The A3 algorithm is used by a GSM network to
authenticate a GSM mobile phone. The GSM A3 algorithm is
a one-way function implemented in the subscriber identity module (SIM).
roaming, the authentication center (AUC) of the home network provides
three security parameters (R, SRES, KC):
R: 128-bit random number
challenge, uniquely generated for each authentication
Ki: mobile’s fixed 128-bit secret
SRES: 32-bit response to challenge
Each GSM network is free to
choose its own A3 algorithm.
Other topics in our resources on GSM related to A3 Authentication include: