trip report

Trip report: Tor trainings for the Dutch and Belgian police

In January I did Tor talks for the Dutch regional police, the Dutch national police, and the Belgian national police. Jake and I also did a brief inspirational talk at Bits of Freedom, as well as the closing keynote for the Dutch National Cyber Security Centre's yearly conference.

You may recall that one of my side hobbies lately has been teaching law enforcement about Tor — see my previous entries about teaching the FBI about Tor in 2012 and visiting the Stuttgart detectives in 2008 back when we were discussing data retention in Germany. Before this blog started I also did several Tor talks for the US DoJ, and even one for the Norwegian Kripos.

Now is a good time to talk to the Dutch police, first because they're still smarting from the DigiNotar disaster in 2011, but second because of their 2012 ambitions to legalize breaking into foreign computers when they aren't sure what country they're in. (I say legalize because they already did it!)

Below are some discussion points that made an impression on me.

  • I started the trip with a talk to about 80 people from the Dutch regional police. Apparently each regional police group has basically one cybercrime person, and pretty much all of them came to learn about Tor. These are the people who advise their police groups about how to handle Tor cases, so they're exactly the ones who need to know about services like ExoneraTor. (Afterwards, one of the national police thanked me heartily for teaching the regional police about Tor, since it makes *his* job easier.)
  • One issue that came up repeatedly during the talks: what if a bad guy runs a Tor exit relay to provide plausible deniability when somebody shows up as his door? My first thought is that anybody who runs a Tor exit relay in order to attract *less* attention from the police is crazy: if you want to be ignored, you should use a botnet or whatever to do your bad things, nobody will learn that it's you, end of story. Until we educate every law enforcement person on the planet about Tor, there will always be people who raid every IP address on their suspect list without ever knowing what Tor is. The second point they found interesting was that Tor relays never write any traffic to disk; so if your suspect has bad stuff on his hard drive and says it was because of the Tor relay, he's lying. Of course, disk encryption complicates the situation (which is why, counterintuitively, we recommend *not* using disk encryption on your exit).
  • Did you know that the Dutch police have their own internal anonymity network? They started out using a secret subnet ("nobody knows that it's the Dutch police, until somebody figures out that it is"). Apparently now they do smarter things like grabbing addresses from Dutch ISPs so they can blend in better. But that's still not perfect: if they borrow an IP address for 36 hours, then that's a 36-hour window where if you can recognize any of the traffic as Dutch police, you can link the rest of the traffic to them too. I hear their new generation of client-side software has an option for using Tor; I wonder if that means the Tor Browser Bundle, or just tunnelling the traffic through Tor naked? More details here and here. (Two points for transparency and open standards!)
  • When we met with the US DEA earlier in January, many people there said they use Tor for their job. Most people in the Dutch national police meeting said they used it often. On the other hand, most people in the Dutch regional police meeting said they certainly did not use it, "because that would be inappropriate." We have some more educating left to do.
  • One regional Dutch police woman told us that they know how to check if it's a Tor exit IP, but sometimes they do the raid anyway "to discourage people from helping Tor." I later told that statement to one of the national police, and he was shocked, said that was illegal, and said he'd look into it. Alas, I'm not optimistic that anything will come of it: giving investigators discretion about how to act can be both good and bad.
  • It took me a few hours to get the regional police comfortable enough to discuss, but by the end they were answering each other's questions — which is one of my main goals, since I won't be there later to answer them. The best example was one detective who stood up and explained that in his opinion they are focusing way too much on Tor ("because we can't break it"), while at the same time there are many other crimes they *can* fight, like criminals using file sharing networks, and they're ignoring those. Certainly Tor gets a lot of publicity (last year a Dutch TV show stirred up a media fear frenzy about Tor that resulted in a Dutch Parliament member calling to ban it), but according to this detective there's a lot more crime elsewhere. My response: "Did everybody hear that?" It works best when police hear statements like this from their peers rather than from me.
  • Here's an argument based on discussions with Karen Reilly for responding about child porn and banning Tor. A lot of people think that it's about trading off the good for the bad. On the one hand, you have a girl in Syria who is alive right now because of Tor. On the other hand, you have a girl in America who is harmed by some jerk and the jerk uses Tor. So, how do you balance these two? How do you decide which one is more important, or more 'valuable' to the world? The answer is that it's the wrong question to ask: you aren't actually going to save the girl in America by getting rid of Tor. Whereas getting rid of Tor *would* harm the girl in Syria (along with a wide variety of people and groups around the world).
