Received: from sog-mx-1.v43.ch3.sourceforge.com ([172.29.43.191] helo=mx.sourceforge.net) by sfs-ml-4.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1YPBIx-0004Vv-Hu for bitcoin-development@lists.sourceforge.net; Sat, 21 Feb 2015 14:45:15 +0000 Received-SPF: pass (sog-mx-1.v43.ch3.sourceforge.com: domain of gmail.com designates 74.125.82.43 as permitted sender) client-ip=74.125.82.43; envelope-from=mh.in.england@gmail.com; helo=mail-wg0-f43.google.com; Received: from mail-wg0-f43.google.com ([74.125.82.43]) by sog-mx-1.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1YPBIv-00007k-VF for bitcoin-development@lists.sourceforge.net; Sat, 21 Feb 2015 14:45:15 +0000 Received: by mail-wg0-f43.google.com with SMTP id z12so18118701wgg.2 for ; Sat, 21 Feb 2015 06:45:08 -0800 (PST) MIME-Version: 1.0 X-Received: by 10.180.82.129 with SMTP id i1mr4395156wiy.77.1424529907970; Sat, 21 Feb 2015 06:45:07 -0800 (PST) Sender: mh.in.england@gmail.com Received: by 10.194.188.11 with HTTP; Sat, 21 Feb 2015 06:45:07 -0800 (PST) In-Reply-To: References: Date: Sat, 21 Feb 2015 15:45:07 +0100 X-Google-Sender-Auth: 9AAX5U1Er0GDDQ2cC5S2pAtL_zc Message-ID: From: Mike Hearn To: Adam Back Content-Type: multipart/alternative; boundary=f46d044280fa22f920050f9a371f 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: 1YPBIv-00007k-VF Cc: Bitcoin Dev Subject: Re: [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: Sat, 21 Feb 2015 14:45:15 -0000 --f46d044280fa22f920050f9a371f Content-Type: text/plain; charset=UTF-8 > > For downloading transactions unless you frequently receive > transactions you wont be fetching every block. Or are you assuming > bloom filters dialled up to the point of huge false positives? You > said otherwise. > Well, what I mean is, bitcoinj already gets criticised for having very low FP rates, but even with those rates we're applying them to hundreds of thousands of transactions per sync. So it's still enough FPs to trigger at least one per block, often several, yet people tell us this isn't enough to give meaningful privacy. > Relatedly I think bitcoin could do with a store-and-forward message > bus with privacy and strong reliability via redundancy (but less > redundancy maybe than consensus all-nodes must receiving and agree and > store forever). > Yup, see here: https://www.bitcoinauthenticator.org/subspace/ https://groups.google.com/forum/#!topic/bitcoinj/_S15jo5mcDI Subspace looks like it's developing into what we need. > You seem to be saying at one point that Tor is useless against > pervasive eavesdropper threat model No, Tor is effective against in that threat model. What I meant is that without Tor, someone doing wire intercepts isn't going to be fazed by using multiple peers together, and with Tor it's not clear that syncing from multiple peers in parallel gives much an additional win. Also, getting Tor practical enough to activate by default is tricky. Though the same people who are doing Subspace are trying it out to see what happens. secondly that other types of attackers are disinterested (how do we know > that?) or maybe that you > dont care about privacy vs them (maybe some users do!) > Some of my opinions are based on experience of HTTPS deployments, where many of the same issues apply. > It would certainly be nice to get real privacy from a wider range of > attackers but nothing (current situation) is clearly worse; using > block bloom filters we'd make the pervasive case harder work, and the > nosy full node learn nothing. Yes, but what's the best way to fix that? The calculation goes like this: we have ~80 hours of hacking time to spend on privacy this quarter. Do we: a) Do wire encryption b) Make Bloom filter clients smarter c) Optimise Tor d) Do a new PIR protocol from scratch and possibly run out of time having failed to launch Of these (d) is the least appealing to me, especially because I don't feel like submitting SPV related stuff to Bitcoin Core any more. If I were to work on the protocol it'd be in the context of Bitcoin XT, which rules out consensus changes or other things that rely on miners. Wire encryption would probably raise the bar for our spooky friends quite a lot, with minimal effort. The ROI looks good, compared to more complex PIR. --f46d044280fa22f920050f9a371f Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
For downloading transactions unless you frequently receive
transactions you wont be fetching every block.=C2=A0 Or are you assuming bloom filters dialled up to the point of huge false positives?=C2=A0 You said otherwise.

Well, what I mean is, b= itcoinj already gets criticised for having very low FP rates, but even with= those rates we're applying them to hundreds of thousands of transactio= ns per sync. So it's still enough FPs to trigger at least one per block= , often several, yet people tell us this isn't enough to give meaningfu= l privacy.
=C2=A0
Relatedly I think bit= coin could do with a store-and-forward message
bus with privacy and strong reliability via redundancy (but less
redundancy maybe than consensus all-nodes must receiving and agree and
store forever).=C2=A0

Yup, see here:


<= /div>
Subspace looks like it's developing into what we need.
<= div>=C2=A0
You seem to be saying at one point that To= r is useless against
pervasive eavesdropper threat model

No, Tor= is effective against in that threat model. What I meant is that without To= r, someone doing wire intercepts isn't going to be fazed by using multi= ple peers together, and with Tor it's not clear that syncing from multi= ple peers in parallel gives much an additional win.

Also, getting Tor practical enough to activate by default is tricky. Thou= gh the same people who are doing Subspace are trying it out to see what hap= pens.

secondly that other types of=C2= =A0attackers are disinterested (how do we know that?) or maybe that you
dont care about privacy vs them (maybe some users do!)

Some of my opinions are based on experience of HTTPS deploy= ments, where many of the same issues apply.
=C2=A0
It would certainly be nice to get real privacy from a wider range o= f
attackers but nothing (current situation) is clearly worse; using
block bloom filters we'd make the pervasive case harder work, and the nosy full node learn nothing.

Yes, but what= 's the best way to fix that?

The calculation g= oes like this: =C2=A0we have ~80 hours of hacking time to spend on privacy = this quarter. Do we:

a) Do wire encryption
b) Make Bloom filter clients smarter
c) Optimise Tor
d) Do a new PIR protocol from scratch and possibly run out of time having = failed to launch

Of these (d) is the least appeali= ng to me, especially because I don't feel like submitting SPV related s= tuff to Bitcoin Core any more. If I were to work on the protocol it'd b= e in the context of Bitcoin XT, which rules out consensus changes or other = things that rely on miners. Wire encryption would probably raise the bar fo= r our spooky friends quite a lot, with minimal effort. The ROI looks good, = compared to more complex PIR.
--f46d044280fa22f920050f9a371f--