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Consumable authentication protocol and system

  • US 7,197,642 B2
  • Filed: 02/15/2001
  • Issued: 03/27/2007
  • Est. Priority Date: 02/15/2000
  • Status: Expired due to Fees
First Claim
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1. A consumable authentication protocol for validating the existence of an untrusted authentication chip, the protocol includes the steps of:

  • calling a test function with a known incorrect value, one or more times, in a trusted authentication chip to generate an expected invalid response;

    in the event that the expected invalid response is not received considering the untrusted authentication chip to be invalid;

    otherwise, generating a secret random number and calculating a signature for the random number using a signature function, in the trusted authentication chip;

    encrypting the random number and the signature using a symmetric encryption function using a first secret key, in the trusted authentication chip;

    passing the encrypted random number and signature from the trusted authentication chip to an untrusted authentication chip;

    decrypting the encrypted random number and signature with a symmetric decryption function using the first secret key, in the untrusted authentication chip;

    calculating a signature for the decrypted random number using the signature function in the untrusted authentication chip;

    comparing the signature calculated in the untrusted authentication chip 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 authentication chip as part of the test function;

    encrypting the random number together with the data message by the symmetric encryption function using the second secret key, in the trusted authentication chip;

    comparing the two versions of the random number encrypted together with the data message using the second key, in the trusted authentication chip;

    in the event that the two versions match, considering the untrusted authentication chip and the data message to be valid;

    otherwise, considering the untrusted authentication chip and the data message to be invalid.

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