Received: from sog-mx-4.v43.ch3.sourceforge.com ([172.29.43.194] helo=mx.sourceforge.net) by sfs-ml-2.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1VdLEn-0001HG-On for bitcoin-development@lists.sourceforge.net; Mon, 04 Nov 2013 14:34:41 +0000 Received-SPF: pass (sog-mx-4.v43.ch3.sourceforge.com: domain of gmail.com designates 209.85.223.169 as permitted sender) client-ip=209.85.223.169; envelope-from=pieter.wuille@gmail.com; helo=mail-ie0-f169.google.com; Received: from mail-ie0-f169.google.com ([209.85.223.169]) by sog-mx-4.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1VdLEn-0003uB-2C for bitcoin-development@lists.sourceforge.net; Mon, 04 Nov 2013 14:34:41 +0000 Received: by mail-ie0-f169.google.com with SMTP id ar20so12735651iec.28 for ; Mon, 04 Nov 2013 06:34:35 -0800 (PST) MIME-Version: 1.0 X-Received: by 10.50.129.39 with SMTP id nt7mr11944012igb.13.1383575675761; Mon, 04 Nov 2013 06:34:35 -0800 (PST) Received: by 10.50.141.136 with HTTP; Mon, 4 Nov 2013 06:34:35 -0800 (PST) In-Reply-To: <20131104142621.GA2190@petertodd.org> References: <20131104142621.GA2190@petertodd.org> Date: Mon, 4 Nov 2013 15:34:35 +0100 Message-ID: From: Pieter Wuille To: Peter Todd Content-Type: text/plain; charset=ISO-8859-1 X-Spam-Score: -1.6 (-) X-Spam-Report: Spam Filtering performed by mx.sourceforge.net. See http://spamassassin.org/tag/ for more details. -1.5 SPF_CHECK_PASS SPF reports sender host as permitted sender for sender-domain 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (pieter.wuille[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature 0.0 URIBL_BLOCKED ADMINISTRATOR NOTICE: The query to URIBL was blocked. See http://wiki.apache.org/spamassassin/DnsBlocklists#dnsbl-block for more information. [URIs: petertodd.org] X-Headers-End: 1VdLEn-0003uB-2C Cc: Ittay Eyal , Bitcoin Dev Subject: Re: [Bitcoin-development] Auto-generated miner backbone X-BeenThere: bitcoin-development@lists.sourceforge.net X-Mailman-Version: 2.1.9 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 04 Nov 2013 14:34:41 -0000 On Mon, Nov 4, 2013 at 3:26 PM, Peter Todd wrote: > The correct, and rational, approach for a miner is to always mine to > extend the block that the majority of hashing power is trying to extend. > The current relay rules don't give you that information at all, but they > can if we do two things: > > 1) Relay all blocks that meet the PoW target. (as suggested in the > paper) > > 2) Relay block headers that nearly meet the PoW target. > > Mining strategy is now to mine to extend the first block you see, on the > assumption that the earlier one probably propagated to a large portion > of the total hashing power. But as you receive "near-blocks" that are > under the PoW target, use them to estimate the hashing power on each > fork, and if it looks like you are not on the majority side, switch. Doesn't that mean that by selective blocking these near-PoW headers, you can bias peers into preferring to mine on those with near-PoW headers, turning the attack around? Of course, because of their size, headers are likely much harder to slow down (in propagation speed) than full blocks... -- Pieter