  • The day after I did the talk to the regional police, I did a short talk at Bits of Freedom, an EFF-like digital rights nonprofit in Amsterdam. They held a "Boffel" for many of their supporters to show up and socialize. It was a really great crowd — these are smart people who care. It was like a tiny CCC congress. And now that I've been clearly complimentary to them, you'll be able to properly interpret my next statement: many of the Dutch police would have fit in just fine at the Boffel. People came up to me at the NCSC conference days later and said "I liked your talk!" and I genuinely couldn't tell if they meant my talk at the regional police or my talk at Bits of Freedom. There were some exceptions, sure, but most of the Dutch police I talked to have somehow managed to not get ground down by their job and lose track of the civil liberties angle. I wonder what their trick is.
  • Rejo Zenger (from BoF) and two others are working to create a Dutch organization to run fast Tor exit relays, to gather donations and centrally handle abuse complaints — like Zwiebelfreunde in Germany, Nos Oignons in France, DFRI in Sweden, and NoiseTor in the US. That's great! Please help them out however you can.
  • At the NCSC conference, Jake and I did an open Q&A session on the first day, and did the closing keynote (slides) on the second day. Both talks went very well (imagine what would happen if Jake and I practiced any of our talks together before giving them! :). We now have invites to come to all sorts of CERTs around the world; the woman managing the conference is moving to Europol shortly and wants us to come talk there; and one of the heads of NCSC wants us to come back and help the Netherlands with their general direction and strategy. We should try to connect them to local Dutch Tor advocates as much as we can, since after all we have software to write.
  • I'm afraid I missed most of the other talks at the conference (and I missed the alternate conference entirely), but I did see Peter Zinn's well-choreographed talk about what the Dutch national police should be focusing on. His conclusion was that the Netherlands should focus on being the "safest country in the world wrt cybercrime by 2017". I had to restrain myself from yelling out the word externalities! during his talk: if their plan is to convince cybercriminals to go elsewhere, and then the neighboring countries like Belgium become cyber-hives-of-scum-and-villainy, that's not going to end well for anybody.
  • One person in the Belgian FCCU (Federal Computer Crime Unit) suggested during a break in the discussion that maybe Belgium should block all connections from the Tor network *to* any Belgian IP space. By now there's almost no such thing as a new question for me during these talks, but I have to admit that this one took me by surprise. Eventually I produced the right answer: "The Internet community would destroy you. 'Great Firewall of Belgium'? 'Adopt a Belgian dissident'? Nobody would take you seriously again as an alleged democracy." In any case, my friend at RIPE tells me that technically, it's harder than it sounds for Belgium to do this scale of blocking.
  • I got into a discussion with the Belgian police about how they don't regard their Internet filtering as "censorship". In my experience, the way it starts is some legislators decide there's something so horrible on the Internet that it justifies filtering. From there, they delegate to some quasi-governmental organization which comes up with a list (in some totally non-transparent fashion) of verboten URLs. Inevitably, the list contains more types of content than the original reason for setting up the filtering; and inevitably, there's no redress mechanism to get off the list if you shouldn't be on it. The Belgian police assured me that they only filter a small set of URLs, and that each of them is discussed and transparently decided about in a democratic fashion. And then they wouldn't tell me what's on their list.
  • I met a US FBI agent and a US Secret Service agent who are "permanently" stationed with the Dutch national police. They acted just like normal Dutch police, except I guess they're paid by the United States to be Dutch police. Weird world we live in.
  • In each of the three police meetings, somebody suggested an alternate model for Tor where a judge should get to decide whether a given Tor user should be deanonymized. (While in America we don't trust our judges, in Europe they really do.) Putting aside for a moment the technical fact that building in a backdoor would mean that criminals can exploit it too (this argument doesn't work on them), I tried to press on the multi-jurisdictional aspect: we have governments, militaries, and law enforcement from around the world relying on Tor. When I asked the embedded Secret Service guy if he would be ok with the Dutch police having a backdoor to Tor, he said "We like our Dutch colleagues." When I rephrased it to whether he would be ok with the Dutch police knowing what the US police are using Tor for, he paused, smiled, and tactfully said "No comment."
  • Several people at the Dutch cybercrime unit quietly told me they regretted their "break into a Tor hidden service and zero it out" action: it got people upset at them, but more importantly, it *didn't work*. That is, it didn't stop any bad people from doing bad things. Apparently playing whack-a-mole like this doesn't make the criminals go away. And worse, it disrupts the police's other monitoring and infiltration operations.
  • If I wanted to run a hidden service website that had a nation-state adversary, I would a) run a good solid webserver like nginx; b) run it in a VM, in a way that the VM couldn't learn its location — "no looking up its IP", but also more subtle things like "no looking up nameservers", "no looking up reachable wireless access points", etc; and then c) put that VM in a VPS running in a country that hates my adversary. That way even if somebody breaks into the webserver and breaks out of the VM, they're still faced with a frustratingly long bureaucratic step.
  • I took Aaron Gibson and Pepijn Le Heux with me to the Brussels meeting, and took Pepijn again to the Dutch national police meeting. Pepijn is a great guy; I'm hoping to turn him into a Roger replica so he can act as a Dutch Tor resource and so he can help organizations like Bits of Freedom save their country.

Training Journalists in Istanbul

After meeting with SOCA in London, I traveled to Istanbul to teach local and foreign journalists how to use Tor and Tails to keep themselves, their colleagues, and their sources safe online. I also met with the team behind Zero Day, a documentary about all things Internet security, to talk about Tor and the work that I do.

I met with foreign journalists on the first day and local journalists the day after. Around 30 people attended in total, and each training session lasted just over two hours. My presentation covered threats, how you can protect your communication, local data, and external data, as well as how to use the Tor Browser Bundle and Tails. I gave out USB sticks with the Tor Browser Bundle, the short user manual, and the CPJ Journalist Security Guide. PC users were also given USB sticks with Tails.


The feedback has been really positive from everyone who attended, and I have been told that those who were unable to attend have been given the material I handed out. There are some things that can be improved, however:

  • Tor does not prevent somebody watching your Internet traffic from learning that you’re using Tor. In some cases, the fact that you are using Tor and encrypting emails/chat/drives can be a red flag. I am not sure how to best address this in a presentation, other than just say that yes, it can be a red flag.
  • We talked about a few different risks, such as having your phone tapped, your email hacked, and your home or hotel room broken into. Having solid examples and stories helps a lot.
  • I introduced a lot of new technology in a short amount of time. Those who are not familiar with technology such as full disk encryption, GPG, and OTR, would benefit from a longer and more hands-on session.
  • The presentation included screenshots of encrypted email, encrypted chat, and the Tor Browser Bundle. Having a few videos that illustrate how it works, what the user sees, and what the new workflow is will make it easier to understand.
  • The presentation mentioned Bitlocker, FileVault, and TrueCrypt for full disk encryption, but did not go into details. I told everyone how to enable FileVault in OS X, and I should add these step-by-step instructions to the presentation.
  • Tor was originally designed, implemented, and deployed as a project of the U.S. Naval Research Laboratory. We also receive funding via U.S. government organizations. I covered this briefly in my presentation, but could have spent a bit more time talking about the Tor Project, Inc and why we are qualified to talk about Internet security and online anonymity.


I asked a few people to try out Tails and let me know if something was confusing, did not work, or could be improved:

  • Tails has very limited support for Apple hardware. 23 out of 30 attendees were Mac users. I tried booting Tails on my MacBook Air, but OS X was unable to find the USB stick.
  • I am used to the Tor Browser and was surprised to see that was not the default home page.
  • Firefox will start automatically once you are connected to the Internet. Most users did not wait for the Tails website to load before entering another URL in the address bar. Users did not question if they were actually using Tor.
  • One user waited for the Tails website to load, saw the green download button and then asked if he needed to upgrade to a newer version. I wonder if there is a way to let users know which version they are currently using.
  • A few users seemed confused when Pidgin automatically connected to IRC. I wonder if it would be better to have that disabled by default, and instead take users through the process of setting up their own accounts.
  • One user tried the email client, skipped the part where you set up the mail servers, and tried to write an email. I wonder if there is a way to improve this, as most users expect the mail client to work just like the one they are used to in their normal operating system.
  • Tails uses a US keyboard layout by default. This can be confusing for anyone with a different keyboard layout. A few users mentioned that the tap-touchpad-to-click functionality did not work.
  • One user pointed out that there is no logout or shutdown option available when using Tails in Windows XP mode.
  • The shutdown process can look a bit scary for anyone who is not used to Linux, especially the part where it wipes the memory. A friendly splash-screen of some sort would be good.

