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From: Ian Kroozbi <kroozbi@gmail.com>
Date: Fri, 15 Nov 2019 16:29:01 -0600
Message-ID: <CALwkCwwGAwRE4vTPJJObr7q1GqS+d9==DBJc+yRZ+chC+_59SA@mail.gmail.com>
To: bitcoin-dev@lists.linuxfoundation.org
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Subject: [bitcoin-dev] PSBT_GLOBAL_XPUB: Version bytes in xpub
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What=E2=80=99s the rational for including the version bytes in the xpub in =
the
GLOBAL_XPUB field? This was briefly touched upon in an earlier email from
Stepan, but I don=E2=80=99t think it was every fully addressed.

I am not sure if we need the whole xpub or keeping chain_code and
> public_key is enough, but I would suggest to keep other data
> just in case. For example, keeping prefix that defines if the key is used
> for testnet or mainnet may be useful.
>

The version bytes seem to be superfluous data considering the transaction
format and the rest of the PSBT key-values are network agnostic. If we
wanted to attach network data to the PSBT then I think that would be better
served by using a new key.

There is also a potential issue where we could have conflicting versions on
different xpubs in the PSBT. If we remove the version bytes then we can
eliminate this possibility.

I haven=E2=80=99t formed an opinion on whether or not the other data outsid=
e of the
public key and chain code should be included, but I think it would be good
to discuss any rational for either including it or omitting it.

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<div dir=3D"ltr">What=E2=80=99s the rational for including the version byte=
s in the xpub in the GLOBAL_XPUB field? This was briefly touched upon in an=
 earlier email from Stepan, but I don=E2=80=99t think it was every fully ad=
dressed.<br><br><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0=
px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">I am not =
sure if we need the whole xpub or keeping chain_code and<br>public_key is e=
nough, but I would suggest to keep other data<br>just in case. For example,=
 keeping prefix that defines if the key is used<br>for testnet or mainnet m=
ay be useful.<br></blockquote><br>The version bytes seem to be superfluous =
data considering the transaction format and the rest of the PSBT key-values=
 are network agnostic. If we wanted to attach network data to the PSBT then=
 I think that would be better served by using a new key.<br><br>There is al=
so a potential issue where we could have conflicting versions on different =
xpubs in the PSBT. If we remove the version bytes then we can eliminate thi=
s possibility.<br><br>I haven=E2=80=99t formed an opinion on whether or not=
 the other data outside of the public key and chain code should be included=
, but I think it would be good to discuss any rational for either including=
 it or omitting it.</div>

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