[Cryptography] Proposal of a fair contract signing protocol

[Miles Fidelman]

>>>>>> Here is Mok-Kong’s problem statement:
>>>>>>
>>>>>>> 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, to 
>>>>>>> some
>>>>>>> extent delay giving his digital signature and thus have a certain
>>>>>>> finite time interval during which he has no corresponding 
>>>>>>> commitment.
>>>>>>> This is obviously unfair and hence to be avoided, if possible.


It occurs to me that there's something funny about the original problem 
statement.  I'm wracking my brains for a use case.  In the real world

> Bob can however, if he desires, to some
> extent delay giving his digital signature and thus have a certain
> finite time interval during which he has no corresponding commitment.
> This is obviously unfair and hence to be avoided, if possible. 
This is not how things work.

Contract formation tends to fall into several categories, each of which 
has sequencing and timing considerations:

- Formal offer/accept sequencing (e.g., when buying a house). Generally, 
this involves sequential actions/committments:
-- formal offer - the offerer makes a commitment that's good until 
accepted/rejected or times out
-- formal acceptance - the seller accepts (or rejects) the offer - 
generally, a contract exists upon acceptance, usually subject to 
completion of some actions within a period of time - at this point, the 
seller can't change their mind and accept a higher offer
-- the paperwork is simply ratification, after-the-fact
-- legally, the contract exists when the offer is formally accepted

- Negotiated contracts of various sorts:
- It's a sequential process by it's very nature - offer, counter-offer, 
proposed edits, etc.
- In most cases, there are revised copies of documents going back and 
forth, until the last party agrees to the other party's (parties') edits 
- typically by simply signing the document and returning it for 
counter-signature
- Again, there's a sequential nature to it

Gambling of various sorts:
- bets are placed, up to a time window (e.g., at a horse race, a 
Roulette table, a lottery ticket)
- effectively, a bunch of contracts come into existence as each bet is 
placed (the house is obligated to pay off, based on the results of the 
event)

In the case of the original problem statement, I'm having a hard time 
finding where there's any kind of issue to be addressed in the first place:

> 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 has, presumably, offered an article for sale, or Alice has requested 
a quote.  Depending on the circumstances, that may create a contractual 
relationship.  (E.g., when a store advertises an item for sale, at a 
price, for a time - they're legally obligated to deliver.)

> Bob can however, if he desires, to some
> extent delay giving his digital signature and thus have a certain
> finite time interval during which he has no corresponding commitment.
> This is obviously unfair and hence to be avoided, if possible. 

In the case of an item offered for sale, as in a store, Bob is 
contractually committed at the time of making an offer.  Signatures 
(digital or otherwise) don't apply.

In the case of a bidding situation - like offering a house for sale, Bob 
has the final word - he can accept or reject all offers.  Alice is 
committed when she makes the offer, Bob is committed LATER, when he 
accepts the offer.  Acceptance of one (of several) offers makes it a 
contract (and can be made verbally).  Details of the purchase & sale 
agreement are worked out later.

Delays and steps are generally built into the process, sometimes with 
firm deadlines ("offers will be accepted until midnight on <date>", 
"this offer is good for 90 days").

It's not clear at all that there's any advantage, or unfairness involved 
in Bob having an ability to delay affixing a signature (digital or 
otherwise) to the final document.  (Which is different than any 
unfairness, or imbalance of power, that stems from who has the last word 
in a negotiation process.)

---
It's kind of hard debating a solution to a problem that may not actually 
exist.

Miles Fidelman



-- 
In theory, there is no difference between theory and practice.
In practice, there is.  .... Yogi Berra