Received: from sog-mx-3.v43.ch3.sourceforge.com ([172.29.43.193] helo=mx.sourceforge.net) by sfs-ml-4.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1Rc6B0-0005Rk-0q for bitcoin-development@lists.sourceforge.net; Sun, 18 Dec 2011 02:08:34 +0000 X-ACL-Warn: Received: from mail-vx0-f175.google.com ([209.85.220.175]) by sog-mx-3.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1Rc6Az-0008PT-3G for bitcoin-development@lists.sourceforge.net; Sun, 18 Dec 2011 02:08:33 +0000 Received: by vcbf1 with SMTP id f1so3298715vcb.34 for ; Sat, 17 Dec 2011 18:08:27 -0800 (PST) MIME-Version: 1.0 Received: by 10.52.91.109 with SMTP id cd13mr8903182vdb.92.1324170475374; Sat, 17 Dec 2011 17:07:55 -0800 (PST) Received: by 10.52.178.167 with HTTP; Sat, 17 Dec 2011 17:07:55 -0800 (PST) X-Originating-IP: [99.43.178.25] In-Reply-To: <4EED378A.8090303@parhelic.com> References: <82659F61-0449-47BB-88DC-497E0D02F8A1@ceptacle.com> <1324158558.26106.140661012932641@webmail.messagingengine.com> <4EED378A.8090303@parhelic.com> Date: Sat, 17 Dec 2011 20:07:55 -0500 Message-ID: From: Jeff Garzik To: Jordan Mack Content-Type: text/plain; charset=ISO-8859-1 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: 1Rc6Az-0008PT-3G Cc: bitcoin-development@lists.sourceforge.net Subject: Re: [Bitcoin-development] Protocol extensions 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: Sun, 18 Dec 2011 02:08:34 -0000 On Sat, Dec 17, 2011 at 7:44 PM, Jordan Mack wrote: > While using DHT for storage of the block chain is an intriguing concept, > I do not see how it is feasible. As Gavin noted, DHT is a system that is > difficult to impossible to guarantee against data loss or manipulation. > > Even if we found a way to store the block chain in DHT, how would > transactions be verified? As Gavin noted, you could ask the network, but > cannot necessarily trust the peers you are connected to. Verification of > the full block chain allows the client to trust no one. Well, the block chain data itself is internally self-validating. As long as you know the latest block's hash -- a big "if" -- there is no problem downloading all other block chain data from DHT or any other untrusted source. In a malicious case, you would notice latest-hash differs from non-malicious and wind up downloading multiple chains, when walking hashes backwards through a DHT/lookup table. So, a bit more work but nothing fundamentally less secure _on a trust basis_. Of course, I was focusing on data validation, which ignores other factors such as DoS'ing the DHT. -- Jeff Garzik exMULTI, Inc. jgarzik@exmulti.com