Patent ID: 7210038

Claim:
A method for validating the untrusted integrated circuit, the method includes the steps of: generating a secret random number and calculating a signature for the random number using a signature function, in a trusted integrated circuit; encrypting the random number and the signature using a symmetric encryption function using a first secret key, in the trusted integrated circuit; passing the encrypted random number and signature from the trusted integrated circuit to an untrusted integrated circuit; decrypting the encrypted random number and signature with a symmetric decryption function using the first secret key, in the untrusted integrated circuit; calculating a signature for the decrypted random number using the signature function in the untrusted integrated circuit; comparing the signature calculated in the untrusted integrated circuit with the signature decrypted; in the event that the two signatures match, encrypting the decrypted random number together with a data message read from the untrusted chip by the symmetric encryption function using a second secret key and returning it together with the data message to the trusted integrated circuit; encrypting the random number together with the data message by the symmetric encryption function using the second secret key, in the trusted integrated circuit; comparing the two versions of the random number encrypted together with the data message using the second key, in the trusted integrated circuit; in the event that the two versions match, considering the untrusted integrated circuit and the data message to be valid; otherwise, considering the untrusted integrated circuit and the data message to be invalid.