Abstract: There is provided a method for authenticating a mobile device user against an authenticating system connected to a client computer accessible to said user. The authenticating system uses a communication channel to send to the client computer a logon screen. This logon screen contains a 2D-code embedding, a URL of the authenticating system and a challenge generated by the authenticating system. With a 2D-code reader in the user's mobile device the URL and the challenge are decoded. The user then inputs a password and a response to the challenge is computed. The response is sent together with the user ID to the authenticating system. The authenticating system is able to ascertain that the response to the challenge necessarily comes from the user thereby verifying his identity. Once the user is authenticated, the authenticating system pushes to the client computer (identified by the challenge) a welcome screen.

Abstract: The invention relates to a method for authenticating a user of a mobile device (10) against a remote authenticating system (30) which is connected to a client computer accessible to said user, which comprises: i—reading a 2D-code displayed to the client computer (40) by means of a 2D-code reader provided in said mobile device, a URL address of the authenticating system and a codified challenge generated by authenticating system being embedded in said 2D-code; ii—processing said codified challenge and computing a response to it using a personal secret, which is a string of characters univocally related to a user identifier (user ID) of said user of the mobile device and to a time stamp; iii—sending a message to the authenticating system which includes a tuple (100) whose elements are said user ID, the challenge and its response; iv—analyzing the tuple elements and determining the tuple is valid if the response to the challenge has been generated using the personal secret of the user whose user identifier is