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Thu, 10 Oct 2019 09:16:17 -0700 (PDT) To: bitcoin-dev@lists.linuxfoundation.org References: <42cd5ffd-63e8-b738-c4ea-13d0699b1268@purse.io> From: Braydon Fuller Openpgp: preference=signencrypt Autocrypt: addr=braydon@purse.io; keydata= xsFNBFsEkasBEAC4oPJQsFWAM0OjNJlYUxJbTV8bo1TgXwZdNZWewG6fvQQ+iGGImy/a5h10 /9V+/Ctio8ayAfpk6V3z/vxq8IdPVcsWccHLnguaAEEhYnKdGZfsohcQMO4LR63R6vPrUYUJ ehVzt2YZ5F495iRDKwbQLXbmXF9vLtaKuf/6hbVmlG7bM59eVKcvpE8EKm95Lpw+CBE3uKc3 RxTcKHgo6QrkClm19GNDDkmHxM/k+hGT3M+sXGhgpL2940AGKsXuTPghgLQ+5seBWtzuWV31 Uf0ltHx6Ks1w0mlgZZ+u4wlljMHIBKLr4cYDOF8AYxyVcPzuQLdRjIIKEgpMDQW7ftbgGM/q hgGg2mN036KTUfT1HkmT82Z3D3z4ACJ/bY/J+mJw0baqcJpezndd1M6dnDNF9Slst2Mr+Loe JdN1tY5kk6/OWwAI5L15hmdiRWUBryJqun7sy23cmVPSOrtaIfl7/SEFJ+MuXbK53+mFGT2P CpdRzV4MrKr9qbBaXkkhvEfoL2z6VwIFBprqZjthPHcHR8r6QSTpZdsD+7+qoq2o4MDUqP54 5a3kGI3l6VW767VE/NUIocyO7Z9D/EZOCk22ElTLTCzWm0JvxxGJoalebLQcGey/A9WWGOv/ ydwvTry3PWAzrrXNt43McHHwZXU4vSLnAtAxQy06Nt9wsWo+2QARAQABzSFCcmF5ZG9uIEZ1 bGxlciA8YnJheWRvbkBwdXJzZS5pbz7CwZcEEwEIAEECGwMFCwkIBwIGFQgJCgsCBBYCAwEC HgECF4ACGQEWIQRbfcWNkP7B6ZCjELryTyMtEIs61AUCXL9UPwUJA5v2FAAKCRDyTyMtEIs6 1HOwEACedBLpkYrFeLANxD25USZunMt4KA58ZkY7Ap2m7KFcxjZD07YIjtxJyMLhHhMz6pR7 fF5BFHbl8CtAhpTuz5Sj9X3K0eilNsXvdx18+3RMUpFVAwlEEev707q6zNqKsRd1CG7e0k4o 28YAgwbt42UIPUoKTcEpT4C51sDa5d4NZsGnFcXeEdpBSQVi56vap0eJrQTSFpV0sG497HNN p96ErrGpqlOkTofcBeytpQbhH9kbP58PMABwU3tmoMFhT0kklPPZatv7RDLmC8cra5muXEwd wv7ggauHbMbV3U1xZ/BNPwHm7jO1ygqR6Q4Y98miRUP4yH9SJsnr+q7bpD4yOUy/qP0Ve0Y0 jFgX4e4DrnckO/2rG4lB2SbKiAWAOW5aGTnUAZt6agegXY62kHpuUHGcgYkeQqDWKLZWjFAA vj8Gm5f+1thWk+4I0rFQBtaAoitd+qKPWFYSojjvKH4PLqoOV413qxZbrRlGxZb2TkJnxYpO imOq/H6bHCnJUA8NI1v5rXmGQXfwhofMX9dHpGK864G+i59AX9L0EEQngDXZPlSEkyISaBY7 JFBhuIPcY8MrhUkNWl1G2RcssjHeexmo2qNrKH4bWFF7xCCTmdGUSoHzaHDe/cIqmI0aRkqf HQ4MpadD8flLLMqV/ODYfpSD3AuwM/m8Uj9nvfnMRs7BTQRbBJGrARAA3+SVdBJUThjPx/J5 G4A1dd2vKVRRprW+pyJ0XDbNrRVOEnxr3okz2F4Htg72oULwsNcuCmgFxDlxIFMitzZAWbuL fq9FR7snaW3PMlkj44eezq3emYXVv3C3lc6MudAOqkQKNzakyaA/6cNVlQnVmrpctpFHtUNi oeivM9IeCP52scTH84qeRZofmnedc3FAxKMJ9OZi4Miigsd/DhzhUqbAePrCMlQQsM/HXSNs 2qoMK3Bo6lcHzV7qyI9w19tmFouX06ULnAAM1dJZcCUL31FLtaIrGbcXA+99a8dlOUb68rj9 9H3V3zDjJscDBgJ2mziuuS/naG/NK+RVhVh3KqtViC62nGgA1tS1aLKZ7KDeyzu4FiE2bCPh 6b4IlIQijzqwTyPJt+0Muf2FYxir9GwgMnVqJ/fYaT671RCcUrkq2krVzdHq/HX7A8Hyfftc BMEt4yZJt/bZ7ryyWJ8PlQJP3HGqz+hpHmwrwmJgj5RbmktVMw3RAEipJrEHD1Q7wIhPNYpy 6FIwFlDxwpUQOUYGEZYww9LRZiapN0FeDcFp6CUMRgJH24ZQzFk8J5N4PAzZrIZfQba71bDA z3902PDt66qiIiG2muTbd8eIeCzx9RxWhDmQclzXn5WxfPU6l0E9NgLNFoNCppLaTz2S/Gxw ZzrSduMLfVlhKPDjv2EAEQEAAcLBZQQYAQIADwUCWwSRqwIbDAUJAeEzgAAKCRDyTyMtEIs6 1MLqD/9vMXLRhe5w6oBKuL0tj+ChLhkQEM66Q7O4urWmvl8yf/ThNi0/LydGAYawCUWud2ph aOg4vH0IUvUhlLDRcYc2MdfwJi8aj8G7YC/OUKwwFDfYyY9zIk1C5yXn6LigkjOL0PyYI0MM 2gk64t/PK+Rny8jz6QjwZ4AMsoTpo698LSYS7LcvOETp+3yz0LYtkPP36FqoG2hudjh015Gk DSIHWckot4TJXK8OOHOuKwUz2fteGsFeM4bmTiArCRXsAkRWo0VbA6hPinK0Zr/xLNSYIx94 IXe5q9ISZc6ceuWyisVsUZxUgJJGyNSvXXwx4zoSS7BXyTo7syjpKd09nhCL3QGfuHugJ/1/ DCaNtKUu2C+rUe1Ux6/qteCVUsAM+bDfDBQ/vS1tnyn9OVBTOZqXvChL4f+MAN2Wws/+Llxw DqGMX6YC/ZBWM56XGApL1zj93nygxbN8s8yXqqMQNghTjwj9IqyaNQcKO/AslSmFlW6RXz1Y