Earlier I said I would forward to the list a posting I did on digital time-stamping, describing the Haber and Stornetta system. But I'll instead repost Stu Haber's comments, for more detail. --Tim
Date: Sun, 19 Jun 1994 21:52:29 -0700 From: stuarth@netcom.com (Stuart Haber) To: cypherpunks@toad.com Cc: stuarth@netcom.com Subject: coming soon: secure digital time-stamping in practice Sender: owner-cypherpunks@toad.com Precedence: bulk Status: RO
On Thursday, June 16 Tim May very nicely described a digital time-stamping scheme:
The canonical reference for digital timestamping is the work of Stu Haber and Scott Stornetta, of Bellcore. Papers presented at various Crypto conferences.
See below for pointers to the papers.
Their work involves having the user compute a hash of the document he wishes to be stamped and sending the hash to them, where they merge this hash with other hashes (and all previous hashes, via a tree system) and then they *publish* the resultant hash in a very public and hard-to-alter forum, such as in an ad in the Sunday New York Times.
In their parlance, such an ad is a "widely witnessed event," and attempts to alter all or even many copies of the newspaper would be very difficult. (In a sense, this WWE is similar to the "beacon" term Eric Hughes used recently in connection with timed-release crypto.)
Haber and Stornetta plan some sort of commercial operation to do this, and, last I heard, Stornetta was moving to the Bay Area (where else?) to get it started.
We do indeed plan to do just that. Bellcore has spun off a company, Surety Technologies, whose charter is to bring digital time-stamping into widespread use. Resisting the charms of the Bay Area, we decided to stay in New Jersey.
Instead of closing off our trees once a week and publishing their roots in the national edition of the Sunday New York Times, as we've been doing for over two years now (including this week: look for the Public and Commercial Notices towards the end of the main news section of today's paper -- on p. 30 if you get the NY-area edition), we are planning to close our trees at sub-minute intervals and make their roots widely available. By the end of the summer, we plan to have a service bureau (to build the trees) up and running, and client software available to access the service -- both for time-stamping documents and for validating (document, time-stamp certificate) pairs.
This service has not yet been tested in court, so far as I know.
Nor as far as I know. But we do plan to push this issue, on several legal and regulatory fronts, so as to enhance the legal acceptance of appropriately authenticated digital documents.
Here are the references: "How to Time-Stamp a Digital Document," S. Haber and W.S. Stornetta, Journal of Cryptology, vol. 3, pp. 99-111 (1991). A similar version appeared in the CRYPTO '90 Proceedings (Springer-Verlag LNCS, Vol. 537), pp. 437-455.
"Improving the Efficiency and Reliability of Digital Time-Stamping," D. Bayer, S. Haber, and W.S. Stornetta, Sequences II: Methods in Communication, Security, and Computer Science, ed. R.M. Capocelli, A. DeSantis, U. Vaccaro, pp. 329-334, Springer-Verlag (1993).
Stuart Haber | Surety Technologies provides Chief Scientist | Digital Notary(sm) service on the Internet. Surety Technologies, Inc. | General info: info@notary.com stuart@notary.com | (201) 993-8178, fax -8748
.......................................................................... Timothy C. May | Crypto Anarchy: encryption, digital money, tcmay@netcom.com | anonymous networks, digital pseudonyms, zero 408-688-5409 | knowledge, reputations, information markets, W.A.S.T.E.: Aptos, CA | black markets, collapse of governments. Higher Power: 2^859433 | Public Key: PGP and MailSafe available. "National borders are just speed bumps on the information superhighway."