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 675997A1 for ; Fri, 24 Jul 2015 02:26:18 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-pa0-f51.google.com (mail-pa0-f51.google.com [209.85.220.51]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 151DBE8 for ; Fri, 24 Jul 2015 02:26:17 +0000 (UTC) Received: by pabkd10 with SMTP id kd10so5933147pab.2 for ; Thu, 23 Jul 2015 19:26:16 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:message-id:date:from:user-agent:mime-version:to :cc:subject:references:in-reply-to:content-type; bh=kZUFEvNVhvydbGiJIrvZpUTbaSW1E3o6vMfRysldhXY=; b=dBvjUIncS0jSlP4iBjn/3Xw4kIKcyxGyWZd3Ve0oBMrWcTlMGGuzUok3vLYZYLg0/u CJJzdEvH5SjC3Pn/qMzJBfKVrwJichBOXQ5qwNpLHbxb4dpou+mFqj7p2HE4ftogoWai /diy8mR6B5f+gCqaMDichx7H7yAbC66DJDnqW3yuqpVk5eUFjiuYhgoK4EtGH7axB02h wEnZHNJf5RHCNoBk2rQrAHtiu9ejbHhV6xa9CezDpsRcQOmvPGJSFLXpv81kzmwayvhI cv07V4qYuE6eitlKPk5qdwJpOoNvDOQVfED4o6mZH3RzYokm/kc9smeMbcrxx69qI+nA YcNg== X-Gm-Message-State: ALoCoQltovzUjPu0hRxPsRvpnvbtoy95DehCA3EDR3qpUuGj39wDO2hpjGv0rudHrZsMG6ffrl0d X-Received: by 10.70.140.173 with SMTP id rh13mr25851695pdb.24.1437704776617; Thu, 23 Jul 2015 19:26:16 -0700 (PDT) Received: from [10.0.1.14] (c-67-161-88-20.hsd1.wa.comcast.net. [67.161.88.20]) by smtp.googlemail.com with ESMTPSA id y1sm11325231pdy.2.2015.07.23.19.26.15 (version=TLSv1/SSLv3 cipher=OTHER); Thu, 23 Jul 2015 19:26:15 -0700 (PDT) Message-ID: <55B1A254.6070806@voskuil.org> Date: Thu, 23 Jul 2015 19:26:28 -0700 From: Eric Voskuil User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 MIME-Version: 1.0 To: Stefan Richter , gb , Thomas Voegtlin References: <55AFBBE6.3060702@electrum.org> <1437606706.2688.0.camel@yahoo.com> <114b2a76-ebc7-461a-b4bc-10873574d6c4@HUB2.rwth-ad.de> In-Reply-To: Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="OkmUrvXDCLi6n4xBw3E9VrWIcXFRHViOT" X-Spam-Status: No, score=-2.6 required=5.0 tests=BAYES_00,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-dev@lists.linuxfoundation.org Subject: Re: [bitcoin-dev] Making Electrum more anonymous 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, 24 Jul 2015 02:26:18 -0000 This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --OkmUrvXDCLi6n4xBw3E9VrWIcXFRHViOT Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable I've looked at IT-PIR for Libbitcoin. It's certainly more elegant than onion routing for query privacy, but doesn't improve on the collusion problem. As a result the related directory problem would also remain. "This protocol sacrifices some level of privacy to gain robustness. Because of this we need to assume that there is no collusion between some number of servers. In some settings, it is unclear how this requirement can be enforced or detected. This uncertainty may make this protocol less desirable than others with different privacy guarantees." http://www.cypherpunks.ca/~iang/pubs/hybridpir-pets.pdf =46rom the same source, regarding aforementioned options: "An assumption used in many PETs, including mix networks, secret sharing, onion routing and some voting protocols, is that no more than some threshold of agents are colluding against the user to discover the private information." Another option is computationally-bounded CPIR, but from the same source:= "The main problem with the CPIR protocols already discussed is that they do not generally perform queries faster than the trivial