From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sog-mx-4.v43.ch3.sourceforge.com ([172.29.43.194] helo=mx.sourceforge.net) by sfs-ml-2.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1VyE3n-0007uq-DY for bitcoin-development@lists.sourceforge.net; Wed, 01 Jan 2014 05:09:39 +0000 X-ACL-Warn: Received: from zinan.dashjr.org ([192.3.11.21]) by sog-mx-4.v43.ch3.sourceforge.com with esmtp (Exim 4.76) id 1VyE3m-0003r0-Gb for bitcoin-development@lists.sourceforge.net; Wed, 01 Jan 2014 05:09:39 +0000 Received: from ishibashi.localnet (unknown [IPv6:2001:470:5:265:be5f:f4ff:febf:4f76]) (Authenticated sender: luke-jr) by zinan.dashjr.org (Postfix) with ESMTPSA id DB5A110837A7; Wed, 1 Jan 2014 05:09:48 +0000 (UTC) From: "Luke-Jr" To: Peter Todd Date: Wed, 1 Jan 2014 05:09:27 +0000 User-Agent: KMail/1.13.7 (Linux/3.12.6-gentoo; KDE/4.11.2; x86_64; ; ) References: <201312310114.05600.luke@dashjr.org> <20140101045342.GA7103@tilt> In-Reply-To: <20140101045342.GA7103@tilt> X-PGP-Key-Fingerprint: E463 A93F 5F31 17EE DE6C 7316 BD02 9424 21F4 889F X-PGP-Key-ID: BD02942421F4889F X-PGP-Keyserver: hkp://pgp.mit.edu MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Message-Id: <201401010509.27977.luke@dashjr.org> X-Spam-Score: -0.1 (/) X-Spam-Report: Spam Filtering performed by mx.sourceforge.net. See http://spamassassin.org/tag/ for more details. -0.1 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain X-Headers-End: 1VyE3m-0003r0-Gb Cc: bitcoin-development@lists.sourceforge.net Subject: Re: [Bitcoin-development] The insecurity of merge-mining 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: Wed, 01 Jan 2014 05:09:39 -0000 On Wednesday, January 01, 2014 4:53:42 AM Peter Todd wrote: > On Tue, Dec 31, 2013 at 01:14:05AM +0000, Luke-Jr wrote: > > On Monday, December 30, 2013 11:22:25 PM Peter Todd wrote: > > > that you are using merge-mining is a red-flag because without majority, > > > or at least near-majority, hashing power an attacker can 51% attack > > > your altcoin at negligible cost by re-using existing hashing power. > > > > I strongly disagree on this isolated point. Using the same logic, Bitcoin > > is vulnerable to an attacker at negligible cost by re-using existing > > hashing power from mining Namecoin. Any non-scam altcoin is pretty safe > > using merged mining, since any would-be attacker is going to have it in > > their interests to invest in the altcoin instead of attacking it. It's > > only the scam ones that want to pump & dump with no improvements, that > > are really at risk here. > > > > The rational decision for a non-scam altcoin, is to take advantage of > > merged mining to get as much security as possible. There are also some > > possible tricks to get the full security of the bitcoin miners even when > > not all participate in your altcoin (but this area probably needs some > > studying to get right). > > You assume the value of a crypto-currency is equal to all miners, it's > not. > > Suppose I create a merge-mined Zerocoin implementation with a 1:1 > BTC/ZTC exchange rate enforced by the software. You can't argue this is > a scamcoin; no-one is getting rich. There's a 1:1 exchange rate so the > only thing you can do with the coin is get some privacy. But inevitably > some miners won't agree that enabling better privacy is a good thing, or > their local governments won't. Either way, they can attack the Zerocoin > merge-mined chain with a marginal cost of nearly zero. Not necessarily. If Zerocoin was tied directly to Bitcoin proof-of-work, the worst they could do is not-participate by mining empty blocks. > OTOH if the Zerocoin scheme was implemented by embedding ZTC > transactions within standard Bitcoin transactions - even without any > attempt at hiding them - the attackers would need a 50% majority of > hashing power to succeed. Of course potentially slow confirmations is a > trade-off, but that's likely a perfectly OK trade-off in this case. Potentially slow confirmation is also the only shortcoming of using Bitcoin's proof-of-work directly. Luke