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Date: Mon, 16 Jun 2014 08:09:01 -0700
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From: Daniel Rice <drice@greenmangosystems.com>
To: Mike Hearn <mike@plan99.net>
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Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>,
	Lawrence Nahum <lawrence@greenaddress.it>
Subject: Re: [Bitcoin-development] instant confirmation via payment protocol
 backwards compatible proto buffer extension
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If you're hoping the instant providers list won't need to scale then you're
essentially saying that we need a solution to the double spend problem.
That is a good point. Double spends are one of the biggest issues remaining
in the protocol. I've seen so many people talk about bad experiences trying
to spend Bitcoin at a restaurant and waiting an hour for confirmations.
This entire BIP extension is a band aid for double spends. If double spends
are not resolved, there will be a million instant providers in the long run
and if double spends are resolved then this BIP extension is completely
unnecessary. Is solving doublespends off the table?

What if we solved doublespends like this: If a node receives 2 transactions
that use the same input, they can put both of them into the new block as a
proof of double spend, but the bitcoins are not sent to the outputs of
either transactions. They are instead treated like a fee and given to the
block solver node. This gives miners the needed incentive and tools to end
doublespends instead of being forced to favor one transaction over the
other.

I will write up a BIP if this seems like a practical approach.


On Mon, Jun 16, 2014 at 5:19 AM, Mike Hearn <mike@plan99.net> wrote:

> Looking good! I think this is much better than the original draft. Agree
> with Andreas that supports_instant is simply equal to
> (supported_instant_providers.size() > 1) which makes it redundant.
>
> Daniel is right that putting every possible provider in the Payment
> message might not scale in a world where there are huge numbers of
> instant-confirmation providers, but I'm hoping that we never have to scale
> to that size, because if we did that'd rather imply that Bitcoin has become
> useless for in-person payments without trusted third parties and avoiding
> that is rather the whole point of the project :) So I'm OK with some
> theoretical lack of scalability for now.
>
> A more scalable approach would be for the user to send the name and
> signature of their "instant provider" every time and the merchant just
> chooses whether to ignore it or not, but as Lawrence points out, this is
> incompatible with the provider charging extra fees for "instantness". But
> should we care? I'm trying to imagine what the purchasing experience is
> like with optional paid-for third party anti-double-spend protection.
> Ultimately it's the merchant who cares about this, not me, so why would I
> ever pay? It makes no sense for me to pay for double spend protection for
> the merchant: after all, I'm honest. This is why it doesn't make sense for
> me to pay miners fees either, it's the *receiver* who cares about
> confirmations, not the sender.
>
> So I wonder if a smarter design is that the user always submits the
> details of their instantness provider and we just don't allow for optional
> selection of instantness. I'm not sure that works, UX wise, so is having a
> less scalable design to support it worthwhile?
>
>
> ------------------------------------------------------------------------------
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> Find What Matters Most in Your Big Data with HPCC Systems
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<div dir=3D"ltr"><div>If you&#39;re hoping the instant providers list won&#=
39;t need to scale then you&#39;re essentially saying that we need a soluti=
on to the double spend problem. That is a good point. Double spends are one=
 of the biggest issues remaining in the protocol. I&#39;ve seen so many peo=
ple talk about bad experiences trying to spend Bitcoin at a restaurant and =
waiting an hour for confirmations. This entire BIP extension is a band aid =
for double spends. If double spends are not resolved, there will be a milli=
on instant providers in the long run and if double spends are resolved then=
 this BIP extension is completely unnecessary. Is solving doublespends off =
the table?</div>
<div><br></div><div>What if we solved doublespends like this: If a node rec=
eives 2 transactions that use the same input, they can put both of them int=
o the new block as a proof of double spend, but the bitcoins are not sent t=
o the outputs of either transactions. They are instead treated like a fee a=
nd given to the block solver node. This gives miners the needed incentive a=
nd tools to end doublespends instead of being forced to favor one transacti=
on over the other.</div>
<div><br></div><div>I will write up a BIP if this seems like a practical ap=
proach.</div></div><div class=3D"gmail_extra"><br><br><div class=3D"gmail_q=
uote">On Mon, Jun 16, 2014 at 5:19 AM, Mike Hearn <span dir=3D"ltr">&lt;<a =
href=3D"mailto:mike@plan99.net" target=3D"_blank">mike@plan99.net</a>&gt;</=
span> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex"><div dir=3D"ltr"><div class=3D"gmail_extra">=
Looking good! I think this is much better than the original draft. Agree wi=
th Andreas that supports_instant is simply equal to (supported_instant_prov=
iders.size() &gt; 1) which makes it redundant.</div>

<div class=3D"gmail_extra"><br></div><div class=3D"gmail_extra">Daniel is r=
ight that putting every possible provider in the Payment message might not =
scale in a world where there are huge numbers of instant-confirmation provi=
ders, but I&#39;m hoping that we never have to scale to that size, because =
if we did that&#39;d rather imply that Bitcoin has become useless for in-pe=
rson payments without trusted third parties and avoiding that is rather the=
 whole point of the project :) So I&#39;m OK with some theoretical lack of =
scalability for now. </div>

<div class=3D"gmail_extra"><br></div><div class=3D"gmail_extra">A more scal=
able approach would be for the user to send the name and signature of their=
 &quot;instant provider&quot; every time and the merchant just chooses whet=
her to ignore it or not, but as Lawrence points out, this is incompatible w=
ith the provider charging extra fees for &quot;instantness&quot;. But shoul=
d we care? I&#39;m trying to imagine what the purchasing experience is like=
 with optional paid-for third party anti-double-spend protection. Ultimatel=
y it&#39;s the merchant who cares about this, not me, so why would I ever p=
ay? It makes no sense for me to pay for double spend protection for the mer=
chant: after all, I&#39;m honest. This is why it doesn&#39;t make sense for=
 me to pay miners fees either, it&#39;s the <i>receiver</i>=C2=A0who cares =
about confirmations, not the sender.</div>

<div class=3D"gmail_extra"><br></div><div class=3D"gmail_extra">So I wonder=
 if a smarter design is that the user always submits the details of their i=
nstantness provider and we just don&#39;t allow for optional selection of i=
nstantness. I&#39;m not sure that works, UX wise, so is having a less scala=
ble design to support it worthwhile?</div>

</div>
<br>-----------------------------------------------------------------------=
-------<br>
HPCC Systems Open Source Big Data Platform from LexisNexis Risk Solutions<b=
r>
Find What Matters Most in Your Big Data with HPCC Systems<br>
Open Source. Fast. Scalable. Simple. Ideal for Dirty Data.<br>
Leverages Graph Analysis for Fast Processing &amp; Easy Data Exploration<br=
>
<a href=3D"http://p.sf.net/sfu/hpccsystems" target=3D"_blank">http://p.sf.n=
et/sfu/hpccsystems</a><br>_______________________________________________<b=
r>
Bitcoin-development mailing list<br>
<a href=3D"mailto:Bitcoin-development@lists.sourceforge.net">Bitcoin-develo=
pment@lists.sourceforge.net</a><br>
<a href=3D"https://lists.sourceforge.net/lists/listinfo/bitcoin-development=
" target=3D"_blank">https://lists.sourceforge.net/lists/listinfo/bitcoin-de=
velopment</a><br>
<br></blockquote></div><br></div>

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