Thanks to my wonderful hosts for providing me with a place to stay, great food, suggestions on what to see in Istanbul, and for organizing and hosting the training sessions.

Meeting With SOCA in London

In January I met with the Serious Organised Crime Agency (SOCA) in London, UK. One of the challenges when dealing with online threats (cybercrime/e-crime) is understanding which leads not to follow. My goal was to help them understand what Tor is, how it works (both from a user and a relay operator point of view), and what it can and cannot do.

I talked about the Tor software ecosystem, including ExoneraTor (the website that tells you whether a given IP address was a Tor relay), and mentioned that we list all official projects on our website. I also mentioned Roger’s trip to the FBI conference in October 2012, and talked about some of the experiences we have had teaching US-based law enforcement about Tor.

Overall, I would say the meeting went well. They learned more about Tor and the projects we are working on, and they are aware that the protections that prevent us from figuring out what Tor users are doing - and who they are - is what’s keeping all Tor users safe.

Trip report, 29c3

Jacob and I did another Tor talk at CCC this year. This time we focused on explaining all the various Tor project components (mostly development-related) that need help from the broader community.

The talk went well, but we were in the smaller room, and we and the conference organizers had failed to communicate that it was meant to be more of a workshopy atmosphere. We had a lot of people there who just wanted to see the sequel to our spectacle last year, and it meant we turned away many hundred Tor enthusiasts. Live and learn I guess. I did end up holding a post-talk Tor Q&A session that lasted for seven hours.

I'm still patiently waiting for the official video to emerge [Edit: here it is!], but in the meantime there's a youtube copy of the video stream; you can look at the slides too.

Some other highlights from Congress:

  • Be sure to watch the DoJ/NSA whistleblower talk (blurb).
  • We talked to Christian Grothoff about NAT piercing for Flash Proxy. One of the main deficiencies in the current Flash Proxy design is that the censored user needs to be reachable on the Internet (i.e. not behind a firewall or NAT). While we can't expect the flash proxy bridge running in a browser to be able to craft arbitrary packets (required for most NAT piercing tricks), Peter Palfrader pointed out that we *can* expect the Flash Proxy facilitator to be able to send such packets on behalf of each volunteer bridge. Cute trick — wonder if it'll work.
  • I introduced Harry Halpin (W3C) to David Fifield (Flash Proxy). Web browsers are trying to catch up to Skype in terms of real-time media interactions. That means UDP flows, NAT piercing, link encryption, and more, all in the browser. Flash Proxy could sure make use of all that. And the folks working on the WebRTC specifications could use some broader use cases.
  • I met several great people from Bits of Freedom, the Dutch NGO that is a sort of hybrid EFF/ACLU for the Netherlands. It seems like only a few years ago that we were lamenting that Europe has too few advocacy organizations to challenge bad laws and policies — data retention, ACTA, etc. That's changing!
  • I talked to Linus Nordberg, who runs several fast exits in Sweden as part of DFRI and has been pondering running a bunch of bridges too. The question is: what are the tradeoffs between running both the bridges and exits on the same network (more centralization) vs partitioning them so they run on distinct netblocks? Counterintuitively, due to the "no more than one node on a given /16" rule in Tor's path selection strategy, centralizing the bridges and exits on the same netblock actually improves safety against some adversaries. My recommendation to him was that having more bridges and exits is still better than not, even though the diversity issues remain open and complex research questions.
  • I also talked to Linus about what we should do with relays whose exit policies only allow ports commonly used for plaintext traffic. Is that a hint that they're set up by jerks to sniff traffic? Or did the operator not even think about that issue? Should we set the BadExit flag for them? It seems that's a tough arms race for us to win, since they could just choose to exit to a few more ports and suddenly they blend back in. Ultimately I think we need to work harder to establish relationships with all the fast exit relays. We're doing pretty well in terms of knowing the operators of the CCC relays, the relays, the Akamai relays, etc. Will we eventually get to the point where we can cap the bandwidth weights for relays that we haven't met personally? Perhaps we can even bring back the Named or Valid flags for real? In any case, the short-term answer is "send them mail and start a conversation".
  • I talked to trams about sandboxing Flash. It would be great to ship the Tor Browser Bundle with some wrappers that prevent Flash from doing scary things. (Ok, it would be even better to wrap the whole OS, but let's not get hasty.) He has a set of protection wrappers that work on OS X, but his next question is what behaviors to allow? I suggested that to start, we should pick exactly the behaviors Youtube uses — then we'll make a lot of Tor users happier while still not opening the attack surface too much. Next messy steps include "that's nice for OS X users, but what about Windows users?" and "How does this relate to FF17's new plugin-container notion?"
  • I met with the Wau Holland Foundation board about having WHF be our European coordinator for exit relay funding. It's tricky to get everything organized in a way that's compatible with non-profit laws in both the US and Germany, and also in a way where the community understands how the relationships work. We're getting closer.
  • I met with Andy Isaacson of Noisebridge, which operates several fast exits in the US under its Noisetor project. I'd like to sign Noisebridge up to be a US-based coordinator for exit relay funding. But Andy quite reasonably worries that once we start giving Noisetor money for exits, the individual contributions they get to run their exits will disappear. One resolution might be to do one of those "matching funding" deals, where we offer to match every dollar they raise up to some amount. Ultimately, I hope they work with their community to make a plan that lets them either grow the capacity or diversity of the relays they run, or extend the lifetime of their existing relays.
  • I talked to bunnie about the open laptop he's working on. Over in Torouter land, we've had a series of experiences where we pick what looks like a fine architecture for a tiny Tor relay. We work with the vendor, help everything go smoothly, and then at the last minute it seems like the vendor goes sideways with some for-profit proprietary alternate plan. :( I really want to live in a world where a fully open platform exists — hardware design and documentation, firmware, device drivers, software, everything. If you can do anything to help bunnie succeed, please do!

