Date: Wed, 21 Oct 2020 03:05:35 +0000
To: Rusty Russell <rusty@rustcorp.com.au>,
 Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
From: ZmnSCPxj <ZmnSCPxj@protonmail.com>
Reply-To: ZmnSCPxj <ZmnSCPxj@protonmail.com>
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Cc: John Barboza <johnbarboza@gmail.com>
Subject: Re: [bitcoin-dev] Progress on bech32 for future Segwit Versions
	(BIP-173)
Precedence: list


> Anecdata: c-lightning doesn't allow withdraw to segwit > 0. It seems
> that the contributor John Barboza (CC'd) assumed that future versions
> should be invalid:
>
> if (bip173) {
> bool witness_ok =3D false;
> if (witness_version =3D=3D 0 && (witness_program_len =3D=3D 20 ||
> witness_program_len =3D=3D 32)) {
> witness_ok =3D true;
> }
> /* Insert other witness versions here. */

I believe this is actually my code, which was later refactored by John Barb=
oza when we were standardizing the `param` system.

This was intended only as a simple precaution against creating non-standard=
 transaction, and not an assumption that future versions should be invalid.
The intent is that further `else if` branches would be added for newer witn=
ess versions and whatever length restrictions they may have, as the `/* Ins=
ert other witness versions here.  */` comment implies.

Regards,
ZmnSCPxj