A method for authenticating a mobile device includes: probing by the mobile device a fading channel which connects the mobile device to a first radio base station; determining a secret held in common with the first radio base station as a function of a physical property of the fading channel; storing the in-common secret; receiving a first request for the in-common secret from a second radio base station; and, in response to the first request, sending a proof of knowledge of the in-common secret to the second radio base station.