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 765E6D3D for ; Tue, 6 Aug 2019 01:56:27 +0000 (UTC) X-Greylist: delayed 00:05:16 by SQLgrey-1.7.6 Received: from geekbox.info (mx01.geekbox.info [95.216.118.16]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 23FB54C3 for ; Tue, 6 Aug 2019 01:56:25 +0000 (UTC) Received: from [192.168.1.69] (122-58-55-184-vdsl.sparkbb.co.nz [122.58.55.184]) (Authenticated sender: leo) by geekbox.info (Postfix) with ESMTPSA id 4A59C7004E5 for ; Tue, 6 Aug 2019 01:51:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=leowandersleb.de; s=mail; t=1565056267; bh=YlujNZjz1G6w/jYJdDpvmNHMe81XAHii3YSvO1u+4sg=; h=Subject:To:References:From:Date:In-Reply-To; b=a36y4zy/7jrqTnp4vOqZ5AiXFfWx6Q+gKifJN5a1URcNrPE1/Kb6NLgomCQCe+lVy COAL6XtPARpdvYumytcHWnQ0mSTHdHAfz9lFrDFN8G0cp7Ai7Wbxw6iqBcNAtSceKo wHrOo7MV8WWSHE+YAwkKy7bfKxYUwrhoDvEwLGM0= To: bitcoin-dev@lists.linuxfoundation.org References: <985792b1-e7aa-677b-a7a1-6a5f672da884@riseup.net> <94534006-D560-4C90-9D5D-A3A64B698518@gmail.com> <20190726143738.0be561da@simplexum.com> <3c328312-2bdd-60d9-7425-8db620d09abb@riseup.net> <20190731205018.10ed4302@simplexum.com> <20190802145057.7b81c597@simplexum.com> From: Leo Wandersleb Openpgp: id=FAE4D5168E9EF9F104AA1B2D6B9A1F0CB7C20812 Autocrypt: addr=leo@LeoWandersleb.de; prefer-encrypt=mutual; keydata= mQENBE3ePdoBCADZmTvPyledh9wmNRE+i5k7dUmegSmBpe1kMgzlt3nxwzyE6l3wzT9wen8E clmA4ZCLn77DjxF3Dg9X0sRio9No5r4u6luI0CzM7axvTi+5DWU25b+JGGdhKTMkyfyKBZdT 4xvjLzW9tT7upUuAh9nTcz9MBZS3vhKB1SqiBUdYqj33+2erIQzaYMIZ/crR6FbgDT5dI3gg 2YKJn4rdFy9saA0qngoDPkyU9u5TYtFk8zOreQrFXmXpLiptoxRolF9tqHyn51H4uV8ggIGc xJWRW/i2vBFHSM6ZD7PceWCRU5ehf3h/wat1xtn/H7AB+wcywkYrdg1TLifftwcKYBlzABEB AAG0JUxlbyBXYW5kZXJzbGViIDxMZW9ATGVvV2FuZGVyc2xlYi5kZT6JATgEEwECACIFAk3e PdoCGwMGCwkIBwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJEGuaHwy3wggSrqQH/Amh6+kYnIUM 8X5yicpXd37h/Nqnrs6KIE0nYCZe03tkQytndbWXmf2pBth6CEzqrS+wivU7L8dPdiFQtdEW dDe8bjJ993TsVSyYrPHv549vD4DbjtB8WS7KEkMhhl+uVaC07YXNwOTAkshv4l3G2ll6dmBn LDeF8kSU+DZ1eNzUYHjuUcQYl0XAK5wE7rVpzZUlR0Z5bKNm8QmUPgrZPu6cVRZ6tOD0EMR6 3dcGI5x0fB35gEUasgNYxQ/g2arh66Pg45olKT1bTcrTJYrE8IePElSCIFDrzrZMhStY3TbQ qI3T0vsFGzEeU9M6LmKV8aii4g8o7af0kr4vYS3Nsp65AQ0ETd492gEIAMnahwe+MNliWgpF B+UfrwzfgiLjtizH307HYB67THS4h2+MoBJUAqrV7CQkZ8kMYLBl4D+hvxrXDYte6wTb0kcY X4NTGof8EDBPxUERYJlWbTbLccbA8d3ia++aTtqd9yRHobK8AO4R22cslYV/nQChHc+1/NFV 8V1O67U7XpnxQMUzYIhhvVcUwj+8bw/F3zPzS03PWnDv+gmwHt63w72Dth+P0F93/rI+OiEA kC/7//1ngQ7auqOeWVdqR8Z1s7tI4kxsVkJfqj3wVu+qaso8FpjNGs888xH8xhgXlll8APWj V9Rl3GtpRTdobzNh58jUfGmHh5bcRrYTrtldDwkAEQEAAYkBHwQYAQIACQUCTd492gIbDAAK CRBrmh8Mt8IIEi3MB/0UlpEORi7qBOH9egn/8E9fXj3QGpmQ7IAvzvLjkp3cArerBhObhGJ+ lZ679/9KZ4FxWLDStzGJH3thQstZjcUZzLwTP1sNdY+uPkvOqrzclfPK13z5hJhORD8W0brB UptTvyZthIxNIbY4uSbrvaAJmcPFi3cdKOjZz9XyH8AAxXcWGUjQuqxEc0GuM8h8asaUJesB bE4J+HPZXcAOC3D+qIqvM438Nbb8Pu7yYWrdq5kmbDMg2nPHXUOOovEsXWBGjWEiXWVUei75 5Fumqg5mz4P8/Ry3DwZBuHN3Op77gXogvyeE/B5O6dZzWWpSqBIS6MQcLD1divwi/2vNS4c4 Message-ID: <3a9a9277-130d-fbb2-fa51-6119a2242812@LeoWandersleb.de> Date: Tue, 6 Aug 2019 13:51:02 +1200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Spam-Status: No, score=-1.7 required=5.