From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sog-mx-3.v43.ch3.sourceforge.com ([172.29.43.193] helo=mx.sourceforge.net) by sfs-ml-4.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1Z24rJ-0003oK-IX for bitcoin-development@lists.sourceforge.net; Mon, 08 Jun 2015 21:45:29 +0000 Received-SPF: pass (sog-mx-3.v43.ch3.sourceforge.com: domain of petertodd.org designates 62.13.149.113 as permitted sender) client-ip=62.13.149.113; envelope-from=pete@petertodd.org; helo=outmail149113.authsmtp.com; Received: from outmail149113.authsmtp.com ([62.13.149.113]) by sog-mx-3.v43.ch3.sourceforge.com with esmtp (Exim 4.76) id 1Z24rI-0007EN-GL for bitcoin-development@lists.sourceforge.net; Mon, 08 Jun 2015 21:45:29 +0000 Received: from mail-c237.authsmtp.com (mail-c237.authsmtp.com [62.13.128.237]) by punt15.authsmtp.com (8.14.2/8.14.2/) with ESMTP id t58LjKpg069688; Mon, 8 Jun 2015 22:45:20 +0100 (BST) Received: from muck (bas3-cooksville17-1176329630.dsl.bell.ca [70.29.93.158]) (authenticated bits=128) by mail.authsmtp.com (8.14.2/8.14.2/) with ESMTP id t58LjElO096694 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO); Mon, 8 Jun 2015 22:45:17 +0100 (BST) Date: Mon, 8 Jun 2015 17:44:43 -0400 From: Peter Todd To: "Raystonn ." Message-ID: <20150608214443.GC19826@muck> References: <5574E39C.3090904@thinlink.com> <7E7DF414-6DDB-48A6-9199-D6883209B67D@newcastle.ac.uk> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="Y5rl02BVI9TCfPar" Content-Disposition: inline In-Reply-To: X-Server-Quench: a78f066a-0e27-11e5-9f74-002590a135d3 X-AuthReport-Spam: If SPAM / abuse - report it at: http://www.authsmtp.com/abuse X-AuthRoute: OCd2Yg0TA1ZNQRgX IjsJECJaVQIpKltL GxAVKBZePFsRUQkR aQdMdgoUEkAaAgsB AmMbWVZeVFh7WGs7 bApPbwxDa0lQXgBi T01BRU1TWkFtCWBb c0JhUhB0cQxCNn9z YEdgECFcVBJ6c0As X04BF2obZGY1bX0W BkdcagNUcgZDfk5E aVUrVz1vNG8XDQg5 AwQ0PjZ0MThBJSBS WgQAK04nCWAGAXY1 WwwLFjZnHEEIQTky IR0rJhYVGkpZKkIu PF09WFscUVcJDQlD A0BKBk5VKkIKXSsh AA8IFWIEFyVFTCsZ HgchJARBCSBTXSwQ H1NMTlkGFz9MWyoA QTlUUys2EBA1J09i OCAYOgJTegY/WRcF CRwXR1cw X-Authentic-SMTP: 61633532353630.1024:706 X-AuthFastPath: 0 (Was 255) X-AuthSMTP-Origin: 70.29.93.158/587 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: 1Z24rI-0007EN-GL Cc: Bitcoin Dev , "Patrick Mccorry \(PGR\)" Subject: Re: [Bitcoin-development] New attack identified and potential solution described: Dropped-transaction spam attack against the block size limit 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: Mon, 08 Jun 2015 21:45:29 -0000 --Y5rl02BVI9TCfPar Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Jun 08, 2015 at 02:33:54PM -0700, Raystonn . wrote: > > the attack would be expensive. >=20 > For attacks being waged to destroy Bitcoin by filling all blocks with spa= m transactions, the attack succeeds when the attacker is well funded. This= gives well-funded private and/or public entities the means to destroy Bitc= oin if they desire. This is only true after the block size limit was imple= mented. Without the block size limit, the spam doesn=E2=80=99t harm Bitcoi= n. It simply enriches miners at the cost of the spammers, which is a nicel= y antifragile quality. There will always be a blocksize limit based on technological considerations - the network has a finite bandwidth limit. Without a blocksize limit the attacker would just flood the network until the bandwidth usage became so great that consensus would fail, rendering Bitcoin both worthless, and insecure. The worst an attacker flooding the network with transactions with a blocksize limit can do is raise costs, without harming security. Keep in mind, that at some point it'd be cheaper to just 51% attack the network. Based on the current block subsidy of 25BTC/MB that's at the point where transaction fees are 25mBTC/KB, which corresponds to <$2/tx fees - not that cheap, but still quite affordable for a large percentage of Bitcoin's users right now. And that's the *absolute worst-case* attack possible. --=20 'peter'[:-1]@petertodd.org 0000000000000000127ab1d576dc851f374424f1269c4700ccaba2c42d97e778 --Y5rl02BVI9TCfPar Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- iQGrBAEBCACVBQJVdgzJXhSAAAAAABUAQGJsb2NraGFzaEBiaXRjb2luLm9yZzAw MDAwMDAwMDAwMDAwMDAxMjdhYjFkNTc2ZGM4NTFmMzc0NDI0ZjEyNjljNDcwMGNj YWJhMmM0MmQ5N2U3NzgvFIAAAAAAFQARcGthLWFkZHJlc3NAZ251cGcub3JncGV0 ZUBwZXRlcnRvZC5vcmcACgkQwIXyHOf0udwI5Af+P9/eGwhIlSG9k+BJMlfne4OZ 9ca47vdZX/p7Ef+3suIGWjq4pGb4n1qX8mstjnhqxUdsENShWv6Yd5Yoy/Ap+3Z6 ZtUtoeZ0eZCYAvaKMsuglIsV01/vtjdldRIKXEAE1UWap0Ivmjjs5o357u5Gnuep ttw2EQg91M4qkKh10siZXd7i+nMsvA7zJILee72HaiaCi3FFwX630s4co8dBTHHt T9AC6wg69a2D9SAHhf3n5EiqDoLWJ/FiSJwXJTt79j7+MHnyCF2TjAqqVJtbhnNO zh/pG+Xz6sGjM92v2Y/PyvKbzaschvli5cWdcITHCG0itDlvN7trbNLra8nV/g== =iHNc -----END PGP SIGNATURE----- --Y5rl02BVI9TCfPar--