The Authentication center is a key component of the GSM (Global System for mobile communications). It validates any security information management (SIM) card attempting network connection. It also provides security to third parties. Each network SIM card is assigned with a unique key (Ki), the same Ki is present in the AUC. During the Authentication process, the Ki is used with the subscriber’s IMSI (International Mobile Subscriber Identity) number. This process begins when a subscriber requests a network signal. The encryption algorithm is known as A3.