Date: Tue, 21 Jul 2015 09:04:12 -0400
From: Peter Todd <pete@petertodd.org>
To: Jorge =?iso-8859-1?Q?Tim=F3n?= <jtimon@jtimon.cc>
Message-ID: <20150721130412.GA4551@savin.petertodd.org>
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	<55A9421B.6040605@jrn.me.uk> <55AC29DB.4060800@jrn.me.uk>
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Cc: bitcoin-dev@lists.linuxfoundation.org
Subject: Re: [bitcoin-dev] BIP 102 - kick the can down the road to 2MB
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On Tue, Jul 21, 2015 at 11:26:35AM +0200, Jorge Tim=F3n via bitcoin-dev wro=
te:
> I still disagree. Using height instead of time may make the
> implementation more complex by requiring some additional preparations
> but using height is in fact a simpler design. Why relay on clocks that
> we know will differ in different computers and places when we have a
> universal tick with every block?

The Bitcoin protocol fundementally uses time in a consensus-critical
manner anyway; miners vote on what time it is via the median time
mechanism.

Triggering events based on median time is compatable with consensus and
gives more human scale predictability as to when events may happen. In
addition the median time is guaranteed to be monotonic by the consensus
rules.

See the version bits proposal for an example of its use:

https://gist.github.com/sipa/bf69659f43e763540550#Specification


Having said that, in general triggering events without verifying a
supermajority of miner support can be very dangerous. Without miner
support the chain is insecure, and can be attacked. For instance a
blocksize limit increase that a majority of miners choose not to
implement raises huge risks of reorg for any miners who attempt to
create large blocks, and huge risks of payment reversal for any
merchants accepting transactions in such blocks. Note how with BIP102,
extending the original Bitcoin chain is inherently an attack on the
Garzik chain.

For that reason I think BIP102 is extremely poorly designed. I can only
conclude that Jeff Garzik is either deliberately trolling us and/or
manipulating discussion with a badly designed proposal that he doesn't
actually expect to be adopted verbatim, or is incompetent.

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