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Date: Sat, 16 May 2015 11:52:34 +0100
Message-ID: <CAE-z3OVNUyEwryKyAYvwokFdY6a8v7uDVRgnxGG7oSk29j86GA@mail.gmail.com>
From: Tier Nolan <tier.nolan@gmail.com>
Cc: Bitcoin Development <bitcoin-development@lists.sourceforge.net>
Content-Type: multipart/alternative; boundary=001a1133e3f61c6c3b051630c248
Subject: Re: [Bitcoin-development] [BIP] Normalized Transaction IDs
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On Sat, May 16, 2015 at 4:58 AM, Stephen <stephencalebmorse@gmail.com>
wrote:

> We should make sure to consider how BIP34 affects normalized transaction
> ids, since the height of the block is included in the scriptSig ensuring
> that the txid will be different. We wouldn't want to enable replay attacks
> in the form of spending coinbase outputs in the same way they were spent
> from a previous block.
>
> So maybe normalized txids should strip the scriptSigs of all transactions
> except for coinbase transactions? This seems to make sense, since coinbase
> transactions are inherently not malleable anyway.
>

That is a good point.  Since the point is the change is to use good
practice right back until the genesis block, maybe the scriptSig for
coinbases could be replaced by the height expressed as a varint.  That
means that all coinbases get a unique normalized txid.  The coinbases with
duplicate txids still wouldn't be spendable though.

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<div dir=3D"ltr"><br><div class=3D"gmail_extra"><br><div class=3D"gmail_quo=
te">On Sat, May 16, 2015 at 4:58 AM, Stephen <span dir=3D"ltr">&lt;<a href=
=3D"mailto:stephencalebmorse@gmail.com" target=3D"_blank">stephencalebmorse=
@gmail.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">We shoul=
d make sure to consider how BIP34 affects normalized transaction ids, since=
 the height of the block is included in the scriptSig ensuring that the txi=
d will be different. We wouldn&#39;t want to enable replay attacks in the f=
orm of spending coinbase outputs in the same way they were spent from a pre=
vious block.<br>
<br>
So maybe normalized txids should strip the scriptSigs of all transactions e=
xcept for coinbase transactions? This seems to make sense, since coinbase t=
ransactions are inherently not malleable anyway.<br></blockquote><div><br><=
/div><div>That is a good point.=C2=A0 Since the point is the change is to u=
se good practice right back until the genesis block, maybe the scriptSig fo=
r coinbases could be replaced by the height expressed as a varint.=C2=A0 Th=
at means that all coinbases get a unique normalized txid.=C2=A0 The coinbas=
es with duplicate txids still wouldn&#39;t be spendable though.<br></div></=
div></div></div>

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