Received: from sog-mx-1.v43.ch3.sourceforge.com ([172.29.43.191] helo=mx.sourceforge.net) by sfs-ml-3.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1USlKJ-00072C-Lw for bitcoin-development@lists.sourceforge.net; Thu, 18 Apr 2013 09:40:23 +0000 Received-SPF: pass (sog-mx-1.v43.ch3.sourceforge.com: domain of gmail.com designates 209.85.214.179 as permitted sender) client-ip=209.85.214.179; envelope-from=mh.in.england@gmail.com; helo=mail-ob0-f179.google.com; Received: from mail-ob0-f179.google.com ([209.85.214.179]) by sog-mx-1.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1USlKI-0004q3-TI for bitcoin-development@lists.sourceforge.net; Thu, 18 Apr 2013 09:40:23 +0000 Received: by mail-ob0-f179.google.com with SMTP id x4so411896obh.24 for ; Thu, 18 Apr 2013 02:40:17 -0700 (PDT) MIME-Version: 1.0 X-Received: by 10.182.101.169 with SMTP id fh9mr5072448obb.2.1366277548337; Thu, 18 Apr 2013 02:32:28 -0700 (PDT) Sender: mh.in.england@gmail.com Received: by 10.76.167.169 with HTTP; Thu, 18 Apr 2013 02:32:28 -0700 (PDT) In-Reply-To: <20130418092824.GA10184@savin> References: <453bfc69-b2ab-4992-9807-55270fbda0db@email.android.com> <20130418090444.GA30995@savin> <20130418092824.GA10184@savin> Date: Thu, 18 Apr 2013 11:32:28 +0200 X-Google-Sender-Auth: QBzFldR6OBwwEyzDkrw89PS7v_s Message-ID: From: Mike Hearn To: Peter Todd Content-Type: multipart/alternative; boundary=e89a8ff1cab4eef24304da9f47e4 X-Spam-Score: -0.5 (/) 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 (mh.in.england[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record 1.0 HTML_MESSAGE BODY: HTML included in message 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: 1USlKI-0004q3-TI Cc: Bitcoin Dev Subject: Re: [Bitcoin-development] Anti DoS for tx replacement 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, 18 Apr 2013 09:40:23 -0000 --e89a8ff1cab4eef24304da9f47e4 Content-Type: text/plain; charset=UTF-8 > ...and actually, that's not a problem if the defender is online, because > they can just broadcast the highest sequence numbered tx, which blocks > further broadcasts by the attacker. Good point - transactions can be ordered by highest version seen before they're signature checked. Even without that improvement it's still rather tricky to win the race though. I'm intending on making a prototype for myself at some point soon, probably in bitcoinj. I've been making notes and writing some initial code - I did successfully replace a transation on my own little testnet, then I figured I'd submit the patch so it's easier for others to play with it. But I haven't got the whole thing working end to end yet. --e89a8ff1cab4eef24304da9f47e4 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable

=
...and actually, that's not a problem if= the defender is online, because
they can just broadcast the highest sequence numbered tx, which blocks
further broadcasts by the attacker.

G= ood point - transactions can be ordered by highest version seen before they= 're signature checked. Even without that improvement it's still rat= her tricky to win the race though.

I'm intending on making a prototype for= myself at some point soon, probably in bitcoinj. I've been making note= s and writing some initial code - I did successfully replace a transation o= n my own little testnet, then I figured I'd submit the patch so it'= s easier for others to play with it. But I haven't got the whole thing = working end to end yet.
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