Tor projects win two Access Innovation Awards

In December I attended the award ceremony for the 2012 Access Innovation Awards. Their finalists included three projects that Tor maintains or co-maintains: OONI (a framework for writing open network censorship measurement tests, and for making the results available in an open way; see its git repo), Flash Proxy (a creative way to let people run Tor bridges in their browser just by visiting a website; see its git repo), and HTTPS Everywhere (a Firefox extension to force https connections for websites that support https but don't use it by default; see its git repo). Of these, OONI and Flash Proxy ended up being winners in their respective categories.

(The Access Innovation Prize gave $100,000 across 5 categories to individuals, organizations and networks who submitted "the best actionable ideas on how to use information technology to promote and enable human rights and deliver social good.")

I'm happy that people are recognizing some of the cool projects that Tor works on. But more than that, it's interesting to watch how our projects are integrating into the broader community. The HTTPS Everywhere website is hosted by EFF, and the tool is co-developed by EFF and The Tor Project. The Flash Proxy submission was actually submitted by the New America Foundation's OTI group, where they plan to work on integrating the Flash Proxy badge into a Facebook app (don't worry, they're splitting the prize money with David Fifield, the main Flash Proxy developer). We (Tor) wouldn't be able to have this reach if we didn't have these other organizations working on our topics too.

More generally, the line around what counts as a Tor project has been getting blurrier over the years. We're a community based around free software and transparent design and development, and when we encounter somebody else who is "doing it right", we embrace them and offer whatever resources we can to help them succeed. One nice example is Nathan Freitas of Guardian — he started maintaining an Android version of Tor, and we liked how he was doing it, so we called him a Tor developer. When Nathan uses his Tor affiliation to get funders to listen to him about mobile security issues, everybody wins. Similarly, while David Fifield spends most of his time being a Stanford grad student, he's made such progress on Flash Proxy that we're paying a second Flash Proxy developer to help him with Windows deployment. It's great that OTI is working in this pluggable transport space too. There's no shortage of hard problems and development tasks to go around.

I'm glad I attended the awards evening. I confess that I was worried it would be full of media hype, with journalists lined up to write hasty and shallow articles. (I suppose I'm jaded by being followed around at hacker conferences by journalists with quotas and deadlines. But I was particularly worried this time because both OONI and Flash Proxy are young projects, and we'd be wisest to make some real progress before drawing mainstream media attention to them.) Instead, the attendees were a variety of enthusiastic, not-very-technical New York City residents. Most of them hadn't heard of Tor and had only a very general understanding of Internet privacy and censorship issues; so I had my work cut out for me in terms of advocacy and awareness-building. Highlights included conversations with people from Committee to Protect Journalists, Human Rights Watch, and several similar organizations — these are exactly the sort of orgs that needs the neutral censorship measurement results that OONI aims to provide.

