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Wed, 17 Feb 2021 14:27:45 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=riseup.net; s=squak; t=1613600865; bh=yHygSGc6Azja0S46l05Uia0+h2HZz25mZcarViDjDq0=; h=To:From:Subject:Date:From; b=D0KHdi4ME60/Vb+J3juHAkaUTfi0QtKMO91T+91sLMfCgZHT+vsQHI5+erIZTeNAL uFLc2T1SU2zO0Z+5TMk/pzSTAh2IJ+FWZTAv5yjSXQ+2EBmvj4a/oRoKuXJtopLe0J tW08dqCGvZc6hS/3mmiFY1K7Jj4FbTrErU9krm8g= X-Riseup-User-ID: 2F1B4BA80DD799708F8B3E5CB481493D8C6C6A2483435447A0D2987CA7919F27 Received: from [127.0.0.1] (localhost [127.0.0.1]) by fews1.riseup.net (Postfix) with ESMTPSA id 4Dgssr6pndz5vSh for ; Wed, 17 Feb 2021 14:27:41 -0800 (PST) To: bitcoin-dev@lists.linuxfoundation.org From: Chris Belcher Autocrypt: addr=belcher@riseup.net; prefer-encrypt=mutual; keydata= xsFNBFPk74oBEACzBLjd+Z5z7eimqPuObFTaJCTXP7fgZjgVwt+q94VQ2wM0ctk/Ft9w2A92 f14T7PiHaVDjHxrcW+6sw2VI2f60T8Tjf+b4701hIybluWL8DntG9BW19bZLmjAj7zkgektl YNDUrlYcQq2OEHm/MGk6Ajt2RA56aRKqoz22e+4ZA89gDgamxUAadul7AETSsgqOEUDI0FKR FODzoH65w1ien/DLkG1f76jd0XA6AxrESJVO0JzvkTnJGElBcA37rYaMmDi4DhG2MY4u63VE 8h6DyUXcRhmTZIAj+r+Ht+KMDiuiyQcKywCzzF/7Ui7YxqeAgjm5aPDU2E8X9Qd7cqHQzFM7 ZCqc9P6ENAk5a0JjHw0d0knApboSvkIJUB0j1xDIS0HaRlfHM4TPdOoDgnaXb7BvDfE+0zSz WkvAns9oJV6uWdnz5kllVCjgB/FXO4plyFCHhXikXjm1XuQyL8xV88OqgDFXwVhKrDL9Pknu sTchYm3BS2b5Xq1HQqToT3I2gRGTtDzZVZV0izCefJaDp1mf49k2cokDEfw9MroEj4A0Wfht 0J64pzlBYn/9zor5cZp/EAblLRDK6HKhSZArIiDR1RC7a6s7oTzmfn0suhKDdTzkbTAnDsPi Dokl58xoxz+JdYKjzVh98lpcvMPlbZ+LwIsgbdH4KZj7mVOsJwARAQABzR9DaHJpcyBCZWxj aGVyIDxmYWxzZUBlbWFpbC5jb20+wsF+BBMBAgAoBQJT5O+KAhsDBQkSzAMABgsJCAcDAgYV CAIJCgsEFgIDAQIeAQIXgAAKCRDvc06md/MRKS8jD/9P9fSYSIVjltL9brAMfIu7wJn0H0lX TbcuCM2uQitJ3BNxI3c7aq5dEby27u5Ud54otncDJuRPQVDKs6H7t1rInitgJ1MTQ9/aQGFA btKcgtVIMFbeClzTTfWr4W7fE45NI7E9EANgk5JfmWh3U+KINYLF5RtqynYocrsP6zOV+G9A HCpBemd9TN60CoMLMyMzTHEW1oQffaVAXY8DgthEYO/odWYIod7VTmEm0zU1aSysPqMwPWNm 8XIl0f8SfKQyZlAU8e1eCFVCenkE44FKC5qQNYc2UxexEYtfCWChTGc4oHKxIyYmTCCefsQF LvgwtvlNHRXHSDKSPSNcRcpl8DFpNEKrmMlkJ8Mx+YR05CydlTQ0bI3FBohJC+UHrjD5I3hA wJUC1o+yVSOEd+zN3cG1EECIwkEQSmBgG5t/le2RdzfXOdpf9ku2/zoBpq00R54JxUKlfRM7 OPTv7X+1AKHkxOySdCZwGgvdh2Whuqs4kTvtco00gCFM9fBd5oi1RJuHtxHsj8+/XU15UItb jeo96CIlM5YUeoRLPT5mxZYWgYAARFeSFReNq/Tuwq9d8EokUrtAyrPayznliy53UJfWDVzl 925c0Cz0HWaP2fWj+uFcj/8K0bhptuWJQy0Poht1z3aJC1UjEgr1Xz8I7jeSJmIlA9plcJw2 k4dhWc7BTQRT5O+KARAAyFxAM28EQwLctr0CrQhYWZfMKzAhCw+EyrUJ+/e4uiAQ4OyXifRr ZV6kLRul3WbTB1kpA6wgCShO0N3vw8fFG2Cs6QphVagEH8yfQUroaVxgADYOTLHMOb7INS8r KI/uRNmE6bXTX27oaqCEXLMycqYlufad7hr42S/T8zNh5m2vl6T/1Poj2/ormViKwAxM+8qf xd8FNI4UKmq2zZE9mZ5PiSIX0qRgM0yCvxV39ex/nhxzouTBvv4Lb1ntplR/bMLrHxsCzhyM KDgcX7ApGm+y6YEsOvzw9rRCRuJpE4lth8ShgjTtNTHfklBD6Ztymc7q7bdPWpKOEvO5lDQ6 q8+KfENv862cOLlWLk7YR2+mHZ1PXGhWC7ggwEkfGJoXo0x8X+zgUKe2+9Jj4yEhfL0IbFYC z2J5d+cWVIBktI3xqkwLUZWuAbE3vgYA4h8ztR6l18NTPkiAvpNQEaL4ZRnAx22WdsQ8GlEW dyKZBWbLUdNcMmPfGi5FCw2nNvCyN6ktv5mTZE12EqgvpzYcuUGQPIMV9KTlSPum3NLDq8QI 6grbG8iNNpEBxmCQOKz2/BuYApU2hwt2E44fL8e6CRK3ridcRdqpueg75my6KkOqm8nSiMEc /pVIHwdJ9/quiuRaeC/tZWlYPIwDWgb8ZE/g66z35WAguMQ+EwfvgAUAEQEAAcLBZQQYAQIA DwUCU+TvigIbDAUJEswDAAAKCRDvc06md/MRKaZwD/9OI3o3gVmst/mGx6hVQry++ht8dFWN