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From: Johnson Lau <jl2012@xbt.hk>
In-Reply-To: <201704202028.53113.luke@dashjr.org>
Date: Thu, 27 Apr 2017 03:31:38 +0800
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Message-Id: <06E90C6D-8B4C-40A7-8807-8811A27AE401@xbt.hk>
References: <201704202028.53113.luke@dashjr.org>
To: Luke Dashjr <luke@dashjr.org>
Cc: bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Segwit v2
Precedence: list

I prefer not to do anything that requires pools software upgrade or =
wallet upgrade. So I prefer to keep the dummy marker, and not change the =
commitment structure as suggested by another post.

For your second suggestion, I think we should keep scriptSig empty as =
that should be obsoleted. If you want to put something in scriptSig, you =
should put it in witness instead.

Maybe we could restrict witness to IsPushOnly() scriptPubKey, so miners =
can=E2=80=99t put garbage to legacy txs. But I think relaxing the =
witness program size to 73 bytes is enough for any purpose.

> On 21 Apr 2017, at 04:28, Luke Dashjr via bitcoin-dev =
<bitcoin-dev@lists.linuxfoundation.org> wrote:
>=20
> Since BIP 141's version bit assignment will timeout soon, and needing =
renewal,=20
> I was thinking it might make sense to make some minor tweaks to the =
spec for=20
> the next deployment. These aren't critical, so it's perfectly fine if =
BIP 141=20
> activates as-is (potentially with BIP 148), but IMO would be an =
improvement if=20
> a new deployment (non-BIP148 UASF and/or new versionbit) is needed.
>=20
> 1. Change the dummy marker to 0xFF instead of 0. Using 0 creates =
ambiguity=20
> with incomplete zero-input transactions, which has been a source of =
confusion=20
> for raw transaction APIs. 0xFF would normally indicate a >32-bit input =
count,=20
> which is impossible right now (it'd require a >=3D158 GB transaction) =
and=20
> unlikely to ever be useful.
>=20
> 2. Relax the consensus rules on when witness data is allowed for an =
input.=20
> Currently, it is only allowed when the scriptSig is null, and the =
scriptPubKey=20
> being spent matches a very specific pattern. It is ignored by =
"upgrade-safe"=20
> policy when the scriptPubKey doesn't match an even-more-specific =
pattern.=20
> Instead, I suggest we allow it (in the consensus layer only) in =
combination=20
> with scriptSig and with any scriptPubKey, and consider these cases to =
be=20
> "upgrade-safe" policy ignoring.
>=20
> The purpose of the second change is to be more flexible to any future=20=

> softforks. I consider it minor because we don't know of any =
possibilities=20
> where it would actually be useful.
>=20
> Thoughts?
>=20
> Luke
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