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Date: Tue, 19 May 2015 10:13:17 +0100
Message-ID: <CAE-z3OXC-uCYQmhGJd2ZVfLrEbAZVhEz0ejkbwmcRgK3kbjSrg@mail.gmail.com>
From: Tier Nolan <tier.nolan@gmail.com>
Cc: Bitcoin Development <bitcoin-development@lists.sourceforge.net>
Content-Type: multipart/alternative; boundary=001a11432f14934b4505166bb898
Subject: Re: [Bitcoin-development] [BIP] Normalized Transaction IDs
Precedence: list

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On Tue, May 19, 2015 at 9:28 AM, Christian Decker <
decker.christian@gmail.com> wrote:

> Thanks Stephen, I hadn't thought about BIP 34 and we need to address this
> in both proposals. If we can avoid it I'd like not to have one
> transaction hashed one way and other transactions in another way.
>

The normalized TXID cannot depend on height for other transactions.
Otherwise, it gets mutated when been added to the chain, depending on
height.

An option would be that the height is included in the scriptSig for all
transactions, but for non-coinbase transctions, the height used is zero.

I think if height has to be an input into the normalized txid function, the
specifics of inclusion don't matter.

The previous txid for coinbases are required to be all zeros, so the
normalized txid could be to add the height to the txids of all inputs.
Again, non-coinbase transactions would have heights of zero.


> Is there a specific reason why that was not chosen at the time?
>

I assumed that since the scriptSig in the coinbase is specifically intended
to be "random" bytes/extra nonce, so putting a restriction on it was
guaranteed to be backward compatible.

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<div dir=3D"ltr"><div class=3D"gmail_extra"><div class=3D"gmail_quote">On T=
ue, May 19, 2015 at 9:28 AM, Christian Decker <span dir=3D"ltr">&lt;<a href=
=3D"mailto:decker.christian@gmail.com" target=3D"_blank">decker.christian@g=
mail.com</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote" style=
=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir=
=3D"ltr"><span style=3D"font-size:13.1999998092651px;line-height:19.7999992=
370605px">Thanks Stephen, I hadn&#39;t thought about BIP 34 and we need to =
address this in both proposals.=C2=A0</span><span style=3D"font-size:13.199=
9998092651px;line-height:19.7999992370605px">If we can avoid it I&#39;d lik=
e not to have one transaction hashed one way and other transactions in anot=
her way.</span></div></blockquote><div><br></div><div>The normalized TXID c=
annot depend on height for other transactions.=C2=A0 Otherwise, it gets mut=
ated when been added to the chain, depending on height.<br><br></div><div>A=
n option would be that the height is included in the scriptSig for all tran=
sactions, but for non-coinbase transctions, the height used is zero.<br><br=
></div><div>I think if height has to be an input into the normalized txid f=
unction, the specifics of inclusion don&#39;t matter.<br></div><div><br></d=
iv><div>The previous txid for coinbases are required to be all zeros, so th=
e normalized txid could be to add the height to the txids of all inputs.=C2=
=A0 Again, non-coinbase transactions would have heights of zero.<br></div><=
div>=C2=A0</div><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8e=
x;border-left:1px #ccc solid;padding-left:1ex"><div dir=3D"ltr"><div><span =
style=3D"font-size:13.1999998092651px;line-height:19.7999992370605px">Is th=
ere a specific reason why that was not chosen at the time?<br></span></div>=
</div></blockquote><div><br></div><div>I assumed that since the scriptSig i=
n the coinbase is specifically intended to be &quot;random&quot; bytes/extr=
a nonce, so putting a restriction on it was guaranteed to be backward compa=
tible.<br></div><div>=C2=A0</div></div></div></div>

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