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From: Mark Friedenbach <mark@friedenbach.org>
Date: Sun, 14 Jun 2015 19:47:15 -0700
Message-ID: <CAOG=w-tJjzrR_REJOShULfSO=T3ueHko-oQHdhqMCdZD0G_BDA@mail.gmail.com>
To: Gregory Maxwell <gmaxwell@gmail.com>
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Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] [RFC] Canonical input and output ordering
 in transactions
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There's another important use case which you mentioned Greg, that also
requires special exemption: compact commitments via mid-state compression.

The use case is an OP_RETURN output sorted last, whose last N bytes are a
commitment of some kind. A proof of the commitment can then use mid state
compression to elide the beginning of the transaction.

How do you make a special exemption for this category of outputs? I can't
think of a very clean way of doing so that doesn't require an ugly
advertising of sort-order exemptions.

The fact that we have two different existing use cases which conflict with
soft-fork enforcement, I'm quiet concerned that there are either other
things we aren't thinking of or haven't invented yet which would be
affected.

On Sun, Jun 14, 2015 at 7:33 PM, Gregory Maxwell <gmaxwell@gmail.com> wrote:

> On Mon, Jun 15, 2015 at 2:29 AM, Rusty Russell <rusty@rustcorp.com.au>
> wrote:
> > The softfork argument I find the most compelling, though it's tempting
> > to argue that every ordering use (including SIGHASH_SINGLE) is likely
> > a mistake.
>
> Oh.
>
> Hm.
>
> It is the case that the generalized sighash flag design I was thinking
> about was actually completely neutral about ordering, and yet still
> replaced SINGLE.
>
> I need to think a bit on that.
>
>
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> Bitcoin-development@lists.sourceforge.net
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<div dir=3D"ltr"><div><div>There&#39;s another important use case which you=
 mentioned Greg, that also requires special exemption: compact commitments =
via mid-state compression.<br><br>The use case is an OP_RETURN output sorte=
d last, whose last N bytes are a commitment of some kind. A proof of the co=
mmitment can then use mid state compression to elide the beginning of the t=
ransaction.<br><br></div>How do you make a special exemption for this categ=
ory of outputs? I can&#39;t think of a very clean way of doing so that does=
n&#39;t require an ugly advertising of sort-order exemptions.<br><br></div>=
The fact that we have two different existing use cases which conflict with =
soft-fork enforcement, I&#39;m quiet concerned that there are either other =
things we aren&#39;t thinking of or haven&#39;t invented yet which would be=
 affected.<br></div><div class=3D"gmail_extra"><br><div class=3D"gmail_quot=
e">On Sun, Jun 14, 2015 at 7:33 PM, Gregory Maxwell <span dir=3D"ltr">&lt;<=
a href=3D"mailto:gmaxwell@gmail.com" target=3D"_blank">gmaxwell@gmail.com</=
a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"margin:0=
 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class=3D"">On =
Mon, Jun 15, 2015 at 2:29 AM, Rusty Russell &lt;<a href=3D"mailto:rusty@rus=
tcorp.com.au">rusty@rustcorp.com.au</a>&gt; wrote:<br>
&gt; The softfork argument I find the most compelling, though it&#39;s temp=
ting<br>
&gt; to argue that every ordering use (including SIGHASH_SINGLE) is likely<=
br>
&gt; a mistake.<br>
<br>
</span>Oh.<br>
<br>
Hm.<br>
<br>
It is the case that the generalized sighash flag design I was thinking<br>
about was actually completely neutral about ordering, and yet still<br>
replaced SINGLE.<br>
<br>
I need to think a bit on that.<br>
<div class=3D"HOEnZb"><div class=3D"h5"><br>
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