Patent ID: 7080256

Claim:
A method for authenticating a smart card (SIM) in a messaging network, wherein an algorithm and a secret key are stored in a smart card (SIM), whereby for authentication the network or a network component first transfers a random number (RAND) to the smart card, a response signal (SRES) is generated therefrom in the smart card by means of the algorithm and the secret key (K i ) and transmitted to the network or network component, characterized in that to form the response signal (SRES) the secret key (K i ) and the random number (RAND) are each split into at least two parts (K 1 , K 2 ; RAND 1 , RAND 2 ), one of the parts (RAND 1 , RAND 2 ) of the transferred random number (RAND) is encrypted with the aid of one or more parts (K 1 , K 2 ) of the secret key (K i ) by means of a one- or multistep algorithm.