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-1.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1Vn7Hg-0001XG-GI for bitcoin-development@lists.sourceforge.net; Sun, 01 Dec 2013 13:42:04 +0000 Received-SPF: pass (sog-mx-3.v43.ch3.sourceforge.com: domain of gmail.com designates 209.85.215.182 as permitted sender) client-ip=209.85.215.182; envelope-from=mh.in.england@gmail.com; helo=mail-ea0-f182.google.com; Received: from mail-ea0-f182.google.com ([209.85.215.182]) by sog-mx-3.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1Vn7Hf-0007Qc-D4 for bitcoin-development@lists.sourceforge.net; Sun, 01 Dec 2013 13:42:04 +0000 Received: by mail-ea0-f182.google.com with SMTP id o10so10892297eaj.13 for ; Sun, 01 Dec 2013 05:41:57 -0800 (PST) X-Received: by 10.14.194.195 with SMTP id m43mr61108227een.13.1385905317097; Sun, 01 Dec 2013 05:41:57 -0800 (PST) Received: from [192.168.1.105] (84-75-251-165.dclient.hispeed.ch. [84.75.251.165]) by mx.google.com with ESMTPSA id b42sm60784953eem.9.2013.12.01.05.41.54 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sun, 01 Dec 2013 05:41:54 -0800 (PST) Sender: Mike Hearn Content-Type: multipart/signed; boundary="Apple-Mail=_17D355D8-753C-45A2-861A-5ACAF4110DDC"; protocol="application/pkcs7-signature"; micalg=sha1 Mime-Version: 1.0 (Mac OS X Mail 7.0 \(1822\)) From: Mike Hearn In-Reply-To: Date: Sun, 1 Dec 2013 14:41:52 +0100 Message-Id: <5E4597E4-C1C7-4536-8CF0-82EDD7715DAB@plan99.net> References: To: Andreas Schildbach X-Mailer: Apple Mail (2.1822) 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 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (mh.in.england[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature X-Headers-End: 1Vn7Hf-0007Qc-D4 Cc: bitcoin-development@lists.sourceforge.net Subject: Re: [Bitcoin-development] Floating fees and SPV clients 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: Sun, 01 Dec 2013 13:42:04 -0000 --Apple-Mail=_17D355D8-753C-45A2-861A-5ACAF4110DDC Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=windows-1252 > As long as the tx is not confirmed (by a broadcast), apps can offer to > bump up the fee a little bit. Unfortunately there are risks to that approach.=20 The most obvious one is that nodes could keep sending reject messages to = get wallets to attach ridiculously high fees. If half a wallets peers do = this and the other half don=92t, then effectively the wallet will double = spend against itself. The bad nodes can keep the fat transaction and = send it directly to a corrupt miner, no broadcast. If some other miner = includes the original normal transaction, no problem, just take it out = of the current block. If the corrupt miner finds the current block, they = get to claim huge fee premiums. Quite apart from the problem of malicious nodes/miners, how would you = represent this in the wallet GUI? Current wallets are designed on the = assumption that 1 payment =3D=3D 1 transaction =3D=3D 1 paid fee. If a = single payment could have several different fees, and there=92s no way = to know which you will actually pay until later, then complexity would = explode. Even the notion of balance would become even more complicated = than it already is. So I really don=92t like the idea of creating different transactions = depending on error messages from remote nodes. The only time when it = could make sense is if *all* nodes reject a transaction. Then (assuming = no MITM) you can assume the first transaction can be thrown away and a = new attempt made. But if you think about what the UI flows for that would look like - it=92s= just a mess. There are other risks to fee estimation. Let=92s say wallet authors = create transactions with exactly the estimated fee needed to get into = the next block. But due to mempool skew, estimates vary, and so those = transactions don=92t propagate cleanly everywhere. Now we have two = problems: 1) Unpredictable failure to enter the mempools can lead to double = spending and slow confirmations 2) Wallet authors may be tempted to ensure that doesn=92t happen by = taking the estimate, adding 10% and using that. But then if a bunch of = popular wallets all do the same thing, the estimation algorithm might = get confused and decide that as everyone seems to be attaching a fee of = X+10%, the correct estimate for what fee to attach is X+10%. Then = wallets would immediate raise their attached fees again and you=92d = enter into a infinite upward spiral. The more I think about this, the more complicated it gets. It=92s tempting to try and just push all the complexity onto the = merchant side, but one of the best things about Bitcoin is there isn=92t = any strong notion of =93merchant=94 - that=92s inherent to being peer to = peer. So just hand-waving and saying sellers will deal with complicated = fee processes is just a punt. --Apple-Mail=_17D355D8-753C-45A2-861A-5ACAF4110DDC Content-Disposition: attachment; filename=smime.p7s Content-Type: application/pkcs7-signature; name=smime.p7s Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIIMcjCCBjQw ggQcoAMCAQICAR4wDQYJKoZIhvcNAQEFBQAwfTELMAkGA1UEBhMCSUwxFjAUBgNVBAoTDVN0YXJ0 Q29tIEx0ZC4xKzApBgNVBAsTIlNlY3VyZSBEaWdpdGFsIENlcnRpZmljYXRlIFNpZ25pbmcxKTAn BgNVBAMTIFN0YXJ0Q29tIENlcnRpZmljYXRpb24gQXV0aG9yaXR5MB4XDTA3MTAyNDIxMDE1NVoX DTE3MTAyNDIxMDE1NVowgYwxCzAJBgNVBAYTAklMMRYwFAYDVQQKEw1TdGFydENvbSBMdGQuMSsw KQYDVQQLEyJTZWN1cmUgRGlnaXRhbCBDZXJ0aWZpY2F0ZSBTaWduaW5nMTgwNgYDVQQDEy9TdGFy dENvbSBDbGFzcyAxIFByaW1hcnkgSW50ZXJtZWRpYXRlIENsaWVudCBDQTCCASIwDQYJKoZIhvcN AQEBBQADggEPADCCAQoCggEBAMcJg8zOLdgasSmkLhOrlr6KMoOMpohBllVHrdRvEg/q6r8jR+EK 75xCGhR8ToREoqe7zM9/UnC6TS2y9UKTpT1v7RSMzR0t6ndl0TWBuUr/UXBhPk+Kmy7bI4yW4urC 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