From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sog-mx-3.v43.ch3.sourceforge.com ([172.29.43.193] helo=mx.sourceforge.net) by sfs-ml-1.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1Vdkwt-0000k1-Ix for bitcoin-development@lists.sourceforge.net; Tue, 05 Nov 2013 18:01:55 +0000 X-ACL-Warn: Received: from mail-pd0-f174.google.com ([209.85.192.174]) by sog-mx-3.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1Vdkwq-0001Pj-6M for bitcoin-development@lists.sourceforge.net; Tue, 05 Nov 2013 18:01:55 +0000 Received: by mail-pd0-f174.google.com with SMTP id z10so8898925pdj.19 for ; Tue, 05 Nov 2013 10:01:46 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:message-id:date:from:user-agent:mime-version:to :subject:references:in-reply-to:content-type; bh=KP2ZTEl5q+983Y2ohb/79c8pkvKZZdA5RGnNP+Pja78=; b=Er5tbyQSyQmC5lQ+UnznbOL+xZDd86VgLAwHIYtBliEP3DfhILB2riK2PVNgZr9Q+j wh86xZlAGJBqLZyvAo4l3rFmsdb4e/sHbPN1vdcyAlkmzxSlMMSO7u1QOhGf8GKEug3k yjBOsGsp8knJe26SUeWi3/+mqBQOUFwt6iC/yJipRYO2oM1Rw6g055vt7UKTegikTaek coMaOfJU7w+RK9v9+z8r0SXzUmfHvyPPpoJBVWl0agYYQqsraS0xer4TcoQNSJrvlUEU qVGz0AOEKnw5nVHgmQ2AijYjzyjzi6GpQVjD9warwZPdz7djqLT2gbuHoqcvzsY1HaXU vf2Q== X-Gm-Message-State: ALoCoQm1XMn3WF46ow08e9+ReqDAshID47hGwwO/tYMMgLPdCxAmJC12/FIX0S6AcjkwVdi8kIJV X-Received: by 10.68.235.72 with SMTP id uk8mr24239990pbc.93.1383673069738; Tue, 05 Nov 2013 09:37:49 -0800 (PST) Received: from [10.45.134.5] (c-24-5-81-164.hsd1.ca.comcast.net. [24.5.81.164]) by mx.google.com with ESMTPSA id gh3sm15211998pbb.2.2013.11.05.09.37.48 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 05 Nov 2013 09:37:49 -0800 (PST) Message-ID: <52792CF2.10709@intersango.com> Date: Tue, 05 Nov 2013 09:37:54 -0800 From: Patrick User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130922 Icedove/17.0.9 MIME-Version: 1.0 To: bitcoin-development@lists.sourceforge.net References: <20131105170541.GA13660@petertodd.org> In-Reply-To: Content-Type: multipart/alternative; boundary="------------090602090807040407030304" X-Spam-Score: 1.0 (+) X-Spam-Report: Spam Filtering performed by mx.sourceforge.net. See http://spamassassin.org/tag/ for more details. -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [209.85.192.174 listed in list.dnswl.org] 0.0 URIBL_BLOCKED ADMINISTRATOR NOTICE: The query to URIBL was blocked. See http://wiki.apache.org/spamassassin/DnsBlocklists#dnsbl-block for more information. [URIs: doubleclick.net] 1.0 HTML_MESSAGE BODY: HTML included in message X-Headers-End: 1Vdkwq-0001Pj-6M Subject: Re: [Bitcoin-development] BIP proposal - patch to raise selfish mining threshold. X-BeenThere: bitcoin-development@lists.sourceforge.net X-Mailman-Version: 2.1.9 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 05 Nov 2013 18:01:55 -0000 This is a multi-part message in MIME format. --------------090602090807040407030304 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit The ratio of honest miners that mine the first block they see is > 0.5 Your proposed solution would reduce that ratio to 0.5 In other words your proposed change would make the attack you describe easier not harder. On 11/05/2013 09:26 AM, Ittay wrote: > That sounds like selfish mining, and the magic number is 25%. That's > the minimal pool size. > Today the threshold is 0% with good connectivity. > > If I misunderstood your point, please elaborate. > > Ittay > > > > On Tue, Nov 5, 2013 at 12:05 PM, Peter Todd > wrote: > > On Tue, Nov 05, 2013 at 11:56:53AM -0500, Ittay wrote: > > Hello, > > > > Please see below our BIP for raising the selfish mining threshold. > > Looking forward to your comments. > > > > > 2. No new vulnerabilities introduced: > > Currently the choice among equal-length chains is done arbitrarily, > > depending on network topology. This arbitrariness is a source of > > vulnerability. We replace it with explicit randomness, which is > at the > > control of the protocol. The change does not introduce > executions that were > > not possible with the old protocol. > > Credit goes to Gregory Maxwell for pointing this out, but the random > choice solution does in fact introduce a vulnerability in that it > creates incentives for pools over a certain size to withhold blocks > rather than immediately broadcasting all blocks found. > > The problem is that when the pool eventually choses to reveal the > block > they mined, 50% of the hashing power switches, thus splitting the > network. Like the original attack this can be to their benefit. For > pools over a certain size this strategy is profitable even without > investing in a low-latency network; Maxwell or someone else can > chime in > with the details for deriving that threshold. > > I won't get a chance to for a few hours, but someone should do the > analysis on a deterministic switching scheme. > > -- > 'peter'[:-1]@petertodd.org > 0000000000000005e25ca9b9fe62bdd6e8a2b4527ad61753dd2113c268bec707 > > > > > ------------------------------------------------------------------------------ > November Webinars for C, C++, Fortran Developers > Accelerate application performance with scalable programming models. Explore > techniques for threading, error checking, porting, and tuning. Get the most > from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60136231&iu=/4140/ostg.clktrk > > > _______________________________________________ > Bitcoin-development mailing list > Bitcoin-development@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/bitcoin-development --------------090602090807040407030304 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit
The ratio of honest miners that mine the first block they see is > 0.5

Your proposed solution would reduce that ratio to 0.5

In other words your proposed change would make the attack you describe easier not harder.

On 11/05/2013 09:26 AM, Ittay wrote:
That sounds like selfish mining, and the magic number is 25%. That's the minimal pool size. 
Today the threshold is 0% with good connectivity. 

If I misunderstood your point, please elaborate. 

Ittay 



On Tue, Nov 5, 2013 at 12:05 PM, Peter Todd <pete@petertodd.org> wrote:
On Tue, Nov 05, 2013 at 11:56:53AM -0500, Ittay wrote:
> Hello,
>
> Please see below our BIP for raising the selfish mining threshold.
> Looking forward to your comments.

<snip>

> 2. No new vulnerabilities introduced:
> Currently the choice among equal-length chains is done arbitrarily,
> depending on network topology. This arbitrariness is a source of
> vulnerability. We replace it with explicit randomness, which is at the
> control of the protocol. The change does not introduce executions that were
> not possible with the old protocol.

Credit goes to Gregory Maxwell for pointing this out, but the random
choice solution does in fact introduce a vulnerability in that it
creates incentives for pools over a certain size to withhold blocks
rather than immediately broadcasting all blocks found.

The problem is that when the pool eventually choses to reveal the block
they mined, 50% of the hashing power switches, thus splitting the
network. Like the original attack this can be to their benefit. For
pools over a certain size this strategy is profitable even without
investing in a low-latency network; Maxwell or someone else can chime in
with the details for deriving that threshold.

I won't get a chance to for a few hours, but someone should do the
analysis on a deterministic switching scheme.

--
'peter'[:-1]@petertodd.org
0000000000000005e25ca9b9fe62bdd6e8a2b4527ad61753dd2113c268bec707



------------------------------------------------------------------------------
November Webinars for C, C++, Fortran Developers
Accelerate application performance with scalable programming models. Explore
techniques for threading, error checking, porting, and tuning. Get the most 
from the latest Intel processors and coprocessors. See abstracts and register
http://pubads.g.doubleclick.net/gampad/clk?id=60136231&iu=/4140/ostg.clktrk


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