!!! Overview
[{$pagename}] (AuC) is a [Global System for Mobile Communications] component to authenticate each [SIM] card that attempts to connect to the [GSM] core network (typically when the [Mobile Station] is powered on). 

Once the [authentication] is successful, the [Home Location Register] is allowed to manage the [SIM] and services described above. 

An [encryption] key is also generated that is subsequently used to [encrypt] all wireless communications ([voice], [SMS], etc.) between the [mobile Device] and the [GSM] core network.

If the [authentication] fails, then no services are possible from that particular combination of [SIM] card and [Mobile Network Operators] attempted. There is an additional form of [identification] check performed on the [IMEI] of the [mobile Device] described in the [EIR] section below, but this is not relevant to the [AuC] processing.

Proper implementation of security in and around the AuC is a key part of an operator's strategy to avoid SIM cloning.

The AuC does not engage directly in the authentication process, but instead generates data known as triplets for the MSC to use during the procedure. The security of the process depends upon a shared secret between the AuC and the [SIM] called the Ki. The Ki is securely burned into the [SIM] during manufacture and is also securely replicated onto the AuC. This Ki is never transmitted between the AuC and SIM, but is combined with the IMSI to produce a challenge/response for identification purposes and an encryption key called Kc for use in over the air communications.

!! More Information
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