To: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
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From: Thomas Voegtlin <thomasv@electrum.org>
Message-ID: <56a0c721-4bae-7b99-0ca3-d0834756fc31@electrum.org>
Date: Wed, 6 Sep 2017 11:26:48 +0200
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Subject: Re: [bitcoin-dev] Proposal: bip32 version bytes for segwit scripts
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On 05.09.2017 21:00, Kabuto Samourai wrote:
> 
> The Electrum approach is nice but may not go far enough, as xpub and zpub
> both list "P2PKH or P2SH." Why not expand the number of version prefixes to
> eliminate the ambiguity?
> 

I agree that this would make sense if we had done it from the start.
However, fixing that now might be difficult.

My "xyz" proposal extends the current format in a way that is very easy
to deploy, because existing software will require minimal changes.
However, if we eliminate the p2sh ambiguity now, wallets will need to
add extra safeguards, in order to prevent scenarios that are currently
allowed, and they will need to handle legacy xpub/xprv differently than
ypub and zpub. This would take much more time to deploy.

In addition, consensus might be more difficult to reach on that; I guess
not all developers will not agree that removing that ambiguity is
useful. Since there is an infinity of possible P2SH scripts, it will
never be possible to remove ambiguity from a master key associated to a
P2SH script. Thus, the benefit of separating P2SH from P2PKH is not as
strong.