Patent ID: 8188840

Claim:
An authenticating method, comprising: A) enabling a transponder to receive a read request that contains a first authentication code; B) enabling the transponder to extract the first authentication code from the read request; C) enabling the transponder to generate and wirelessly transmit a reply signal that contains the first authentication code extracted from the read request in step B), the transponder being authenticated based on the first authentication code contained in the reply signal transmitted; and D) enabling a reader to generate and wirelessly transmit the read request prior to step A), wherein, in this step D), the reader generates the first authentication code based on a first varying value, E) enabling the reader to receive the reply signal; F) enabling the reader to extract the first authentication code from the reply signal; G) enabling the reader to generate a second authentication code based on a second varying value; H) enabling the reader to obtain a difference between the first authentication code extracted thereby from the reply signal in step F) and the second authentication code generated thereby in step G); and I) enabling the reader to authenticate the transponder based on the difference obtained thereby in step H).