<html><head><style>body{font-family:Helvetica,Arial;font-size:13px}</style></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div id="bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px; color: rgba(0,0,0,1.0); margin: 0px; line-height: auto;"><div id="bloop_customfont" style="margin: 0px;">Hi,</div><div id="bloop_customfont" style="margin: 0px;"><br></div><div id="bloop_customfont" style="margin: 0px;">Currently I am writing my master thesis on Privacy in Tor. I started out with looking into ways to improve website fingerprinting. When performing tests, I noticed that an exit node in my country (The Netherlands) was selected more often than other countries. So I took some test and here are the results.</div><div id="bloop_customfont" style="margin: 0px;">In my understanding, one would expect Tor to select exit nodes at random, only taking into account bandwidth of the exit node and guard node relations, this is what I think is going on by reading the source. I would be very happy to receive a more comprehensive explanation of the workings of (exit-)node selection.</div><div id="bloop_customfont" style="margin: 0px;"><br></div><div id="bloop_customfont" style="margin: 0px;">It looks like that exit nodes are not randomly selected and it appears that nodes from my country are more often selected. This can be due to the fact that Tor takes into account the bandwidth provided by a node, but does it also keep in mind where I come from? </div><div id="bloop_customfont" style="margin: 0px;"><div id="bloop_customfont" style="margin: 0px;">If Tor selects an exit node more often when it has more bandwidth, doesn’t that an attacker with many resources an advantage?</div><div id="bloop_customfont" style="margin: 0px;"><br></div></div><div id="bloop_customfont" style="margin: 0px;">I am very happy to hear your explanations and opinions about these results.</div><div id="bloop_customfont" style="margin: 0px;"><br></div><div id="bloop_customfont" style="margin: 0px;">The results of the test shown in the first two pictures was performed in the following way:</div><div id="bloop_customfont" style="margin: 0px;">1. Connect to tor</div><div id="bloop_customfont" style="margin: 0px;">2. Receive list of nodes</div><div id="bloop_customfont" style="margin: 0px;">3. Retrieve exit node IP</div><div id="bloop_customfont" style="margin: 0px;">4. Send NEWYN signal and go to 3. </div><div id="bloop_customfont" style="margin: 0px;"><br></div><div id="bloop_customfont" style="margin: 0px;">The loop (3 -> 4 -> 3) was done about 200 times.</div><div id="bloop_customfont" style="margin: 0px;"><br></div><div id="bloop_customfont" style="margin: 0px;">1. Geolocation of exit node, list of nodes obtained through direct acces (IP) (<a href="http://i62.tinypic.com/vypcgm.png">http://i62.tinypic.com/vypcgm.png</a>)</div><div id="bloop_customfont" style="margin: 0px;">2. Geolocation of exit node; list of nodes obtained through US VPN (<a href="http://i60.tinypic.com/wrg705.png">http://i60.tinypic.com/wrg705.png</a>)</div><div id="bloop_customfont" style="margin: 0px;">3. Blue: total nodes, Red: exit nodes. Both per country, source: <a href="http://onionoo.torproject.org/">onionoo.torproject.org</a> (<a href="http://i62.tinypic.com/1zpnorb.png">http://i62.tinypic.com/1zpnorb.png</a>)</div><div id="bloop_customfont" style="margin: 0px;">4. Distribution from figure 3, the picture that one would observe (after many tries) when random selection of exit nodes would be applied (<a href="http://i62.tinypic.com/286rg9k.png">http://i62.tinypic.com/286rg9k.png</a>)</div><div id="bloop_customfont" style="margin: 0px;">5. Frequency an exit-node was selected, each color represents a single IP of an exit-node. This is in the case without any VPN (http://i62.tinypic.com/k0jxjo.png)</div><div id="bloop_customfont" style="margin: 0px;"><br></div><div id="bloop_customfont" style="margin: 0px;">Thank you,</div><div id="bloop_customfont" style="margin: 0px;">Max</div></div> <div id="bloop_sign_1403177392037376000" class="bloop_sign"><div style="font-family:helvetica,arial;font-size:13px"><br></div></div> <div style="color:black"><br>From: <span style="color:black">Andrew Lewman</span> <a href="mailto:andrew@torproject.is">andrew@torproject.is</a><br>Reply: <span style="color:black">tor-dev@lists.torproject.org</span> <a href="mailto:tor-dev@lists.torproject.org">tor-dev@lists.torproject.org</a><br>Date: <span style="color:black">18 Jun 2014 at 17:41:43</span><br>To: <span style="color:black">tor-dev@lists.torproject.org</span> <a href="mailto:tor-dev@lists.torproject.org">tor-dev@lists.torproject.org</a><br>Subject: <span style="color:black"> Re: [tor-dev] Tor Geolocating exit nodes. <br></span></div><br> <blockquote type="cite" class="clean_bq"><span><div><div></div><div>On 06/18/2014 04:38 AM, JP Wulf wrote:
<br>> This geolocation could perhaps be used to validate the integrity of the
<br>> nodes (how I dont know, maybe by establishing TOR honeypots that can only
<br>> be compromised through traffic through a compromised (owned) exit node).
<br>
<br>The Tor client does not trust the tor network by design. The user can
<br>influence the client to use countries they think are safe. See
<br>https://www.torproject.org/docs/faq.html.en#ChooseEntryExit
<br>
<br>
<br>--
<br>Andrew
<br>pgp 0x6B4D6475
<br>https://www.torproject.org/
<br>+1-781-948-1982
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