From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 24B131782 for ; Sat, 9 Jun 2018 12:45:24 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from outmail148096.authsmtp.net (outmail148096.authsmtp.net [62.13.148.96]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 7CE2A5E2 for ; Sat, 9 Jun 2018 12:45:23 +0000 (UTC) Received: from mail-c245.authsmtp.com (mail-c245.authsmtp.com [62.13.128.245]) by punt24.authsmtp.com. (8.15.2/8.15.2) with ESMTP id w59CjKcY023002; Sat, 9 Jun 2018 13:45:20 +0100 (BST) (envelope-from user@petertodd.org) Received: from petertodd.org (ec2-52-5-185-120.compute-1.amazonaws.com [52.5.185.120]) (authenticated bits=0) by mail.authsmtp.com (8.15.2/8.15.2) with ESMTPSA id w59CjILt048279 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Sat, 9 Jun 2018 13:45:20 +0100 (BST) (envelope-from user@petertodd.org) Received: from [127.0.0.1] (localhost [127.0.0.1]) by petertodd.org (Postfix) with ESMTPSA id 84A57400FB; Sat, 9 Jun 2018 12:45:18 +0000 (UTC) Received: by localhost (Postfix, from userid 1000) id ED7A022043; Sat, 9 Jun 2018 08:45:16 -0400 (EDT) Date: Sat, 9 Jun 2018 08:45:16 -0400 From: Peter Todd To: Sergio Demian Lerner Message-ID: <20180609124516.6ms6t7r5t7ikved6@petertodd.org> References: <20180607171311.6qdjohfuuy3ufriv@petertodd.org> <20180607222028.zbva4vrv64dzrmxy@petertodd.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="n4wv2ezgeeysfdlz" Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170113 (1.7.2) X-Server-Quench: f816e8d2-6be2-11e8-a283-9cb654bb2504 X-AuthReport-Spam: If SPAM / abuse - report it at: http://www.authsmtp.com/abuse X-AuthRoute: OCd2Yg0TA1ZIVwkA IjsJECJaVQIpKltL GxAVKBZePFsRUQkR aQdMdgsUEkAaAgsB Am4bWldeVFh7W2M7 bghPaBtcak9QXgdq T0pMXVMcUwBhckZ4 eloeVhFwcAwIcX9y ZQg0VnFdCUwud1t7 EBtWCGwHMG99OWIX U11RJFFSdQcYLB1A alQxNiYHcQ5VPz4z GA41ejw8IwAXFD5I WR0AIRoXTFwIGjN0 WwoPEH0jEFUZR209 KAZuMVcSEQ4NIg0z N1AlREkZNBlwQhVE GEZDG2dGJkUBQDc3 RQoSRkkQDHVTRj1f agAA X-Authentic-SMTP: 61633532353630.1039:706 X-AuthFastPath: 0 (Was 255) X-AuthSMTP-Origin: 52.5.185.120/25 X-AuthVirus-Status: No virus detected - but ensure you scan with your own anti-virus system. X-Spam-Status: No, score=-2.6 required=5.0 tests=BAYES_00,LOTS_OF_MONEY, RCVD_IN_DNSWL_LOW autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.org Cc: bitcoin-dev Subject: Re: [bitcoin-dev] Trusted merkle tree depth for safe tx inclusion proofs without a soft fork X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Bitcoin Protocol Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 09 Jun 2018 12:45:24 -0000 --n4wv2ezgeeysfdlz Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sat, Jun 09, 2018 at 02:21:17PM +0200, Sergio Demian Lerner wrote: > Also it must be noted that an attacker having only 1.3M USD that can > brute-force 72 bits (4 days of hashing on capable ASICs) can perform the > same attack, so the attack is entirely feasible and no person should acce= pt > more than 1M USD using a SPV wallet. That doesn't make any sense. Against a SPV wallet you don't need that attac= k; with that kind of budget you can fool it by just creating a fake block at f= ar less cost, along with a sybil attack. Sybils aren't difficult to pull off w= hen you have the budget to be greating fake blocks. > Also the attack can be repeated: once you create the "extension point" > block, you can attack more and more parties without any additional > computation. That's technically incorrect: txouts can only be spent once, so you'll need= to do 2^40 work each time you want to repeat the attack to grind the matching = part of the prevout again. --=20 https://petertodd.org 'peter'[:-1]@petertodd.org --n4wv2ezgeeysfdlz Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEFcyURjhyM68BBPYTJIFAPaXwkfsFAlsby9cACgkQJIFAPaXw kfsM0wgAsmhTN3FYpldVECQDPH4DEvXEn9Xh2UtTGrpp0Z+WGKZEQpLOIuFlCCvJ 4pNzKiNT2GPmxtPOK6fIWZU2f9SDFN5x1XmD5544frDwy1eYZ4yw4yLqJ4/D0JYd sH95hduhRcbdZ38LFvb4Vb510fdq9oqVaQkFm0m17751WVbj3WfgaFVeTt6Navws AUq4lZ92ePKTNgreRfeOyJ1v4MCwLm7/+r2gRCfMMsBQgycrTEcST6yToeB87idO xJmrXSyU7FmYviizigbzcA5KStIkJbk5ybjR9u/XrgRYFGEbuVSlvq9s/l+74Wmj j7J8s3RzibRZMtQO1Apb0jt+N3BdxA== =Wmx2 -----END PGP SIGNATURE----- --n4wv2ezgeeysfdlz--