Electronic signature method, program and server for implementing the method

A computer program product on a recordable medium, comprising instructions for controlling a client station having authentication resources with respect to an electronic signature assistance server, said instructions including:

• instructions for generating a private key/public key pair after the establishment of an authenticated channel between the client station and said server;
• instructions for transmitting to the server, via the authenticated channel, a request for a signature certificate generated by means of at least the public key, said request providing to the server information pertaining to at least the public key and excluding the private key;
• instructions for receiving from the server, via the authenticated channel, a signature certificate obtained in response to said request;
• instructions for calculating a cryptographic signature by means of the private key, and then for destroying the private key;
• and instructions for formatting the calculated signature with the aid of the signature certificate received via the authenticated channel.

An electronic signature assistance server, comprising means of authenticating a client station to establish an authenticated communication channel with said client station, means for obtaining a signature certificate in response to a request received from the client station via the authenticated channel and for transmitting said certificate to the client station via the authenticated channel, and means for downloading to the client station a program written in a mobile code language, including instructions for controlling, at least partially, the execution of the following operations by the client station:

• generation of a private key/public key pair at the client station after the establishment of the authenticated channel;
• transmission to the server, via the authenticated channel, of a request for a signature certificate generated by means of at least the public key, said request providing to the server information pertaining to at least the public key and excluding the private key;
• reception, via the authenticated channel, of the signature certificate transmitted by the server in response to said request;
• calculation of a cryptographic signature at the client station by means of the private key, followed by destruction of the private key;
• and formatting of the calculated signature with the aid of the signature certificate received via the authenticated channel.