Abstract: In the disclosed method, users are provided with sets of authentication codes, each set includes a secret, a private key container and a matching public key container, the private and public key container are generated from respectively a first string including a domain name of an authentication server system and a PKI private key and a second string including the same domain name and a matching PKI public key. Upon receipt on the authentication server system of the first strings as a result of a first user reading the respective private key container, an action definition procedure is performed in which the first user is requested to enter a secret of the same set of authentication codes. If a check returns a positive result, the first user can define a set of actions to be performed upon receipt of the second string belonging to the same set of authentication codes.