A method relates to receiving, by a processing device of an authentication server over a public network, an authentication request from a client device, the authentication request comprising a user identifier associated with first factor data, in which the first factor data comprises a password stored in a storage associated with the authentication server, calculating a generator value in view of the first factor data and a second factor data associated with the user identifier, and generating a session key in view of the generator value and a first public key received from the client device.