Patent ID: 7649995

Claim:
A method for authenticating an access terminal having an R-UIM (Removable User Identity Module) card by using a CAVE (Cellular Authentication and Voice Encryption) algorithm, the method comprising steps of: extracting a RAND (random number) that is necessary for calculation of an authentication parameter from random values included in a CHAP (Challenge Handshake Authentication Protocol) Challenge message transmitted by an access network; instructing the R-UIM card to use the CAVE algorithm to calculate an authentication parameter with the RAND; placing the authentication parameter and identification of the access terminal in a CHAP Response message to be transmitted to the access network in response to the CHAP Challenge message, wherein the access terminal is a dual mode access terminal which is able to access heterogeneous communication systems respectively, and wherein the R-UIM card is commonly used for authenticating the access terminal in each of the heterogeneous communication systems.