From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 24F4288A for ; Thu, 30 Jun 2016 11:56:49 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-pf0-f175.google.com (mail-pf0-f175.google.com [209.85.192.175]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 735EA179 for ; Thu, 30 Jun 2016 11:56:48 +0000 (UTC) Received: by mail-pf0-f175.google.com with SMTP id t190so28921010pfb.3 for ; Thu, 30 Jun 2016 04:56:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=voskuil-org.20150623.gappssmtp.com; s=20150623; h=mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=G2NSRMUyl4Q73fC+ezEy76PT2JVYcOfIEs+d0vvjIw8=; b=lPrBpMLtarA/J0ZFhcbgdZzUGBAi8MPi+kxLSbAfkQwOROOslXeHa/gyVkRaLGVLHQ eZbTLlxovt5RNzvVVw/eu6Qga4EedbjECfFr94dgKxU7AQtaDhT1rPP/InYJpQyX6c42 AMTgSvsjNfN6m395pNNvbGPCjRpGQRBIRrZmcZpB+sl0khJxrRKRQx1yMDmkukgI4qBy UANvqIatOLwsyoZInQorFXDoknfy1XmQdsJ1owJ8vlBMjGDLJod5ZFoz0JwTesn6WLVE 3XuLbeT9387BlR/HmCzL2I57T8a9Cqnujk4lMKsYYvm5qYk5qT16mGDkJ4nnq8oPjcs4 pkVg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=G2NSRMUyl4Q73fC+ezEy76PT2JVYcOfIEs+d0vvjIw8=; b=jfHWjntR2njwO4ZLL6N8X7meDRNYClq/TdjLzuccU+guQcMV0cCzJ4Aj/Lm4AjOx9e DQ7sLed/j8IA5YSvPtNekBo9i6bn1gY/OsxR0d0D3lzqfmJt6K7aGf8LC7ldmLEdiLC1 LVnNoZ593bSz0TEl0bRjlUScyK4z6ywt1bUToMzpPXmJT51bgCEGVx/PSgs/f0ro1PnL /fZWIl2Wh0uL2J7BbgQFv2sfPQ6D1Y0briTHoA+3IVAatS57C5orP4DRmGxIA+h1dWa1 WmxjsS6jqxJCVHnTorgwecErIDnIGkqxwp91qHEzFudjX8fPePokBJnrIb8zVD/uEtPW NWug== X-Gm-Message-State: ALyK8tIhImrQaCM3hhXbAmJRknpT24Db1Wi00ayuPYKjAhHja9nLB1g+rFvWV+Tg+NeBXQ== X-Received: by 10.98.9.141 with SMTP id 13mr20584577pfj.130.1467287808035; Thu, 30 Jun 2016 04:56:48 -0700 (PDT) Received: from [10.171.23.222] ([166.170.43.16]) by smtp.gmail.com with ESMTPSA id by5sm5313208pad.36.2016.06.30.04.56.46 (version=TLS1 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Thu, 30 Jun 2016 04:56:47 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (1.0) From: Eric Voskuil X-Mailer: iPhone Mail (13F69) In-Reply-To: <20160629111728.GO13338@dosf1.alfie.wtf> Date: Thu, 30 Jun 2016 13:56:42 +0200 Content-Transfer-Encoding: quoted-printable Message-Id: <2981A919-4550-4807-8ED9-F8C51B2DC061@voskuil.org> References: <87h9cecad5.fsf@rustcorp.com.au> <1E86A00F-0609-4DBC-9543-94AE04CC13C9@voskuil.org> <577234A4.3030808@jonasschnelli.ch> <360EF9B8-A174-41CA-AFDD-2BC2C0B4DECB@voskuil.org> <20160629111728.GO13338@dosf1.alfie.wtf> To: Alfie John X-Spam-Status: No, score=-2.6 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, MIME_QP_LONG_LINE, RCVD_IN_DNSWL_LOW autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.org Cc: Bitcoin Protocol Discussion Subject: Re: [bitcoin-dev] BIP 151 X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Bitcoin Protocol Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 30 Jun 2016 11:56:49 -0000 Hi Alfie, Yes, this is exactly what I meant. The complexity of the proposed constructi= on is comparable to that of Bitcoin itself. This is not itself prohibitive, b= ut it is clearly worthy of consideration. A question we should ask is whether decentralized anonymous credentials is a= pplicable to the authentication problem posed by BIP151. I propose that it i= s not. The core problem posed by BIP151 is a MITM attack. The implied solution (BIP= 151 + authentication) requires that a peer trusts that another is not an att= acker.=20 Authentication of an anonymous peer cannot achieve this objective, since the= peer may be anyone and an attack on privacy can be undetectable. The identi= ty of a peer must be known to the relying peer, either directly or transitiv= ely. DAC is applicable in cases where identity is never required. The prime exam= ple in the paper is that of first-come-first-served name registration. No id= entity is required in that scenario, just proof that a party in question is t= he original registrant. All participants are presumed to be "good". I believe that a distributed anonymous system is fundamentally at odds with i= solation of "good" vs. "bad" participants who comply with protocol rules (Do= S considerations aside), and that any attempt to resolve this conflict will r= esult in the system no longer allowing anonymous participation. I may be mistaken, but I haven't found a way out of this realization. e > On Jun 29, 2016, at 1:17 PM, Alfie John wrote: >=20 > On Tue, Jun 28, 2016 at 06:45:58PM +0200, Eric Voskuil via bitcoin-dev wro= te: >>> then we should definitively use a form of end-to-end encryption between >>> nodes. Built into the network layer. >>=20 >> Widespread application of this model is potentially problematic. It is a >> non-trivial problem to design a distributed system that requires authenti= cation >> but without identity and without central control. In fact this may be mor= e >> challenging than Bitcoin itself. Trust on first use (TOFU) does not solve= this >> problem. >=20 > Maybe the following paper can feed into this discussion: >=20 > "Decentralized Anonymous Credentials" by Christina Garman, Matthew Green, I= an Miers > https://eprint.iacr.org/2013/622.pdf >=20 > Alfie >=20 > --=20 > Alfie John > https://www.alfie.wtf