IiASPBvD3E5EWbqWi6mmqSIOS6CxjU0PncxTBPCXtzxo/WzuHGQg/xtNeQ0T8b2lBScZAw93 qm1IcHXLUe5w/Tap6YaDmSYCIZAdtbHzYfPW4JK7cmvcjvF8jhTFOBEOFVQkTi19G7caVot0 +wL1e2DRHDXAe5CinEpaLBlwHeEu/5j6wc3erohUZlK9IbAclj4iZTQbaq3EyqUXl59dBOON xmL5edJxzVishIYQGIyA9WP1SylXt+kO82NEqZG2OxdXAlzjuJ8C2pAG+nbLtDo4hcsiN/MA aX9/JB7MXclT5ioerF4yNgKEdfq7LmynsTUd8w/Ilyp7AD+BWoujyO94i8h9eKvjf9PvSwxQ uAjRpxne7ZJD8vCsMNXBHSbeEK2LiwStHL/w473viXpDD53J6OLxX6a5RummR+rixbMH7dgK MJQ7FlyDphm3or6CSkGEir1KA0y1vqQNFtHhguFapAWMDKaJjQQNgvZUmOo6hbZqmvUF1OWc d6GA6j3WOUe3fDJXfbq6P9Jmxq64op887dYKsg7xjQq/7KM7wyRcqXXcbBdgvNtVDP+EnzBN HyYY/3ms4YIHE5JHxQ9LV4yPcWkYTvb1XpNIFVbrSXAeyGHVNT+SO6olFovbWIC3Az9yesaM 1aSoTg== Message-ID: <5fcab0fc-6135-7587-7b3c-a314ccd099ca@riseup.net> Date: Wed, 17 Feb 2021 22:27:28 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: [bitcoin-dev] Teleport Transactions: A CoinSwap implementation for Bitcoin X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Bitcoin Protocol Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 17 Feb 2021 22:27:48 -0000 Suppose Alice has bitcoins and wants to send them with maximal privacy, so she creates a special kind of transaction. For anyone looking at the blockchain her transaction appears completely normal with her coins seemingly going from bitcoin address A to address B. But in reality her coins end up in address Z which is entirely unconnected to either A or B. Now imagine another user, Carol, who isn't too bothered by privacy and sends her bitcoin using a regular wallet. But because Carol's transaction looks exactly the same as Alice's, anybody analyzing the blockchain must now deal with the possibility that Carol's transaction actually sent her coins to a totally unconnected address. So Carol's privacy is improved even though she didn't change her behaviour, and perhaps had never even heard of this software. In a world where advertisers, social media and other companies want to collect all of Alice's and Carol's data, such privacy improvement would be incredibly valuable. And also the doubt added to every transaction would greatly boost the fungibility of bitcoin and so make it a better form of money. This undetectable privacy can be developed today by implementing CoinSwap. The software could be standalone as a kind of bitcoin mixing app, but it could also be a library that existing wallets can implement allowing their users to send Bitcoin transactions with much greater privacy. For the last few months I've been working on implementing this project. Here it is: https://github.com/bitcoin-teleport/teleport-transactions/ The project can create multi-transaction CoinSwaps (intended to avoid amount correlation), and multi-hop CoinSwaps (intended to stop one single maker being able to unmix a taker's CoinSwap). Just for fun I created a 5-hop CoinSwap on testnet. Here are the transaction IDs of each funding transaction. Each hop has 3 individual transactions. taker's outgoing txes: https://blockstream.info/testnet/tx/f45349bd279bea20b8b218300f8e2416abf28f3858470ad8c5eb2f6cd5ec10a9 