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 8A695279 for ; Fri, 24 Jul 2015 11:12:54 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from outbound.mailhostbox.com (outbound.mailhostbox.com [162.222.225.20]) by smtp1.linuxfoundation.org (Postfix) with ESMTP id A9E0279 for ; Fri, 24 Jul 2015 11:12:47 +0000 (UTC) Received: from [0.0.0.0] (bolobolo1.torservers.net [96.47.226.20]) (using TLSv1 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (No client certificate requested) (Authenticated sender: s7r@sky-ip.org) by outbound.mailhostbox.com (Postfix) with ESMTPSA id 42282782B07; Fri, 24 Jul 2015 11:12:45 +0000 (GMT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sky-ip.org; s=20110108; t=1437736367; bh=DQ8TeHwdeBxaDalsJCu5SKtNMbIgmMjeRf6FUPtc5lM=; h=Reply-To:Subject:References:To:From:Date:In-Reply-To; b=eYN8g9DePqlPrdHtAiaqgn9gyqQtM1NDxldYWyPfdWYCVVFZYJDM7K4dcqsGvgUBa DqklLZFZPZkt8l4W8etl4V0TtgyPPUKZLmwCgEzLRlgc4p70Xcdsp5CNh7vbjqBLyX XRHNrQRjBgTCAKqh9AXNxwZC5Jzt8H5w/FffZch4= Reply-To: s7r@sky-ip.org References: <55AFBBE6.3060702@electrum.org> To: Thomas Voegtlin , bitcoin-dev@lists.linuxfoundation.org From: s7r X-Enigmail-Draft-Status: N1010 Message-ID: <55B21DA7.2020706@sky-ip.org> Date: Fri, 24 Jul 2015 14:12:39 +0300 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: <55AFBBE6.3060702@electrum.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit X-CMAE-Score: 0 X-CMAE-Analysis: v=2.1 cv=I/SYP4Ug c=1 sm=1 tr=0 a=dFCltrIYHCDM1x7031pMDg==:117 a=dFCltrIYHCDM1x7031pMDg==:17 a=ZDnEzkWgAAAA:8 a=-NIMs_s3AAAA:8 a=bvjBBkZ6AAAA:8 a=JAI3OqB5mnwA:10 a=N659UExz7-8A:10 a=ag1SF4gXAAAA:8 a=MRO7xvu3lxBIMu5qaUgA:9 a=q3gmBntzxxUII_ge:21 a=OBT9Xan99dpYmU7y:21 a=pILNOxqGKmIA:10 X-Spam-Status: No, score=-0.3 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,URIBL_BLACK autolearn=no version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.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 11:12:54 -0000 Hi, I think this would be too complicated in practice and you'd have to defend against many other types of attacks, including but not limited to Sybil attacks, misbehaving servers not responding to requests, misbehaving servers not forwarding requests, you'd need some kind of directory servers or master servers which sign and authenticate the public server keys, otherwise someone can poison that data and provide the clients with wrong server keys. Secondly, you'd not use RSA for this, but rather Ed25519 which is faster, more cpu efficient and provides better security. Last but not least, I don't see this as a major issue and I really thin it is not worth your time. Better work on electrum server defenses, hardening them against DoS. After all, Electrum is a SPV based Bitcoin wallet, so it cannot be more anonymous than Bitcoin itself, which we already know it is pseudonymous, not anonymous and transactions can /will be linked to addresses. This is just a limitation of Bitcoin as it is today, and using SPV you assume the risk of trusting the server, it's just how SPV should work. As a pro, it gives you the ability to sync immediately and not download the entire blockchain. Privacy concerned people should run their own Electrum server and make it accessible via .onion, and connect the bitcoind running on the electrum server host only to other onion peers (onlynet=tor). We should highlight that using Electrum with Tor cannot leak more that some addresses belong to the same wallet, which is not the end of the world. On 7/22/2015 6:51 PM, Thomas Voegtlin via bitcoin-dev wrote: > Hello, > > Although Electrum clients connect to several servers in order to fetch > block headers, they typically request address balances and address > histories from a single server. This means that the chosen server knows > that a given set of addresses belong to the same wallet. That is true > even if Electrum is used over TOR. > > There have been various proposals to improve on that, but none of them > really convinced me so far. One recurrent proposal has been to create > subsets of wallet addresses, and to send them to separate servers. In my > opinion, this does not really improve anonymity, because it requires > trusting more servers. > > 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 pubkeys > * 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 encrypted > requests to M > * M dispatches the client's requests to the corresponding servers 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 client. > * The client decrypts the encrypted response with k_addr_i > > What do you think? What are the costs and benefits of such an approach? > > (Note: this will not work if all servers, or a large fraction of them, > are controlled by the same entity that controls M) > > > Thomas > _______________________________________________ > bitcoin-dev mailing list > bitcoin-dev@lists.linuxfoundation.org > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev >