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 413C1E3A for ; Sat, 29 Aug 2015 05:41:07 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-ig0-f172.google.com (mail-ig0-f172.google.com [209.85.213.172]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 0C706AB for ; Sat, 29 Aug 2015 05:41:06 +0000 (UTC) Received: by igbuu8 with SMTP id uu8so2042635igb.1 for ; Fri, 28 Aug 2015 22:41:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=message-id:date:from:user-agent:mime-version:to:subject :content-type:content-transfer-encoding; bh=DSBbGfPdxKE5sOPOPoZrK5VqtcrNe1O45ynJi76pz9E=; b=cenxidLA71E8jeam9YvXSirNdR1eAS4v2owUvWO0OUH5Ho/r3b57bXLLSNgmGsxbxF z283Ynm+O7JSCZkh9sl0AsTBV5SLrz6m9u0yq5Rpm03c5H64z1Qjb2C3JDWOre247DP9 1N07Tpe6OJ3bcDzfs0sYnDZPs/VKmUSH7VNe2fNGV2IPAfc+hCF/y47NbyK/aa12J20w Y/sItvdGKL3ftXIjq++B4lXAEFHB/PlbzJWPXWSmwcqLw4hmysMye+/A0LMT/vqP9NGr VDqleOmjuytS3qOJrL1kmUjo9zG/r5Nx7nscCpg8WUxP7svmsp5ufrvGZ81/UjVQN+Ky xelA== X-Received: by 10.50.59.211 with SMTP id b19mr6039346igr.42.1440826865449; Fri, 28 Aug 2015 22:41:05 -0700 (PDT) Received: from justin-mbp.local (c-98-237-121-184.hsd1.pa.comcast.net. [98.237.121.184]) by smtp.googlemail.com with ESMTPSA id p79sm6582624iop.15.2015.08.28.22.41.04 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 28 Aug 2015 22:41:04 -0700 (PDT) Message-ID: <55E145EF.3060801@gmail.com> Date: Sat, 29 Aug 2015 01:41:03 -0400 From: "Justin M. Wray" User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 MIME-Version: 1.0 To: bitcoin-dev@lists.linuxfoundation.org Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-2.7 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, FREEMAIL_FROM, 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 Subject: [bitcoin-dev] Variable Block Size Proposal 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: Sat, 29 Aug 2015 05:41:07 -0000 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 Hey Bitcoiners! While I am an avid Bitcoin supporter, long-term user, and have done development work on tools and platforms surrounding Bitcoin, I have been very busy these past few weeks and haven't had a chance to fully (or closely) monitor the Block Size debate. I'm familiar with the basics, and have read abstracts about the front-running proposals (BIP 100, 101, and 102). Though I've honestly not read those in depth either. With that said, I was driving the other day and thought of a potential idea. I'll be clear, this is just an idea, and I haven't fully fleshed it out. But I thought I'd throw it out there and see what people thought. My Goal: Provide a variable block size that provides for sustainable, long-term growth, and balances the block propagation, while also being mindful of potential spam attacks. The Proposal: Every 2016 blocks (approximately every two weeks, at the same time the difficulty is adjusted), the new block size parameters are calculated. The calculation determines the average (mean) size of the past 2016 blocks. This "average" size is then doubled (200%) and used as the maximum block size for the subsequent 2016 blocks. At any point, if the new maximum size is calculated to be below 1MB, 1MB is used instead (which prevents regression from our current state). Introduce a block minimum, the minimum will be 25% of the current maximum, calculated at the same time (that is, every 2016 blocks, at the same time the maximum is calculated). All blocks must be at least this size