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 53C2D3364 for ; Tue, 30 Jul 2019 21:27:29 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mx1.riseup.net (mx1.riseup.net [198.252.153.129]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id D227AA8 for ; Tue, 30 Jul 2019 21:27:28 +0000 (UTC) Received: from capuchin.riseup.net (capuchin-pn.riseup.net [10.0.1.176]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (Client CN "*.riseup.net", Issuer "COMODO RSA Domain Validation Secure Server CA" (verified OK)) by mx1.riseup.net (Postfix) with ESMTPS id 76BF71A3057; Tue, 30 Jul 2019 14:27:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=riseup.net; s=squak; t=1564522048; bh=qtL9BaYzcpRjz5dHxqxW/ga0DaLecE4qKoxLXmndPUw=; h=Subject:To:References:From:Date:In-Reply-To:From; b=Btezl52yy6eBBddVCIy5BrKJX2e9CwV13h7j+ptQmZEx/oEIlyzSUXjaczpNbSLjQ INnyq6VnFMYb+fh3Kg8hjy20MVQsVrlU3Yvyt1UhK1hGAc787axUzZWc6umXVCZ50L jpyNWqLkRZz7p1tSl2ib8s70xXD9BeO3gpU2n1Mc= X-Riseup-User-ID: 2BD52709D48E8E2CCE987A49EE9C94A5EA147332FF2E2B4CF2F61515519D9D7C Received: from [127.0.0.1] (localhost [127.0.0.1]) by capuchin.riseup.net (Postfix) with ESMTPSA id 7354B12054B; Tue, 30 Jul 2019 14:27:27 -0700 (PDT) To: "David A. Harding" , Bitcoin Protocol Discussion References: <985792b1-e7aa-677b-a7a1-6a5f672da884@riseup.net> <20190727193417.cxf544dbempencql@ganymede> From: Chris Belcher Openpgp: preference=signencrypt Autocrypt: addr=belcher@riseup.net; prefer-encrypt=mutual; keydata= mQINBFPk74oBEACzBLjd+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+LwIsgbdH4KZj7mVOsJwARAQABtB9DaHJpcyBCZWxj aGVyIDxmYWxzZUBlbWFpbC5jb20+iQI+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 k4dhWbkCDQRT5O+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+EwfvgAUAEQEAAYkCJQQYAQIA 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: <96722b03-9aa0-5e3d-25ed-c644c26d5a27@riseup.net> Date: Tue, 30 Jul 2019 22:27:17 +0100 MIME-Version: 1.0 In-Reply-To: <20190727193417.cxf544dbempencql@ganymede> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-2.7 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, 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 X-Mailman-Approved-At: Wed, 31 Jul 2019 13:17:09 +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, 30 Jul 2019 21:27:29 -0000 On 27/07/2019 20:34, David A. Harding wrote: > > Timelocking bitcoins, especially for long periods, carries some special > risks in Bitcoin: > > 1. Inability to sell fork coins, also creating an inability to influence > the price signals that help determine the outcome of chainsplits. > > 2. Possible inability to transition to new security mechanisms if > a major weakness is discovered in ECC or a hash function. > Far future locks are problematic. In my proposal I've only considered locked coins for only 6 months because of exactly these reasons. The market competition between airdrops should still exist after 6 months so lockers will still get a chance to sell their airdrops. And any ECC-alternative or hash-function-alternative fork will probably take a couple of months to be designed, implemented and deployed as well, giving a chance for lockers to move coins. > An alternative to timelocks might be coin age---the value of a UTXO > multiplied by the time since that UTXO was confirmed. Coin age may be > even harder for an attacker to acquire given that it is a measure of > past patience rather than future sacrifice. It also doesn't require > using any particular script and so is flexible no matter what policy the > coin owner wants to use (especially if proof-of-funds signatures are > generated using something like BIP322). I'm becoming more and more convinced that coin age is also a valid method of proving a sacrifice. Using coin age also has a benefit that less block space is used, because using timelocks requires a new on-chain transaction to be made every 6 months or whatever the locking period is. Perhaps JoinMarket should accept all three methods of proving a sacrifice: burning, timelocking and aging. I could imagine that makers would first lock coins for 6 months to create a fidelity bond they could immediately use, and after the timelock expires leave that coin unspent and use its age as the fidelity bond. For what its worth, I mostly considered burning coins because the maths for it is easy (the value of such a bond is just V^2), and because it provides a boundary condition (locking up coins for infinity time is the same as burning them). I doubt anybody will actually do it in practice. > - BIP158 users who have saved their past filters to disk can use them to > determine which blocks subsequent to the one including the UTXO may > contain a spend from it. However, since a UTXO can be spent in the > same block, they'd always need to download the block containing the > UTXO (alternatively, the script could contain a 1-block CSV delay > ensuring any spend occurred in a later block). If BIP158 filters > become committed at some point, this mechanism is upgraded to SPV-level > security. This scheme could be attacked using address reuse. An attacker could create an aged coin on a heavily-reused address, which would force an SPV client using this scheme to download all the blocks which contain this reused address which could result in many gigabytes of extra download requirement. So to fix this: a condition for aged coins is that their address has not been reused, if the coin is on a reused address then the value of the fidelity bond becomes zero.