Patent ID: 7991994

Claim:
An authentication method in a network including a secure server, an authentication server, and at least a terminal (HT) which hosts an personal token (SE) said authentication method comprising; a. in the secure server, performing a calculation on the basis of a random (RAND) and a secret key thereby producing derived key material (Ck, Ik); b. sending said derived key material (Ck, Ik) together with said random and together with additional data (AUTN, XRES, MAC, SQN, Ak, AMF) from the secure server (SS) to the authentication server (AS); c. in said authentication server, modifying at least part of said additional data (MAC*, SQN*) by means of at least part of said derived key material (Ck, Ik); d. sending said additional data (AUTN, AUTN*, XRES, MAC, SQN, Ak, AMF, Mac*, SQN*) and said random (RAND) through the hosting terminal to said personal token; e. in the personal token, performing a calculation based on the received random (RAND) for re-computing said at least part of said derived key material (Ck, Ik) as used in the authentication server for modifying said part of the additional data; f. in the token, using said re-computed at least part of the derived key material for interpreting the modified part of the received additional data.