Received: from sog-mx-2.v43.ch3.sourceforge.com ([172.29.43.192] helo=mx.sourceforge.net) by sfs-ml-2.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1YOmwZ-0000gu-FK for bitcoin-development@lists.sourceforge.net; Fri, 20 Feb 2015 12:44:31 +0000 Received-SPF: pass (sog-mx-2.v43.ch3.sourceforge.com: domain of gmail.com designates 209.85.216.51 as permitted sender) client-ip=209.85.216.51; envelope-from=adam.back@gmail.com; helo=mail-qa0-f51.google.com; Received: from mail-qa0-f51.google.com ([209.85.216.51]) by sog-mx-2.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1YOmwX-0005lT-OI for bitcoin-development@lists.sourceforge.net; Fri, 20 Feb 2015 12:44:31 +0000 Received: by mail-qa0-f51.google.com with SMTP id i13so12114045qae.10 for ; Fri, 20 Feb 2015 04:44:24 -0800 (PST) MIME-Version: 1.0 X-Received: by 10.140.232.5 with SMTP id d5mr23667546qhc.78.1424436264364; Fri, 20 Feb 2015 04:44:24 -0800 (PST) Sender: adam.back@gmail.com Received: by 10.96.150.233 with HTTP; Fri, 20 Feb 2015 04:44:24 -0800 (PST) Date: Fri, 20 Feb 2015 12:44:24 +0000 X-Google-Sender-Auth: RmjMFhEAHEvoHmgfjT-OjRjf7PQ Message-ID: From: Adam Back To: Bitcoin Dev Content-Type: text/plain; charset=UTF-8 X-Spam-Score: -1.5 (-) 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 (adam.back[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record 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: 1YOmwX-0005lT-OI Subject: [Bitcoin-development] bloom filtering, privacy 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, 20 Feb 2015 12:44:31 -0000 I saw there was some discussion on this topic on the bitcoinj list. (I dont think I can post there without subscribing probably.) Someone had posted about the lack of privacy provision from the current implementation parameters and real-world factors similar to described in this academic paper http://eprint.iacr.org/2014/763.pdf Mike had posted a detailed response on the topic on why its complex and becomes bandwidth inefficient to improve it usefully. https://groups.google.com/forum/#!msg/bitcoinj/Ys13qkTwcNg/9qxnhwnkeoIJ The basic summary of which I think is that its not even intended to provide any practical privacy protection, its just about compacting the query for a set of addresses. So I was wondering what about changing to committing a bloom filter of the addresses in the block. Its seems surprising no one thought of it that way before (as it seems obvious when you hear it) but that seems to address the privacy issues as the user can fetch the block bloom filters and then scan it in complete privacy. (Someone appeared on bitcoin wizards IRC a while back and made this observation.) From there its a question of fetching the candidate TXOs. Am I missing anything? Adam