Patent ID: 6876747

Claim:
A method for providing security mobility between two cellular systems comprising: requesting access to a first cellular system by a mobile device; authenticating the mobile device by the first cellular system; generating at least one second ciphering key for a second cellular system, the at least one second ciphering key generated by an interoperability authentication center at the first cellular system and by the mobile device separately, the generating being performed concurrently with the authenticating; encrypting traffic between the mobile device and the first cellular system using at least one first ciphering key for the first cellular system; approving a handoff of the traffic of the mobile device from the first cellular system to the second cellular system; sending the at least one second ciphering key from the first cellular system to the second cellular system; and performing handoff by the mobile device from the first cellular system to the second cellular system, traffic between the mobile device and the second cellular system being encrypted using the at least one second ciphering key, wherein ciphering of the traffic is maintained during handoff, wherein the authenticating comprises: sending an authentication request including an International Mobile Subscriber Identity (IMSI) of the mobile device to the authentication center at the first cellular system; generating authentication vectors by the authentication center, the authentication vectors including at least a value and an encrypted version of the value; sending the value to the mobile device; encrypting the value at the mobile device to create a response and sending the response to the first cellular system; and comparing the response with the encrypted version at the first cellular system, the mobile device being authenticated if the response and the encrypted version are the same.