New Protocol for Mutual Authentication in GSM Networks

How can mutual authentication be achieved in GSM networks without synchronization issues?

Is it possible to design a new protocol for mutual authentication between the Mobile Station (MS), Visitor Location Register (VLR), and Home Location Register (HLR) without introducing any synchronization problems?

Solution: New Protocol for Mutual Authentication

The new protocol allows mutual authentication between the Mobile Station (MS), Visitor Location Register (VLR), and Home Location Register (HLR) without introducing any synchronization issues. It relies on long-term shared secret keys and symmetric-key operations for authentication.

In order to achieve mutual authentication in GSM networks without synchronization issues, a new protocol has been designed. This protocol ensures that the Mobile Station (MS), Visitor Location Register (VLR), and Home Location Register (HLR) can authenticate each other without encountering any problems related to synchronization.

Registration and Key Establishment:

1. MS sends its identity (IMSI) to the VLR for registration.

2. VLR forwards the IMSI to the HLR to request the long-term secret key (Ki) associated with the MS.

3. HLR responds to VLR with the MS's long-term secret key (Ki).

Authentication Initiation:

4. When authentication is required, VLR generates a random number (RAND_VLR) and sends it to the MS.

Authentication at MS:

5. MS receives the RAND_VLR and uses it, along with Ki, to compute the expected authentication response (RES_MS) using a symmetric-key algorithm (e.g., AES) and sends it back to the VLR.

Authentication at VLR:

6. VLR, upon receiving RES_MS, performs the same computation using Ki and RAND_VLR to get the expected RES_VLR.

Mutual Authentication:

7. VLR generates a new random number (RAND_HLR) and sends it to the HLR along with the expected RES_VLR.

Authentication at HLR:

8. HLR, upon receiving RAND_HLR, uses Ki to compute the expected RES_HLR using the same symmetric-key algorithm.

Mutual Authentication Confirmation:

HLR compares the received RES_VLR from VLR with the locally computed RES_HLR. If they match, HLR confirms the mutual authentication.

Final Authentication:

10. HLR sends the expected RES_HLR back to VLR.

Completion of Authentication:

11. VLR compares the received RES_HLR with the locally computed RES_VLR. If they match, VLR confirms the mutual authentication.

Access Granted:

12. If the mutual authentication is successful, VLR allows the MS access to the network services.

This new protocol ensures mutual authentication between MS, VLR, and HLR while avoiding any synchronization issues. It relies solely on long-term shared secret keys and symmetric-key operations, making it suitable for practical implementation in GSM networks.