From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sog-mx-2.v43.ch3.sourceforge.com ([172.29.43.192] helo=mx.sourceforge.net) by sfs-ml-1.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1VyDp6-0001q6-TH for bitcoin-development@lists.sourceforge.net; Wed, 01 Jan 2014 04:54:28 +0000 Received-SPF: pass (sog-mx-2.v43.ch3.sourceforge.com: domain of petertodd.org designates 62.13.149.43 as permitted sender) client-ip=62.13.149.43; envelope-from=pete@petertodd.org; helo=outmail149043.authsmtp.co.uk; Received: from outmail149043.authsmtp.co.uk ([62.13.149.43]) by sog-mx-2.v43.ch3.sourceforge.com with esmtp (Exim 4.76) id 1VyDp5-0004vF-Mk for bitcoin-development@lists.sourceforge.net; Wed, 01 Jan 2014 04:54:28 +0000 Received: from mail-c235.authsmtp.com (mail-c235.authsmtp.com [62.13.128.235]) by punt17.authsmtp.com (8.14.2/8.14.2/) with ESMTP id s014sH25031960; Wed, 1 Jan 2014 04:54:17 GMT Received: from tilt (dhcp186-112.theedge.ca [216.108.186.112]) (authenticated bits=128) by mail.authsmtp.com (8.14.2/8.14.2/) with ESMTP id s014s8dn021751 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO); Wed, 1 Jan 2014 04:54:14 GMT Date: Tue, 31 Dec 2013 23:53:42 -0500 From: Peter Todd To: Luke-Jr Message-ID: <20140101045342.GA7103@tilt> References: <20131230232225.GA10594@tilt> <201312310114.05600.luke@dashjr.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="ew6BAiZeqk4r7MaW" Content-Disposition: inline In-Reply-To: <201312310114.05600.luke@dashjr.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-Server-Quench: c40c3855-72a0-11e3-b802-002590a15da7 X-AuthReport-Spam: If SPAM / abuse - report it at: http://www.authsmtp.com/abuse X-AuthRoute: OCd2Yg0TA1ZNQRgX IjsJECJaVQIpKltL GxAVKBZePFsRUQkR aQdMdgMUElQaAgsB AmIbW1BeVVl7WGU7 aQtXcwRdalRPVwN0 UUlLXVdaExppT18B BxpdWk0sdwdHf3tx K0dmW3lZEhd+dRV+ SktRCGoENGd9aWFK U10KfwNWbQNKfBpM agF+USdcZitlM3Bw LCUyIzs2PDMaJClL TwUKNVcfR1o+VgI8 SlgDGy4iFlAfRjki ZxsoYlsRBkkcd0Az N1onVjoA X-Authentic-SMTP: 61633532353630.1023:706 X-AuthFastPath: 0 (Was 255) X-AuthSMTP-Origin: 216.108.186.112/587 X-AuthVirus-Status: No virus detected - but ensure you scan with your own anti-virus system. X-Spam-Score: -1.5 (-) X-Spam-Report: Spam Filtering performed by mx.sourceforge.net. See http://spamassassin.org/tag/ for more details. -1.5 SPF_CHECK_PASS SPF reports sender host as permitted sender for sender-domain -0.0 SPF_PASS SPF: sender matches SPF record X-Headers-End: 1VyDp5-0004vF-Mk 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 04:54:29 -0000 --ew6BAiZeqk4r7MaW Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable 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. >=20 > I strongly disagree on this isolated point. Using the same logic, Bitcoin= is=20 > vulnerable to an attacker at negligible cost by re-using existing hashing= =20 > power from mining Namecoin. Any non-scam altcoin is pretty safe using mer= ged=20 > mining, since any would-be attacker is going to have it in their interest= s to=20 > invest in the altcoin instead of attacking it. It's only the scam ones th= at=20 > want to pump & dump with no improvements, that are really at risk here. >=20 > The rational decision for a non-scam altcoin, is to take advantage of mer= ged=20 > mining to get as much security as possible. There are also some possible= =20 > tricks to get the full security of the bitcoin miners even when not all= =20 > participate in your altcoin (but this area probably needs some studying t= o get=20 > 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. 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. --=20 'peter'[:-1]@petertodd.org 000000000000000f9102d27cfd61ea9e8bb324593593ca3ce6ba53153ff251b3 --ew6BAiZeqk4r7MaW Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQEcBAEBCAAGBQJSw59VAAoJECSBQD2l8JH72RUH/jKGDjjsqGMcsDzPstXj5LyV XKw35/j5yYqRTK7Lsloyuz5qUTuCgcSkHp8dSzqBiP9LcN+EF+XH2eyuQv892Zzk 4ejFilQefX397xUMFaqbOyMfA3JxnPLJ0NbesRjrZZcqYhfvgi5nPZAwDxCP/Ttv QuLmtK+9VN+YOdQYMEyUeGAGzjMKz0cRTYFKQijOyMHxm0dSjo5ZCfHZS3lW0F5U oblB67H3NWSYoqZIR83fnygdAReETF+igwwnfahul0GGHipQw1nFUmXRkPrPJO/5 J/WqTUA4FecHNxzKwFKHN80tDYEz3LCxFe4iu7AfZ9RfZgIcFxLJv4gsX/lAYlo= =qNgu -----END PGP SIGNATURE----- --ew6BAiZeqk4r7MaW--