Patent ID: 8812840

Claim:
A method of authentication in which there is pre-authentication of a first device ( 10 ) by a second device ( 1 ) to determine whether the authentication of the second device by the first device is to be completed, the first device and the second device communicating with each other via a wireless connection, the method comprising the steps of: receiving by the second device an authentication request from the first device entity; verifying by the second device, in response to the authentication request, whether the first device is in a transmission field of the second device, wherein the verifying step comprises: sending, by the second device ( 1 ), a first challenge value (c); receiving ( 23 ), by the first device ( 10 ), a second challenge value (c′) corresponding to the first challenge value (c) sent by the second device ( 1 ); applying, by the first device ( 10 ), to the received second challenge value (c′) a non-secret predefined transformation (g) to obtain a first transformed value (r) and then sending ( 24 ) the first transformed value (r) obtained; receiving ( 24 ′), by the second device, a third transformed value (r′) corresponding to the first transformed value (r) sent by the first device; comparing ( 25 ′), by the second device, the received third transformed value (r′) to a second transformed value (r″) obtained by applying the predefined transformation (g) to the first challenge value (c) sent by the second device and considering the verifying to have succeeded only if the difference between the second transformed value (r″) obtained and the received third transformed value (r′) is below a predefined threshold (m); and the second device ( 1 ) proceeds with authentication in response to the authentication request from the first device ( 10 ) only if the verifying by the second device has succeeded.