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5250	10320	Hello, and welcome to my Aerospace Village talk on wireless privacy issues in aviation.
10320	14540	I really, really appreciate the opportunity to share our research in this area,
14540	20220	even under these fairly unusual circumstances. And I also want to take the time to commend the
20220	24660	organization around the village, which is a great initiative that brings together so many
24660	30320	stakeholders in order to tackle security issues in aviation. If you don't know me,
30320	35440	my name is Martin Strohmeyer. I am working at the Cyber Defense Campus of Armistice Science
35440	41600	and Technology in Switzerland. And I'm also a junior research fellow at the University of Oxford.
42700	47900	So, let's dive in. When we speak about wireless privacy, what do we mean?
48020	53820	The heart of the issue is that we cannot normally prevent access to wireless signals that are being
53820	60120	sent. On a wire channel, if we physically control all of the lines and nodes, the number of possible
60120	66620	adversaries is normally limited. In contrast, the wireless channel is inherently broadcast,
66620	72460	as you can see here. It is typically omnidirectional and there are no physical containment
72460	79020	measures possible. So, sending or receiving messages does not require you to physically tap
79020	85720	into the network infrastructure. Based on this inherent broadcast property, I want to concentrate
85720	92760	on two attack primitives today. The first one is eavesdropping. So, a breach of the confidentiality
92760	98960	of the transmitted data. This is a well-established concept, of course, and can fundamentally be
98960	104640	prevented through the use of encryption. Our phones, laptops do this fairly securely
105560	110220	and hassle-free these days, despite the occasional breakdown.
111580	117560	The second one is location privacy. Often, we do not want to prevent the content of the
117560	124420	communication data being exposed, but also the position of the participants. This gains additional
124420	131060	importance in wireless networks. Users are often mobile and we can track their movements over time
131060	137660	simply by estimating where the signals come from. Such tracking has many positive use cases.
137660	143080	For example, if you're in a museum, standing in front of a painting and a system can deliver
143080	150080	matching information to you. However, tracking also facilitates many high-profile privacy breaches.
151580	158380	So, let's apply these concepts to aviation. Here, we have to understand first that the
158380	163440	threat model of aviation has changed drastically over the past decade or so.
164000	169440	First, aviation is moving away from analog technologies, such as voice or radar,
169440	173840	and increasingly using digital communication networks and automation.
174380	181040	The second aspect is just as important, which is the widespread availability of cheap,
181040	187360	hard, and software, as well as knowledge about aviation protocols. These two developments
187360	192400	combined lead to the fact that many more people are capable of affecting wireless
192920	198900	air traffic communication systems than before, and practically anyone can listen to wireless
199600	207220	aviation communications these days. In short, the threat model has moved from a purely nation-state
207220	213220	actor model to a whole range of groups with different capabilities and motivations.
213830	219210	In today's talk, it is actually sufficient to focus on the purely passive eavesdroppers,
219700	225500	as observing the communication is entirely sufficient to exploit many of the privacy
225500	231220	issues in aviation. Now, let's look at some real-world examples of confidentiality and
231220	235920	location privacy issues in different aviation protocols, which were collected from our own
235920	242060	research over the years. First, we will talk about the data link ACARS, which has been deployed for
242060	249900	decades and is still in use by most larger aircraft around the world. Let me just say at
249900	255620	this point that all of these examples now are, of course, anonymized. Still, you can intuitively see
255620	262380	that this is not good. A lot of very critical data is absolutely sent in the clear, and neither Sally
262380	268100	here nor Tom would be happy if they knew that their medical information is being broadcast,
268100	274320	not only to ground staff, but also to anyone listening in the 300-mile radius of the aircraft.
