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 1Yx2SF-0005ch-P3 for bitcoin-development@lists.sourceforge.net; Tue, 26 May 2015 00:10:47 +0000 Received-SPF: pass (sog-mx-2.v43.ch3.sourceforge.com: domain of petertodd.org designates 62.13.149.84 as permitted sender) client-ip=62.13.149.84; envelope-from=pete@petertodd.org; helo=outmail149084.authsmtp.net; Received: from outmail149084.authsmtp.net ([62.13.149.84]) by sog-mx-2.v43.ch3.sourceforge.com with esmtp (Exim 4.76) id 1Yx2SE-0007CB-7b for bitcoin-development@lists.sourceforge.net; Tue, 26 May 2015 00:10:47 +0000 Received: from mail-c237.authsmtp.com (mail-c237.authsmtp.com [62.13.128.237]) by punt18.authsmtp.com (8.14.2/8.14.2/) with ESMTP id t4Q0AdKh095744; Tue, 26 May 2015 01:10:39 +0100 (BST) Received: from savin.petertodd.org (75-119-251-161.dsl.teksavvy.com [75.119.251.161]) (authenticated bits=128) by mail.authsmtp.com (8.14.2/8.14.2/) with ESMTP id t4Q0AZjO074831 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO); Tue, 26 May 2015 01:10:37 +0100 (BST) Date: Mon, 25 May 2015 20:10:34 -0400 From: Peter Todd To: Mike Hearn Message-ID: <20150526001034.GF21367@savin.petertodd.org> References: <20150525212638.GB12430@savin.petertodd.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="zGQnqpIoxlsbsOfg" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Server-Quench: a3530f08-033b-11e5-9f74-002590a135d3 X-AuthReport-Spam: If SPAM / abuse - report it at: http://www.authsmtp.com/abuse X-AuthRoute: OCd2Yg0TA1ZNQRgX IjsJECJaVQIpKltL GxAVKBZePFsRUQkR aQdMdAQUFVQNAgsB AmMbW1VeUV17Wms7 bA9PbARUfEhLXhtr VklWR1pVCwQmRRhg Bm90CGZycAFOe38+ Z0diWnAVDUd/dkYr QkZJFW4FN3phaTUa TUkOcAdJcANIexZF O1F8UScOLw51Pz4z GA41ejw8IzhbLzxQ TwcRGBo5Rl0XViU1 WREEEi5nF1xNWj4y KRNuMFMEGE8aPwA4 IB4vVF9ce0RKT1wG UikA X-Authentic-SMTP: 61633532353630.1024:706 X-AuthFastPath: 0 (Was 255) X-AuthSMTP-Origin: 75.119.251.161/587 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 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [62.13.149.84 listed in list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record X-Headers-End: 1Yx2SE-0007CB-7b Cc: Bitcoin Dev Subject: [Bitcoin-development] Cost savings by using replace-by-fee, 30-90% 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: Tue, 26 May 2015 00:10:47 -0000 --zGQnqpIoxlsbsOfg Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, May 26, 2015 at 12:03:09AM +0200, Mike Hearn wrote: > CPFP also solves it just fine. CPFP is a significantly more expensive way of paying fees than RBF, particularly for the use-case of defragmenting outputs, with cost savings ranging from 30% to 90% Case 1: CPFP vs. RBF for increasing the fee on a single tx ---------------------------------------------------------- Creating an spending a P2PKH output uses 34 bytes of txout, and 148 bytes of txin, 182 bytes total. Let's suppose I have a 1 BTC P2PKH output and I want to pay 0.1 BTC to Alice. This results in a 1in/2out transaction t1 that's 226 bytes in size. I forget to click on the "priority fee" option, so it goes out with the minimum fee of 2.26uBTC. Whoops! I use CPFP to spend that output, creating a new transaction t2 that's 192 bytes in size. I want to pay 1mBTC/KB for a fast confirmation, so I'm now