Abstract: The present invention relates to a method of authenticating a user of a communication terminal (1), on which at least one application (3) is installed, at a service (4) on a service server (2). The method is characterized in that an initiation request, which contains an address identifier of the communication terminal (1), is generated by the application (3) for initiating a session and is transmitted to the service server (2), the service server (2) after receipt of the initiation request automatically generates and transmits a request specific key (OTP) to the communication terminal (1) and the application (3) subsequently generates an access request in the session, wherein the application (3) integrates the received request specific key (OTP) automatically in the access request, and the access request is automatically transmitted from the communication terminal (1) to the service server (2) in the session. Furthermore a respective application (3) and a respective system are described.