Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 8534A94E for ; Sun, 20 Dec 2015 04:24:54 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from s47.web-hosting.com (s47.web-hosting.com [199.188.200.16]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id F2F2510C for ; Sun, 20 Dec 2015 04:24:53 +0000 (UTC) Received: from localhost ([::1]:38229 helo=server47.web-hosting.com) by server47.web-hosting.com with esmtpa (Exim 4.85) (envelope-from ) id 1aAVYC-000ypv-CN; Sat, 19 Dec 2015 23:24:52 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Date: Sat, 19 Dec 2015 23:24:52 -0500 From: jl2012 To: Chris Priest In-Reply-To: References: <20151219184240.GB12893@muck> <219f125cee6ca68fd27016642e38fdf1@xbt.hk> Message-ID: X-Sender: jl2012@xbt.hk User-Agent: Roundcube Webmail/1.0.5 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - server47.web-hosting.com X-AntiAbuse: Original Domain - lists.linuxfoundation.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - xbt.hk X-Get-Message-Sender-Via: server47.web-hosting.com: authenticated_id: jl2012@xbt.hk X-Source: X-Source-Args: X-Source-Dir: X-From-Rewrite: unmodified, already matched X-Spam-Status: No, score=-2.6 required=5.0 tests=BAYES_00,RCVD_IN_DNSWL_LOW autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.org X-Mailman-Approved-At: Sun, 20 Dec 2015 04:34:22 +0000 Cc: bitcoin-dev@lists.linuxfoundation.org, nbvfour@gmail.com Subject: Re: [bitcoin-dev] We need to fix the block withholding attack X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Bitcoin Development Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 20 Dec 2015 04:24:54 -0000 Chris Priest 於 2015-12-19 22:47 寫到: > On 12/19/15, jl2012 wrote: >> Chris Priest via bitcoin-dev 於 2015-12-19 22:34 寫到: >>> Block witholding attacks are only possible if you have a majority of >>> hashpower. If you only have 20% hashpower, you can't do this attack. >>> Currently, this attack is only a theoretical attack, as the ones with >>> all the hashpower today are not engaging in this behavior. Even if >>> someone who had a lot of hashpower decided to pull off this attack, >>> they wouldn't be able to disrupt much. Once that time comes, then I >>> think this problem should be solved, until then it should be a low >>> priority. There are more important things to work on in the meantime. >>> >> >> This is not true. For a pool with 5% total hash rate, an attacker only >> needs 0.5% of hash rate to sabotage 10% of their income. It's already >> enough to kill the pool >> >> > > This begs the question: If this is such a devastating attack, then why > hasn't this attack brought down every pool in existence? As far as I'm > aware, there are many pools in operation despite this possibility. It did happen: https://www.reddit.com/r/Bitcoin/comments/28242v/eligius_falls_victim_to_blocksolution_withholding/ The worst thing is that the proof for such attack is probabilistic, not deterministic. A smarter attacker may even pretend to be many small miners, make it even more difficult or impossible to prove who are attacking. > Then shouldn't this be something the pool deals with, not the bitcoin > protocol? The only solution is to ask for KYC registration, unless one could propose a cryptographic solution that does not require a consensus fork.