From: Rusty Russell <rusty@rustcorp.com.au>
To: Gavin Andresen <gavinandresen@gmail.com>, Gregory Maxwell <greg@xiph.org>
In-Reply-To: <CABsx9T1vBRMYm6rLuqzvOxD0eABE4saF44JzZjMF3iUU==Nz0Q@mail.gmail.com>
References: <CAAS2fgRwfQNYxCmDPAnVudyAti9v8PPXQjxe9M13pmrFxKcSCQ@mail.gmail.com>
	<CABsx9T1vBRMYm6rLuqzvOxD0eABE4saF44JzZjMF3iUU==Nz0Q@mail.gmail.com>
User-Agent: Notmuch/0.20.2 (http://notmuchmail.org) Emacs/24.5.1
	(x86_64-pc-linux-gnu)
Date: Sat, 05 Dec 2015 09:13:16 +1030
Message-ID: <871tb16diz.fsf@rustcorp.com.au>
MIME-Version: 1.0
Content-Type: text/plain
Cc: Bitcoin Dev <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Blockchain verification flag (BIP draft)
Precedence: list

Gavin Andresen via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org>
writes:
> Overall, good idea.
>
> Is there a write-up somewhere describing in detail the 'accidental selfish
> mining' problem that this mitigates? I think a link in the BIP to a fuller
> description of the problem and how validation-skipping makes it go away
> would be helpful.
>
> RE: which bit to use:  the draft versionbits BIP and BIP101 use bit 30; to
> avoid confusion, I think it would be better to use bit 0.

Yes, BIP9 need to be adjusted (setting bit 30 means BIP9 counts it as a
vote against all softforks).  BIP101 uses bits 0,1,2 AFAICT, so perhaps
start from the other end and use bit 29?  We can bikeshed that later
though...

> I agree with Jannes Faber, behavior with respect to SPV clients should be
> to only tell them about fully validated headers.

A delicate balance.  If we penalize these blocks too much, it's
disincentive to set the bit.  Fortunately it's easy for SPV clients to
decide for themselves, I think?

Cheers,
Rusty.