Patent ID: 7757084

Claim:
A method of validating a consumable authentication integrated circuit, the method comprising the steps of: calling, in a trusted authentication integrated circuit, a test function multiple times with a known incorrect value, the test function either generating an expected invalid response or not generating an expected invalid response and invalidating the consumable integrated circuit; if the invalid response is generated, in the trusted integrated circuit, generating a secret random number and calculating its signature using a signature function; encrypting, in the trusted integrated circuit, the random number and its signature using a symmetric encryption function with a first secret key; calling, in the consumable integrated circuit, a read function with the encrypted random number and signature from the trusted integrated circuit, the read function: decrypting the encrypted random number and signature using a symmetric decryption function with the first secret key; calculating a signature for the decrypted random number using the signature function; comparing the calculated and decrypted signatures; and if the signatures match, encrypting the decrypted random number and a data message read from the consumable integrated circuit using the symmetric encryption function with a second secret key; calling, in the trusted integrated circuit, the test function with the data message and the encrypted random number and data message from the consumable integrated circuit, the test function: encrypting the random number and the data message using the symmetric encryption function with the second secret key; comparing the encrypted random numbers and data messages; if they match, validating the consumable integrated circuit; and if they do not match, invalidating the consumable integrated circuit.