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Authentication of consumable items

  • US 7,509,292 B2
  • Filed: 08/08/2003
  • Issued: 03/24/2009
  • Est. Priority Date: 07/15/1997
  • Status: Expired due to Fees
First Claim
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1. A method for validating the authenticity of an untrusted chip, the method includes the steps of:

  • a) generating a random number and applying an asymmetric encrypt function to the random number using a public key to produce a first variable;

    b) passing the first variable to the untrusted chip;

    c) receiving a third variable together with a data message read from the untrusted chip, the third variable having been generated, in the untrusted chip, by a process including;

    d) decrypting the first variable with an asymmetric decrypt function using a secret key to produce a second variable, the public and secret keys being a public-private key pair;

    e) applying the asymmetric encrypt function to the second variable together with the data message using the secret key to produce the third variable;

    f) decrypting the third variable with the asymmetric decrypt function and using the public key to generate a fourth variable and comparing the fourth variable with the generated random number and the received data message;

    g) in the event of a match, considering the untrusted chip and the data message to be valid;

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

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