Method of securing exchanges between an applicant node and a destination node

Procedure for preserving the security of exchanges between a requesting node (N4) and a recipient node (N1), belonging these nodes to a network (2) communication, said method comprising the following steps performed by a firewall ( Serv): - a step (F1) of receiving a request (M1, M3) sent by the requesting node for an access to the recipient node; - A step (F7) sending a reply (M4) to the request, said response comprising an authentication test, addressed to the recipient node, and a session key, for use for exchanges between the applicant nodes and recipient, characterized in that it is at least a secret to be shared with at least one other applicant, different node of the session key associated with the recipient node, the response sent to the requesting node further comprises that secret.