protocol." Where the "trivial protocol" in our problem is full blockchain download. WRT an alternative CPIR proposed in 2007: "The idea behind their protocol is to add noise to the query in a way that the server cannot discover which record the client is interested in, but with the secret information that the client has, she can remove the noise from the server=E2=80=99s response." This is the idea behind stealth prefix queries: https://github.com/libbitcoin/libbitcoin-explorer/wiki/bx-fetch-stealth =46rom our perspective, another important objective of query privacy is allowing the caller make the trade-off between the relative levels of privacy and performance - from absolute to non-existent. In some cases privacy is neither required nor desired. Prefix filtering accomplishes the client-tuning objective. It also does not suffer server collusion attacks nor is it dependent on computational bounds. The primary trade-off becomes result set (download) size against privacy. e On 07/23/2015 05:23 AM, Stefan Richter wrote: > This looks like a prime application for this PIR > library: http://percy.sourceforge.net/apidocs/index.html >=20 > Eric Voskuil via bitcoin-dev > schrieb am Do., 23. Jul= i > 2015 um 02:07 Uhr: >=20 > This is a good point. I didn't delve into the specifics of > implementation due to the larger issues that I raised. Libbitcoin S= erver > uses CurveZMQ, an implementation of CurveCP. >=20 > http://curvecp.org > http://curvezmq.org > https://en.bitcoin.it/wiki/Libbitcoin_Server >=20 > e >=20 > On 07/22/2015 04:11 PM, gb via bitcoin-dev wrote: > > Why RSA? > > > >> > >> Here is an idea, inspired by TOR, on which I would like to have = some > >> feedback: We create an anonymous routing layer between Electrum > servers > >> and clients. > >> > >> * Each server S publishes a RSA public key, KS > >> * Each client receives a list of available servers and their pub= keys > >> * For each wallet address, addr_i, a client chooses a server S_i= , > and a > >> RSA keypair (K_addr_i, k_addr_i) > >> * The client creates a list of encrypted requests. Each request > contains > >> addr_i and K_addr_i, and is encrypted with the pubkey KS_i of S_= i > >> * The client chooses a main server M, and sends the list of encr= ypted > >> requests to M > >> * M dispatches the client's requests to the corresponding server= s S_i > >> (without the client's IP address.) > >> * Each server decrypts the requests it receives, performs the > request, > >> and encrypts the result with K_addr_i > >> * M receives encrypted responses, and forwards them to the clien= t. > >> * The client decrypts the encrypted response with k_addr_i >=20 > _______________________________________________ > bitcoin-dev mailing list > bitcoin-dev@lists.linuxfoundation.org > > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev >=20 --OkmUrvXDCLi6n4xBw3E9VrWIcXFRHViOT Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQEcBAEBAgAGBQJVsaJUAAoJEDzYwH8LXOFOOpgH/jUhkByUd9sDL6f3BTdU4Q1t HQyQ6NZD+yOrXhFI0nUAmPwBChqKszBHgktcKBH0m26YGLRcb2IQq6DS1swELX8Q 6dXTrQjkRdswUvTeqMSwk+Hx+Tria9CO5CBV89hblhHLAlj04JwgU4IqomeBFPXa c6+k+WyyBpkm4RueXUpr+qNojgp0uiYA5mXqbN97JfEeSiujm1x7o04R3IOSRb56 jxMb+bF2vCkRE3j6yn0BAqwGnDZq2C+Q0VdtfZgRnSlhK1NaVH0UEgfEbuhKEfn/ 24s5i4iVAzCXANMGwkX6lh5WnxM1rsL6uzEnNwFMt8s6uizTMq5ltzOn3LeW0g0= =c8VF -----END PGP SIGNATURE----- --OkmUrvXDCLi6n4xBw3E9VrWIcXFRHViOT--