Date: Fri, 21 Aug 2015 15:21:53 -0700
From: Peter Todd <pete@petertodd.org>
To: Tom Harding <tomh@thinlink.com>
Message-ID: <20150821222153.GD7450@muck>
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	<55D5AA8E.7070403@bitcoins.info> <55D67017.9000106@thinlink.com>
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In-Reply-To: <55D7575B.6030505@thinlink.com>
Cc: bitcoin-dev@lists.linuxfoundation.org
Subject: Re: [bitcoin-dev] Dynamically Controlled Bitcoin Block Size Max Cap
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On Fri, Aug 21, 2015 at 09:52:43AM -0700, Tom Harding wrote:
> On 8/20/2015 5:37 PM, Peter Todd wrote:
> > On Thu, Aug 20, 2015 at 05:25:59PM -0700, Tom Harding via bitcoin-dev w=
rote: >> I found that small miners were not at all disadvantaged by large
> blocks. >> > > You used 20% as the size of the large miner, with all the
> small miners > having good connectivity with each other. > > That is
> *not* the scenario we're worried about. The math behind the > issue is
> that the a miner needs to get their blocks to at least 33% of > hashing
> power, but more than that is unnecessary and only helps their >
> competition; you simulated 20%, which is under that threshold. Equally,
> > why are you assuming the small miner group is well connected to each >
> other? > > You probably didn't get any replies because your experiment
> is obviously > wrong and misguided, and we're all busy. >
>=20
> I gave the small miners collectively the same hashrate as the large
> miners in the original test.  I made them well-connected because
> everyone was well-connected intra-partition in the original test.
>=20
> I just varied one thing: the size of the miners.  This is a principle of
> experiment design, in science.
>=20
> Next you'll probably claim that second-order and cross-term effects
> dominate.  Maybe you can find the time to prove it.

This is a security issue: if you can find a likely scenario where the
system fails, that's a problem and we need to fix it.

You've taken the scenario where the system fails, and changed the
conditions to create a scenario where it works. That's not particularly
interesting or noteworthy.

To use a car analogy, Pieter Wuille has shown that the brake cylinders
have a fatigue problem, and if used in stop-and-go traffic regularly
they'll fail during heavy braking, potentially killing someone. You've
countered with a study of highway driving, showing that if the car is
only used on the highway the brakes have no issues, claiming that the
car design is perfectly safe.

--=20
'peter'[:-1]@petertodd.org
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