in order to be valid, for blocks that do not have enough transactions to meet the 25%, padding will be used. This devalues the incentive to mine empty blocks in either an attempt to deflate the block size, or to obtain a propagation advantage. Miners will be incentivized to include transactions, as the block must meet the minimum. This should ensure that even miners wishing to always mine the minimum are still confirming Bitcoin transactions. At the block in which this is introduced the maximum would stay at 1MB for the subsequent 2016 blocks. With the minimum being enforced of 256KB . Example: * Average Block Size for the last 2016 blocks: 724KB * New Maximum: 1448KB * New Minimum: 362KB Example: (Regression Prevention) * Average Block Size for the last 2016 blocks: 250KB * New Maximum: 1MB * New Minimum: 256KB The Future: I believe that the 1MB regression prevention might need to be changed in the future, to prevent a large mining population from continually deflating the block size (and keeping us at the 1MB limit). For this, the hard limit could be changed in the future manually, through a process similar to the current one, though hopefully with far less urgency and hysteria. Another option is to add an additional calculation, preventing the new maximum from being lower than 75% of the current maximum. This would substantially slow down a block-size deflation attack. Example of Block-Size Deflation Attack Prevention: * Average Block Size for the last 2016 blocks: 4MB * New Maximum: 8MB * New Minimum: 2MB * Average Block Size for the last 2016 blocks: 2MB * New Maximum: 6MB (2 * 200% = 4, 4< 75% of 8, So use 8 * .75 = 6) * New Minimum: 1.5MB This would provide a maximum growth of 200% per recalculation, but a maximum shrinkage of 75%. Request For Comments: I'd love to hear your thoughts. Why wouldn't this work? What portion is flawed? Will the miners support such a proposal? Would this even solve the block size issue? I will note that I don't find the 100% and 25% to be hard and fast in my idea. Those we're just the values that initially jumped out at me. I could easily see the minimum being anything below 50% (above 50% and the network can never adjust to smaller block sizes). I could also see the maximum being anything over 100%. Lastly, if a inflation attack is a valid concern, a hard upper limit could be set (or the historical 32MB limit could remain). I think the great part about this variable approach is that the network can adjust to address spikes in volume and readjust once those spikes dissipate. - -- Thanks! - ----- Justin M. Wray -----BEGIN PGP SIGNATURE----- Comment: GPGTools - https://gpgtools.org iQIcBAEBCgAGBQJV4UXvAAoJENo/Q5Xwcn83ZWEP/iXAlNk5p9OlOPNSoHkECcxe AcartxMLrmOvAZVudU4+239TEvwPydmYX/ptmBYgrvRJfm/TWmi0ZbTioxbxTIWM IlNta1Y8IOHOEgBCtSW01j1PFHIzkBHQGIuqrKHhjcNVGbegXlPm3Da0gjNuTBIe IV58gf1OfYK2XjuCMQMvo3VyXUKhqbOvBNnZXr+Qo2sAtanmxHQ+TU/gjA02L9LO bb8WqQDj/veGnMexGh/X58tfQ5KCfLO401F7KnConDaFdKVDikp32zaSXZ7JWf/K OeseHW1OHHVdYpHvh5VG5GLtYYB5rnq8g7B0/kyx5n4ldB6GkLxzH9CPB0vxpMnZ dVCS/+EUe/wkHrpRVNhMwP8XfG+8gv9upKg6H/u39XmpL2H2G4cKeot5xRiWRNqY oJclAeIhDTL1bx/9e/VqvM91ESWpBLs+O8Mh9OzgfbN3gKR6BuoWHNwM9jSMDAT1 YzwdneSvAEFzgELMlae2QIzAUHno9qkHMkDVbdY3bBtSM9Xz4ditGgnq1D40ZZ+J zx5WVY7HCebgbk7T35xgKzSKQSEG9zFNW5Dvq66Se3Zpc5vCPw7Q2xwjjPz3zdXQ Lub0ohVWTzKr05tN1e/nu6keiY5cXRZ0w2MtHb19jtdWyoHEWWHanfOZjgbVSsuA saFCydA7O4E4BFxgtNze =JthX -----END PGP SIGNATURE-----