Abstract: The invention relates to a method for authenticating a user (10) at an entity (16), the method comprising the steps of detecting, by means of a contact module (20) of the entity (16), a contacting of the user (10) made in a browser of a terminal (12), and sending, by means of the contact module (20), a network address of an authentication module (24) of the entity (16) to a mobile device (14) of the user (10) in an authentication message, verifying the acceptability of an entity certificate of the authentication module (24) by means of the mobile device (14) based on the network address, and verifying acceptability of a user certificate of the mobile device (14) by means of the authentication module (24), and in case the entity certificate and the user certificate are acceptable, authenticating the user (10) at the entity (16) by establishing a communication channel (114, 120, 114, 120) between the mobile device (14) and the authentication module (24), whereas in case the entity certificate or the user certif