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED autolearn=no version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.org X-Mailman-Approved-At: Tue, 06 Aug 2019 04:39:17 +0000 Subject: Re: [bitcoin-dev] Improving JoinMarket's resistance to sybil attacks using fidelity bonds 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: Tue, 06 Aug 2019 01:56:27 -0000 On 8/6/19 7:04 AM, Chris Belcher via bitcoin-dev wrote: > However, there _is_ a cost to being a sybil attacker. If we define > honest makers as entities who run just one maker bot, and dishonest > makers as entities who run multiple maker bots, then we can say that > running a dishonest maker operation requires a sacrifice of fee income, > because someone doing that would earn more money if they ran an honest > maker instead. This happens because of the quadratic V^2 term in the > formula calculating the fidelity bond value, which provides this > incentive for lumping together fidelity bonds. This V^2 is probably the > most important part for privacy. As established above, there will emerge a market to lock coins, so these locks will be readily available without having to buy them. Even with V^2 there is no reason to amass more coins beyond a certain point. Running the biggest 5 V^2 scores should be pretty solid to get in on many coin joins. > Another way is to require the bond signature proofs to involve the > one-time taker identifier, and so be different every time. This > basically requires fidelity bond privkeys to be online in hot wallets, > and so should massively increase the difficulty of renting TXOs because > the maker and the TXO owner need to be in constant real-time communication. Requiring the bond to reside on a hot wallet would be a massive disadvantage. No matter how you look at the whole problem of sibyl attacks, the honest maker will have operational costs and gain fees and the sibyl attacker will have the same plus profit from the deanonymization. As long as makers hunt marginal profits, the sibyl attacker having the higher margin from deanonymization will always win. The fidelity bonds would make this even worse, as increased complexity and entry cost would not favor more makers but less even before the centralization incentive mentioned above (V^2). To say that old holders have bitcoins laying around that they can use for such bonds is a fallacy as they could just as well rent them out on a bonds market. How about turning this upside down and shift the incentives from being taker to being maker by introducing a mandatory fee? If each join costs 1% per maker, people would initially gasp and reject to update to that version but those who do, will do to become makers, increasing the maker count massively and eventually most people in frequent need of joining will also become makers to offset the costs of being takers. With these changed rules again the sibyl attackers would still have their competitive edge and would flood the market with even more cheap offers but now everybody would have an incentive to do the same and as makers have to have the UTXOs, it's not free to sibyl attack already. LW