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 1WYLbW-0008OS-NU for bitcoin-development@lists.sourceforge.net; Thu, 10 Apr 2014 20:29:46 +0000 Received-SPF: pass (sog-mx-1.v43.ch3.sourceforge.com: domain of gmail.com designates 209.85.223.181 as permitted sender) client-ip=209.85.223.181; envelope-from=pieter.wuille@gmail.com; helo=mail-ie0-f181.google.com; Received: from mail-ie0-f181.google.com ([209.85.223.181]) by sog-mx-1.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1WYLbV-0007pm-Vy for bitcoin-development@lists.sourceforge.net; Thu, 10 Apr 2014 20:29:46 +0000 Received: by mail-ie0-f181.google.com with SMTP id tp5so4517272ieb.12 for ; Thu, 10 Apr 2014 13:29:40 -0700 (PDT) MIME-Version: 1.0 X-Received: by 10.50.4.74 with SMTP id i10mr18938969igi.43.1397161780691; Thu, 10 Apr 2014 13:29:40 -0700 (PDT) Received: by 10.50.141.135 with HTTP; Thu, 10 Apr 2014 13:29:40 -0700 (PDT) In-Reply-To: References: Date: Thu, 10 Apr 2014 22:29:40 +0200 Message-ID: From: Pieter Wuille To: Tier Nolan 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 X-Headers-End: 1WYLbV-0007pm-Vy Cc: Bitcoin Dev , Paul Rabahy Subject: Re: [Bitcoin-development] Chain pruning 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: Thu, 10 Apr 2014 20:29:47 -0000 On Thu, Apr 10, 2014 at 10:12 PM, Tier Nolan wrote: > On Thu, Apr 10, 2014 at 7:32 PM, Pieter Wuille > wrote: >> >> If you trust hashrate for determining which UTXO set is valid, a 51% >> attack becomes worse in that you can be made to believe a version of >> history which is in fact invalid. > > > If there are invalidation proofs, then this isn't strictly true. I'm aware of fraud proofs, and they're a very cool idea. They allow you to leverage some "herd immunity" in the system (assuming you'll be told about invalid data you received without actually validating it). However, they are certainly not the same thing as zero trust security a fully validating node offers. For example, a sybil attack that hides the actual best chain + fraud proofs from you, plus being fed a chain that commits to an invalid UTXO set. There are many ideas that make attacks harder, and they're probably good ideas to deploy, but there is little that achieves the security of a full node. (well, perhaps a zero-knowledge proof of having run the validation code against the claimed chain tip to produce the known UTXO set...). -- Pieter