3GPP AKA authentication for cellular IoT

How AKA Works

3GPP AKA (Authentication and Key Agreement) is the foundation of cellular authentication. The protocol uses a shared root key K (Ki for legacy SIMs, K for 5G) stored in both the SIM and the home network. The authentication flow: when a device requests network access, the home network generates an authentication vector containing a random challenge RAND, an expected response XRES, encryption key CK, integrity key IK, and authentication token AUTN. The serving network forwards RAND and AUTN to the device. The SIM uses K and the challenge to compute its response RES and derive CK and IK. The…