Message-ID: <558651FD.1010308@thinlink.com>
Date: Sat, 20 Jun 2015 22:56:13 -0700
From: Tom Harding <tomh@thinlink.com>
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To: Eric Lombrozo <elombrozo@gmail.com>
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Cc: bitcoin-development@lists.sourceforge.net
Subject: Re: [Bitcoin-development] F2Pool has enabled full replace-by-fee
Precedence: list

On 6/20/2015 5:54 PM, Eric Lombrozo wrote:
> Perhaps it isn=92t prudent to push out changes to the relay policy that=
 make these exploits even easier right now - but we NEED to be applying s=
ome kind of pressure on the merchant end to upgrade their stuff to be mor=
e resilient so that we have more room for changes on things like relay po=
licy without significant disruption to the network.
>

There's no need to worry about causing more problems by relaying
double-spends.  After a year of watching, it's clear that already only
20% of hash power strictly obeys first-seen.

http://i.imgur.com/0bYXrjn.png

It may be surprising that
 - The period of ambiguity is very short - just 2 seconds
   (this makes sense, given the .5s median propagation time)
 - Fast double-spends between 2 and 15 seconds are less successful
 - The steady-state 80% respend success rate is reached after just 15
seconds

The >30s data point includes txes that were respent after a long time,
sometimes months.  Those longer-term respends are to be expected, as
people reclaim stuck txes.

Paying attention to double-spends is an opportunity for wallets and
merchants .  With 140 Bitcoin XT nodes online, you're probably already
receiving them.  Most wallets, including vanilla core, don't even alert
when a double-spend of a wallet transaction appears in a block - even
though there may still be time to withhold delivery of the goods/services=
=2E

If FSS RBF gains miner share, fewer successful zero-conf double-spends
will occur.  Only radical twisted logic finds that to be an undesirable
result.