From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 62E46C59 for ; Sun, 20 Dec 2015 03:34:28 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-io0-f175.google.com (mail-io0-f175.google.com [209.85.223.175]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 779ED135 for ; Sun, 20 Dec 2015 03:34:27 +0000 (UTC) Received: by mail-io0-f175.google.com with SMTP id o67so126142625iof.3 for ; Sat, 19 Dec 2015 19:34:27 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:in-reply-to:references:date:message-id:subject :from:to:cc:content-type; bh=ael5RfA+GHNUTJ7VPOZ1DE2cDiH7Qy9Rl94kGeAE5n8=; b=xRH135w13Ms6BaP+Nj2rpEkJDKu4LXIfp460In8TgaE45LX0q6rd7zBRUh0Kbg2qz3 cipiyVboSdlN0iDr8pRrVcxVgwPxvjIrRl7uOV19qZyrRcq9jiYlNWUSzZd8t0iWECMZ KcRJDWDBkTNZ6EIhokX7glJPmY5yS/JRcqtBdGP0u9/28/BXckwUzfDHqXg20mhVwFdW Ueggd+1bxaFeYaPXjWLmNl/GADKTD3m+/V7BPW1Dm6CYW1mtcWcQRweV665bqeLrtiiH glit56y2MpeRk87uqR1oq8B1ISqOU9pI1G7yqIwDQhIa5D9g+YVpp4Isw2LrfbZeYW4K bzfw== MIME-Version: 1.0 X-Received: by 10.107.40.76 with SMTP id o73mr8947525ioo.157.1450582466785; Sat, 19 Dec 2015 19:34:26 -0800 (PST) Sender: nbvfour@gmail.com Received: by 10.36.20.142 with HTTP; Sat, 19 Dec 2015 19:34:26 -0800 (PST) In-Reply-To: <20151219184240.GB12893@muck> References: <20151219184240.GB12893@muck> Date: Sat, 19 Dec 2015 19:34:26 -0800 X-Google-Sender-Auth: 4ZApz5glazOnLDjIgdqZ-dPbSNk Message-ID: From: Chris Priest To: Peter Todd Content-Type: text/plain; charset=UTF-8 X-Spam-Status: No, score=-2.6 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, FREEMAIL_FROM, 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 Cc: bitcoin-dev@lists.linuxfoundation.org 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 03:34:28 -0000 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. On 12/19/15, Peter Todd via bitcoin-dev wrote: > At the recent Scaling Bitcoin conference in Hong Kong we had a chatham > house rules workshop session attending by representitives of a super > majority of the Bitcoin hashing power. > > One of the issues raised by the pools present was block withholding > attacks, which they said are a real issue for them. In particular, pools > are receiving legitimate threats by bad actors threatening to use block > withholding attacks against them. Pools offering their services to the > general public without anti-privacy Know-Your-Customer have little > defense against such attacks, which in turn is a threat to the > decentralization of hashing power: without pools only fairly large > hashing power installations are profitable as variance is a very real > business expense. P2Pool is often brought up as a replacement for pools, > but it itself is still relatively vulnerable to block withholding, and > in any case has many other vulnerabilities and technical issues that has > prevented widespread adoption of P2Pool. > > Fixing block withholding is relatively simple, but (so far) requires a > SPV-visible hardfork. (Luke-Jr's two-stage target mechanism) We should > do this hard-fork in conjunction with any blocksize increase, which will > have the desirable side effect of clearly show consent by the entire > ecosystem, SPV clients included. > > > Note that Ittay Eyal and Emin Gun Sirer have argued(1) that block > witholding attacks are a good thing, as in their model they can be used > by small pools against larger pools, disincentivising large pools. > However this argument is academic and not applicable to the real world, > as a much simpler defense against block withholding attacks is to use > anti-privacy KYC and the legal system combined with the variety of > withholding detection mechanisms only practical for large pools. > Equally, large hashing power installations - a dangerous thing for > decentralization - have no block withholding attack vulnerabilities. > > 1) http://hackingdistributed.com/2014/12/03/the-miners-dilemma/ > > -- > 'peter'[:-1]@petertodd.org > 00000000000000000188b6321da7feae60d74c7b0becbdab3b1a0bd57f10947d >