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From: Peter Todd <pete@petertodd.org>
Date: Wed, 30 Dec 2015 20:32:43 +0000
To: =?ISO-8859-1?Q?Emin_G=FCn_Sirer?= <el33th4x0r@gmail.com>
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	<bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] How to preserve the value of coins after a fork.
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On 30 December 2015 12:22:43 GMT-08:00, "Emin Gün Sirer" <el33th4x0r@gmail.com> wrote:
>On Wed, Dec 30, 2015 at 3:16 PM, Peter Todd <pete@petertodd.org> wrote:
>
>> Note how transaction malleability can quickly sabotage naive notions
>of
>> this idea.
>>
>
>Bitcoin-United relies on a notion of transaction equivalence that
>doesn't
>involve the transaction hash at all, so it should be immune to
>malleability
>issues and compatible with segwit.
>
From the post, two transactions are equal if they "consume the same
>inputs
>and result in the same outputs, not counting the miner fee. Simple
>pay-to-pubkey-hash and pay-to-script-hash transactions are
>straightforward.
>Multikey transactions are evaluated for equivalency by their inputs and
>outputs, so it is allowable for a 2-out-of-3 payment to be signed by
>one
>set of two keys on Dum and another set of two keys on Dee, as long as
>the
>transaction consumes the same coins and produces the same outputs. Not
>that
>we'll ever encounter such a case, but making this point helps
>pedagogically
>with getting across the notion of transaction equivalence. What counts
>are
>the consumed inputs and the destination and amounts of the outputs."

You seem to not be familiar with how multisig transactions on Bitcoin work - 99.9% of the time theyre hidden behind p2sh and there is no way to know what keys are involved. Equally, multisig is just one of many complex scripts possible.

Look into what a segwit transaction hashes - that's a better notion of non-malleable transaction. But even then lots of transactions are malleable, and its easy to trigger those cases intentionally by third parties.

Most likely any Bitcoin United scheme would quickly diverge and fail; much simpler and more predictable to achieve convincing consensus, e.g. via proof of stake voting, or Adam Bank's extension blocks suggestions. (or of course, not trying to force controversial forks in the first place)

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