RDT4mSKdAogbdDqmguGc05kUaOSkqSb0bL34iQ/dm4PyVxjSGSDRr8TQOjQGz0rSEh6Q+LZ9 zRltkmEMkdkyWQZ4tYsBbQv2TU+tCfKMIUCZ7xEHuvjAKZIms9Ers3zVS+PcRr9i6mvMtbNM ufP9MwSx7PqsHuv/PWdoI3uwanxYzk1GTLALMsy2icLBfAQYAQIAJgIbDBYhBFt9xY2Q/sHp kKMQuvJPIy0QizrUBQJcv1RFBQkDm/YaAAoJEPJPIy0QizrUjvoP/R6Wi8Ol1QiOWrxLZyL9 NYtU1Q+P46R8Q0d6gFRkrC9MKJlzaTRzPxdaWyJURnh1pXHbykB3/b6Bg/WN7o7Wips8KIhL PzrNUiCZIsrBxUR29no7NzU6o7rSuu/9j5OfiyW/jViRJ3oi1jdYdFx7qx/56j1I54q6NHAk i2AoG07RbXsRsh0x5vv4VIEFNwRRHmn/d185NTDeoVj9IanVhF6zna9M2iX3AgUOLovF7PiM d/oF5XDwuzEDiBIorGi4WTqiCDjl7menb657af1DsPV68gKCiVFQNwfbawtUzUBasfaCFkR5 NuXWFqYN/305vlK/IN2GDPrwwOFsQK9pG4fYDDC5Pi9fy9wLrwtlebRuraLCHsiho8mYtEhM QTU7oQwWga9Ax6BXbnStmX1kEev41CEEvnaVtqzuT0VKJjnre/7z8+bRC1tbqvN5CKTQ1k3d 5uwFqCBOxtoY6NLmYT37zFq34etKgpqCri6lEMtM57icMd4SPaADSXly/EyUTPbb/iGvQVOS NFPpY30rTBA8rJJ5Iawe1OjG2dcYwKkFfGjGU7bbHp9ClG1d3YM7kDxVkgdIVAWhEY905HB4 KXQZd0eW19JjNwLVMNzgBh07BiaXl16tWY+P7pQdPrbLctiIVqsYx+IU74M7riDEMTGjsosr lL56VCOJffiN9F1L Message-ID: Date: Thu, 10 Oct 2019 09:16:16 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Language: en-US X-Spam-Status: No, score=-2.0 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, RCVD_IN_DNSWL_NONE 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: Thu, 10 Oct 2019 16:20:30 +0000 Subject: Re: [bitcoin-dev] Chain width expansion 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: Thu, 10 Oct 2019 16:16:20 -0000 On 10/4/19 4:31 PM, Tier Nolan via bitcoin-dev wrote > [..] At root, the requirement is that peers can prove their total chain= POW. [...] Indeed, it's currently necessary to receive all of the chain headers to determine. It would be interesting to have a succinct chainwork proof for all cases. Chainwork being a sum of the total proof-of-work in a chain. Such proofs currently only require a few headers for common cases and the other cases can be identified. > In regard to your proposal, I think the key is to limit things by peer,= rather than globally. [...] Yeah, there should be enough width available for every active connection, only one chain of headers is requested at a time per peer. Peer based limiting is susceptible to Sybil attacks; A peer could broadcast a few low-work header chains, reconnect and repeat ad nauseam. The delay for the next set of headers is based on the chainwork of the last received headers from the peer. The peer could change identity and run into the same limit. The unrequested header rate is tracked per peer.= A header chain with more chainwork will be requested at a faster rate than a header chain with less chainwork. The chainwork is compared to the current fully validated chain. Honest peers with more chainwork will have a time advantage over dishonest peers with less chainwork. For example, let's assume a case that the initial chain of headers was dishonest and with low chainwork. The initial block download retrieves the header chain from a single loader peer first. Once recent time is reached, header chains are downloaded from all outgoing peers. A single honest peer will have an advantage over many dishonest peers. Thus, as you have mentioned, there is a security assumption that there is at least one connected honest node.