Update app.py

app.py

@@ -26,14 +26,16 @@ def derive_key(custom_key, key_size):
     hasher = SHA256.new()
     hasher.update(custom_key.encode('utf-8'))
     full_hash = hasher.digest()
-    # Truncate to desired key size (16, 24, or 32 bytes)
-    return full_hash[:key_size // 8]
+    # Convert key_size to integer before division
+    return full_hash[:int(key_size) // 8]
 
 def encrypt_string(plain_text, key, key_size):
     """Encrypt a string using AES in CBC mode with specified key size."""
     try:
         if not plain_text:
             return "Error: Please provide text to encrypt."
+        if not key:
+            return "Error: Please provide a key."
         derived_key = derive_key(key, key_size)
         plain_text_bytes = plain_text.encode('utf-8')
         iv = get_random_bytes(AES.block_size)
@@ -49,6 +51,8 @@ def decrypt_string(encrypted_text, key, key_size):
     try:
         if not encrypted_text:
             return "Error: Please provide encrypted text."
+        if not key:
+            return "Error: Please provide a key."
         derived_key = derive_key(key, key_size)
         raw = base64.b64decode(encrypted_text)
         iv = raw[:AES.block_size]