From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sog-mx-4.v43.ch3.sourceforge.com ([172.29.43.194] helo=mx.sourceforge.net) by sfs-ml-1.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1W3bp1-0003T2-7f for bitcoin-development@lists.sourceforge.net; Thu, 16 Jan 2014 01:32:39 +0000 Received-SPF: pass (sog-mx-4.v43.ch3.sourceforge.com: domain of gmail.com designates 209.85.217.170 as permitted sender) client-ip=209.85.217.170; envelope-from=gmaxwell@gmail.com; helo=mail-lb0-f170.google.com; Received: from mail-lb0-f170.google.com ([209.85.217.170]) by sog-mx-4.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1W3bp0-00035k-Ee for bitcoin-development@lists.sourceforge.net; Thu, 16 Jan 2014 01:32:39 +0000 Received: by mail-lb0-f170.google.com with SMTP id u14so1443704lbd.29 for ; Wed, 15 Jan 2014 17:32:31 -0800 (PST) MIME-Version: 1.0 X-Received: by 10.112.135.102 with SMTP id pr6mr3144581lbb.43.1389835951659; Wed, 15 Jan 2014 17:32:31 -0800 (PST) Received: by 10.112.198.65 with HTTP; Wed, 15 Jan 2014 17:32:31 -0800 (PST) In-Reply-To: References: <20140113133746.GI38964@giles.gnomon.org.uk> <20140114225321.GT38964@giles.gnomon.org.uk> <20140115230901.GA25135@netbook.cypherspace.org> Date: Wed, 15 Jan 2014 17:32:31 -0800 Message-ID: From: Gregory Maxwell To: Jeremy Spilman Content-Type: text/plain; charset=UTF-8 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 (gmaxwell[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: 1W3bp0-00035k-Ee Cc: "bitcoin-development@lists.sourceforge.net" Subject: Re: [Bitcoin-development] unlinakble static address? & spv-privacy (Re: Stealth Addresses) 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, 16 Jan 2014 01:32:39 -0000 On Wed, Jan 15, 2014 at 5:02 PM, Jeremy Spilman wrote: > Choosing how many bits to put in the prefix may be difficult, particularly > if transaction load changes dramatically over time. 0 or 1 bits may be > just fine for a single user running their own node, whereas a central > service might want 4 or 5 bits to keep their computation costs scalable. Ignoring prefixes the cost for each reusable address is only a small percentage of the full node cost (rational: each transaction has one or more ECDSA signatures, and the derivation is no more expensive), so I would only expect computation to be an issue for large centralized services. (non-full nodes suffer more from just the bandwidth impact). I'd point out that regardless of how long the desired prefix is, the encoded prefix should probably always be constant length in all reusable addresses. If you don't want a particular prefix then the sender should just pick random data for the rest of the space. There is no need to publish any additional distinguishing data in the form of how long the prefix is.