclause E.8. CTS-MS CTS-FP CTS Radio Interface B1 B1 Store Kc in CTS-ME Store Kc in CH1 Ka Ka Kc Kc CTS-FPE Figure E2: Cipher Key setting ETSI ETSI TS 100 929 V7.2.0 (1999-11) 81 (GSM 03.20 version 7.2.0 Release 1998) E.3.3.3 Starting of the ciphering and deciphering processes The CTS-MS and the CTS-FP must co-ordinate the instants at which the enciphering and deciphering processes start. This procedure takes place under control of the CTS-FP some time after the completion of the authentication procedure. No information elements for which protection is needed must be sent before the ciphering and deciphering processes are operating. The transition from clear text mode to ciphered mode proceeds as follows: The CTS-FP starts deciphering and sends in clear text to the CTS-MS a specific message, here called "Start cipher". After the message "Start cipher" has been correctly received by the CTS-MS, the CTS-MS will commence both the enciphering and deciphering. Finally, enciphering in the CTS-FP starts as soon as a frame or a message from the CTS- MS has been correctly deciphered at the CTS-FP. The starting of enciphering and deciphering processes is shown in figure E3. CTS-MS CTS-FP CTS Radio Interface Start deciphering and Start enciphering deciphering “Start cipher” ciphered frame Start deciphering Start enciphering o.k. ciphered connection Figure E3: Starting of the enciphering and deciphering processes E.3.3.4 Synchronisation The ciphering stream at one end and the deciphering stream at the other end must be synchronised, for the enciphering bit stream and the deciphering bit stream to coincide. The underlying synchronisation scheme is described in GSM 03.20, Annex C. E.3.4 Structured procedures with CTS local security relevance The following structured procedures are mainly related to the local security or at least involve CTS local security functions and procedures. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 82 (GSM 03.20 version 7.2.0 Release 1998) E.3.4.1 Local Part of the Enrolment of a CTS-MS onto a CTS-FP According to GSM 02.56 and GSM 03.56 the CTS-MS/CTS-FP enrolment is the procedure, which generates an association between a certain CTS-MS and a certain CTS-FP, i.e. a CTS-MS/CTS-FP pair is established. The following CTS local security aspects are covered by the enrolment: - The enrolment includes a means of authorisation to use the CTS-FP, i.e. the CTS-PIN is necessary in the enrolment procedure. It is mandatory that the CTS-PIN is activated. - The authentication key Ka is generated and distributed to the CTS-MS and the CTS-FP. - The CTSMSI is initially allocated and submitted from the CTS-FP to the CTS-MS - The IFPEI is transmitted from the CTS-FP to the CTS-MS. E.3.4.1.1 Local part of the enrolment procedure The procedure described assumes that the CTS-MS or the CTS-FP have the knowledge of the radio parameters to be used on the CTS radio interface to enable initial connection (see GSM 02.56 and GSM 03.56). As specified in GSM 02.56 and GSM 03.56, only a CTS-MS subscribed to an operator which has roaming agreement with the CTS-FP's operator shall be allowed to enrol to that CTS-FP. The following procedure is followed: - An enrolment state is triggered by MMI at the CTS-MS and at the CTS-FP; - The user enters the CTS-PIN at the CTS-MS; - The CTS-MS derives the FPAC from the CTS-PIN. The FPAC also resides in the CTS-FP, thus the knowledge of the CTS-PIN gives authorisation to perform enrolment; - An initial connection is established on the CTS radio interface; - The CTS-MS and the CTS-FP exchange random initial values (RIMS and RIFP); - The CTS-MS and the CTS-FP both calculate an authentication key Ka = B2(FPAC, RIMS, RIFP); - The CTS-MS and CTS-FP perform a mutual authentication according to subclause 3.2.1 using Ka . Since Ka is derived from the CTS-PIN, this mutual authentication proves the authorisation of the user; - The CTS-MS and CTS-FP determine a ciphering key Kc = B1(Ka, RIMS) and switch to ciphering mode according to the procedure described in subclause E.3.3; - The CTS-MS transmits (encrypted) to the CTS-FP the IMSI, and the IMEI; - In order to avoid double enrolment, the CTS-FP checks if the IMSI is already enrolled; - The CTS-FP checks the GSM operator's identity of the CTS-MS and determines whether the CTS-MS subscriber is allowed to enrol on that CTS-FP; - In case of licensed band the Supervising part of the enrolment is performed if required (see subclause E.4.4.3.4.); - The CTS-FP determines the CTSMSI; - The CTS-FP transmits (encrypted) the Ka, the IFPEI and the CTSMSI; - The CTS-MS stores the Ka, the CTSMSI and the IFPEI on the MS-SIM; - The CTS-FP stores the Ka, the IMSI, the IMEI, CTSMSI in a non volatile memory of the CTS-FPE; - The enrolment procedure is completed (possible non security related procedures). If a failure occurs during this local security procedure, intermediate values related to this procedure shall be deleted and the enrolment shall be aborted. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 83 (GSM 03.20 version 7.2.0 Release 1998) CTS-SN CTS-FP CTS-MS CTS Radio Interface Enter user MMI Enter CTS- PIN Derive FPAC from CTS-PIN Calculate KINIT=B2(FPAC,RIMS,RIFP) Establish initial connection on the CTS radio interface RIMS RIFP Calculate KINIT=B2(FPAC,RIMS,RIFP) Mutual authentication CTS-MS/CTS-FP using KINIT Calculate Kcx=B1(KINIT,RIMS) Determine CTSMSI Store CTS-FPE : Kax,CTSMSI,IMSI,IMEI Store MS-SIM : Ka,CTSMSI,IFPEI Calculate Kcx=B1(KINIT,RIMS) Ciphered connection IMSI, IMEI CTSMSI, Ka, IFPEI Supervising part of the enrolment procedure Finish enrolment procedure Figure E4: Local part of the enrolment procedure ETSI ETSI TS 100 929 V7.2.0 (1999-11) 84 (GSM 03.20 version 7.2.0 Release 1998) E.3.4.2 General Access procedure Once the CTS-MS is enrolled onto a CTS-FP, the CTS-MS may access the CTS-FP for user communication on the fixed network or for local CTS related procedures or as part of the local security for CTS supervising procedures. The access procedures shall generally involve the following sub-procedures: - Identification as described in subclause E.3.1.2; - Mutual authentication using the Ka defined during the enrolment in order to authenticate the identities on the CTS radio interface as described in subclause E.3.2.1; - Generation of a new Kc and starting to cipher the link on the CTS radio interface as described in subclause E.3.3; - Update of the CTSMSI because it has been used in clear text for identification, as described in subclause E.3.1.2.2; CTS-MS CTS Radio Interface CTS-FP Compute Kc = B1(Ka, CH1) and switch to encryption Mutual CTS-MS/CTS-FP authentication using Ka OK OK Compute Kc = B1(Ka, CH1) and and switch to encryption ciphered connection Identification OK OK CTSMSI update procedure OK OK Figure E5: The general access procedure Authentication and start of ciphered connection shall usually be performed before any sensitive signalling data or user data is transmitted on the CTS radio interface. In the following sub-subclauses, some specific access procedures are described with respect the CTS local security. E.3.4.2.1 Attachment The attachment procedure is used to attach a CTS-MS to a CTS-FP. A pre-condition is, that the CTS-MS is enrolled with the CTS-FP. The attachment procedure shall be performed whenever the CTS-MS is switched on within the range of a CTS-FP or when it comes into the range of the CTS-FP. The attachment procedure shall include all sub-procedures of the general access procedure as described above. Additionally the IMEI of the CTS-MS may be transmitted to the CTS-FP at attachment, in order to support the tracking or IMEI as described in subclause E.4.5. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 85 (GSM 03.20 version 7.2.0 Release 1998) E.3.4.2.2 CTS local security data update The CTS local security data update procedure is performed in order to determine a new temporary identity CTSMSI and a new cipher key Kc. This procedure may be a part of a non security related procedure or it is used for the main purpose of local security data update. A regular CTSMSI update procedure shall be defined in order to insure user confidentiality. The CTS local security data update contains all sub-procedures of the general access procedure. It is initiated by the CTS-FP. E.3.4.3 De-enrolment of a CTS-MS According to GSM 02.56 the de-enrolment of a CTS-MS is the procedure which cancels the association between a certain CTS-MS and a certain CTS-FP. A de-enrolment procedure of a CTS-MS from a CTS-FP can be either initiated by the CTS-FP (network or FP command) or by a user specific action to de-enrol one or several CTS-MS from a CTS-FP. E.3.4.3.1 De-enrolment initiated by the CTS-FP The following procedure is followed: - The CTS-FP sends a de-enrolment command to the CTS-MS; - The CTS-MS and the CTS-FP perform mutual authentication according to subclause E.3.2.1 using Ka; - The CTS-MS deletes data related to CTS-FP i.e. Ka, CTSMSI, IFPEI, and confirms de-enrolment; - The CTS-FP deletes data related to that CTS-MS i.e. Ka, CTSMSI, IMSI, IMEI; - The de-enrolment is completed (possible non security related procedures). E.3.4.3.2 De-enrolment initiated by a CTS-MS The de-enrolment procedure when initiated by a CTS-MS is an MMI procedure that requires the knowledge of the CTS- PIN. The following procedure applies : When remote MMI is used : - the user enters a specific de-enrolment menu or command at the CTS-MS; - attachment is performed on the MS/FP interface ; - the user enters the CTS-PIN at the CTS-MS; - The CTS-FP checks the CTS-PIN and sends a list of all enrolled CTS-MSs to the CTS-MS; - The list is displayed at the CTS-MS and the user selects one (or several) CTS-MS(s) for de-enrolment; - The list of CTS-MS(s) which are selected for de-enrolment, is sent to the CTS-FP; - Data related to the de-enrolled CTS-MSs, i.e. the Ka, the IMSI, the CTSMSI, the IMEI are deleted in the CTS- FP; - The de-enrolment is completed (possible non security related procedures). ETSI ETSI TS 100 929 V7.2.0 (1999-11) 86 (GSM 03.20 version 7.2.0 Release 1998) E.4 CTS supervising security system This subclause is applicable is case of licensed band only. In the following sub-clauses the functions and procedures related to the CTS supervising security are defined. The following system elements and interfaces according to GSM 03.56 are involved: - The CTS-FP (consisting of the CTS-FPE and the FP-SIM); - The CTS-MS (consisting of the CTS-ME and the MS-SIM); - The CTSHLR/AuC; - The CTS-SN; - The HLR/AuC; - The CTS radio interface between the CTS-MS and the CTS-FP; - The CTS fixed network interface; - The GSM radio interface. E.4.1 Supervision data and supervision data protection This sub-clause describes the mechanisms to be used by theCTS operator to set and modify the supervision data to be used in a CTS-MS/CTS-FP environment. E.4.1.1 Structure of supervision data Supervision data are sent as structured information elements which may consist of: 1) Short commands, e.g., information data requests, identification, de-intialisation of the CTS-FP,de-enrolment of a CTS-MS, ...; 2) Download of data and parameters, e.g., radio parameters, timer settings, CTS-SN directory number; E.4.1.2 Supervision data protection The supervision data are protected by a signature. The signature of data is performed following a valid CTS-FP authentication by the CTS-SN as described in chapter E.4.3.1. The signature is performed using the B6 algorithm and a secret key Kop shared between the CTS-SN and the CTS-FP. The secret key Kop is generated during the CTS-FP authentication at the CTS-AuC using the authentication key KiFP a random vector and the A8' algorithm: Kop= A8'(KiFP, RAND1). Data signature is performed using a random vector RAND2 generated by the CTS-FP, Data the sequence that has been signed, Kop and the B6 algorithm. The concatenation of Data and RAND2 is referred to as Data2. Some data are associated with a validity period indication (relative time). Before the validity timer expires, the CTS-FP must contact the CTS-SN in order toupdate those data. It should be noted that supervision data carry data related to CTS subscription and therefore to the CTS-FP. Therefore, the operator will issue supervision data following a successful CTS-FP authentication by the CTS-HLR. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 87 (GSM 03.20 version 7.2.0 Release 1998) CTS-FP CTS Fixed Network Interface CTS-SN B6 Kop Kop RAND2 MAC2 B6 = Data2=Data/RAND2 MAC2 Yes/No? Figure E6: Generation of the signature of the supervision data E.4.1.3 Key management The SIM card manufacturer delivers an FP-SIM card that includes a mechanism to authenticate the signature of the supervision data issued by the CTS-SN. This mechanism consists of the B6 algorithm that enables authentication of thesignature using a secret key KOP. This key is not accessible on the FP-SIM card. E.4.2 CTS subscriber identity A CTS specific identity is assigned to a subscriber of the CTS service. This identity (IFPSI) enables unique identification of a CTS subscriber at communication with the CTS-SN. It can be noted that the subscription to the CTS service does not assume subscription of every CTS-MS that want to operate CTS on a given CTS-FP. There is one CTS subscription per CTS-FP, and therefore one identity to check no matter how many CTS-MS are enrolled to that CTS-FP. Nevertheless, the CTS operator may also require the authentication of the CTS-MS. And therefore the MS-SIM identity (IMSI) will identify a CTS-MS subscriber at communication with the CTS-SN. For more details see also GSM 03.56. E.4.3 Identity authentication with the CTS operator and the PLMN According to the definitions given in GSM 02.56, the procedure of authentication of the FP-SIM is required for the CTS initialisation, CTS-MS enrolment onto a CTS-FP, and network access procedure (e.g. operation data update). Similarly, the procedure of authentication of the MS-SIM is required for the CTS-MS enrolment onto a CTS-FP. Additionally identity authentication may also be part of other CTS specific procedures. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 88 (GSM 03.20 version 7.2.0 Release 1998) E.4.3.1 Authentication of the CTS-FP The authentication of the CTS-FP via the fixed network procedure consists of the following exchange between the CTS- FP and the CTS-HLR through the CTS-SN: - The CTS-FP sends the IFPSI to the CTS-HLR through the fixed line and through the CTS-SN; - The CTS-AuC computes the authentication result (SRES) using the KiFP key associated to the IFPSI and a random challenge (RAND); - The CTS-SN receives from the CTS-HLR the authentication vector (SRES (1,…, n), RAND (1,…,n)) according to the general authentication procedure described in GSM 03.20; - The CTS-SN transmits a RAND1 and a random value Data1 to the CTS-FP via the fixed network; - The CTS-FP and the CTS-HLR generate a key Kop derived from the KiFP and using A8' algorithm; - The CTS-FP performs an authentication using Kop and B5 computes the signature ofData1, say MAC1; - The CTS-FP transmits the signature MAC1 to the CTS-SN; - The CTS-SN tests MAC1 for validity. = yes/no CTS-FP CTS fixed network interface MAC1 RAND1 CTS-SN CTSHLR/ AuC Kop A8’ KiFP Kop B5 MAC1 Data1 Figure E7: Authentication of the CTS-FP E.4.3.2 Authentication of the CTS-MS This procedure requires that the CTS-SN has an interface to the HLR in order to receive the challenge/response pairs for authentication of the CTS-MS. It is a normal GSM authentication procedure as described in GSM03.20[7], the CTS-FP acting as a relay: - The CTS-MS sends the IMSI to the HLR through the CTS-FP and through the CTS-SN; - The AuC generates the authentication result (SRES) using the Ki key associated with the IMSI and a random challenge (RAND); - The CTS-SN receives the authentication vector (SRES (1,…, n), RAND (1,…,n)) according to the general authentication procedure described in GSM 03.20; - The CTS-SN transmits a RAND, 1 ≤x ≤n, to the CTS-MS via the CTS-FP.; - The CTS-MS performs an authentication using Ki and A3 according to the authentication procedure described in GSM 03.20 and computes the signature of RANDx: SRESRANDx; ETSI ETSI TS 100 929 V7.2.0 (1999-11) 89 (GSM 03.20 version 7.2.0 Release 1998) - The CTS-MS transmits via the CTS-FP the signature SRESRANDx to the CTS-SN; - The CTS-SN tests SRESRANDx for validity. CTS-MS CTS Radio Interface A3 = SRES yes/no Ki CTS-FP CTS fixed network interface RAND SRESRAND SRESRAND RAND CTS-SN HLR/ AuC SRES,RAND Figure E8: Authentication of the CTS-MS via the CTS fixed network interface E.4.4 Secure operation control According to GSM 03.56, signalling for operation control of the local CTS may take place on different signalling planes: - on the CTS fixed network interface using a CTS-SN application signalling; - on the GSM Radio Interface using the GSM layer 3 signalling. The means of operation control of the local CTS for these two signalling planes is described in the subsequent subclauses. E.4.4.1 GSM layer 3 signalling GSM layer 3 signalling can be used to provide CTS data. It is not initiated on request of the local CTS but included in a normal GSM layer 3 signalling procedure. These data are downloaded to the CTS-MS through the GSM Radio Interface and transferred to the CTS-FP during an access procedure according to subclause E.3.4.2. Whenever the CTS-FP gets new CTS operation data it contacts the CTS-SN through the Fixed Network and performs Operation Data Update procedure according to subclause E.4.4.3.4.1. E.4.4.2 CTS application signalling via the Fixed Network CTS may use a specific application protocol on the fixed network interface for operation control purposes. Communication via the fixed network interface may include authentication of the subscriber identity as described in subclause E.3.2. Due to the fact, that a false CTS-SN can easily be set up, protection of operation data as described in subclause E.4.1.2, is required. Operation control via the CTS fixed network interface is generally initiated by the local CTS, i.e. the CTS-FP, triggered by time or event control. An initiation from the CTS-SN to the CTS-FP, is generally not applicable due to missing means of addressing a specific terminal, i.e. the CTS-FP in the fixed network (PSTN case). ETSI ETSI TS 100 929 V7.2.0 (1999-11) 90 (GSM 03.20 version 7.2.0 Release 1998) However, this shall not exclude that the CTS-SN initiate operation control, if certain network configurations allow this feature. E.4.4.3 CTS operation control procedures E.4.4.3.1 Initialisation of a CTS-FP According to GSM 02.56 and GSM 03.56 the CTS-FP initialisation is the procedure where the CTS-FP is downloaded with the necessary data in order to provide CTS service. The following procedure applies: - An initialisation state is triggered by MMI at the CTS-FP; - The CTS-FP retrieves the CTS-SN directory number from the FP-SIM; - The CTS-FP contacts the CTS-SN through the fixed line; - Authentication of the CTS-FP is performed as described in subclause E.4.3.2.1; - The CTS-SN sends operation data to the CTS-FP; these data are protected as described in subclause E.4.1.2; - The CTS-FP authenticates the signature of the operation data sent from the CTS-SN; - The CTS-FP is considered as being initialised. E.4.4.3.2 De-initialisation of a CTS-FP The CTS-FP is considered as being de-initialised if it does not have the necessary data to provide CTS service. This may happen either because: 1 a timer associated to the CTS data has expired and therefore the CTS-FP cannot offer CTS service; 2 a network control mechanism requires CTS-FP de-initialisation; 3 the CTS-FP has been disconnected from the PSTN connection and from the main power for a period of time; 4 the FP-SIM has been removed and a new SIM card inserted in the CTS-FPE. As the CTS-SN has in general no means to address the CTS-FP, the de-initialisation command is sent when the CTS-FP accesses the CTS-SN. Case 1 The principle of the time/event controlled mechanism is, that some operation data has a limited validity period. The duration of this period, i.e. a timer, is controlled by the CTS operator. The operation data is related to one CTS-subscriber that is to the FP-SIM. An authentication of the CTS-FP by the CTS- SN and a token authentication by the CTS-FP is performed in the operation data update procedure as described in subclause E.4.4.3.4.1. Therefore, the update of the operation data does not require a CTS-MS being enrolled to the CTS-FP. Before the expiry of the validity period timer a data update procedure is triggered as described in subclause E.4.4.3.4.1. If the validity period expires without an update of the operation data, the CTS-FP is de-initialised and the operation data are deleted from the CTS-FP. Case 2 In case 2, the de-initialisation procedure is the following: - The CTS-FP contacts the CTS-SN; - The CTS-SN performs authentication of the CTS-FP as described in chapter E.4.3.2.1; ETSI ETSI TS 100 929 V7.2.0 (1999-11) 91 (GSM 03.20 version 7.2.0 Release 1998) - The CTS-SN sends a de-initialisation command using the data protection mechanism described in chapter E.4.2.1; - The CTS-FP authenticates the signature and deletes the operation data; - De-initialisation is performed. The CTS-FP de-initialisation does not imply CTS-MS de-enrolment; the data related to CTS-MS/CTS-FP pair are not deleted from the CTS-FP but CTS service cannot be granted. Case 3 As some operation data might be related to the location of the CTS-FP, if the CTS-FP is disconnected from the PSTN connection for a certain time (see [4]), the CTS-FP is considered as being de-initialised and the operation data are deleted from the CTS-FP. Case 4 The operation data are related to the FP-SIM. If a new FP-SIM is inserted in the CTS-FPE the previously stored data should be deleted. The CTS-FP is therefore de-initialised. E.4.4.3.3 Enrolment From the CTS supervising security point of view the following requirements have to be fulfilled: - According to the definitions given in the CTS stage 1 service description, enrolment shall include authentication of the CTS-subscriber (FP-SIM). - In addition, if required by the CTS operator an authentication of the CTS-MS subscriber can be performed. (GSM 02.09). - The local CTS shall receive operation data - The CTS shall operate in accordance with the settings of this operation data. Two supervising security methods are defined for enrolment. They are described in the subsequent subclauses. E.4.4.3.3.1 Enrolment conducted via the CTS fixed network interface If indicated by the CTS subscription information at the CTS-FP the supervising part of the enrolment is conducted via the CTS fixed network interface. In this case, after the local part of the enrolment procedure is performed as described in subclause E.3.4.1.1 (we have reached the stage where the CTS-MS transmits through the CTS interface the IMSI, the CTS-FP checks that the IMSI is not enrolled yet), the following procedure applies: - The CTS-FP calls the CTS-SN through the fixed line; - The IFPSI and the IMSI are transmitted from the CTS-FP to the CTS-SN; Equipment identities (IMEI, IFPEI) can be transmitted for verification; - The CTS-HLR performs authentication of the CTS-FP using the authentication key KiFP,A8' and B5 authentication algorithm as described in subclause E.4.3.2.1; - After successful authentication of the CTS-FP, the CTS-SN may require the authentication of the CTS-MS. The generation of triplets is achieved in the HLR using the Ki authentication key and the A3 algorithm as described in subclause E.4.3.2.2; - The CTS-FP checks the validity of the signature as described in subclause E.4.1.2; - The CTS-FP and the CTS-MS exchange data (as described in the local security part of the enrolment procedure (E.3.4.1.1); - The CTS-FP indicates successful enrolment to the CTS-MS; ETSI ETSI TS 100 929 V7.2.0 (1999-11) 92 (GSM 03.20 version 7.2.0 Release 1998) - The enrolment is finished. CTS-HLR CTS-SN CTS-MS CTS-FP Contact the CTS-SN IFPSI,IMSI,IFPEI,IMEI Authentication of the FP-SIM Local part of the enrolment procedure Local part of the enrolment (followed): data exchange HLR Authentication of the signed data Enrolment finished Fixed network interface Authentication of the MS-SIM Figure E9: CTS supervising security: enrolment of a CTS-MS onto a CTS-FP via the CTS fixed network interface E.4.4.3.4 Supervising security in the CTS-FP/CTS-SN access procedure E.4.4.3.4.1 Update of operation data The update of operation data is required due to the fact, that the validity of some operation data is limited by an operator controlled timer. The operation data can be updated without a CTS-MS being attached to the CTS-FP, as FP-SIM authentication is performed through the fixed network interface. This allows transparency of the operation control to the user and avoids unnecessary de-initialisation if the user has not performed attachment for a long period of time. Update of operation is performed via the fixed network interface and the following steps apply : - Before the validity period expires, the CTS-FP contacts the CTS-SN and requires data update; - The CTS-HLR authenticates the FP-SIM through the fixed network interface; - the CTS-HLR checks the subscription validity and sends a new set of operation data to the CTS-FP; - The CTS-FP authenticates the data signature and starts a new timer; - The update procedure is finished. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 93 (GSM 03.20 version 7.2.0 Release 1998) CTS-HLR CTS-SN CTS-FP Fixed network interface Contact the CTS-SN IFPSI,IFPEI Authentication of the FP-SIM Timer expiring Check subscription validity for IFPSI new data (Tval) Perform data signature Signed data Authenticate Data signature End of operation data update procedure Figure E10: Update of operation data via the CTS fixed network interface As this timer is an essential part of the CTS operation control, it shall be securely situated within the CTS-FP, i.e. it shall not be possible to reset the time except by valid operations described in this subclause. The security requirements on the timer values and the timer itself are described in subclause E.6. E.4.5 Equipment checking Equipment checking can be seen as part of the initialisation, of the enrolment or of the operation data update procedures: Checking the IFPEI can be part of the initialisation and operation data update procedures. Checking the IFPEI and the IMEI can be part of the enrolment procedure. E.4.6 FP-SIM card checking The FP-SIM presence should be verified and no CTS operation should be allowed if the FP-SIM is not at least present. Furthermore, specific CTS operations should meet the following requirements: - The CTS-FP initialisation procedure should not be possible if the CTS-FP does not include a valid FP-SIM card, i.e. that contain minimum information to contact the CTS-SN or to operate CTS service. - The enrolment procedure of a CTS-MS on a CTS-FP should not be initiated if the MS-SIM operator's identity is in the list of forbidden operators of the FP-SIM. - CTS operation should not be allowed if there is not a valid FP-SIM card in the CTS-FPE. The MS-SIM verification follows the normal GSM requirements. The GSM subscription is checked whenever the CTS- MS accesses the PLMN (authentication performed using the IMSI, Ki and A3 in the MS-SIM card). ETSI ETSI TS 100 929 V7.2.0 (1999-11) 94 (GSM 03.20 version 7.2.0 Release 1998) The MS-SIM card is not tied to the CTS-ME as all the relevant data for local security are stored in the MS-SIM card. If after successful enrolment on a given CTS-FP, the CTS-ME have been changed, no re-enrolment should be needed. The CTS-FP will store the new IMEI sent in the access procedure in association with the local security data. If the FP-SIM card has been extracted from the CTS-FPE, the latter should check the identity of the new SIM card. If a new FP-SIM card has been inserted in the CTS-FPE, CTS-FP should be re-initialised. E.5 Other CTS security features In GSM 02.56 the requirements of a series of additional security services and functions for the CTS are defined. They should provide, amongst others, protection against misuse of equipment This subclause describes the CTS security features that concern: - secure storage of sensitive data in CTS-MS; - secure storage of sensitive data in CTS-FP; - CTS-FP de-initialisation; - CTS-FP reprogramming protection. E.5.1 Secure storage of sensitive data and software in the CTS-MS E.5.1.1 Inside CTS-ME The storage of the IMEI should be according the requirements described in GSM 02.09. Secure storage of sensitive data inside non-volatile memory of the CTS-ME should follow the directives in GSM 02.56. E.5.2 Secure storage of sensitive data and software in CTS-FP The IFPEI is stored in the CTS-FPE according to the same requirements for storage of the IMEI as described in GSM 02.09. Other sensitive data shall be stored securely. The timer for operation control should be stored in a secure way. E.5.3 CTS-FP reprogramming protection Reprogramming shall only be possible by the manufacturer of the CTS-FP and authorised services. The specification of the method is up to the manufacturer. E.6 FP Integrity In case of licensed mode, the CTS-FP while servicing its user(s) should perform as instructed by the CTS-SN. In both licensed and license exempt modes, a potential entry point for various kinds of CTS misuse would be to alter a type- approved CTS-FP. It is therefore of paramount importance that the local CTS security and in particular the CTS-FP itself provide reliable countermeasures against CTS-FP misuses through manipulation of its hardware and/or software. The purpose of this subclause is a) to identify explicitly the threats b) to explore ways how to provide protection c) to consider the verification of protection mechanisms ETSI ETSI TS 100 929 V7.2.0 (1999-11) 95 (GSM 03.20 version 7.2.0 Release 1998) E.6.1 Threats Threats have been identified and the importance of the corresponding need for a countermeasure was classified. The following ranking was used: 1. Essential; Protection is essential for secure operation of CTS in general; 2. Important; Protection is important but failure has limited impact; 3. Desirable; Protection is desirable but failure has only local impact. Table E1 shows the sensitive information that the FP contains and the importance of the countermeasure(s) against possible manipulation. It is understood that when an item is mentioned in Table 1that changing its value in an unauthorised way is a threat. Table E1: Sensitivity of FP maintained information Item Type of data Rank CTS-FP software (note 1) constant 1 IFPEI constant 2 IFPSI (licensed mode) constant 2 CTS-PIN constant 2 Secret