From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sog-mx-1.v43.ch3.sourceforge.com ([172.29.43.191] helo=mx.sourceforge.net) by sfs-ml-4.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1RhaYM-0002OW-NY for bitcoin-development@lists.sourceforge.net; Mon, 02 Jan 2012 05:35:22 +0000 Received-SPF: pass (sog-mx-1.v43.ch3.sourceforge.com: domain of m.gmane.org designates 80.91.229.12 as permitted sender) client-ip=80.91.229.12; envelope-from=gcbd-bitcoin-development@m.gmane.org; helo=lo.gmane.org; Received: from lo.gmane.org ([80.91.229.12]) by sog-mx-1.v43.ch3.sourceforge.com with esmtp (Exim 4.76) id 1RhaYJ-0007dr-G0 for bitcoin-development@lists.sourceforge.net; Mon, 02 Jan 2012 05:35:22 +0000 Received: from list by lo.gmane.org with local (Exim 4.69) (envelope-from ) id 1RhaY8-0004Dd-6J for bitcoin-development@lists.sourceforge.net; Mon, 02 Jan 2012 06:35:08 +0100 Received: from 70-36-134-180.dsl.dynamic.sonic.net ([70.36.134.180]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 02 Jan 2012 06:35:08 +0100 Received: from tyrell.elden by 70-36-134-180.dsl.dynamic.sonic.net with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 02 Jan 2012 06:35:08 +0100 X-Injected-Via-Gmane: http://gmane.org/ To: bitcoin-development@lists.sourceforge.net From: Elden Tyrell Date: Sun, 1 Jan 2012 21:04:03 -0800 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Complaints-To: usenet@dough.gmane.org X-Gmane-NNTP-Posting-Host: 70-36-134-180.dsl.dynamic.sonic.net User-Agent: Unison/2.1.6 X-Spam-Score: -1.9 (-) 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 (tyrell.elden[at]gmail.com) -0.0 SPF_HELO_PASS SPF: HELO matches SPF record 0.0 DKIM_ADSP_CUSTOM_MED No valid author signature, adsp_override is CUSTOM_MED -0.0 SPF_PASS SPF: sender matches SPF record -1.6 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain 1.2 NML_ADSP_CUSTOM_MED ADSP custom_med hit, and not from a mailing list X-Headers-End: 1RhaYJ-0007dr-G0 Subject: [Bitcoin-development] does "stubbing" off Merkle trees reduce initial download bandwidth? 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, 02 Jan 2012 05:35:22 -0000 Satoshi's paper mentions that storage requirements for the blockchain can be reduced by deleting transactions whose outputs have been spent. If I understand correctly, this technique can only be used for reducing *storage* requirements, not *bandwidth* needed for the initial chain download by a high-security client that doesn't trust any of its peers -- right? The rule is "trust the longest valid chain of blocks". Part of a block being "valid" is that each transaction's inputs are unspent and their sum exceeds the transaction's outputs unless it is a coinbase. This cannot be verified for "stubbed out" transactions -- they have outputs but no inputs, and aren't coinbases. So a paranoid client booting up for the first time needs to be given an un-stubbed chain, right? Of course, if a client decided to accept a stubbed blocks only when the sum of the difficulties in the blocks after it exceeds some number N, then attacking it could be made very expensive by picking a large enough N. Please let me know if I have misunderstood something.