Patent ID: 8606318

Claim:
A method for determining validity of a mobile subscriber identifier in a mobile communication terminal, the method comprising: storing, respectively, a first and a second temporary identifier assigned from a network in a memory and a Subscriber Identification Module (SIM) card of the terminal; when a network authentication event occurs, comparing the first temporary identifier stored in the memory with the second temporary identifier stored in the SIM card and determining whether the second temporary identifier in the SIM card has a value within a valid range; when it is determined that the first and second temporary identifiers do not have a value within the valid range, performing an authentication with the network using an International Mobile Subscriber Identity (IMSI); initializing the second temporary identifier stored in the SIM card to a preset value when the first temporary identifier in the memory and the second temporary identifier in the SIM card, respectively, are not the same as a result of the comparison; and determining to transmit the second initialized temporary identifier to the network.