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From: Tier Nolan <tier.nolan@gmail.com>
Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] Mechanics of a hard fork
Date: Thu, 7 May 2015 22:24:45 +0100	[thread overview]
Message-ID: <CAE-z3OVgX9S0sJqq-iFdkZn_wK-a=Vs4VpNwxpcagDEYFzNSDQ@mail.gmail.com> (raw)
In-Reply-To: <20150507200023.GI63100@giles.gnomon.org.uk>

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In terms of miners, a strong supermajority is arguably sufficient, even 75%
would be enough.

The near total consensus required is merchants and users.  If (almost) all
merchants and users updated and only 75% of the miners updated, then that
would give a successful hard-fork.

On the other hand, if 99.99% of the miners updated and only 75% of
merchants and 75% of users updated, then that would be a serioud split of
the network.

The advantage of strong miner support is that it effectively kills the fork
that follows the old rules.  The 25% of merchants and users sees a
blockchain stall.

Miners are likely to switch to the fork that is worth the most.  A mining
pool could even give 2 different sub-domains.  A hasher can pick which
rule-set to follow.  Most likely, they would converge on the fork which
paid the most, but the old ruleset would likely still have some hashing
power and would eventually re-target.

On Thu, May 7, 2015 at 9:00 PM, Roy Badami <roy@gnomon.org.uk> wrote:

> I'd love to have more discussion of exactly how a hard fork should be
> implemented.  I think it might actually be of some value to have rough
> consensus on that before we get too bogged down with exactly what the
> proposed hard fork should do.  After all, how can we debate whether a
> particular hard fork proposal has consensus if we haven't even decided
> what level of supermajority is needed to establish consensus?
>
> For instance, back in 2012 Gavin was proposing, effectively, that a
> hard fork should require a supermajority of 99% of miners in order to
> succeed:
>
> https://gist.github.com/gavinandresen/2355445
>
> More recently, Gavin has proposed that a supermoajority of only 80% of
> miners should be needed in order to trigger the hard fork.
>
>
> http://www.gavintech.blogspot.co.uk/2015/01/twenty-megabytes-testing-results.html
>
> Just now, on this list (see attached message) Gavin seems to be
> aluding to some mechanism for a hard fork which involves consensus of
> full nodes, and then a soft fork preceeding the hard fork, which I'd
> love to see a full explanation of.
>
> FWIW, I think 80% is far too low to establish consensus for a hard
> fork.  I think the supermajority of miners should be sufficiently
> large that the rump doesn't constitute a viable coin.  If you don't
> have that very strong level of consensus then you risk forking Bitcoin
> into two competing coins (and I believe we already have one exchange
> promissing to trade both forks as long as the blockchains are alive).
>
> As a starting point, I think 35/36th of miners (approximately 97.2%)
> is the minimum I would be comfortable with.  It means that the rump
> coin will initially have an average confirmation time of 6 hours
> (until difficulty, very slowly, adjusts) which is probably far enough
> from viable that the majority of holdouts will quickly desert it too.
>
> Thoughs?
>
> roy
>
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  reply	other threads:[~2015-05-07 21:24 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-05-07 20:00 [Bitcoin-development] Mechanics of a hard fork Roy Badami
2015-05-07 21:24 ` Tier Nolan [this message]
2015-05-07 21:42   ` Roy Badami
2015-05-07 21:49     ` Pieter Wuille
2015-05-07 22:08       ` Roy Badami
2015-05-08  2:16         ` Adam Back
2015-05-08  2:35         ` Pieter Wuille
2015-05-08  3:12           ` Cameron Garnham

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