TRANSMISSION OF A ONE-TIME KEY VIA INFRARED SIGNAL

Method and system for authenticating a user, by means of a temporarily used alien terminal 2, to a server 3 that can be reached via a network 4, particularly via the Internet, and that renders an online service accessible, wherein the user first of all authenticates himself to the server 3 using his own mobile terminal 1 by transmitting private access data for accessing the online service, wherein a secret session password is generated and is interchanged between the server 3 and the mobile terminal 1, wherein the session password is available to the server 3 and to the mobile terminal 1 after the interchange, wherein the session password is sent via an infrared link 5 from the mobile terminal 1 to the alien terminal 2 and from the latter via a data line 9 to the server 3, wherein the server 3 collates the session password obtained from the alien terminal 2 with the one that is available to it, wherein the server 3 permits the alien terminal 2 to access the online service if the collation is successful.