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Date: Wed, 27 May 2015 12:11:26 +0200
Message-ID: <CANEZrP0QMHp9PwBr=ekkujtA+=LXbgiL4xkXRSmcOGqaLJEp0g@mail.gmail.com>
From: Mike Hearn <mike@plan99.net>
To: Mark Friedenbach <mark@friedenbach.org>
Content-Type: multipart/alternative; boundary=047d7b5d34fa4324d705170d7716
Cc: Bitcoin Development <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] Consensus-enforced transaction
 replacement via sequence numbers
Precedence: list

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>
> Sequence numbers appear to have been originally intended as a mechanism
> for transaction replacement within the context of multi-party transaction
> construction, e.g. a micropayment channel.
>

Yes indeed they were. Satoshis mechanism was more general than micropayment
channels and could do HFT between any set of parties.


> As it happens, this cannot be made safe in the bitcoin protocol as
> deployed today, as there is no enforcement of the rule that miners include
> the most recent transaction in their blocks.
>

Safe is relative - this is the same logic the original replace-by-fee
argument uses. There's no enforcement that miners use any particular
ordering of transactions.

As I believe out of all proposed protocols Satoshi's is still the most
powerful, I would suggest that any change to the semantics on nSequence be
gated by a high bit or something, so the original meaning remains available
if/when resource scheduling and update flood damping are implemented. That
way people can try it out and if miners are breaking things too frequently
by ignoring the chronological ordering people can abandon protocols that
rely on it, and if they aren't they can proceed and benefit from the
greater flexibility.

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<div dir=3D"ltr"><div class=3D"gmail_extra"><div class=3D"gmail_quote"><blo=
ckquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left=
-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;paddi=
ng-left:1ex"><div dir=3D"ltr">Sequence numbers appear to have been original=
ly intended as a mechanism for transaction replacement within the context o=
f multi-party transaction construction, e.g. a micropayment channel. </div>=
</blockquote><div><br></div><div>Yes indeed they were. Satoshis mechanism w=
as more general than micropayment channels and could do HFT between any set=
 of parties.</div><div>=C2=A0</div><blockquote class=3D"gmail_quote" style=
=3D"margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(20=
4,204,204);border-left-style:solid;padding-left:1ex"><div dir=3D"ltr">As it=
 happens, this cannot be made safe in the bitcoin protocol as deployed toda=
y, as there is no enforcement of the rule that miners include the most rece=
nt transaction in their blocks.<br></div></blockquote><div><br></div><div>S=
afe is relative - this is the same logic the original replace-by-fee argume=
nt uses. There&#39;s no enforcement that miners use any particular ordering=
 of transactions.</div><div><br></div><div>As I believe out of all proposed=
 protocols Satoshi&#39;s is still the most powerful, I would suggest that a=
ny change to the semantics on nSequence be gated by a high bit or something=
, so the original meaning remains available if/when resource scheduling and=
 update flood damping are implemented. That way people can try it out and i=
f miners are breaking things too frequently by ignoring the chronological o=
rdering people can abandon protocols that rely on it, and if they aren&#39;=
t they can proceed and benefit from the greater flexibility.</div><div><br>=
</div></div></div></div>

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