Authentication methods are used to authenticate, a device1 having an ESN1 (electronic serial number), a device2 having an ESN2, and/or a user of the devices. In one implementation, device1 receives the ESN2 in a near-field signal; derives an authentication result as a function of the ESN1 and ESN2; and sends the authentication result to an authenticator device to use in completing authentication. Authentication is confirmed when the device1 authentication result matches an authentication result independently generated by the authenticator device, which is provisioned with the ESN1 and ESN2. In a second implementation, device1 generates a RAND1 (random number) and sends the RAND1 to device2 over a near-filed link. An authenticator device confirms authentication upon receiving the same RAND1 from both device1 and device2.