Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id E5E2B4264 for ; Wed, 31 Jul 2019 23:28:59 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from pectw.vm.bytemark.co.uk (pectw.vm.bytemark.co.uk [80.68.92.123]) by smtp1.linuxfoundation.org (Postfix) with ESMTP id EC4417ED for ; Wed, 31 Jul 2019 23:28:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=pectw.net; s=dkim_test; h=Content-Type:Content-Transfer-Encoding:MIME-Version: References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From:Sender:Reply-To: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=dnG3/LW7sal9PcyiMWK4N8UiVvRSgSMZMCAeVMB0B14=; b=XXYB8xpuE7DQubqvdLLMOgkQpu csKAV+4DQlXznks3+b0Y41P43LpfLSzw421bVAXB+CqfDHKbaFe1rArYMaydrf93p2mMQkKku2pYj QVUsvxC9So078NU0z0q3D0OQK; Received: from host109-153-202-196.range109-153.btcentralplus.com ([109.153.202.196] helo=svetlana.localhost) by pectw.vm.bytemark.co.uk with esmtpsa (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1hsy1h-0000u4-3E; Wed, 31 Jul 2019 23:28:57 +0000 From: Alistair Mann To: "Kenshiro []" Date: Thu, 01 Aug 2019 00:28:56 +0100 Message-ID: <2084819.YBhD99MD1N@dprfs-d5766> User-Agent: KMail/4.14.2 (Linux/4.4.0-18-generic; KDE/4.14.2; x86_64; ; ) In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Spam-Status: No, score=-2.0 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU 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: Thu, 01 Aug 2019 02:12:47 +0000 Cc: Bitcoin Protocol Discussion Subject: Re: [bitcoin-dev] Add a moving checkpoint to the Bitcoin protocol X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Bitcoin Protocol Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 31 Jul 2019 23:29:00 -0000 On Wednesday 31 Jul 2019 14:53:25 Kenshiro [] wrote: >> How would a (potentially, state-sponsored) netsplit lasting longer than >> N be handled? > > It would be detected by the community much before reaching the reorg limit > of N blocks (it's 24 hours) so nodes could stop until the netsplit is > fixed. A netsplit cannot be detected but merely be suspected where the p2p protocol does allow arbitrary connecting/disconnecting of any peer: there's no difference between a remote net being split off, that net having nothing to say, and that net choosing to disconnect. Detection then mandates manual, out- of-band communications, which is error prone and centralising. I also observe 'stopping nodes' during netsplits introduces several attack vectors. Among them: create a netsplit, which stops the nodes, turn off the netsplit, repeat. A sequence of 365 actors causing their own small netsplits could effectively stop Bitcoin at the cost (to them) of no Internet for one day a year as the rolling netsplit could never be fixed. > In the extreme case no one notice the network split during more than N > blocks (24 hours) and there are 2 permanent forks longer than N, nodes from > one branch could delete their local history so they would join the other > branch. > > P.S.: To be clearer, in this example I set an N value of 144 blocks, which > is approximately 24 hours. I've seen estimates of China hosting more than 51% of hashpower. Say they conduct a netsplit. Does your suggestion mean that it's the rest of the world that has to delete their local history because they lack the hashpower to assert themselves as the proper branch? If so, I think having to delete actual history everywhere across the globe but China is not a price worth paying to limit reorgs to 24 hours. I am unconvinced that the moving checkpoint you describe would improve Bitcoin. -- Alistair Mann