https://blockstream.info/testnet/tx/40ea5c9e478b66fa3f615c2b8d3accfd69308443d90a5353de669767cb02c51f https://blockstream.info/testnet/tx/8fe245e9c433127af4df8ff8853650808e3281fed7de6bfda62066a3fd3ad36e maker[0] funding txes: https://blockstream.info/testnet/tx/3d9b879866ad136f9fe6e80599e1b97d610b6330be3ab4aa7df4161fce1e41d4, https://blockstream.info/testnet/tx/fa11e778d135be28b4e35498fc668c5aba7c70dcc43334b39e7488bd1259e8be, https://blockstream.info/testnet/tx/a7713452bab711c09be83a8c630fb91127771ed99cf15b528eacd28b00ba6b20, maker[1] funding txes: https://blockstream.info/testnet/tx/245e1e87d83a4bef06ceb8933c758137ee2f7ba7aa66800ebb7103707d5de5f7, https://blockstream.info/testnet/tx/15727b91e09a80634587f6210bdcba8808b93e4a780c55dd113ee85314db45c4, https://blockstream.info/testnet/tx/94e4e4e9e8fc2012158ed068145c8b883c295b37f5b3b6cba7a21c229d4da103, maker[2] funding txes: https://blockstream.info/testnet/tx/1384d58e534543e22e4f23a367728bff12177ee9af01b036c397cfca9bbe2eb8, https://blockstream.info/testnet/tx/eff3b1367f403c13927ddcb01c6d3c5c0d46076f7cb4419f8a18d6b62d884540, https://blockstream.info/testnet/tx/617c52caec2f7f17f3ebd1cab80233cdc1b414591f1cc49affbd828ffec10278, maker[3] funding txes (also taker's incoming txes): https://blockstream.info/testnet/tx/8fde61974a4e0801ae5b76b620e2effd6c837310c1bd76d738216451ae1226e3, https://blockstream.info/testnet/tx/6491b85ef73a8f88e276a9b0f951c09e0367851a83aa49ffee8f8ad095f50de2, https://blockstream.info/testnet/tx/363b6803b7e3ed45472277448ce9938e3e73167a67762d6a9ac621243b8db019, The so-called taker organized the whole thing. They decided what the CoinSwap amount should be (0.05 tBTC in this case), decided which makers to route over depending on their fees, how many transactions and makers there would be. The only thing the makers do is follow the protocol and collect their CoinSwap fees, they are not meant to even know their position in the route. Because the taker chose how much bitcoin to coinswap and when, they paid a fee to each maker to provide an incentive for the makers to keep the software running. To a passive observer of the blockchain a single-hop CoinSwap is as private as a multi-hop, so I suspect in practice most users will just create 2-hop CoinSwaps. The project is still a work in progress. All kinds of attacks are possible right now, so the it shouldn't be used on mainnet with real money yet. Also right now the CoinSwap addresses created by the project appear as 2-of-2 multisignature addresses, but the plan is to use ECDSA-2P which will make them look the same as regular single-signature addresses which is needed before the thing massively improves privacy and fungibility. CoinSwap is the next generation of bitcoin on-chain privacy tech. It improves on CoinJoin because it breaks the transaction graph, and even improves the privacy of people who don't use it. CoinSwap also uses less block space for the same privacy and therefore is cheaper in miner fees. Links: * Design document: https://gist.github.com/chris-belcher/9144bd57a91c194e332fb5ca371d0964 * Discussion: `##coinswap` IRC channel on the freenode network