paying 418uBTC of transaction fees. On the other hand, had I use RBF, my wallet would have simply rebroadcast t1 with the change address decreased. The rules require you to pay 2.26uBTC for the bandwidth consumed broadcasting it, plus the new fee level, or 218uBTC of fees in total. Cost savings: 48% Case 2: Paying multiple recipients in succession ------------------------------------------------ Suppose that after I pay Alice, I also decide to pay Bob for his hard work demonstrating cryptographic protocols. I need to create a new transaction t2 spending t1's change address. Normally t2 would be another 226 bytes in size, resulting in 226uBTC additional fees. With RBF on the other hand I can simply double-spend t1 with a transaction paying both Alice and Bob. This new transaction is 260 bytes in size. I have to pay 2.6uBTC additional fees to pay for the bandwidth consumed broadcasting it, resulting in an additional 36uBTC of fees. Cost savings: 84% Case 3: Paying multiple recipients from a 2-of-3 multisig wallet ---------------------------------------------------------------- The above situation gets even worse with multisig. t1 in the multisig case is 367 bytes; t2 another 367 bytes, costing an additional 367uBTC in fees. With RBF we rewrite t1 with an additional output, resulting in a 399 byte transaction, with just 36uBTC in additional fees. Cost savings: 90% Case 4: Dust defragmentation ---------------------------- My wallet has a two transaction outputs that it wants to combine into one for the purpose of UTXO defragmentation. It broadcasts transaction t1 with two inputs and one output, size 340 bytes, paying zero fees. Prior to the transaction confirming I find I need to spend those funds for a priority transaction at the 1mBTC/KB fee level. This transaction, t2a, has one input and two outputs, 226 bytes in size. However it needs to pay fees for both transactions at once, resulting in a combined total fee of 556uBTC. If this situation happens frequently, defragmenting UTXOs is likely to cost more in additional fees than it saves. With RBF I'd simply doublespend t1 with a 2-in-2-out transaction 374 bytes in size, paying 374uBTC. Even better, if one of the two inputs is sufficiently large to cover my costs I can doublespend t1 with a 1-in-2-out tx just 226 bytes in size, paying 226uBTC. Cost savings: 32% to 59%, or even infinite if defragmentation w/o RBF costs you more than you save --=20 'peter'[:-1]@petertodd.org 0000000000000000134ce6577d4122094479f548b997baf84367eaf0c190bc9f --zGQnqpIoxlsbsOfg Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- iQGrBAEBCACVBQJVY7n2XhSAAAAAABUAQGJsb2NraGFzaEBiaXRjb2luLm9yZzAw MDAwMDAwMDAwMDAwMDAwMjY1YzI3NDRmMDJmNGI1MTlhMDEzYzE3MTlkYTU1YTYx NTBkZjNhOWFkNTM4OWIvFIAAAAAAFQARcGthLWFkZHJlc3NAZ251cGcub3JncGV0 ZUBwZXRlcnRvZC5vcmcACgkQJIFAPaXwkfuPIQf/YsiTcXxa+V2RhHaIdXCE71Nu sD8jfsfba0+AUzRHqGvf/xwpNwtMe3WWcPnCQBxSQpmYE3a8wm04E6McS2IkwH3e xv2F2NEXiemxcejWkBTNQmUXeTrRk2o/VyLmzsNx2r3ZCZgilOdCxQZHLBrFlD78 kmxRt4KJRAg2MEScJ3/EMDgONum8ayOK4piL1W4PyrUCmG8xSwDM8n6V3VLiFDRo 0/tdKslMsh2Gp3a3POejnvxX6cqtvZDINYdx40f+Bi3Er1d22L7Iwwj+A96fSyO4 R26EHAsQmETANrfUfMyFWMHhBMQwt6ab5IPHa3tUBpQZBv0ktO0/OUj6UXKugg== =OUT9 -----END PGP SIGNATURE----- --zGQnqpIoxlsbsOfg--