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-2.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1XD2Zy-0000sJ-Am for bitcoin-development@lists.sourceforge.net; Fri, 01 Aug 2014 02:28:22 +0000 Received-SPF: pass (sog-mx-4.v43.ch3.sourceforge.com: domain of gmail.com designates 209.85.220.176 as permitted sender) client-ip=209.85.220.176; envelope-from=gmaxwell@gmail.com; helo=mail-vc0-f176.google.com; Received: from mail-vc0-f176.google.com ([209.85.220.176]) by sog-mx-4.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1XD2Zx-0001st-IV for bitcoin-development@lists.sourceforge.net; Fri, 01 Aug 2014 02:28:22 +0000 Received: by mail-vc0-f176.google.com with SMTP id id10so5668970vcb.7 for ; Thu, 31 Jul 2014 19:28:15 -0700 (PDT) MIME-Version: 1.0 X-Received: by 10.220.74.10 with SMTP id s10mr2839095vcj.61.1406860095900; Thu, 31 Jul 2014 19:28:15 -0700 (PDT) Received: by 10.52.187.132 with HTTP; Thu, 31 Jul 2014 19:28:15 -0700 (PDT) In-Reply-To: <3826251.5rGb1MfKOu@crushinator> References: <3826251.5rGb1MfKOu@crushinator> Date: Thu, 31 Jul 2014 19:28:15 -0700 Message-ID: From: Gregory Maxwell To: Matt Whitlock Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable 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 (gmaxwell[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 X-Headers-End: 1XD2Zx-0001st-IV Cc: Bitcoin Development 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, 01 Aug 2014 02:28:22 -0000 On Thu, Jul 31, 2014 at 6:38 PM, Matt Whitlock wrot= e: > It would make more sense to introduce a new script opcode that pushes the= current block height onto the operand stack. Then you could implement arbi= trary logic about which blocks the transaction can be valid in. This would = require that the client revalidate all transactions in its mempool (really,= only those making use of this opcode) whenever the chain tip changes. Transactions that become invalid later are have pretty severe consequences because they might mean that completely in an absence of fraud transactions are forever precluded due to a otherwise harmless reorg. While there may be uses for that, the resulting outputs should be considered differently fungible=E2=80=94 like coinbases which are immature= =E2=80=94 and should probably be only used with great caution... not as a mechanism for ordinary transactions.