1. A method comprising: receiving identification information from a device; sending a first challenge to a device, the first challenge selected from a database associated with the received identification information, the database including a plurality of first challenges and a plurality of stored responses, each stored response associated with a first challenge; receiving a volatile response from the device, the volatile response determined in the device according to a sequence of challenge values generated in the device on the basis of the first challenge; and authenticating the device by comparing the received volatile response with the stored response associated with the sent first challenge.