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Date: Tue, 28 Apr 2015 14:53:58 +0200
Message-ID: <CABm2gDpsv8mp3hjMfT_okaMQmW4AmCiFAz43dBR1M-rzntqfSg@mail.gmail.com>
From: =?UTF-8?B?Sm9yZ2UgVGltw7Nu?= <jtimon@jtimon.cc>
To: Kalle Rosenbaum <kalle@rosenbaum.se>
Content-Type: text/plain; charset=UTF-8
Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] Proof of Payment
Precedence: list

Forget it, sorry, I misunderstood the proposal entirely, re-reading
with more care...

On Tue, Apr 28, 2015 at 2:41 PM, Kalle Rosenbaum <kalle@rosenbaum.se> wrote:
> Hi Jorge,
>
> I don't think I understand the question. Proof of Payment is used to prove
> that you have the credentials needed for a certain transaction. It does not
> care where in the blockchain the transaction is. Or if it's in the
> blockchain at all.
>
> /Kalle
>
> So at the low level, how does a "proof of payment" differ from just proving
> that a given transaction is in a given block (what SPV nodes take as proof
> of payment today)?
>
> On Apr 27, 2015 2:42 PM, "Kalle Rosenbaum" <kalle@rosenbaum.se> wrote:
>>
>> "Or a really high lock_time, but it would not make it invalid, just
>> delayed."
>>
>> Ok, this was a bad idea, since nodes would have to keep it in memory.
>> Please disregard that idea...
>>
>> Kalle
>>
>> Den 27 apr 2015 14:35 skrev "Kalle Rosenbaum" <kalle@rosenbaum.se>:
>> >
>> > >
>> > > Some more use cases might be:
>> > > Waiting in comfort:
>> > >  - Send a payment ahead of time, then wander over and collect the
>> > > goods
>> > > after X confirmations.
>> > >
>> > > Authorized pickup :
>> > >  - Hot wallet software used by related people could facilitate the use
>> > > of 1 of N multisig funds.  Any one of the N wallets could collect
>> > > goods
>> > > and services purchased by any of the others.
>> >
>> > I like this one, because it shows the power of reusing the transaction
>> > data structure.
>> >
>> > >
>> > > Non-monetary gifts:
>> > >  - Sender exports spent keys to a beneficiary, enabling PoP to work as
>> > > a
>> > > gift claim
>> > >
>> > > Contingent services:
>> > >  - Without Bob's permission, a 3rd party conditions action on a
>> > > payment
>> > > made from Alice to Bob.  For example, if you donated at least .02 BTC
>> > > to
>> > > Dorian, you (or combining scenarios, any of your N authorized family
>> > > members), can come to my dinner party.
>> >
>> > This is an interesting one.
>> >
>> > >
>> > > I tried out your demo wallet and service and it worked as advertised.
>> > >
>> > > Could the same standard also be used to prove that a transaction COULD
>> > > BE created?  To generalize the concept beyond actual payments, you
>> > > could
>> > > call it something like proof of payment potential.
>> >
>> > I guess it's possible, but we'd have to remove the txid from the output,
>> > since there is none. This is a way of saying "I'm in control of these
>> > addresses". The other party/parties can then verify the funds on the
>> > blockchain and watch those addresses for changes. Maybe there are some
>> > interesting use cases here. Ideas?
>> >
>> > >
>> > > Why not make these proofs permanently INVALID transactions, to remove
>> > > any possibility of their being mined and spending everything to fees
>> > > when used in this way, and also in cases involving reorganizations?
>> >
>> > Yes. Initially I thought it would be enough that the funds are already
>> > spent, but I think you're right here. Reorgs could be a problem. Worse, you
>> > also might want to prove 0-confirmation transactions, in which case it's a
>> > huge security problem. Someone might intercept the PoP and publish it on the
>> > bitcoin network, spending all the funds. But I still would like wallets to
>> > be able to build/verify PoPs with little or no modifications. Could we
>> > possibly change the version number on the PoP to something other than 1?
>> > Maybe 2^4-1? Or a really high lock_time, but it would not make it invalid,
>> > just delayed. Any suggestions here?
>> >
>> > >
>> > > I agree that PoP seems complementary to BIP70.
>> > >
>> > >
>> >
>> > Thank you very much for your comments!
>> >
>> > /Kalle
>>
>>
>>
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>