Abstract: A system for a second dynamic authentication of an electronic signature by a signing user of a document having signature keys located in a key container, using signer enrolment and signature applications connected to the server, wherein the system includes a secure hardware module to be connected to the signature server, including a system for building an activation challenge from a key identifier, and an initialisation password given by the signer, in order to issue the challenge to the signature server, which then requests a computing application to compute a one-time password to be sent to the signer.