275600	280700	Further privacy issues in this area include information about personal belongings by crew
280700	286940	that you could just go and collect, and, of course, our favorite example that often serves
286940	292780	to drive the point home, full credit card data for higher value transactions in onboard duty-free
292780	299960	shopping. This credit card thing is indeed still ongoing with some airlines in 2020, despite
299960	306960	notifications provided years ago. Some people in the industry have actually acknowledged that
306960	313340	there's an issue with this, and they came up with what you can see here. If you're watching this
313340	318560	recording, you can maybe take an extended look at these messages and figure out quickly what is wrong
318560	326340	here before I spoil it. But for now, let me tell you. As you may have guessed, this type of ACARS
326340	332720	data link encryption is using a monoalphabetic substitution cipher that is broken in minutes.
332820	338960	It is used by a wide range of private, military, and even government aircraft, and again, this has
338960	346720	been going on for more than a decade now. Still, this data link issue, we could say it is fairly
346720	352020	straightforward, and this could still be solved with better crypto solutions that are standardized
352020	359320	and verified. Honestly, some of them even exist in aviation, but operators of aircraft and airlines
359840	367800	still believe they're too expensive. As a last point on this issue, if you believe that using
367800	372560	satellite communication for your data link will avoid any of these issues with software-defined
372560	379260	radios, then think again. This here is an example of military aircraft using ACARS, which sent out
379260	384820	detailed flight information in advance and regular updates about its movements, which can easily be
384820	394010	received by any third party. This is also a good time to transition to a second topic, location
394010	400770	privacy. We know that everybody is being tracked on the ground using your mobile phone. However,
400770	405630	in the air it is a bit different. With aircraft broadcasting their position to other aircraft
405630	410770	and air traffic control to safeguard themselves and the whole airspace, the communication
411790	416790	is not supposed to be encrypted and anyone can listen to the same information.
416990	424190	So tracking aircraft globally with ease is absolutely a thing. Here we can see that even
424190	433570	the US president is being tracked, in this case during the campaign of the 2016 election.
433810	441430	So let's take a closer look at this problem. First, we need to talk about metadata. Maybe you're
441430	446690	familiar with the MAC address of your network phones and laptops. Well, basically the same thing
446690	452930	exists for aircraft. It is a unique 24-bit identifier which is hard-coded into the transponder
452930	460250	of any aircraft and provided by the International Civil Aviation Organization. This idea is
460250	465790	practically never changed unless the aircraft is sold, making it perfect for any sustained
465790	472050	tracking purposes. To make the connection between this identifier and the owner or operator,
472050	477870	you can employ all sorts of different databases and websites available publicly on the internet,
477870	481670	which is something that we did and you can see here.
484830	489990	So this is a visual representation of all non-European government aircraft visiting
489990	495530	Europe over a single year. You can clearly identify some hotspots,
495530	500750	unsurprisingly in London or Paris, but also in Switzerland or Nice.
506230	511410	From this, we were also able to identify dozens of high-profile multilateral meetings
511410	519130	with five or more attendees during the considered time period. From the World Economic Forum to NATO
519130	525810	summits. This is, for example, Davos, I think one or two years ago, and you can clearly see
525810	530490	all of the different government aircraft landing at Zurich airport.
533360	539800	One striking example of the impact of these issues for governments is provided by two
539800	545080	investigative journalists who have set up a Twitter bot that is connected to a receiver based
545080	551460	at Geneva airport. It tweets out arrivals and departures by a set of aircraft used by authoritarian
551460	557920	governments, and it is known that this is tracked by several organizations watching corruption on
557920	563340	the world. And the public awareness has created formal investigations such as this one,
563340	567690	where the vice president of Equatorial Guinea had some of their assets seized.
