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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, 6 Oct 2015 16:20:31 +1000	[thread overview]
Message-ID: <20151006062030.GB1054@navy> (raw)
In-Reply-To: <CA+w+GKRjURkV40iG=6RLhFyQ-t2G_YAinKk7Os_8zK4+hyYJaw@mail.gmail.com>

On Mon, Oct 05, 2015 at 06:46:28PM +0200, Mike Hearn via bitcoin-dev wrote:
> The example is this: find someone that accepts 1-block confirmed
> transactions in return for something valuable. There are plenty of them out
> there. Once the soft fork starts, send a P2SH transaction that defines a
> new output controlled by OP_CLTV. It will be incorporated into the UTXO set
> by all miners because it's opaque (p2sh).
> 
> Now send a transaction that pays the merchant, and make it spend your
> OP_CLTV output with an invalid script. New nodes will reject it as a rule
> violator. Old nodes won't.

Old nodes running bitcoind will see it as OP_NOP2, and will reject it
unless they've manually disabled SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS,
which (aiui) has been available since bitcoin 0.10 [0], but not backported
to 0.8 or 0.9.

[0] https://github.com/bitcoin/bitcoin/commit/0391423

That covers about 4700/5880 nodes going by bitnodes.21.co; but I can't
tell how many miners it covers.

Further, AIUI, nodes running 0.8 or 0.9 will still apply IsStandard()
checks to scripts attempting to spend p2sh outputs [1], so will also
fail to either mine or relay your OP_NOP2 payment.

[1] https://github.com/bitcoin/bitcoin/commit/6259937

> So at some point an old miner will create a
> block containing your invalid transaction, the merchant will think they got
> paid, they'll give you the stuff and the fraud is done.

My understanding is that this isn't supposed to be a problem because you
won't be able to find an old miner that will do that; released versions
of bitcoin already block it by default.

Sure, someone could disable those checks and not pay attention to a soft
fork that will cause their blocks to be orphaned, but I'm not seeing why
that's any different a threat compared to someone deliberately mining
invalid blocks to do 1-confirmation doublespends against merchants not
running a full node.

At least, that's my understanding, and I'm not an expert, so corrections
appreciated.

Cheers,
aj


  reply	other threads:[~2015-10-06  6:20 UTC|newest]

Thread overview: 93+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-10-02  1:57 [bitcoin-dev] Let's deploy BIP65 CHECKLOCKTIMEVERIFY! 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 [this message]
2015-10-07  6:13                 ` Micha Bailey
2015-10-05 13:29   ` Jorge Timón
2015-10-05 13:24 ` Jorge Timón
  -- strict thread matches above, loose matches on Subject: below --
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 13:30             ` 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
2015-10-07 15:00     ` 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
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

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