To: Daniel Weigl <Daniel.Weigl@mycelium.com>,
	Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
References: <5735D3A4.7090608@mycelium.com>
From: Jochen Hoenicke <hoenicke@gmail.com>
Message-ID: <573716D4.3000108@gmail.com>
Date: Sat, 14 May 2016 14:15:16 +0200
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Subject: Re: [bitcoin-dev] Bip44 extension for P2SH/P2WSH/...
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Am 13.05.2016 um 15:16 schrieb Daniel Weigl via bitcoin-dev:
> 
> With SegWit approaching it would make sense to define a common derivation scheme how BIP44 compatible wallets will handle P2(W)SH (and later on P2WPKH) receiving addresses.
> I was thinking about starting a BIP for it, but I wanted to get some feedback from other wallets devs first.
>

The discussion so far shows that starting a new BIP is a very good idea.
 Otherwise everyone would do it slightly different.

With P2(W)SH you mean P2WPKH embedded in P2SH, right?  P2WSH is
completely different and used for example for multisig.


> In my opinion there are two(?) different options: 

To summarize, option 1 means one account that supports both non-segwit
and segwit addresses.  With option 2 you have one p2pkh-only account and
one segwit-only account, which are completely separated.

I personally would vote for option 1.  Scanning twice the addresses can
be avoided with Aaron's trick.  The second disadvantage remains:

> 	-) If you have the same xPub/xPriv key in different wallets, you need to be sure both take care for the different address types

A non-segwit wallet would ignore all segwit outputs, which means that
the balance it shows is smaller (and it doesn't show transactions that
spend from previous segwit outputs).  I don't see that this can lead to
losing money except maybe when sweeping the account with a p2pkh-only
wallet and then throwing the xprv away.

Of course, you can also do option 2 and let it appear to the user as if
it was only one account, but what is the advantage over option 1 in that
case?  Also you need two xpubs to watch this joined account.

  Jochen