10.4 GSM Auth

10.4 GSM Auth

1. Algorithms

   • Two Main Algorithms often combined into a single algorithm
     • A3 for Authentication
     • A8 for encryption key generation = Kc
     • Located in both SIM and Home Users NW
     • Standardisation of A3/A8 not required, operators can chose their own
   • COMP 128
     • Weak algor thats suceptible to allow Ki to be exposed with enough effort

2. Auth Security Issues

   • Communications are carried over core NW shared by operators
     • Use of IPSEC to secure comms between different NW operators Networks
     • Historically a trusted NW using SS7 Protocols
   • AuC requires logical and Physical protection
     • DB of Ki's stored in AUC
     • Access must be restricted
     • Ki's transported from SIM manufactured to NW operator in encrypted form