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From: Anthony Towns <aj@erisian•com.au>
To: bitcoin-dev@lists•linuxfoundation.org
Subject: Re: [bitcoin-dev] Let's deploy BIP65 CHECKLOCKTIMEVERIFY!
Date: Tue, 13 Oct 2015 03:06:37 +1000	[thread overview]
Message-ID: <20151012170637.GA21399@navy> (raw)
In-Reply-To: <1444633370859.8a298e9c@Nodemailer>

On Mon, Oct 12, 2015 at 12:02:51AM -0700, digitsu412 via bitcoin-dev wrote:
> First I think your unsaid assumption about the fragility of a soft
> fork showing incorrect confirmations is dependent on the percentage
> of hash power that didn't upgrade.  If using your same numbers this
> was only 5% of the hash power, the attack is effectively not effective
> (u less the attacker knew an exact merchant that was unfortunately on
> the minority of the network. 

Actually, just to take this scenario more explicitly...

Say you've got 5% of hashpower running on old software, along with,
say, 1500 nodes; and meanwhile you've got 95% of hashpower running new
software, along with 4000 nodes.

There's still about 750 nodes running 0.9 or 0.8 of 5400 total according
to bitnodes.21.co/nodes, so those numbers seems at least plausible to
me for the first week or two after a soft-fork is activated.

Eventually an old-rules block gets found by the 5% hashpower. The 4000
new nodes and 95% of hashpower ignore it, of course. With 8 random
connections, old nodes should have 92% chance of seeing an old node
as a peer, so I think around ~1300 of them should still be a connected
subgraph, and the old-rules block should get propogated amongst them
(until two new-rules blocks come along and orphan it).

An SPV client with 12 random connections here has 96% chance of having one
of the ~1300 old nodes as a peer, and if so, will see the old-rules block,
that will be orphaned, and may be at risk from double-spends as a result.

So I think even with just 5% hashpower and ~30% of nodes left running
the old version, a "damaging soft fork" still poses a fairly high risk to
someone receiving payments via an SPV client, and trusting transactions
with few confirmations.

Cheers,
aj


  parent reply	other threads:[~2015-10-12 17:06 UTC|newest]

