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	<CAAcC9ys5sUxVfOjogFiF3gzk51D_L=QQkOYevTH=qbh_RkA3Hw@mail.gmail.com>
From: Bram Cohen <bram@bittorrent.com>
Date: Thu, 23 Feb 2017 15:13:43 -0800
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To: Chris Priest <cp368202@ohiou.edu>, 
	Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
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Subject: Re: [bitcoin-dev] A Better MMR Definition
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On Thu, Feb 23, 2017 at 9:53 AM, Chris Priest via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

>
> What problem does this try to solve, and what does it have to do with
> bitcoin?
>

I can't speak to MMRs (they look a bit redundant with the actual blockchain
history to my eye) but circling back to utxo commitments, the benefits are
that it enables actual proofs of non-fraud: You can prove the validity of a
block based on just the previous block (and maybe some previous headers
because of mining rewards) and can prove to a light node that a utxo hasn't
been spent yet.

A major factor in the way of getting utxo commitments in blocks is
performance. The txo set is of course vastly larger and more unwieldy. If
you make the utxo commitments trail by a small fixed number of blocks
(between 2 and 5) their latency problems shouldn't be a big deal as long as
the overall performance is good enough. My thesis is that with appropriate
format and implementation tricks it's possible to get performance good
enough to no longer be a gating factor to deployment.

Disappointingly there hasn't been any feedback about my implementation,
just discussion about merkle sets generally.

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<div dir=3D"ltr"><div class=3D"gmail_extra"><div class=3D"gmail_quote">On T=
hu, Feb 23, 2017 at 9:53 AM, Chris Priest via bitcoin-dev <span dir=3D"ltr"=
>&lt;<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" target=3D"_bl=
ank">bitcoin-dev@lists.linuxfoundation.org</a>&gt;</span> wrote:<br><blockq=
uote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc =
solid;padding-left:1ex"><div><div class=3D"h5"><br>
</div></div>What problem does this try to solve, and what does it have to d=
o with bitcoin?<br></blockquote><div><br></div><div>I can&#39;t speak to MM=
Rs (they look a bit redundant with the actual blockchain history to my eye)=
 but circling back to utxo commitments, the benefits are that it enables ac=
tual proofs of non-fraud: You can prove the validity of a block based on ju=
st the previous block (and maybe some previous headers because of mining re=
wards) and can prove to a light node that a utxo hasn&#39;t been spent yet.=
=C2=A0</div><div><br></div><div>A major factor in the way of getting utxo c=
ommitments in blocks is performance. The txo set is of course vastly larger=
 and more unwieldy. If you make the utxo commitments trail by a small fixed=
 number of blocks (between 2 and 5) their latency problems shouldn&#39;t be=
 a big deal as long as the overall performance is good enough. My thesis is=
 that with appropriate format and implementation tricks it&#39;s possible t=
o get performance good enough to no longer be a gating factor to deployment=
.=C2=A0</div><div><br></div><div>Disappointingly there hasn&#39;t been any =
feedback about my implementation, just discussion about merkle sets general=
ly.=C2=A0</div></div></div></div>

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