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From: Peter Todd <pete@petertodd.org>
To: Eric Lombrozo <elombrozo@gmail.com>
Cc: Bitcoin Dev <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] On the security of softforks
Date: Fri, 18 Dec 2015 04:18:45 -0800	[thread overview]
Message-ID: <20151218121845.GB22789@muck> (raw)
In-Reply-To: <em9d607452-50c0-4aa2-941e-7b637a287a70@platinum>

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On Fri, Dec 18, 2015 at 03:02:36AM +0000, Eric Lombrozo via bitcoin-dev wrote:
> First of all, that's an expensive beer!
> 
> Second of all, any consensus rule change risks non-full-validating
> or non-upgraded nodes seeing invalid confirmations...but assuming a
> large supermajority (i.e. > 95%) of hashing power is behind the new
> rule, it is extremely unlikely that very many invalid confirmations
> will ever be seen by anyone. The number of confirmations you require

To clarify, because the 95% of upgraded hashing power is creating valid
blocks from the point of view of the remaining 5%, that 95% majority
will continually reorg the 5% non-upgrading chain. This ensures that the
invalid chain remains short, and thus the # of invalid confirmations
possible remains small. For instance, the chance of getting one invalid
confirmation is 0.05^1 = 5%, two invalid confirmations 0.05^2 = 0.25%, three
0.05^3 = 0.01% etc.

Whereas with a hard fork, the 5% of miners will continue mining on their
own chain. While that chain's length will increase more slowly than
normal, the # of confirmations that non-upgraded clients will see on it
are unbounded.


Anyway, we should write this up as a BIP - there's been a tremendous
amount of misinformation, even flat out lies, floating around on this
subject.

-- 
'peter'[:-1]@petertodd.org
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  reply	other threads:[~2015-12-18 12:18 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-12-18  2:30 [bitcoin-dev] On the security of softforks Pieter Wuille
2015-12-18  2:47 ` Jonathan Toomim
2015-12-18  3:02   ` Eric Lombrozo
2015-12-18 12:18     ` Peter Todd [this message]
2015-12-19 15:48       ` Bryan Bishop
2015-12-18  3:10   ` jl2012
2015-12-18  5:32     ` Jorge Timón
2015-12-18  6:12   ` Anthony Towns
2015-12-19  1:36   ` Chris
2015-12-19 17:46   ` Andrew
2015-12-20  4:14   ` Rusty Russell
2015-12-20 19:16     ` jl2012

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