operator Key (KOP) (licensed mode) variable 1 Supervising authentication key (KiFP) associated with IFPSI (licensed mode) constant 1+ PLMN permitted variable in licensed mode and constant in license exempt mode 1 Timers (counters), Limits (note 2) variable 1 Radio parameters (GFL, etc.) + operation parameters variable in licensed mode and constant in license exempt mode 1 Local keys (Ka) and security parameters variable 2 Service parameters (addressing, operator ids) variable 2 CTS algorithms (A3/A8, MAC) constant (1,2) NOTE 1: If the FP software is reprogrammable there should be a mechanism that authenticates the identity of the reprogramming agent (FS algorithm can be a protection against unauthorised reprogramming). NOTE 2: Clock should continue to run or new information should be obtained from the network when FP power is lost or fixed line connection removed. In case of license exempt mode, it is of prime importance that radio parameters and the list of the mobiles allowed to enroll to that CTS-FP (PLMN permitted) is stored in a secure way and cannot be modified. E.6.1.1 Changing of FP software CTS-FPEs will store their software in non-volatile memory that can be (re)programmed at the factory or at authorised service centres. Current technology provides so-called flash memories for this purpose. Reprogrammability is advantageous from production and service point of view but, at the same time, it can be misused to reprogram the FP to operate not according to the standards. Reprogramming may be executed via the manufacturer provided interface(s) or via direct access to the storage. Thus the FP reprogramming protection should protect against: a) unauthorised reprogramming access via offered interface (test, fixed line, SIM interface, radio interface); b) Reprogramming via direct access to system software storage; c) Reprogramming via physical exchange (replacing storage modules). NOTE: The actual protection mechanisms do not have to be standardised but the level of protection should be defined. There should be no (trapdoor) mechanism to bypass the protection mechanisms. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 96 (GSM 03.20 version 7.2.0 Release 1998) E.6.1.2 Changing of IFPEI Each, CTS-FPE contains an identity (IFPEI).The IFPEI can be used (associated to the IFPSI) for local security and network security procedures. The Fixed Part Equipment is uniquely defined by the IFPEI. The IFPEI is stored in a secure way in accordance with the requirements for storage of the IMEI as described in GSM 02.09. E.6.1.3 Changing of IFPSI and operator and subscription related keys (KiFP, KOP) These values are stored in the FP-SIM; the IFPSI can only be read and not updated while the operator and the subscription related keys are used in the FP-SIM and cannot be accessed. E.6.1.4 Changing of timers and timer limits The CTS-FP operation is partially under control of timers. When timer values are stored in E2PROM memory there should be a protection against malicious reprogramming. The use of external timer hardware should only be allowed when accompanied with comprehensive protection countermeasures. E.6.1.5 Changing of radio usage parameters This annex defines mechanisms to protect the parameters that will set the radio usage characteristics during transport to the local CTS system. In addition these parameters should be protected when stored inside the CTS-FPE. E.6.2 Protection and storage mechanisms In this subclause some basic approaches for realising CTS-FP integrity mechanisms are described. The mechanisms are divided into three groups. One group targets the protection of data that is stored In a static or semi-static way in re-programmable non-volatile memory. The second group targets timer values that change frequently. A third group targets physical protection aspects. E.6.2.1 Static or semi static values Data that is stored permanently or changes seldomly are either stored on the FP-SIM (KOP,, KiFP, IFPSI), or might be stored in write-once memory cells (Ka), the place of storage could be defined. Thus some form of physical security is necessary. Furthermore, specific standards in term of technology (e.g. NIST FIPS1-40-1) can be used. E.6.2.2 Timers If timer stored values can be accessed (e.g. when they are stored in physically accessible E2PROM) they can be protected in the same spirit as static data but the mechanism should be tailored for frequent update of the values to be protected. Alternatively, these values could be stored in the main processor chip. E.6.2.3 Physical protection Physical protection should prevent that it being easy to reprogram (flash) memory with CTS-FP system software through direct physical access to the memory chip or the physical exchange critical hardware components. It should also protect electrical sensing mechanisms against obvious attacks, e.g., by resetting components. E.7 Type approval issues The test houses cannot perform a security evaluation of a CTS-FP to verify if the CTS-FP meets the requirements on security. However, each CTS-FP comes with a set of cryptographic mechanisms that may effect ordinary type approval procedures. There should be no bypass mechanisms to critical security mechanisms for such type approval procedures. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 97 (GSM 03.20 version 7.2.0 Release 1998) E.8 Security information to be stored in the entities of the CTS This clause gives an overview of the security related information and the places where this information is stored in the CTS. The entities of the CTS where security information is stored are: - CTS home location register (CTS-HLR); - CTS service node (CTS-SN); - CTS authentication centre (CTS-AuC); - CTS fixed part equipment (CTS-FPE); - FP-SIM card; - CTS mobile equipment (CTS-ME); - MS-SIM card. E.8.1 Entities and security information E.8.1.1 CTS-HLR The CTS-HLR stores permanently: - The IFPSI; - The authentication key KiFP. The CTS-HLR receives and stores (possibly after processing): - The mobile equipment identity IMEI; - The IFPEI. E.8.1.2 CTS-SN The CTS-SN receives and stores possibly after processing: - KOP associated to a given IFPSI; - Subscription timers; - RAND value associated to an authentication and key generation procedure; - SRES the result of the authentication procedure; - The B5, B6 algorithms. E.8.1.3 CTS-AuC In the CTS authentication centre are implemented: - The authentication algorithm A3; - The key generation algorithm A8. