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-2.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1YJaEI-00041s-WE for bitcoin-development@lists.sourceforge.net; Fri, 06 Feb 2015 04:09:19 +0000 Received-SPF: pass (sog-mx-1.v43.ch3.sourceforge.com: domain of dashjr.org designates 85.234.147.28 as permitted sender) client-ip=85.234.147.28; envelope-from=luke@dashjr.org; helo=zinan.dashjr.org; Received: from 85-234-147-28.static.as29550.net ([85.234.147.28] helo=zinan.dashjr.org) by sog-mx-1.v43.ch3.sourceforge.com with esmtp (Exim 4.76) id 1YJaEH-0003q0-Ro for bitcoin-development@lists.sourceforge.net; Fri, 06 Feb 2015 04:09:18 +0000 Received: from ishibashi.localnet (unknown [IPv6:2001:470:5:265:61b6:56a6:b03d:28d6]) (Authenticated sender: luke-jr) by zinan.dashjr.org (Postfix) with ESMTPSA id 2E0EA108039B; Fri, 6 Feb 2015 04:08:45 +0000 (UTC) X-Hashcash: 1:25:150206:bitcoin-development@lists.sourceforge.net::vUSah/JxBmHmG1Eh:ak79r X-Hashcash: 1:25:150206:justusranvier@riseup.net::ZFEv2V=C=1arD32n:v30K From: Luke Dashjr To: bitcoin-development@lists.sourceforge.net Date: Fri, 6 Feb 2015 04:08:42 +0000 User-Agent: KMail/1.13.7 (Linux/3.14.27-gentoo; KDE/4.12.5; x86_64; ; ) References: <20150204142323.DEC4BE2DCDE@quidecco.de> <54D431FD.9020904@riseup.net> In-Reply-To: <54D431FD.9020904@riseup.net> X-PGP-Key-Fingerprint: E463 A93F 5F31 17EE DE6C 7316 BD02 9424 21F4 889F X-PGP-Key-ID: BD02942421F4889F X-PGP-Keyserver: hkp://pgp.mit.edu MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Message-Id: <201502060408.43700.luke@dashjr.org> X-Spam-Score: 8.5 (++++++++) X-Spam-Report: Spam Filtering performed by mx.sourceforge.net. See http://spamassassin.org/tag/ for more details. 0.0 TVD_RCVD_IP Message was received from an IP address -1.5 SPF_CHECK_PASS SPF reports sender host as permitted sender for sender-domain -0.0 SPF_PASS SPF: sender matches SPF record 10.0 AWL AWL: Adjusted score from AWL reputation of From: address X-VA-Spam-Flag: YES X-Spam-Flag: YES X-Headers-End: 1YJaEH-0003q0-Ro Cc: Justus Ranvier Subject: [Bitcoin-development] [SPAM] Re: determining change addresses using the least significant digits 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: Fri, 06 Feb 2015 04:09:19 -0000 On Friday, February 06, 2015 3:16:13 AM Justus Ranvier wrote: > On 02/04/2015 02:23 PM, Isidor Zeuner wrote: > > Hi there, > > > > traditionally, the Bitcoin client strives to hide which output > > addresses are change addresses going back to the payer. However, > > especially with today's dynamically calculated miner fees, this may > > often be ineffective: > > > > A user sending a payment using the Bitcoin client will usually > > enter the payment amount only up to the number of digits which are > > considered to be significant enough. So, the least significant > > digits will often be zero for the payment. With dynamically > > calculated miner fees, this will often not be the case for the > > change amount, making it easy for an observer to classify the > > output addresses. > > > > A possible approach to handle this issue would be to add a > > randomized offset amount to the payment amount. This offset amount > > can be small in comparison to the payment amount. > > Another possible approach is to randomize the number of change outputs > from transaction to transaction. > > Doing this, it would be possible to make change outputs that mimic > real spends (low number of s.d.) This uses more data. Why not just round change down (effectively rounding fee up)? Luke