[Cryptography] Proposal of a fair contract signing protocol

[Ray Dillinger]

On 07/01/2016 02:27 PM, mok-kong shen wrote:

> If Bob chooses to go the first way, the protcol completes and the
> fiarness definiton applies. If Bob chooses to go the second way,
> the protocol never completes and, since the fairness definition
> only deals with a completed protocol, it has no chance of being
> considered at all.

If your fairness definition only deals with a completed
protocol, but one of the participants has the power to
stop the protocol short of completion, in possession of
the EXACT SAME evidence of the contract that they would
have had it been completed, and is able to PREVENT the
other from having such evidence - then your protocol
conforms to your fairness definition without being fair
in any meaningful way.

If we had the power to force people to *COMPLETE* protocols
then designing security and cryptography applications would
be easy.  We don't.

				Bear

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