[Cryptography] Proposal of a fair contract signing protocol

Adrian McCullagh amccullagh at live.com
Sun Jun 12 20:45:15 EDT 2016

>>> When a contract in digital from is to be signed online by Alice and
>>> Bob, an issue concerning the fairness of the signing process crops up
>>> as follows: If Alice first signs the document and sends it to Bob, it
>>> means she has committed to something (e.g. ready to purchase an article
>>> from Bob at a certain price). Bob can however, if he desires, at least
>>> to some extent arbitrarily delay giving his digital signature, i.e.
>>> having a period during which he has no corresponding commitment. This
>>> is obviously unfair and thus to be avoided, if possible.
>> Contracts as legal commitments are not operative until signed
>> by all parties.  Software commitments, when competently implemented,
>> are the same.
>> The fairness issue arises, to some extent, if there is a period
>> of time during which Bob may have the *option* of signing or not,
>> after Alice has already signed.

Dear All,

I do not understand the unfairness that is being discussed.  

>From a contract law position, any signed message from Alice is at most simply an offer which can either be accepted  or rejected by Bob.  There is no committment by either party at law until both are in agreement.  

Alice’s intention until Bob signs is actually irrelevant.  The issue is if Bob delays too long then at law there may be through conduct or lack thereof, a rejection of the offer sent by Alice, which will be decided on the reasonable person approach.  That is, what would a reasonable person viewing the activities of both parties conclude based upon the relevant actions or inactions of either party.

The law especially contract law has some very perculiar rules when dealing with non face to face communications; the postal rule in particular but this rule has rightly been cut down substantially over the years by the courts. 

In dealing with near instantaneous communications like email I do not see any unfairness.  

It is always possible for the contract to involve counterparts which involves two copies of the same document; one signed by Alice and the other signed by Bob.  The counterparts are exchanged so that each party then has 2 copies of the signed document with appropriate signatures included.

This type of contracting has been around for more than a century.

Am I missing something from this discussion.

Kind Regards

Dr. Adrian McCullagh
Ph.D. LL.B. (Hons) B.App. Sc. (Computing)

ODMOB Lawyers
Email: ajmccullagh57 at gmail.com
Email: amccullagh at live.com
MOB: +61 401 646 486
SKYPE: admac57

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