Patent ID: 7941672

Claim:
A method for generating a secret quantity based on an identifier of an individual integrated circuit, comprising combining a first digital word derived from a physical parameter network with a second word to form the secret quantity, the secret quantity being a word resulting from the combining, the second word being generated internal to the integrated circuit and stored in a non-volatile memory element of the integrated circuit, the physical parameter network measuring a fixed, single value of an electrical parameter of the integrated circuit, the measured value of the electrical parameter being sensitive to technological and manufacturing process variations of the integrated circuit, the measured value forming an identifier of the individual integrated circuit and being converted to the first digital word, revoking the secret quantity, generating a new second word, and combining the first digital word with the new second word to form a new secret quantity, the new secret quantity being a new word resulting from the combining, the new secret quantity being based on the new second word and on the fixed, single value of the electrical parameter of the integrated circuit, without replacing the integrated circuit to provide the new secret quantity, the new secret quantity being generated, after revoking the secret quantity, under control of a controller located within a secure area of the integrated circuit.