Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 61C7A8D4 for ; Fri, 6 Nov 2015 14:08:13 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from mout.perfora.net (mout.perfora.net [74.208.4.196]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 8D7FC140 for ; Fri, 6 Nov 2015 14:08:12 +0000 (UTC) Received: from mail-ig0-f176.google.com ([209.85.213.176]) by mrelay.perfora.net (mreueus001) with ESMTPSA (Nemesis) id 0MEm44-1ZfoWX2ide-00G7YC for ; Fri, 06 Nov 2015 15:08:11 +0100 Received: by igvi2 with SMTP id i2so32782541igv.0 for ; Fri, 06 Nov 2015 06:08:11 -0800 (PST) MIME-Version: 1.0 X-Received: by 10.50.178.142 with SMTP id cy14mr370507igc.18.1446818891023; Fri, 06 Nov 2015 06:08:11 -0800 (PST) Received: by 10.50.180.132 with HTTP; Fri, 6 Nov 2015 06:08:10 -0800 (PST) In-Reply-To: References: <563BE746.5030406@voskuil.org> Date: Fri, 6 Nov 2015 15:08:10 +0100 X-Gmail-Original-Message-ID: Message-ID: From: Adam Back To: Chris Priest Content-Type: text/plain; charset=UTF-8 X-Provags-ID: V03:K0:BMRuSNV3DdMqgsQ3jBBILCbWxTYd+OmFmwidftWH4/bUPVc7qez J7QIdeG5hLCEHZBlUWDs26uVOWU9vHNnkmF19FhCD6QILlvk9w0c+YxuevjT7v/vsqmlx/R W59l7cYXJ/NCHtSaiNr5YNMdrOGs2lTA6XvqwIOdw1WXRF3n8D5iWzWNhDXudHEp1CBIGAi KSwrf1OEGxJDq32/EY8Qw== X-UI-Out-Filterresults: notjunk:1;V01:K0:tvjAIWFP/W0=:GQBY2WRUcJuIRBNp25XUf7 HM5AfPfItFXJZqkyiy030sREI37N6mwMvNUlhowI5zysZ4bxsqz3lh5+8o1WESHO2Dd8LhpSO I6DSQcG4tLNLF9JfHZd1KEbIi0/P93/Rm57SIozkiw4lweAp+LT7H7fCqBk/XmYA3gybr+ykW IofciBICTmKTiOaetQrQ94sBEDUmnu1RPjBAx/159kLh6hGLl5gjpqxXEs+o4QeCqjyC2SQdx pY149R2GK/EP0MwEPHZQHlv08kGKDVKuRlYUPGndW/HChWJGMF5jIM6/wQSXzUk4dIsLdj0R5 Y/UhpyN2anZwAQF6hutUVrUOrFx4IDs9GfTFEWJT0hZ7YHQyIIVGXTt1SHZORE1bd8rmwXIRC VR53IkDusR/yPTM2NSvWufU69yAA0att5q41RyIAfLCZvcC2gWhMMSATHdzM1CtvkeY2mPiqS BCskXTFFw6PDSuw8gR/QiYbmHxN1hfitaCQElP5WTuBrHvGi5dYdBr0mH7FzgUaBoGusjbx6O UQHpD6Zv5mp2haYgFKEDygpEUo15/1o5rSAOOFkiRcNrFFsCKrrQaa+4yl3IlKMmHTu7YcOaT s3MFgDGSxo4bIQtlAdV5PGFYyMIrpNj6D8AEpiuzHhgL8gj+41OraVQXiIg7HNFWw9mMt32s6 +dXugWEYY/212894wu3+5WST/0FnvO9IlA8ttazjivOMBwSdB4fEv3XsJ8hlM5mTXYoriWp6R WkipGUK+fZ8EUide X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.org Cc: Bitcoin Dev Subject: Re: [bitcoin-dev] summarising security assumptions (re cost metrics) X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Bitcoin Development Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 06 Nov 2015 14:08:13 -0000 You're right that it is better that there be more APIs than fewer, that is less of a single point of failure. It also depends what you mean by APIs: using an API to have a second cross-check of information is quite different to building a wallet or business that only interfaces with the blockchain via a 3rd party API. There are different APIs also: some are additive eg they add a second signature via multisig, but even those models while better can still be a mixed story for security, if the user is not also checking their own full-node or checking SPV to make the first signature. Power users and businesses using APIs instead of running a full-node, or instead of doing SPV checks, should be clear about the API and what security they are delegating to a third party, and whether they have a reason to trust the governance and security competence of the third party: in the simplest case it can reduce their and their users security below SPV. The bigger point however, which Erik explained, was: widespread use of APIs as a sole means of interfacing with the blockchain also contributes to reducing network security for everyone, because it erodes the consensus rule validation security described under "Validators" in the OP. Adam On 6 November 2015 at 09:05, Chris Priest wrote: > On 11/5/15, Eric Voskuil via bitcoin-dev > wrote: >> On 11/05/2015 03:03 PM, Adam Back via bitcoin-dev wrote: >>> ... >>> Validators: Economically dependent full nodes are an important part of >>> Bitcoin's security model because they assure Bitcoin security by >>> enforcing consensus rules. While full nodes do not have orphan >>> risk, we also dont want maliciously crafted blocks with pathological >>> validation cost to erode security by knocking reasonable spec full >>> nodes off the network on CPU (or bandwidth grounds). >>> ... >>> Validators vs Miner decentralisation balance: >>> >>> There is a tradeoff where we can tolerate weak miner decentralisation >>> if we can rely on good validator decentralisation or vice versa. But >>> both being weak is risky. Currently given mining centralisation >>> itself is weak, that makes validator decentralisation a critical >>> remaining defence - ie security depends more on validator >>> decentralisation than it would if mining decentralisation was in a >>> better shape. >> >> This side of the security model seems underappreciated, if not poorly >> understood. Weakening is not just occurring because of the proliferation >> of non-validating wallet software and centralized (web) wallets, but >> also centralized Bitcoin APIs. >> >> Over time developers tend to settle on a couple of API providers for a >> given problem. Bing and Google for search and mapping, for example. All >> applications and users of them, depending on an API service, reduce to a >> single validator. Imagine most Bitcoin applications built on the >> equivalent of Bing and Google. >> >> e >> >> > > I disagree. I think blockchain APIs are a good thing for > decentralization. There aren't just 3 or 4 blockexplorer APIs out > there, there are dozens. Each API returns essentially the same data, > so they are all interchangeable. Take a look at this python package: > https://github.com/priestc/moneywagon