Thread overview: 101+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-09-27 18:50 Peter Todd
2015-09-27 20:26 ` jl2012
2015-09-27 20:27   ` Peter Todd
2015-09-27 20:27 ` Mark Friedenbach
2015-09-27 20:41 ` Btc Drak
2015-09-28 10:10 ` s7r
2015-09-28 10:48 ` Mike Hearn
2015-09-28 11:00   ` Adam Back
2015-09-28 11:40     ` Mike Hearn
2015-09-28 12:20       ` Eric Lombrozo
2015-09-28 12:26         ` Mike Hearn
2015-09-28 12:44           ` Eric Lombrozo
2015-09-28 12:54             ` Mike Hearn
2015-09-29  6:17               ` Eric Lombrozo
2015-09-29 12:02                 ` Mike Hearn
2015-09-28 14:05       ` Btc Drak
2015-09-28 14:17         ` Mike Hearn
2015-09-28 21:12     ` odinn
2015-09-28 22:16       ` Dave Scotese
2015-09-28 11:04   ` Eric Lombrozo
2015-09-28 12:47   ` Tier Nolan
2015-09-28 13:01   ` Gavin Andresen
2015-09-28 13:28     ` Peter Todd
2015-09-28 13:43       ` Gavin Andresen
2015-09-28 14:14         ` Peter Todd
2015-09-28 13:21   ` Peter Todd
2015-09-28 13:41     ` Mike Hearn
2015-09-28 14:29       ` Peter Todd
2015-09-28 14:33         ` Mike Hearn
2015-09-28 14:43           ` Peter Todd
2015-09-28 14:51             ` Mike Hearn
2015-09-28 15:05               ` Peter Todd
2015-09-28 15:38                 ` Mike Hearn
2015-09-28 16:52                   ` jl2012
2015-09-28 17:14                     ` Mike Hearn
2015-09-28 23:17                       ` Jorge Timón
2015-09-29 12:07                         ` Mike Hearn
2015-09-29 15:09                           ` [bitcoin-dev] Why soft-forks? was: " Santino Napolitano
2015-09-29 13:30             ` [bitcoin-dev] " Jonathan Toomim (Toomim Bros)
2015-09-29 15:59               ` jl2012
2015-09-29 19:54                 ` odinn
2015-09-29 18:31   ` Gregory Maxwell
2015-09-30 17:11     ` Mike Hearn
2015-09-30 17:58       ` Jorge Timón
2015-10-01 14:23         ` Tom Harding
2015-09-30 18:15       ` Adam Back
2015-09-30 19:26       ` Jeff Garzik
2015-09-30 19:56         ` Mike Hearn
2015-09-30 20:37           ` Jorge Timón
2015-09-30 21:06             ` Mike Hearn
2015-09-30 22:14               ` Jorge Timón
2015-10-01  0:11                 ` Jorge Timón
2015-09-30 22:17           ` Jeff Garzik
2015-09-30 23:25             ` Gregory Maxwell
2015-09-30 20:15       ` Gregory Maxwell
2015-09-30 21:01         ` Mike Hearn
2015-09-30 22:59           ` Gregory Maxwell
2015-10-01  4:08           ` [bitcoin-dev] Crossing the line? [Was: Re: Let's deploy BIP65 CHECKLOCKTIMEVERIFY!] Tao Effect
2015-10-01 16:39             ` Jeff Garzik
2015-10-01 20:17               ` Milly Bitcoin
2015-10-02 12:23               ` Mike Hearn
2015-10-02 13:14                 ` jl2012
2015-10-02 14:10                   ` Marcel Jamin
2015-10-02 16:37                 ` Gregory Maxwell
2015-10-07 15:00     ` [bitcoin-dev] Let's deploy BIP65 CHECKLOCKTIMEVERIFY! Anthony Towns
2015-10-07 15:46       ` Jonathan Toomim (Toomim Bros)
2015-10-07 16:02         ` Eric Lombrozo
2015-10-07 16:25           ` Eric Lombrozo
2015-10-07 16:26           ` Jonathan Toomim (Toomim Bros)
2015-10-07 16:38         ` Anthony Towns
2015-10-10  7:23       ` Anthony Towns
2015-10-12  7:02       ` digitsu
2015-10-12 16:33         ` Anthony Towns
2015-10-12 17:06         ` Anthony Towns [this message]
2015-10-13  0:08           ` digitsu
2015-09-29 20:03 ` Wladimir J. van der Laan
2015-09-30  4:05   ` Rusty Russell
2015-09-30  6:19     ` Adam Back
2015-09-30 12:30       ` Mike Hearn
2015-09-30 15:55         ` Jorge Timón
2015-09-30 19:17           ` John Winslow
2015-10-01  0:06             ` Rusty Russell
2015-09-30 17:14         ` Adam Back
2015-10-01  0:04       ` Rusty Russell
2015-10-02  1:57 NotMike Hearn
2015-10-02  2:12 ` GC
2015-10-05 10:59   ` Mike Hearn
2015-10-05 11:23     ` Jeff Garzik
2015-10-05 11:28       ` Mike Hearn
2015-10-05 12:04         ` Jorge Timón
2015-10-05 12:08           ` Clément Elbaz
2015-10-05 12:16             ` Jorge Timón
2015-10-05 12:29               ` Clément Elbaz
2015-10-05 15:42                 ` Jorge Timón
2015-10-05 12:10           ` Mike Hearn
2015-10-05 15:33             ` Jorge Timón
2015-10-05 16:46               ` Mike Hearn
2015-10-06  6:20                 ` Anthony Towns
2015-10-07  6:13                 ` Micha Bailey
2015-10-05 13:29   ` Jorge Timón
2015-10-05 13:24 ` Jorge Timón

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