Sender and receiver non-repudiation (fwd)

[Jim Choate]

---------- Forwarded message ----------
Date: Tue, 3 Jul 2001 17:48:31 +0300 (EET DST)
From: Helger Lipmaa <helger at tml.hut.fi>
To: Panayiotis Kotzanikolaou <pkotzani at unipi.gr>
Cc: cryptography at wasabisystems.com
Subject: Re: Sender and receiver non-repudiation

On Tue, 3 Jul 2001, Panayiotis Kotzanikolaou wrote:

> The problem in this scheme is that Bob signs and sends the proof after
> he has received M. Bob can receive M and never send a receipt.
>
> By using a trusted delivery service, it is easy to produce
> non-repudiation evidence both for the sender and the receiver.
> Is there any cryptographic protocol that "forces" Bob to produce
> non-repudiation evidence during execution?

Answering only to this concrete question: the kind of things you want are
accomplished by contract signing protocols. A few recent papers:

Optimistic Protocols for Fair Exchange(N. Asokan, Matthis Schunter,
Michael Waidner, 1996)

Optimal Efficiency of Optimistic Contract Signing(Birgit Pfitzmann,
Matthias Schunter, Michael Waidner, PODC 98)

Optimistic synchronous multi-party contract signing(N. Asokan, Birgit
Baum-Waidner, Matthias Schunter, and Michael Waidner, dec 1998)

Asynchronous protocols for optimistic fair exchange(N. Asokan, Victor
Shoup, Michael Waidner, may 1998)

Optimistic asynchronous multi-party contract signing(Birgit Baum-Waidner
and Michael Waidner, nov 1998)

Optimistic fair exchange of digital signatures(N. Askon, Victor Shoup,
Michael Waidner, oct 1999)

Abuse-free Optimistic Contract Signing(Juan Garay, Markus Jakobsson, Phil
MacKenzie, CRYPTO '99)

Abuse-free Multi-party Contract Signing( Juan Garay, Phil MacKenzie, DISC
'99)

Provable Secure Certified Mail(Birgit Pfitzmann, Matthias Schunter,
Michael Waidner, 2000)

Analysis of Abuse-Free Contract Signing( Vitaly Shmatikov, John C.
Mitchell, 2000)

06/23/01 Optimistic Asynchronous Multi-Party Contract Signing with Reduced
Number of Rounds(Birgit Baum-Waidner, eprint 2001/044)

(you can find links to them at
http://www.tml.hut.fi/~helger/crypto/link/protocols/contract.html)

Answering more generally: it does not help you to get non-repudiation.
Nothing does, unless Bob is able to prove that you signed this document
consiously, being sober, and generally, that you MEANT to sign it.

Helger




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