the uii of the tag the first rn 16 the security parameter the ch 16 and the encrypted newrn 16 and authentication data received at step s 220 the authentication server authenticates the tag on the basis of the message received from the reader s 240 first the authentication server searches the secret key k related to the uii and creates the session key from the first rn 16 and the k various algorithms may be used with respect to a method for creating the session key and in the embodiment of the present invention an example in which the tag and the reader use the same algorithm will be described however the present invention is not limited thereto after the authentication server creates the session key the authentication server decrypts the encrypted newrn 16 by using the session key to find a newrn 16 the authentication data is acquired by calculating xor the ch 16 and the found newrn 16 the authentication server compares the authentication data value received from the reader with an authentication data value acquired by itself as the comparison result if the two values are equal to each other it is determined that the authentication has succeeded and if the two values are different from each other it is determined that the authentication has failed.