570810	575650	However, the lack of privacy actually extends much beyond governments and also affects corporate
575650	580770	activities as well. We took a look at the activities of different corporations in Europe
580770	585730	during a single year by tracking the movements of corporate aircraft and relating them to stock
585730	594430	market moving merchant acquisition activities. And indeed, in six out of the seven cases that we
594430	598970	examined, we could find a decent to really, really good signal with landings in the immediate
598970	605310	surroundings of the target. In five cases, these visits came up to 25 days before, and three even
605310	610870	within a week, with many of these cases exercising significant share price changes on the day of the
610870	617650	announcement. Let's look at one case for illustration. Here we can see the flights of a large
617650	622710	American medical company to the city of Basel in Switzerland, where the headquarter of the takeover
622710	629330	target actually was. This is a zoomed in version of the same image showing the actual dates and
629330	635810	times of the landings at the airport. Indeed, we can see several flights around the end of January,
635810	639430	just before the acquisition was announced, as you can see in this.
640270	647330	We can even go further and look at some later visits to Basel, highlighted here,
647330	652570	which came a day before the acquisition was completed. This illustrates just how much we
652570	656310	can learn about the activities of public corporations through watching their flight
656310	663690	movements. By last year, this was also picked up in the mainstream media, as you can see here,
663690	670930	for example, in this Bloomberg article. So, is there anything that can be done about this?
670930	675350	Surely many people are aware of these tracking issues by now and want to prevent them where
675350	681970	possible. Why are we in this situation in the first place anyway? Well, first I want to spell
681970	687590	out clearly why we don't have any proper security and privacy by design in these technologies.
688350	694270	A good case study is the novel ADS-B protocol, which has only been made mandatory in some
694270	700090	advanced countries just this year, but was actually conceived in the mid-1990s with a
700090	706770	much, much different threat model as discussed before. Why it takes this long is due to a host
706770	713030	of reasons, including strict certification and testing requirements, and a wish for maximum
713030	721310	interoperability across the globe. If we look a bit closer, things get even worse, as ADS-B is
721310	727290	built on hard and software standards developed by Lincoln Labs in the 1970s. Now it should be
727290	733830	very obvious that wireless security has moved much faster outside aviation than inside during this
733830	743190	time. But if we cannot have privacy by design, what is being done? The first and most notable
743190	748630	mitigation is to hide sensitive aircraft from public websites through block lists maintained
748630	755190	by flight authorities. The aircraft are either entirely hidden or they are anonymized as shown
755190	761130	here. Of course, this approach is entirely useless from a security researcher's point of view,
761130	767350	as the data is still all available. It is simply not displayed anymore. So while this
767350	773370	certainly qualifies as security theater, it at least shows that some people do care about their privacy.
774890	780870	The second mitigation approach would be to obscure the ownership within all of the publicly
780870	788070	available records. Private aircraft are often registered via shell companies or bank trusts,
788070	792690	sometimes the whole network of them, which makes it difficult to get all of the information
794390	800070	that you need from the metadata. However, one single slip of the operational security
800630	806690	and the information is out forever, or at least until you buy a new aircraft, which honestly even
806690	812050	the richest of the rich do not do every other week. We can find the data on social media
812050	818950	or dozens of dedicated plane spotting websites, which with a really large community of physical
818950	825670	spotters is super quick and reliable. Of course, when your aircraft's delivery contain your company
825670	829970	logo, there's certainly the question why you're trying to hide your ownership through a shell
829970	835850	company in the first place. If you see your aircraft land at any given airport, we will
835850	842990	immediately know who you are. A third interesting observation is that some military and government
842990	850890	aircraft are clearly aware of the privacy issue of their broadcast and switch them off for takeoff
850890	858410	and landings in order to conceal the origin and the destinations. Unfortunately, this also does
858410	864150	not help against any reasonable competent observer, because the aircraft are still required
864150	871210	to send out their identity and their altitude, which in the end makes it fairly easy to localize
871210	876970	them, for example, using multi-iteration or any really dense sensor network.
878370	885530	That leaves us with one last option. You could simply not use your own private aircraft, but
885530	891550	instead rely on commercial air transport options. Heads of government have been known to fly coach
891550	897290	from time to time, but whatever their motives were, it can certainly not have been for privacy reasons,
897290	903410	as we can see in this excellent example of the then British Prime Minister David Cameron
903410	910090	eating Pringles on an easy jet. This was broadcast all over the internet before he had even landed.