Trip report, German Foreign Office

In September, Karen and I attended a conference at the German Foreign Office to help
them decide what role Germany and the EU should have at regulating the sale of censorship and surveillance tools to dictators:


  • I liked Eric King (from Privacy International)'s suggestion that when companies are submitting their tools for export evaluation, they should be required to submit their brochures too. Some of these companies are just shameless in terms of how they pitch their tool in terms of number of bloggers you can round up per unit time. He convinced me that controlling "the worst of the worst" in terms of how they can present their product will influence how these products spread.
  • That said, these were all (foreign) policy experts, not technologists. They all seemed to take it for granted that you could draw a line between "bad" products and acceptable / dual-use products. I tried to hold back from saying "every time you people try to come up with legal phrasings about what technologies are ok, you end up putting tools like mine on the wrong side of the line." In retrospect, I should have said it more loudly.
  • They were really proud to have Tor representatives there. Having us there let them show the world that they had "real technologists" at their meeting. There were several cases where the whole breakout session turned to me and wanted to know what Tor thought about the given question.
  • I met a nice man who worked for a telco/DPI company that deploys its products in the Middle East. He raised a compelling argument: "Look, you folks are the ones that mandated backdoors in the telco equipment we produce, using the term 'lawful intercept'. And now you're surprised and upset when bad people use these same backdoors? You made us build it that way!" It certainly is easier for officials in countries like Germany to think of the world as divided between "good" places and "bad" places, but it sure isn't that simple.

Trip report, ACM CCS/WPES

In October I attended WPES and the first day of CCS. There are a bunch of new Tor-related research papers:

  • "Changing of the Guards: A Framework for Understanding and Improving Entry Guard Selection in Tor". Basically Tariq has written a suite of tools for analyzing how likely an adversary is to be able to see a Tor user's circuits given various values for guard selection and guard rotation. Early results include "three guards is probably the wrong number" and "we probably shouldn't rotate guards so often". Later results I hope will include "here's an algorithm for assigning the Guard flag to relays that makes users safer".
  • "Torchestra: Reducing interactive traffic delays over Tor". This paper suggests having two parallel TLS connections between each pair of relays — one for the loud circuits and one for the quiet ones. I've had a series of debates with Rob Jansen over whether this should really help, or if it's just shifting the round-robining to a deeper level (e.g. kernel-level buffers). My current opinion is that it should really help, not because it writes important bytes out faster, but because the other side can *read* important bytes faster — in the current state a relay can't predict which incoming bytes are going to be high-priority, but when high-priority bytes come on a separate TCP connection, it's easy to tell.
  • "Enhancing Tor's Performance using Real-time Traffic Classification". I haven't read it in detail yet, but it looks at using machine learning to classify circuits depending on what sort of traffic they're carrying. This direction is worthwhile, but it skips over the question that Rob and I are currently wrestling with, which is "ok, so you've decided to give lower priority to a circuit. What should you actually do to make that circuit put less load on the network?" See also Rob's Usenix Security paper:
  • "SkypeMorph: Protocol Obfuscation for Tor Bridges". The idea is to use the actual Skype program to make a (TCP) video call between user and bridge, and then drop the call and start up your own UDP traffic flows that mimic Skype's UDP flows in terms of size and timing. I'm not clear that trying to look like Skype is a game we can win (especially with DPI-level adversaries already playing the arms race to detect and block 'real' Skype, and with the wasted bandwidth that comes with pretending to be a Skype video call), but I think we can get a lot of mileage out of a Tor pluggable transport that carries Tor traffic over a UDP flow — especially with recent rumors of a Syrian ISP throttling all TCP flows.
  • "StegoTorus: A Camouflage Proxy for the Tor Anonymity System". Stegotorus is an obfsproxy fork with two goals: first, chop up Tor traffic flows so you can't recognize Tor traffic just by looking for more 586-byte TCP packets than usual; and second, transport those chopped-up flows over a variety of steg modules, to hide the traffic in protocols that the adversary is unwilling to block (as opposed to obfsproxy's goal, which is to make a flow that's hard enough to DPI for that the adversary has to choose between blocking all unrecognized protocols or letting the flows through). Unfortunately, there aren't any great steg modules yet; rather, it aims to be a framework where if you *did* have a great steg module, you could just pop it in.
  • "CensorSpoofer: Asymmetric Communication using IP Spoofing for Censorship-Resistant Web Browsing". It's designed for censored users who mostly consume bytes rather than produce them. This design also uses a UDP stream to deliver the bytes, but they spoof the stream as coming from a plausible-looking voip client rather than from the real source. Then they need some low-latency low-bandwidth way (e.g. instant messaging) to get the upstream packets to the server.
  • There's also "Touching from a Distance: Website Fingerprinting Attacks and Defenses". But I confess I haven't looked at it yet. Website fingerprinting remains a huge and open issue that needs more attention.

