Quote from: trentzb on September 10, 2012, 01:31:27 AM

Give us the answer Stephen!!

Ha, I have only questions.

Well, actually I have scenarios and have no solution to offer.

Take the current lawsuit against Bitcoinica. How do the plaintiffs prove they sent even a single satoshi to Bitcoinica?

The areas where a payment protocol might be used theoretically applies to nearly every transaction but practically that need doesn't arise very often. It definitely isn't needed for buying a donut:
- http://www.youtube.com/watch?v=X53ksjejmns

I probably don't need a digitally signed payment request from Amazon because if their payment page didn't acknowledged my payment my next action is to contact their support. If their system is compromised where I get a fake payment acknowledgement they'll know about the problem long before I notice that nothing showed at my door.

But for transactions where where there is a time component, such as where the payment creates or extinguishes a debt, that's where in practice this protocol becomes more needed.

If I send payment to be applied to my credit card balance, I want to be able to prove they got the payment. That's when I'm going to want them to give me a signed message that not only says what Bitcoin address to send my payment to but the account number that the payment will be applied to as well.

With the blockchain providing the proof that payment was made, this signed payment request from before I pay is all I need then to later prove that I made the payment.

Quote from: Gavin Andresen on September 10, 2012, 12:22:11 AM

We need a payment protocol with non-repudiation built in.

See https://gist.github.com/2217885 for a multisig version (the singlesig version is simpler, but the merchant <-> customer communication will be the same).

From a cursory look into e-signatures it took just minutes to conclude one thing ... what a mess! So even though you and I know that nobody other than the holder of the private key for a Bitcoin address could have produced a signed message, would having that even help the plaintiffs one iota in a lawsuit such as the one referenced above?

There are standards for e-signing that are enforceable but these standards aren't universal around the world, and they can vary state-to-state in the U.S. even. So it is possible that even if Bitcoin supported this protocol, those needing e-signature would probably implement it outside of Bitcoin in the manner needed for the relevant jurisdiction(s).

That being said, if there were a protocol built in and it were to become generally adopted, it would probably find itself becoming a legally recognized method shorly after as well.