Signalling Data Confidentiality – Encryption

Signalling Data Encryption

• Signalling data encryption provides confidentiality for
user identities across air interface
• Applied to selected fields of signalling messages
including:
• International Mobile Equipment Identity (IMEI)
• International Mobile Subscriber Identity (IMSI)
• Calling subscriber directory number (mobile terminating calls)
• Called subscriber directory number (mobile originated calls)
• These fields are not protected on initial connection
• Does not provide for end-to-end encryption

The purpose of signalling data encryption is to ensure the confidentiality of user-related
signalling data which is exchanged between MSs and BTSs by preventing its availability or
disclosed to unauthorised individuals, entities or processes.
When used, this feature applies on selected fields of signalling messages which are exchanged
between MSs and BTSs base stations. The following signalling information elements related
to the user are protected whenever used after initial connection establishment:
· International Mobile Equipment Identity (IMEI).
· International Mobile Subscriber Identity (IMSI).
· Calling subscriber directory number (mobile terminating calls).
· Called subscriber directory number (mobile originated calls).
Note that on initial connection establishment, the signalling information elements (protocol
discriminator, connection reference, message type and MS identities IMSI, TMSI or IMEI) are
not protected.

Summary

This section has covered the following aspects of
GSM security:
• User Identity Confidentiality
• Authentication
• User Data Confidentiality
• Signalling data Confidentiality