[3423] in cryptography@c2.net mail archive
RE: IP: State Govt Will Use Datakey Smart Cards
daemon@ATHENA.MIT.EDU (Arnold G. Reinhold)
Tue Oct 6 14:28:28 1998
In-Reply-To: <C54E91F42C11D2118CED0001FAF8DD668FF49B@sw720x017.visa.com>
Date: Tue, 6 Oct 1998 12:16:53 +0100
To: "Guthrie, Paul" <pguthrie@visa.com>, Ed Gerck <egerck@laser.cps.softex.br>,
Robert Hettinga <rah@shipwright.com>
From: "Arnold G. Reinhold" <reinhold@world.std.com>
Cc: cryptography@c2.net, dcsb@ai.mit.edu
At 8:14 AM -0700 10/6/98, Guthrie, Paul wrote:
>I do like Ed's breakdown of non-repudiation, but would like to add the
>following view:
>Technical repudiation (can repudiation be disproven with mathematical
>certainty)
...
I am not aware of any electronic signature scheme that can disprove
repudiation with "mathematical
certainty." All of the algorithms used in public key signature schemes that
I am aware of rely on mathematical assumptions that have never been proven.
Also all signature schemes rely on the user keeping his or her private key
secret. I don't see how one can prove that no one else knew a secret with
mathematical certainty. While this weakness can be dealt with for a regular
stream of transactions by using tamper resistant smart cards and assigning
some liability to the owner of a key who does not report its loss, large
transactions involving the general public should always require additional
corroboration beyond a single valid electronic signature. This might be an
MPEG of the signing, itself electronically time stamped and signed by a
witnessing notary.
Arnold Reinhold
Got crypto? http://ciphersaber.gurus.com
