Patent ID: 7296147

Claim:
An authentication system comprising a first device and a second device that perform authentication, a key registration apparatus, and a key re-registration apparatus, wherein the key registration apparatus receives input of a second device identifier unique to the second device, generates first key data from the second device identifier according to a key generation algorithm, and transmits the generated first key data to the first device, the first device receives the first key data, stores the received first key data, and authenticates the second device with use of the first key data, the first device further receives key revocation data that shows that the key registration apparatus is revoked and that has been generated by a management organization that manages revocation of key registration apparatuses, and revokes the first key data received from the revoked key registration apparatus, the first device further receives third key data and the second device identifier, stores the third key data and the second device identifier in correspondence, and authenticates the second device with use of the third key data, the second device stores a plurality of pieces of key data in advance, each piece of key data having been generated from the second device identifier according to a different key generation algorithm, selects one of the plurality of pieces of key data as second key data, the selected piece of key data having been generated according to the key generation algorithm, and is authenticated by the first device with use of the second key data, the second device receives the key revocation data, and revokes the second key data, the second device is further authenticated by the first device with use of fourth key data, the fourth key data having been selected from the plurality of pieces of key data and having been generated according to the same key generation algorithm as the third key data, and the key re-registration apparatus receives input of the second device identifier, generates the third key data from the second device identifier according to another key generation algorithm that is different than the key generation algorithm of the key registration apparatus, and transmits the generated third key data and the second device identifier to the first device.