912130	919030	Finally, I want to address a real and effective fix. You could randomize the transponder ID of
919030	925390	sensitive aircraft for each flight, which would stop the trivial tracking of the anonymized
925390	932870	aircraft at least. This one is more or less straightforward in theory. However, the problem
932870	939310	again is in the legacy system and the global compatibility. Oh, and the fact that the flight
939310	947190	authority's security knowledge isn't necessarily the greatest. There was a first deployed attempt
947190	954170	of this about 10 years ago, where researchers were still easily able to correlate the random
954170	962470	identities with the original identity, making the whole thing absolutely useless. To top it off,
962470	968750	the FAA did recommend against using it at the time because of pretty strong safety considerations.
969450	977010	And I think if your regulator recommends against using a system for safety reasons,
977010	983570	that would probably make most people think twice. However, there might be light at the end of the
983570	988810	tunnel because there's a brand new attempt at dealing with aircraft tracking by the FAA,
988810	997010	the so-called privacy ICAO address program. It addresses a few of the issues that we've seen
997010	1002810	here, but the jury is still out on the effectiveness of this one. We've actually
1002810	1008690	now done a preliminary analysis, which I'm not going to spoil here. If you're interested,
1008690	1013150	watch the dedicated talk by Guillaume Michel here in the aerospace village.
1013370	1020290	So let me finish my talk with two takeaway lessons. These two lessons are especially for
1020290	1026210	the aviation community and they're direct results on our research. The first one will not come as
1026210	1033290	news to any longtime DEF CON attendee, but please do not roll your own crypto. Trying to do that
1033290	1039410	has resulted in spectacular fails across many industries and aviation is certainly no exception.
1039610	1045150	The best example is the ACARS disaster, which released recent aircraft with weak proprietary
1045150	1051290	ciphers and leaking their sensitive data, even though they're actively trying to avoid it.
1051290	1059170	Get some help, use known secure standards, and then actually also use these systems,
1059170	1064290	unlike ACARS message security, which has seen virtually no uptake in the wild.
1065550	1071390	The second lesson is where I really, really hope the aerospace village will help to make
1071390	1076350	some improvements by bringing together security researchers and aviation stakeholders.
1076950	1083350	But please, if somebody responsibly discusses security issues in your systems with you,
1083350	1089610	do not shoot them down by replying that there's nothing to see, like in this nice example.
1090850	1097210	After contacting the manufacturer, we only received the reply that the malfunction in crypto was not
1097210	1103130	there to protect anything in the first place and that industry standards or regulations do not
1103130	1111030	require them to build anything better at all. Indeed, they even went as far as to say that all
1111030	1117650	of their users are security experts and would know that their crypto system does not protect anything,
1117650	1122650	which I have a hard time believing, to be honest. In particular, when I take a look
1122650	1127090	at the software option saying encrypt downlink as seen in this screenshot.
1130000	1138120	So, to conclude. First of all, we can say that modern software-defined radio technologies have
1138120	1142680	certainly changed the threat model for wireless aviation networks fundamentally.
1144860	1148480	The integration of privacy by design, on the other hand,
1148480	1155400	into legacy aviation systems after this technology step change is super hard.
1157080	1162120	Combined together, this means that it's trivially possible to track the movements
1162120	1167580	and the communications of many aircraft, both globally and in real time.
1168220	1172960	And most concerningly, all of the currently available mitigation options
1173780	1181960	are absolutely insufficient and more work is needed to find any real fix in this direction.
1184280	1188380	If you're really interested in our privacy research, you can also check out all of the
1188380	1194340	references for our talk on this slide, or you can shoot me some questions in Discord later.
1194760	1199540	Thanks a lot for listening, and I'm really happy to be part of the Aviation Village this weekend.