This recent variety of pluggable-transport designs and research papers is fantastic. It also makes me realize that somebody should put some effort into identifying the various components that a Tor transport system needs, and which papers provide which components. For example, it sounds like SkypeMorph and CensorSpoofer could share the same details for the link encryption and flow control for their UDP stream, rather than inventing two separately. Similarly, the "small upstream channel" requirement from CensorSpoofer reminds me of the similar goal that David's Flashproxy design faces. I see that Tariq and Ian have a new tech report out that gives that a start.

Trip report, October FBI conference

In October I attended an FBI conference, as part of my work to try to keep Tor on good relations with law enforcement. My first goal is to remind them of all the good uses of Tor, so if they ever find themselves lobbying to outlaw anonymity online, they'll understand what they're giving up. The second goal is to make sure they understand what Tor is and how it works, so if they encounter it in their investigations they'll hassle our exit relay operators less. (Here's a great way that one FBI person explained it to me: "I've got 10 leads, and 48 hours before this case doesn't matter anymore. If you can help me understand which leads *not* to follow, I can do my job better.") My third goal is to help them be able to use Tor correctly for their own jobs — remember that diversity of users is part of what makes Tor safe for everybody to use.

Overall, we've been doing a pretty good job at teaching US-based law enforcement about Tor. At the end of the conference, one of the FBI agents took me aside and asked "surely you have *some* sort of way of tracking your users?" When I pointed at various of his FBI colleagues in the room who had told me they use Tor every day for their work, and asked if he'd be comfortable if we had a way of tracing *them*, I think he got it.

I met a nice man from the DEA who worked on the "Farmer's Market" bust. This was in the news a lot back in April, where apparently some people were selling drugs online, and using a Tor hidden service for their website. At the time I thought the news stories could be summarized simply as "idiot drug sellers accept paypal payments, get busted." It turns out they were pretty smart about how to accept paypal payments — they just had random Americans receive the paypal payments, take a cut, and then turn them into a Panama-based digital currency, and the Panama company didn't want to help trace where the money went. The better summary for the news stories should actually have been "idiot drug sellers use hushmail, get busted." Way before they switched to a Tor hidden service, the two main people used Hushmail to communicate. After a subpoena (and apparently a lot of patience since Canada still isn't quite the same as the US), Hushmail rolled over and gave up copies of all the emails. Many more details here:

I should still note that Tor doesn't introduce any magic new silver bullet that causes criminals to be uncatchable when before they weren't. The Farmer's Market people ran their webserver in some other foreign country before they switched to a Tor hidden service, and just the fact that the country didn't want to cooperate in busting them was enough to make that a dead end. Jurisdictional arbitrage is alive and well in the world.

Trip report, Arab Bloggers Meeting, Oct 3-7

Jake, Arturo, and I went to Tunisia Oct 3-7 to teach a bunch of bloggers from Arab countries about Tor and more generally about Internet security and privacy. The previous meetings were in Lebanon; it's amazing to reflect that the world has changed enough that Sami can hold it in his home country now.

The conference was one day of keynotes with lots of press attention, and then three days of unconference-style workshops.

On the keynote day, Jake and Arturo did a talk on mobile privacy, pointing out the wide variety of ways that the telephone network is "the best surveillance tool ever invented". The highlight for the day was when Moez Chakchouk, the head of the Tunisian Internet Agency (ATI), did a talk explicitly stating that Tunisia had been using Smartfilter since 2002, that Smartfilter had been giving Tunisia discounts in exchange for beta-testing their products for other countries in the region like Saudi Arabia, and that it was time for Tunisia to stop wasting money on expensive filters that aren't good for the country anyway.

