Method of authentication

A method of authenticating a user with a service, having the steps of:

• receiving with a host server a request for a unique code from the service over a first secure communication channel in response to the user requesting a session with the service on a first device, wherein the first device has previously been registered with the host server, and wherein the request for a unique code contains no registration credentials;
• generating with the host server the unique code and associating the unique code with a session-identifier, the session-identifier containing information relating to the code request;
• sending the unique code without the session-identifier from the host server to the service over the first secure communication channel, such that the unique code is presented to the first device by the service;
• the host server receiving from a verification application running on the first device the unique code and device-identifying information of the first device acquired by the verification application over a second secure communication channel;
• the host server using:
• the received unique code to retrieve the session-identifier, and
• the device-identifying information to retrieve associated user-identifying information stored on the host server;
• when the user is previously known to the service based on the user-identifying information received by the service from the host server, the host server sending the retrieved user-identifying information to the service over the first secure communication channel, such that the user is authenticated and granted the request for a session on the first device by the server and the first device receives data from the service as part of the session.