Subject: Re: [bitcoin-dev] A Better MMR Definition

From: Bram Cohen <[email-masked]>
Date: Thu, 23 Feb 2017 15:13:43 -0800

On Thu, Feb 23, 2017 at 9:53 AM, Chris Priest via bitcoin-dev <
[email-masked]> 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.