Patent ID: 7860487

Claim:
A method of unlocking a mobile terminal which, prior to being used, is assigned to a radio-communications network managed by an operator, and has stored in a memory a secret key resulting from applying an identity of the mobile terminal and a code of the operator to a security algorithm, the method comprising the following steps: prior to use of the mobile terminal in said network: storing in the memory the identity of the mobile terminal implementing the security algorithm in a security module, said security algorithm being unknown to the operator, and inserting the security module into a service entity that is managed by the operator and that communicates with the mobile terminal via at least the radio-communications network; and after a predetermined term of use of the mobile terminal in said network: in the security module, determining a secret key resulting from applying the terminal identity transmitted by the mobile terminal and the code of the operator to the security algorithm after an update request has been transmitted by the service entity, transmitting the enciphered determined secret key to the mobile terminal over the radio-communications network, and deciphering in the mobile terminal the enciphered secret key, and comparing the deciphered secret key with the stored secret key so as to unlock the mobile terminal when the compared secret keys are identical.