Improving the Efficiency and Reliability of Digital Time-Stamping
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To establish that a document was created after a given moment in time, it is necessary to report events that could not have been predicted before they happened. To establish that a document was created before a given moment in time, it is necessary to cause an event based on the document, which can be observed by others. Cryptographic hash functions can be used both to report events succinctly, and to cause events based on documents without revealing their contents. Haber and Stornetta have proposed two schemes for digital time-stamping which rely on these principles [HaSt 91].
We reexamine one of those protocols, addressing the resource constraint required for storage and verification of time-stamp certificates. By using trees, we show how to achieve an exponential increase in the publicity obtained for each time-stamping event, while reducing the storage and the computation required in order to validate a given certificate.
We show how time-stamping can be used in certain circumstances to extend the useful lifetime of different kinds of cryptographic certifications of authenticity, in the event that the certifying protocol is compromised. This can be applied to digital signatures, or to time-stamping itself, making the digital time-stamping process renewable.
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- [BC+ 88]B. O. Brachtl, D. Coppersmith, M. M. Hyden, S. M. Matyas, Jr., C. H. W. Meyer, J. Oseas, Sh. Pilpel, and M. Shilling. Data authentication using modification detection codes based on a public one way encryption function. U.S. Patent No. 4,908,861, issued March 13, 1990.Google Scholar
- [BC+ 88]a(Cf. C. H. Meyer and M. Shilling, Secure program load with modification detection code. In Securicom 88: 6ème Congrès mondial de la protection et de la sécurité informatique et des communications, pp. 111–130 (Paris, 1988).)Google Scholar
- [Dam 87]I. Damgård. Collision-free hash functions and public-key signature schemes. In Advances in Cryptology—Eurocrypt ’87, Lecture Notes in Computer Science, Vol. 304, pp. 203–217, Springer-Verlag (Berlin, 1988).Google Scholar
- [HaSt 91]S. Haber, W. S. Stornetta, How to time-stamp a digital document, Journal of Cryptography, Vol. 3, No. 2, pp. 99–111 (1991). (Presented at Crypto ’90.)Google Scholar
- [Merk 80]R. C. Merkle, Protocols for public key cryptosystems. In Proc. 1980 Symp. on Security and Privacy, IEEE Computer Society, pp. 122–133 (Apr. 1980).Google Scholar
- [Riv 90]R. L. Rivest. The MD4 message digest algorithm. In Advances in Cryptology—Crypto ’90, Lecture Notes in Computer Science, Vol. 537 (ed. A. J. Menezes, S. A. Vanstone), pp. 303–311, Springer-Verlag (Berlin, 1991).Google Scholar