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 98 (GSM 03.20 version 7.2.0 Release 1998) E.8.1.4 CTS Fixed Part Equipment (CTS-FPE) The CTS-FPE stores permanently: - The encryption algorithm A5/2. The CTS-FPE generates and stores: - The CTS authentication key Ka; - The CTSMSI; - The ciphering key Kc. The CTS-FPE receives and stores (possibly after processing): - The mobile equipment identity IMEI; - The IMSI. The CTS-FPE stores for each CTS-MS/CTS-FP pair a record of data which is needed for access on the CTS Radio Interface. The records are stored as a linear fixed file (see GSM 11.11) and contain: - The authentication key Ka; - The CTSMSI; - The IMSI; - Other, non security relevant information, which are related to a CTS-MS/CTS-FP pair. The structure of the linear fixed file is shown in figure E11: Index (Record Number) Linear fixed file with one record for each CTS-MS/CTS-FP pair (Read/Write) 1 Ka[1], CTSMSI[1], IMSI[1], other data [1] 2 Ka[2], CTSMSI[2], IMSI[2], other data [2] . . . . N Ka[n], CTSMSI[n], IMSI[n], other data [n] Figure E11: Storage of CTS-MS/CTS-FP pair related data on the CTS-FPE The number of records is defined at subscription time and thus determines the number of CTS-FP, a CTS-MS can be enrolled to. E.8.1.5 Fixed Part SIM card (FP-SIM) The FP-SIM includes specific information for CTS purpose. - The IFPSI; - The KiFP; - The KOP; - The list of PLMNs whose subscriber can roam onto the CTS-FP. E.8.1.6 CTS Mobile Equipment (CTS-ME) E.8.1.7 Mobile Station SIM card (MS-SIM) The MS-SIM is a normal GSM SIM card as defined in GSM 11.11 that includes any information for CTS purpose. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 99 (GSM 03.20 version 7.2.0 Release 1998) The MS-SIM stores for each CTS-MS/CTS-FP pair a record of data which is needed for access on the CTS Radio Interface. The records are stored as a linear fixed file (see GSM 11.11) and contain: - the authentication key Ka; - the CTSMSI; - the IFPEI; - other, non security relevant information, which related to a CTS-MS/CTS-FP pair. The structure of the linear fixed file is shown in the figure E12. Index (Record Number) Linear fixed file with one record for each CTS-MS/CTS-FP pair (Read/Write) 1 Ka[1], CTSMSI[1], IFPEI[1], IFPSI[1],other data [1] 2 Ka[2], CTSMSI[2], IFPEI[2], IFPSI[2],other data [2] . . . . N Ka[n], CTSMSI[n], IFPEI[n], IFPSI[n], other data [n] Figure E12: Storage of CTS-MS/CTS-FP pair related data on the CTS-ME The number of records is definedby the mobile manufacturer and thus determines the number of CTS-FP, a CTS-MS can enroll onto. E.9 External specification of security related algorithms This annex specifies the cryptological algorithms and algorithms which are needed to provide the various security features and mechanisms defined in the CTS service description. The following algorithms are considered; - Algorithm A5/2: Ciphering/deciphering algorithm; - Algorithm B1: Ciphering key generation algorithm - Algorithm B2: Authentication key generation algorithm - Algorithm B3: Authentication algorithm - Algorithm B4: Authentication algorithm - Algorithm B5: Message authentication algorithm used for CTS-FP authentication - Algorithm B6: Message authentication algorithm used for signature authentication The A5/2 is specified in GSM 03.20 Annex C. The external specification of the algorithms B1, B2, B3, B4, B5, B6 is defined below. The internal specification is managed by SAGE. E.9.1 Algorithm B1 E.9.1.1 Purpose The B1 algorithm is used to generate the ciphering key Kc from the two random challenges CH1 and the authentication key Ka which is derived from Ka. Location: CTS-ME, CTS-FPE ETSI ETSI TS 100 929 V7.2.0 (1999-11) 100 (GSM 03.20 version 7.2.0 Release 1998) E.9.1.2 Implementation and operational requirements The two input parameters Ka, CH1 and the output parameter Kc of the algorithm shall use the following formats: Ka CH1 Kcx B1 Figure E13: The ciphering key generator B1 - Input 1: Bit string of length |Ka| = 128 bits; - Input 2: Bit string of length |CH1| = 128 bits; - Output: Bit string of length |Kc| = 64 bits. The calculation time of B1 shall not exceed 200 ms. E.9.2 Algorithm B2 E.9.2.1 Purpose The algorithm B2 is used to generate: - The authentication key Ka; - The initial authentication key. This authentication key generation and usage is part of the initialisation method using the CTS Radio Interface. Location: CTS-ME, CTS-FPE E.9.2.2 Implementation and operational requirements The three input parameters FPAC , RIMS , RIFP, and the output parameterKa of the algorithm shall use the following formats: FPAC RIFP Ka B2 RIMS Figure E14: The key generation algorithm B2 - Input 1: Bit string of length |FPAC| respective bit string of length |FPAC| = 128 bit; - Input 2: Bit string of length |RIMS| respective bit string of length |RIMS| = 64 bit; - Input 3: Bit string of length |RIFP| respective bit string of length |RIFP| = 64 bit; - Output: Bit string of length |Ka| = 128 bit. The calculation time of the B2 algorithm shall not exceed 250 ms. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 101 (GSM 03.20 version 7.2.0 Release 1998) E.9.3 Algorithms B3 and B4 E.9.3.1 Purpose The B3 and B4 algorithms are used to perform the mutual authentication via a challenge-response scheme. Location: CTS-ME, CTS-FPE. E.9.3.2 Implementation and operational requirements The two input parameters Ka and CH1 respective CH2 and the output parameter (X)RES1 respective (X)RES2 of the algorithm shall use the following formats: Ka CH1 (X)RES1 B3 Ka CH2 (X)RES2 B4 Figure E15: The response generation by B3 and B4 - Input 1: Bit string of length |Ka| = 128 bit; - Input 2: Bit string of length |CH1| respective bit string of length |CH2| = 128 bit; - Output: Bit string of length |(X)RESP1| respective bit string of length |(X)RESP2| = 128 bit. The calculation time of B3 respective B4 shall not exceed 200ms for one operation. E.9.4 Algorithms B5 and B6 E.9.4.1 Purpose The B5 algorithm is used to perform CTS-FP authentication by the CTS-SN. The B6 algorithm is used by the CTS-FP to authenticate the signature issued by the CTS-SN. Location: CTS-FPE, CTS-SN. E.9.4.2 Implementation and operational requirements The two input parameters Kop and Data1 respective Data2 and the output parameter MAC1 respective MAC2 of the algorithm shall use the following formats: Kop Data1 MAC1 B5 Kop Data2 MAC2 B6 Figure E16: The response generation by B5 and B6 - Input 1: Bit string of length |Kop| = 128 bit; - Input 2: Bit string of length |Data1| respective bit string of length |Data2| = n octets; ETSI ETSI TS 100 929 V7.2.0 (1999-11) 102 (GSM 03.20 version 7.2.0 Release 1998) - Output: Bit string of length |MAC1| respective bit string of length |MAC2| = 64 bit. E.10 Coding of the FPAC and CTS-PIN The CTS-PIN is a local product key. It is initialised at manufacturer customisation. At CTS-FP reset, the PIN code value returns to initial manufacturer value.. The CTS-PIN can be modified by the user ; a pre-condition is to enter the old CTS-PIN. When remote MMI is used, attachment is performed on the MS/FP interface. The CTS-PIN cannot be de-activated. The number of tries is infinite and no blocking mechanism is applied. The FPAC is coded in 128 bits. The CTS-PIN is entered by the user of the CTS on the CTS-MS respective on the CTS-FP. The CTS-PIN is presented as a BCD number of decimal digits (0 - 9), each digit coded in four bits. The number of digits of the CTS-PIN is 8. The CTS-PIN is copied to the FPAC in order to perform the procedures for checking the CTS-PIN entered by the user. As the number of digits of the CTS-PIN is less than 32, the CTS-ME respective the CTS-FP shall pad the unused digits with « F » (hexadecimal presentation of 16) before it is copied to the FPAC. E.11 (informative annex) : Guidelines for generation of random numbers Both the CTS-MS and the CTS-FP must on occasions generate « random » numbers as inputs to security algorithms. Specifically : • the 128-bit input CH1 to the algorithms B1 and B3 is generated by the CTS-FP; • the 128-bit input CH2 to the algorithms B4 is generated by the CTS-MS; • the 64-bit input RIFP to the algorithm B2 is generated by the CTS-FP; • the 64-bit input RIMS to the algorithm B2 is generated by the CTS-MS. This section indicates the requirements on the « randomness » of these values. There are essentially two requirements : non-repetition (for CH1 to CH2, which are the generated many times) and unpredictability. Non-repetition of CH1 and CH2 : The probability that a new value CH1 (or CH2) is the same as any one particular previously generated value of CH1 (or CH2) should not be significantly greater than 2-128 . It is assumed that the number of values of CH1 (or CH2) generated by any CTS-FP will be much less than 2-128. Unpredictability of CH1 and CH2 : It is not necessary for every new CH1 (or CH2) to be « completely random », i.e. to be exactly likely to assume any possible value, independent of all previously generated values. However, the generation must not be easily predictable. Given all previously generated values of the CH1 (or CH2), the probability that a newly generated CH1 (or CH2) will assume any specific value should not be greater than 2-32. Unpredictability of RIFP and RIMS : The probability that RIFP (or RIMS) will assume any specific value should be not greater than 2-32. ETSI ETSI TS 100 929 V7.2.0 (1999-11) 103 (GSM 03.20 version 7.2.0 Release 1998) Annex F (informative): Status of Technical Specification GSM 03.20 Status of Technical Specification GSM 03.20 Date Version Information about changes Release 92 3.3.2 Last common Phase 1/Phase 2 version August 1992 4.0.0 Working version 4 (in CR 03.20-16 (category D) CR 03.20- 11 rev 2 (category B) / CR 03.20- 13 rev 2 (category B) CR 03.20- 14 (category C); all approved by SMG#03 October 1992 4.1.0 CR 03.20-15 rev 2 (category C) approved by SMG#04 January 1993 4.2.0 CR 03.20-17 rev 1 (category D) approved by SMG#05 Titles of annexes are added from version 3.3.0. Annexes are renamed to annex A, B and C (PNE!). Some figures in section 2 are renumbered. June 1993 4.2.1 CR 03.20-22 (category D) approved by SMG#07 October 1993 4.2.2 TS changed to prETS 300 534 April 1994 4.3.0 CR 03.20-24 r1 category F) CR 03.20-25 (category F) approved by SMG#10: TS frozen for Phase 2 by SMG#10 September 1994 4.3.1 ETS 300 534 1st edition February 1996 4.3.2 CR 03.20-A001 (category D) approved by SMG#17: 4.3.3 ETS 300 534 2nd edition Last common Phase 2/Phase 2+ version December 1996 5.0.0 GTS converted to draft prETR 300 929 for Release 96 February 1997 5.1.0 CR 03.20-A002 r1 (category F) CR 03.20-A004 r1 (category A) all approved by SMG#21: May 1997 5.0.1 ETS 300 929 first edition (version 5.1.0 already exists because of CRs approved by SMG#21 in Febr. 1997) August 1997 5.1.1 ETS 300 929 second edition October 1997 5.2.0 CR 03.20-A006 r1 (category B) (GPRS Release 97) CR 03.20-A007 r1 (category B) (GPRS Release 97); all approved by SMG#23 New section 2.3.9 related to GPRS and New normative annex D related to GPRS March 1998 6.0.0 ETS converted to version 6.0.0 because of GPRS Release 97 contents. July 1998 6.0.1 Specification published as TS 100 929 February 1999 7.0.0 CR 03.20-A010 (category B) (CTS Release 98) approved by SMG#28 New annex E related to CTS security July 1999 7.1.0 CR 03.20-A013, (CTS R98: Introduction of CTS-FP authentication and signature generation by CTS-SN) (categoy B) CR 03.20-A014, (CTS R98: CTS Security functions in case of license exempt frequencies) (category F) 03.20-A016 on Correction of the handling of the Ciphering Key Sequence Number (CKSN) (category F) November 1999 7.2.0 CR 03.20-A018; (Clarification on security triplet re-use conditions) (category F) Text and figures: Word 97 Stylesheet: etsiw_70.dot Rapporteur: Henri Gilbert ETSI ETSI TS 100 929 V7.2.0 (1999-11) 104 (GSM 03.20 version 7.2.0 Release 1998) History Document history V7.2.0 November 1999 Publication
|
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.