We did a four-hour Tor training on the first workshop day. We covered what to look for in a circumvention or privacy tool (open source good, open design good, open analysis of security properties good, centralization bad). All the attendees left with a working Tor Browser Bundle install (well, all the attendees except the fellow with the ipad). We got many of them to install Pidgin and OTR as well, but ran into some demo bugs around the Jabber connect server config that derailed some users. I look forward to having the Tor IM Browser Bundle back in action now that we've fixed some Pidgin security bugs.

We did a three-hour general security and privacy Q&A on the second workshop day, covering topics like whether Skype is safe, how else can they do VoIP, how can they trust various software, a demo of what sniffing the network can show, iphone vs android vs blackberry, etc. It ended with a walk-through of how *we* keep our laptops secure, so people could see how far down the rabbit hole they can go.

Syria and Israel seem to be the scariest adversaries in the area right now, in terms of oppression technology and willingness to use it. Or said another way, if you live in Syria or Palestine, you are especially screwed. We heard some really sad and disturbing stories; but those stories aren't mine to tell here.

We helped to explain the implications of the 54 gigs of Bluecoat logs that got published from inside Syria, detailing URLs and the IP addresses that fetched them. (The IP addresses were scrubbed from the published version of the logs, but the URLs, user agents, timestamps, etc still contain quite sensitive info.)

Perhaps most interesting in the Bluecoat logs is the evidence of Bluecoat devices phoning home to get updates. So much for Bluecoat's claims that they don't provide support to Syria. If the US government chose to enforce its existing laws against American companies selling surveillance tools to Syria, it would be a great step toward making Tor users safer in Syria right now: no doubt Syria has some smart people who can configure things locally, but it's way worse when Silicon Valley engineers provide new filter rules to detect protocols like Tor for no additional charge.

The pervasiveness of video cameras and journalists at the meeting was surprising. I'm told the previous Arab blogger meeting was just a bunch of geeks sitting around their laptops talking about how to improve their countries and societies. Now that the Twitter Revolution is hot in the press, I guess all the Western media now want a piece of the action.

On the third workshop day we learned that there was a surveillance corporate expo happening in the same hotel as the blogger meeting. We crashed it and collected some brochures. We also found a pair of students from a nearby university who had set up a booth to single-handedly try to offset the evil of the expo. They were part of a security student group at their university that had made a magazine that talked among other things about Tor, Tunisian filtering, etc. We gave them a big pile of Tor stickers.

On our extra day after the workshops, we visited Moez at his Internet Agency and interviewed him for a few hours about the state of filtering in his country. He confirmed that they renewed their Smartfilter license until Sept 2012, and that they still filter "the groups that want it" (government and schools), but for technical reasons they have turned off the global filters (they broke and nobody has fixed them). We pointed out that since an external company operates their filters — including for their military — then that company not only has freedom to censor anything they want, but they also get to see every single request when deciding whether to censor it. Moez used the phrase "national sovereignty" when explaining why it isn't a great idea for Tunisia to outsource their filtering. Great point: it would be foolish to imagine that this external company isn't logging things for their own purposes, whether that's "improving their product" or something more sinister. As we keep seeing, collecting a large data set and then hoping to keep it secret never seems to work out.

One of the points Jake kept hammering on throughout the week was "if *anything* is being filtered, then you have to realize that they're surveilling *everything* in order to make those filtering decisions." The Syrian logs help to drive the point home but it seems like a lot of people haven't really internalized it yet. We still find people thinking of Tor solely as an "anti-filter" tool and not considering the surveillance angle.

After the meeting with Moez, we went to visit one of the universities. We talked to a few dozen students who were really excited to find us there — to the point that they quickly located a video camera and interviewed us on the spot. They brought us to their security class, and informed the professor that we would be speaking for the first half hour of it. We gave an impassioned plea for them to learn more about Tor and teach other people in their country how to be safe online. I think the group of students there could be really valuable for creating local technical Tor resources. As a bonus, the traditional path for a computer science graduate of this university is to go work at Tunisia Telecom, the monopoly telco that hosts the filtering boxes &mdash the more we can influence the incoming generations, the more the change will grow.

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