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Date: Sun, 28 Jun 2015 17:51:54 +0200
Message-ID: <CABm2gDq31doL62a2HwY8kSuB1zPMhz6OPR0Qa9X7thbZBdNTOQ@mail.gmail.com>
From: =?UTF-8?B?Sm9yZ2UgVGltw7Nu?= <jtimon@jtimon.cc>
To: Mark Friedenbach <mark@friedenbach.org>
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Cc: bitcoin-dev@lists.linuxfoundation.org
Subject: Re: [bitcoin-dev] Original Vision
Precedence: list

On Sun, Jun 28, 2015 at 5:23 PM, Mark Friedenbach <mark@friedenbach.org> wr=
ote:
> UTXO commitments are the nominal solution here. You commit the validator =
state in each block, and then you can prove things like a negative by refer=
encing that state commitment. The trouble is this requires maintaining a ha=
sh tree commitment over validator state, which turns out to be insanely exp=
ensive. With the UTXO commitment scheme (the others are not better) that en=
ds up requiring 15 - 22x more I/O during block validation. And I/O is prese=
ntly a limiter to block validation speed. So if you thought 8MB was what bi=
tcoin today could handle, and you also want this commitment scheme for frau=
d proofs, then you should be arguing for a block size limit decrease (to 50=
0kB), not increase.

What about a TXO and a STXO O(1)-append commitment? That shouldn't
cause that much overhead and you can build UTXO from TXO - STXO.
I know it's not so efficient in some respects but it scales better I think.