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; 
MIME-Version: 1.0
Sender: adam.back@gmail.com
Date: Fri, 20 Feb 2015 12:44:24 +0000
Message-ID: <CALqxMTE2doZjbsUxd-e09+euiG6bt_J=_BwKY_Ni3MNK6BiW1Q@mail.gmail.com>
From: Adam Back <adam@cypherspace.org>
To: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
Content-Type: text/plain; charset=UTF-8
Subject: [Bitcoin-development] bloom filtering, privacy
Precedence: list

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