Abstract: At least one expired decryption key intended to be used for asymmetrical decryption of encrypted data is recovered in a terminal after generation of a cryptographic encryption key/decryption key pair stored in a cryptographic medium such as a microchip card. The expired decryption key is stored in a database accessible to a user of the terminal and encrypted beforehand as a function of the new generated encryption key. In the terminal connected to the cryptographic medium, the encrypted expired encryption key is decrypted as a function of the decryption key stored in the cryptographic medium so that the encrypted data is decrypted as a function of the thus decrypted expired decryption key.

Abstract: In order to apply an electronic signature from a client station having authentication resources at a server, the following steps are carried out: the client station is authenticated at the server, thus establishing an authenticated communication channel; a private key/public key pair is generated at the client station; a signature certificate request generated by means of at least the public key is transmitted from the client station to the server via the authenticated channel; a signature certificate obtained in response to the request is returned via the authenticated channel; this certificate is verified at the client station; an electronic signature is calculated at the client station by means of the private key, after which this private key is destroyed; and the calculated signature is formatted with the aid of the signature certificate received via the authenticated channel.

Abstract: In order to apply an electronic signature from a client station having authentication resources at a server, the following steps are carried out: the client station is authenticated at the server, thus establishing an authenticated communication channel; a private key/public key pair is generated at the client station; a signature certificate request generated by means of at least the public key is transmitted from the client station to the server via the authenticated channel; a signature certificate obtained in response to the request is returned via the authenticated channel; this certificate is verified at the client station; an electronic signature is calculated at the client station by means of the private key, after which this private key is destroyed; and the calculated signature is formatted with the aid of the signature certificate received via the authenticated channel.