WEBVTT 00:05.250 --> 00:10.320 Hello, and welcome to my Aerospace Village talk on wireless privacy issues in aviation. 00:10.320 --> 00:17.720 I really, really appreciate the opportunity to share our research in this area, even under these fairly unusual circumstances. 00:17.820 --> 00:28.640 And I also want to take the time to commend the organization around the village, which is a great initiative that brings together so many stakeholders in order to tackle security issues in aviation. 00:28.840 --> 00:32.220 If you don't know me, my name is Martin Strohmeyer. 00:32.220 --> 00:37.500 I am working at the Cyber Defense Campus of Armistice Science and Technology in Switzerland. 00:37.620 --> 00:41.600 And I'm also a junior research fellow at the University of Oxford. 00:42.700 --> 00:44.540 So, let's dive in. 00:44.580 --> 00:47.900 When we speak about wireless privacy, what do we mean? 00:48.020 --> 00:54.400 The heart of the issue is that we cannot normally prevent access to wireless signals that are being sent. 00:54.400 --> 01:02.540 On a wire channel, if we physically control all of the lines and nodes, the number of possible adversaries is normally limited. 01:02.880 --> 01:08.520 In contrast, the wireless channel is inherently broadcast, as you can see here. 01:08.520 --> 01:14.180 It is typically omnidirectional and there are no physical containment measures possible. 01:14.280 --> 01:21.520 So, sending or receiving messages does not require you to physically tap into the network infrastructure. 01:21.820 --> 01:28.160 Based on this inherent broadcast property, I want to concentrate on two attack primitives today. 01:28.420 --> 01:30.700 The first one is eavesdropping. 01:30.740 --> 01:34.620 So, a breach of the confidentiality of the transmitted data. 01:34.660 --> 01:41.560 This is a well-established concept, of course, and can fundamentally be prevented through the use of encryption. 01:41.800 --> 01:50.220 Our phones, laptops do this fairly securely and hassle-free these days, despite the occasional breakdown. 01:51.580 --> 01:54.320 The second one is location privacy. 01:54.320 --> 02:02.560 Often, we do not want to prevent the content of the communication data being exposed, but also the position of the participants. 02:02.960 --> 02:07.120 This gains additional importance in wireless networks. 02:07.680 --> 02:14.700 Users are often mobile and we can track their movements over time simply by estimating where the signals come from. 02:15.180 --> 02:17.660 Such tracking has many positive use cases. 02:17.660 --> 02:25.100 For example, if you're in a museum, standing in front of a painting and a system can deliver matching information to you. 02:25.180 --> 02:30.080 However, tracking also facilitates many high-profile privacy breaches. 02:31.580 --> 02:35.740 So, let's apply these concepts to aviation. 02:36.240 --> 02:43.440 Here, we have to understand first that the threat model of aviation has changed drastically over the past decade or so. 02:44.000 --> 02:53.840 First, aviation is moving away from analog technologies, such as voice or radar, and increasingly using digital communication networks and automation. 02:54.380 --> 03:05.680 The second aspect is just as important, which is the widespread availability of cheap, hard, and software, as well as knowledge about aviation protocols. 03:05.820 --> 03:22.460 These two developments combined lead to the fact that many more people are capable of affecting wireless air traffic communication systems than before, and practically anyone can listen to wireless aviation communications these days. 03:23.100 --> 03:33.220 In short, the threat model has moved from a purely nation-state actor model to a whole range of groups with different capabilities and motivations. 03:33.830 --> 03:47.260 In today's talk, it is actually sufficient to focus on the purely passive eavesdroppers, as observing the communication is entirely sufficient to exploit many of the privacy issues in aviation. 03:47.820 --> 03:57.640 Now, let's look at some real-world examples of confidentiality and location privacy issues in different aviation protocols, which were collected from our own research over the years. 03:57.720 --> 04:06.300 First, we will talk about the data link ACARS, which has been deployed for decades and is still in use by most larger aircraft around the world. 04:08.400 --> 04:13.480 Let me just say at this point that all of these examples now are, of course, anonymized. 04:13.620 --> 04:17.400 Still, you can intuitively see that this is not good. 04:17.680 --> 04:34.320 A lot of very critical data is absolutely sent in the clear, and neither Sally here nor Tom would be happy if they knew that their medical information is being broadcast, not only to ground staff, but also to anyone listening in the 300-mile radius of the aircraft. 04:35.600 --> 04:53.780 Further privacy issues in this area include information about personal belongings by crew that you could just go and collect, and, of course, our favorite example that often serves to drive the point home, full credit card data for higher value transactions in onboard duty-free shopping. 04:53.940 --> 05:02.500 This credit card thing is indeed still ongoing with some airlines in 2020, despite notifications provided years ago. 05:03.580 --> 05:12.340 Some people in the industry have actually acknowledged that there's an issue with this, and they came up with what you can see here. 05:12.500 --> 05:20.640 If you're watching this recording, you can maybe take an extended look at these messages and figure out quickly what is wrong here before I spoil it. 05:20.700 --> 05:22.560 But for now, let me tell you. 05:23.480 --> 05:32.720 As you may have guessed, this type of ACARS data link encryption is using a monoalphabetic substitution cipher that is broken in minutes. 05:32.820 --> 05:41.440 It is used by a wide range of private, military, and even government aircraft, and again, this has been going on for more than a decade now. 05:42.380 --> 05:53.520 Still, this data link issue, we could say it is fairly straightforward, and this could still be solved with better crypto solutions that are standardized and verified. 05:53.820 --> 06:02.600 Honestly, some of them even exist in aviation, but operators of aircraft and airlines still believe they're too expensive. 06:03.680 --> 06:15.100 As a last point on this issue, if you believe that using satellite communication for your data link will avoid any of these issues with software-defined radios, then think again. 06:15.140 --> 06:27.020 This here is an example of military aircraft using ACARS, which sent out detailed flight information in advance and regular updates about its movements, which can easily be received by any third party. 06:30.050 --> 06:35.070 This is also a good time to transition to a second topic, location privacy. 06:35.590 --> 06:40.130 We know that everybody is being tracked on the ground using your mobile phone. 06:40.130 --> 06:42.590 However, in the air it is a bit different. 06:42.670 --> 06:56.790 With aircraft broadcasting their position to other aircraft and air traffic control to safeguard themselves and the whole airspace, the communication is not supposed to be encrypted and anyone can listen to the same information. 06:56.990 --> 07:02.290 So tracking aircraft globally with ease is absolutely a thing. 07:02.650 --> 07:13.570 Here we can see that even the US president is being tracked, in this case during the campaign of the 2016 election. 07:13.810 --> 07:16.910 So let's take a closer look at this problem. 07:18.090 --> 07:20.530 First, we need to talk about metadata. 07:20.770 --> 07:24.890 Maybe you're familiar with the MAC address of your network phones and laptops. 07:24.970 --> 07:28.210 Well, basically the same thing exists for aircraft. 07:28.610 --> 07:38.570 It is a unique 24-bit identifier which is hard-coded into the transponder of any aircraft and provided by the International Civil Aviation Organization. 07:38.850 --> 07:47.470 This idea is practically never changed unless the aircraft is sold, making it perfect for any sustained tracking purposes. 07:47.490 --> 08:01.670 To make the connection between this identifier and the owner or operator, you can employ all sorts of different databases and websites available publicly on the internet, which is something that we did and you can see here. 08:04.830 --> 08:13.030 So this is a visual representation of all non-European government aircraft visiting Europe over a single year. 08:13.110 --> 08:20.750 You can clearly identify some hotspots, unsurprisingly in London or Paris, but also in Switzerland or Nice. 08:26.230 --> 08:36.290 From this, we were also able to identify dozens of high-profile multilateral meetings with five or more attendees during the considered time period. 08:36.630 --> 08:40.290 From the World Economic Forum to NATO summits. 08:40.570 --> 08:50.490 This is, for example, Davos, I think one or two years ago, and you can clearly see all of the different government aircraft landing at Zurich airport. 08:53.360 --> 09:06.740 One striking example of the impact of these issues for governments is provided by two investigative journalists who have set up a Twitter bot that is connected to a receiver based at Geneva airport. 09:06.960 --> 09:18.920 It tweets out arrivals and departures by a set of aircraft used by authoritarian governments, and it is known that this is tracked by several organizations watching corruption on the world. 09:18.920 --> 09:27.690 And the public awareness has created formal investigations such as this one, where the vice president of Equatorial Guinea had some of their assets seized. 09:30.810 --> 09:37.130 However, the lack of privacy actually extends much beyond governments and also affects corporate activities as well. 09:37.530 --> 09:48.370 We took a look at the activities of different corporations in Europe during a single year by tracking the movements of corporate aircraft and relating them to stock market moving merchant acquisition activities. 09:52.070 --> 10:00.690 And indeed, in six out of the seven cases that we examined, we could find a decent to really, really good signal with landings in the immediate surroundings of the target. 10:00.790 --> 10:11.770 In five cases, these visits came up to 25 days before, and three even within a week, with many of these cases exercising significant share price changes on the day of the announcement. 10:12.170 --> 10:14.610 Let's look at one case for illustration. 10:15.410 --> 10:24.570 Here we can see the flights of a large American medical company to the city of Basel in Switzerland, where the headquarter of the takeover target actually was. 10:24.890 --> 10:31.750 This is a zoomed in version of the same image showing the actual dates and times of the landings at the airport. 10:32.010 --> 10:39.430 Indeed, we can see several flights around the end of January, just before the acquisition was announced, as you can see in this. 10:40.270 --> 10:50.610 We can even go further and look at some later visits to Basel, highlighted here, which came a day before the acquisition was completed. 10:50.790 --> 10:57.270 This illustrates just how much we can learn about the activities of public corporations through watching their flight movements. 10:58.570 --> 11:06.190 By last year, this was also picked up in the mainstream media, as you can see here, for example, in this Bloomberg article. 11:07.510 --> 11:10.930 So, is there anything that can be done about this? 11:10.930 --> 11:16.230 Surely many people are aware of these tracking issues by now and want to prevent them where possible. 11:16.330 --> 11:18.990 Why are we in this situation in the first place anyway? 11:20.130 --> 11:27.590 Well, first I want to spell out clearly why we don't have any proper security and privacy by design in these technologies. 11:28.350 --> 11:43.250 A good case study is the novel ADS-B protocol, which has only been made mandatory in some advanced countries just this year, but was actually conceived in the mid-1990s with a much , much different threat model as discussed before. 11:44.070 --> 11:56.010 Why it takes this long is due to a host of reasons, including strict certification and testing requirements, and a wish for maximum interoperability across the globe. 11:56.650 --> 12:06.290 If we look a bit closer, things get even worse, as ADS-B is built on hard and software standards developed by Lincoln Labs in the 1970s. 12:06.310 --> 12:14.730 Now it should be very obvious that wireless security has moved much faster outside aviation than inside during this time. 12:15.450 --> 12:20.810 But if we cannot have privacy by design, what is being done? 12:21.430 --> 12:30.770 The first and most notable mitigation is to hide sensitive aircraft from public websites through block lists maintained by flight authorities. 12:30.910 --> 12:36.150 The aircraft are either entirely hidden or they are anonymized as shown here. 12:36.330 --> 12:43.510 Of course, this approach is entirely useless from a security researcher's point of view, as the data is still all available. 12:43.510 --> 12:45.710 It is simply not displayed anymore. 12:46.170 --> 12:53.370 So while this certainly qualifies as security theater, it at least shows that some people do care about their privacy. 12:54.890 --> 13:02.870 The second mitigation approach would be to obscure the ownership within all of the publicly available records. 13:03.370 --> 13:16.490 Private aircraft are often registered via shell companies or bank trusts, sometimes the whole network of them, which makes it difficult to get all of the information that you need from the metadata. 13:16.990 --> 13:29.450 However, one single slip of the operational security and the information is out forever, or at least until you buy a new aircraft, which honestly even the richest of the rich do not do every other week. 13:29.950 --> 13:42.290 We can find the data on social media or dozens of dedicated plane spotting websites, which with a really large community of physical spotters is super quick and reliable. 13:42.450 --> 13:51.730 Of course, when your aircraft's delivery contain your company logo, there's certainly the question why you're trying to hide your ownership through a shell company in the first place. 13:51.870 --> 13:57.830 If you see your aircraft land at any given airport, we will immediately know who you are. 13:59.250 --> 14:15.330 A third interesting observation is that some military and government aircraft are clearly aware of the privacy issue of their broadcast and switch them off for takeoff and landings in order to conceal the origin and the destinations. 14:15.570 --> 14:36.970 Unfortunately, this also does not help against any reasonable competent observer, because the aircraft are still required to send out their identity and their altitude, which in the end makes it fairly easy to localize them, for example, using multi-iteration or any really dense sensor network. 14:38.370 --> 14:41.990 That leaves us with one last option. 14:42.330 --> 14:49.090 You could simply not use your own private aircraft, but instead rely on commercial air transport options. 14:49.530 --> 15:05.810 Heads of government have been known to fly coach from time to time, but whatever their motives were, it can certainly not have been for privacy reasons, as we can see in this excellent example of the then British Prime Minister David Cameron eating Pringles on an easy jet. 15:06.410 --> 15:10.090 This was broadcast all over the internet before he had even landed. 15:12.130 --> 15:15.970 Finally, I want to address a real and effective fix. 15:16.170 --> 15:26.970 You could randomize the transponder ID of sensitive aircraft for each flight, which would stop the trivial tracking of the anonymized aircraft at least. 15:27.290 --> 15:31.010 This one is more or less straightforward in theory. 15:31.090 --> 15:37.290 However, the problem again is in the legacy system and the global compatibility. 15:37.690 --> 15:44.370 Oh, and the fact that the flight authority's security knowledge isn't necessarily the greatest. 15:45.290 --> 16:00.590 There was a first deployed attempt of this about 10 years ago, where researchers were still easily able to correlate the random identities with the original identity, making the whole thing absolutely useless. 16:00.630 --> 16:08.750 To top it off, the FAA did recommend against using it at the time because of pretty strong safety considerations. 16:09.450 --> 16:19.910 And I think if your regulator recommends against using a system for safety reasons, that would probably make most people think twice. 16:20.770 --> 16:33.290 However, there might be light at the end of the tunnel because there's a brand new attempt at dealing with aircraft tracking by the FAA, the so-called privacy ICAO address program. 16:33.890 --> 16:41.490 It addresses a few of the issues that we've seen here, but the jury is still out on the effectiveness of this one. 16:41.950 --> 16:47.190 We've actually now done a preliminary analysis, which I'm not going to spoil here. 16:47.350 --> 16:53.150 If you're interested, watch the dedicated talk by Guillaume Michel here in the aerospace village. 16:53.370 --> 16:56.830 So let me finish my talk with two takeaway lessons. 16:57.930 --> 17:03.910 These two lessons are especially for the aviation community and they're direct results on our research. 17:04.050 --> 17:12.370 The first one will not come as news to any longtime DEF CON attendee, but please do not roll your own crypto. 17:12.370 --> 17:19.410 Trying to do that has resulted in spectacular fails across many industries and aviation is certainly no exception. 17:19.610 --> 17:31.290 The best example is the ACARS disaster, which released recent aircraft with weak proprietary ciphers and leaking their sensitive data, even though they're actively trying to avoid it. 17:31.290 --> 17:44.290 Get some help, use known secure standards, and then actually also use these systems, unlike ACARS message security, which has seen virtually no uptake in the wild. 17:45.550 --> 17:56.350 The second lesson is where I really, really hope the aerospace village will help to make some improvements by bringing together security researchers and aviation stakeholders. 17:56.950 --> 18:09.610 But please, if somebody responsibly discusses security issues in your systems with you, do not shoot them down by replying that there's nothing to see, like in this nice example. 18:10.850 --> 18:26.130 After contacting the manufacturer, we only received the reply that the malfunction in crypto was not there to protect anything in the first place and that industry standards or regulations do not require them to build anything better at all. 18:26.810 --> 18:41.170 Indeed, they even went as far as to say that all of their users are security experts and would know that their crypto system does not protect anything, which I have a hard time believing, to be honest. 18:41.290 --> 18:47.090 In particular, when I take a look at the software option saying encrypt downlink as seen in this screenshot. 18:50.000 --> 18:53.060 So, to conclude. 18:53.240 --> 19:02.680 First of all, we can say that modern software-defined radio technologies have certainly changed the threat model for wireless aviation networks fundamentally. 19:04.860 --> 19:15.400 The integration of privacy by design, on the other hand, into legacy aviation systems after this technology step change is super hard. 19:17.080 --> 19:27.580 Combined together, this means that it's trivially possible to track the movements and the communications of many aircraft, both globally and in real time. 19:28.220 --> 19:41.960 And most concerningly, all of the currently available mitigation options are absolutely insufficient and more work is needed to find any real fix in this direction. 19:44.280 --> 19:54.340 If you're really interested in our privacy research, you can also check out all of the references for our talk on this slide, or you can shoot me some questions in Discord later. 19:54.760 --> 19:59.540 Thanks a lot for listening, and I'm really happy to be part of the Aviation Village this weekend.