Abstract: A method for backing a user secret and recovering a user secret. A set of mandatory trustees possessing a public key and a set of non-mandatory trustees possessing a public key are determined. A predetermined limit value of a number of partitions necessary for recovering the secret is selected by the user. A number of primary partitions equal to the number of mandatory trustees is generated in response to the determination that the set of non-mandatory trustees is empty. A number of primary partitions equal to the number of mandatory trustees plus one is generated in response to the determination that the set of non-mandatory trustees is not empty. Each partition is encrypted using the public key of the corresponding trustee and each encrypted partition is stored in a server.

Abstract: A method for authenticating a device comprising a processor and a smart card. A user unlocks the smart card using a PIN code. A secret key Kc of the smart card and the PIN code of the smart card is transmitted to the processor. The processor performs a cryptographic calculation using a secret key Kp of the processor, the PIN code, and Kc. A pattern is generated from the cryptographic calculation by the processor and transmitted to the user. The pattern generated by the device is compared to a pattern memorized by the user.