Method of extending the validity of a cryptographic certificate
First Claim
1. A method of extending the validity of a first cryptographic certificate derived by applying a first cryptographic function to a digital document, which method comprises:
- a) combining a digital representation of said document with a digital representation of said certificate; and
b) applying to the resulting combination during the valid term of said first certificate a different cryptographic function to thereby generate a second certificate attesting to the then current validity of said first certificate.
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Accused Products
Abstract
A cryptographic certificate attesting to the authenticity of original document elements, such as time of creation, content, or source, will lose its value when the cryptographic function underlying the certifying scheme is compromised. The present invention provides a means for extending the reliability of such a certificate by subjecting, prior to any such compromise, a combination of the original certificate and the document digital representation from which that certificate was derived to a scheme based on a different and ostensibly less vulnerable function. The new certificate resulting from this procedure extends the validity of the original authenticity by implacably incorporating the original certificate at a time when that certificate could only have been derived by legitimate means.
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Citations
20 Claims
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1. A method of extending the validity of a first cryptographic certificate derived by applying a first cryptographic function to a digital document, which method comprises:
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a) combining a digital representation of said document with a digital representation of said certificate; and b) applying to the resulting combination during the valid term of said first certificate a different cryptographic function to thereby generate a second certificate attesting to the then current validity of said first certificate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of certifying a digital representation of a document which comprises:
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a) generating a first certificate by applying to said digital representation at least a first cryptographic function; b) combining said first certificate with said digital representation; and c) generating a second certificate by applying to said combination at least one cryptographic function which is different from said first function. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification