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Date: Sun, 11 May 2014 21:41:04 -0700
From: Tom Harding <tomh@thinlink.com>
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Subject: Re: [Bitcoin-development] A statistical consensus rule for reducing
 0-conf double-spend risk
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Christophe Biocca wrote:

> The problem is that since the rule
> isn't enforceable, no miner will wait before mining on the longest
> chain (which is the rational move), and you're back to where we are
> now.

Back up to the miner who decided to include a "seasoned" double-spend in 
his block.  Let's say he saw it 21 seconds after he saw an earlier 
spend, and included it, despite the rule.

The expected cost of including the respend is any revenue loss from 
doing so: (total miner revenue of block)*(fraction of hashpower 
following the rule).  So today, if only 1% of hashpower follows the rule 
(ie a near total failure of consensus implementation), he still loses at 
least .25 BTC.

.25 BTC is about 1000x the typical "double-spend premium" I'm seeing 
right now.  Wouldn't the greedy-rational miner just decide to include 
the earlier spend instead?