From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sog-mx-4.v43.ch3.sourceforge.com ([172.29.43.194] helo=mx.sourceforge.net) by sfs-ml-4.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1XFoZY-0000it-RR for bitcoin-development@lists.sourceforge.net; Fri, 08 Aug 2014 18:07:24 +0000 X-ACL-Warn: Received: from mail-pd0-f175.google.com ([209.85.192.175]) by sog-mx-4.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1XFoZX-0006KI-Ol for bitcoin-development@lists.sourceforge.net; Fri, 08 Aug 2014 18:07:24 +0000 Received: by mail-pd0-f175.google.com with SMTP id r10so7405394pdi.20 for ; Fri, 08 Aug 2014 11:07:17 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:message-id:date:from:user-agent:mime-version:to :subject:references:in-reply-to:content-type :content-transfer-encoding; bh=Dm+JUmGLXgmBCMdmNI+Ir21Q9bGYkmNqD7kKYqvHlkU=; b=OGeZeubIfrwNxD+rw128WJKLvJFJPe7IearqIaC+MoG/MWx0F6bv98AX/I7lwmYLdy JCUxUOvYaddR8vD01hHNyTyynZU9/akXHRoU8z+t2L+8FkNxYUOKPn9v+ZndRyO4bPxY Y32A0IFAYyiO5DZyPGpotc6GbCwpJHVyq4nVcxqmGvDaHt4HTBx/MGntSBiKqesCYMn5 fbx+5IgVGcqZMbWYY+S+Nwr3Kw8cwD23hIlSRPH63ZzL8L8LhvMhkIBdryySvBSI4OPq uKrmYkXfD4pY2glsEDR6kpRBYQlHv5C4PcOWR+UgVR+woBoXLTAHombkFbHMXxzimmic HvSA== X-Gm-Message-State: ALoCoQkUiA8jtI2ACRfpQjEIkM+xDM4QIuePB7j+Tf/UBqNYT04prpBqVax0/UGxIyj+6w8V/T37 X-Received: by 10.70.128.17 with SMTP id nk17mr10273061pdb.89.1407519488161; Fri, 08 Aug 2014 10:38:08 -0700 (PDT) Received: from [192.168.1.89] (99-6-44-248.lightspeed.sntcca.sbcglobal.net. [99.6.44.248]) by mx.google.com with ESMTPSA id ps8sm735643pbb.38.2014.08.08.10.38.07 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Fri, 08 Aug 2014 10:38:07 -0700 (PDT) Message-ID: <53E50B00.8030505@thinlink.com> Date: Fri, 08 Aug 2014 10:38:08 -0700 From: Tom Harding User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Bitcoin Dev References: <53E1A8AF.4030206@thinlink.com> <53E23F49.3020605@thinlink.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: 0.0 (/) X-Spam-Report: Spam Filtering performed by mx.sourceforge.net. See http://spamassassin.org/tag/ for more details. X-Headers-End: 1XFoZX-0006KI-Ol Subject: Re: [Bitcoin-development] deterministic transaction expiration 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: Fri, 08 Aug 2014 18:07:25 -0000 Having explored more drastic approaches, it looks like Kaz' basic idea stands well. His #1... > 1. start setting nLockTime to the current height by default in newly > created transactions (or slightly below the current height, for > reorg-friendliness) is already implemented in bitcoin-qt #2340, and a "final call" on merging it was already sent to this list. After some thought I agree with its policy of eventually setting nLockTime at current-height + 1 by default. This is the "best reasonably expected height" of any tx created right now. It discourages fee-sniping, and if a reorg happens anyway, it won't actually delay inclusion of tx beyond the reasonable expectation sans reorg. However right now, #2340 takes a very cautious approach and sets to current-height - 10 by default, with randomness to mitigate worries about loss of privacy. Kaz' #2, #3 and #4 are future actions. #4 only goes most of the way ... > 4. add a new IsStandard rule rejecting transactions with an nLockTime > more than N blocks behind the current tip (for some fixed value N, to > be determined) ... a janitor mechanism is desirable to purge mempool of txes more than N behind current-height. Nodes dropping a tx N blocks after they became eligible to be mined (the meaning of nLockTime) makes sense. It is not an overloading or new use for nLockTime, but a logical extension of it. As Kaz pointed out, this solves a big problem with expiring by locally measured age: unintentional resurrection.