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[Music]
thank you so much it's really great to
be here after uh uh after one and a half
years of responsible disclosure uh we're
finally able to talk about this this
research we did so we are um we are
midnight
blue this this starts off really well we
are midnight blue and V Bo these are
Carlo Mayer and Jose vetel and together
we form midnight blue uh a security
consulty company based in the
Netherlands um we mainly specialized in
abended system security and critical
infrastructure Communications and stuff
like that you may have heard of us uh
before we investigated vehicle
immobilizer systems broke a few of them
uh found issues in the BlackBerry Q andx
operating system broke a hardened
variant of the myair RFID dchip and uh
and more stuff and obviously this this
Tetra research so some of you may
already have seen our research uh at for
instance CCC camp or maybe the the
deathcon or blackhead talks so today we
will be presenting uh some new material
some old old stuff as well because I
don't think everyone is familiar with it
uh but Neil will be uh some details on
the deanonymization attack that would
allow you to uh more accurately uh
pinpoint who is using Tetra network
works and at what what time uh we're
going to talk about how uh cryptographic
backdoor has uh spread throughout Europe
and the implications that this has in
some very sensitive use cases we have
had multiple reports of vendors
misinforming their own customers so we
will dig into that a little bit and we
will discuss some new developments
regarding Tetra as a
technology so so uh what is Tetra Tetra
is a globally used radio technology uh
there's there's more of them there is
for instance p25 and DMR and and Tetra
pole uh but Tetra is a very very large
one it has been standardized in 1995 by
the Etsy uh organization which also was
involved in standardizing GSM 3G 4G gmr
deck that kind of stuff and it's used
for voice Communications like portable
radios and stuff like that but it's also
used in a data carrying capacity
including like machine to machine
communication IP or serial traffic uh
and what's interesting about Tetra is
that it relies on secret proprietary
cryptography so it's very hard to assess
the actual strength of it and it's being
used globally so its primary use case
was used by police forces uh the vast
majority of police forces around the
world use Tetra with a not POS exception
of the US and France who have tetrao
because French um you may be familiar
with your own national network in the
Netherlands that would be c2000 here
it's
bosset um and there's many many more
places where this is being used by
police uh but there's also use by
military and intelligence Services now
note that these Maps the the countries
that we've highlighted here are places
where we have been able to confirm that
this being used in some some capacity by
use group um there's bound to be much
more out there for which we could not
find the any public documentation or
Tender uh but at the very least these
countries are using this
technology and maybe even more
importantly critical infrastructure is
also using it um parties like airports
Harbors train station energy
distribution networks they use Tetra for
voice communication like Engineers that
need to communicate on site or
surveillance uh Personnel that that
wants to be able to talk uh with these
these portable
handhelds um but it's also used in a in
a data carrying capacity as I mentioned
before so you must imagine that for
instance for energy distribution you can
use Tetra to carry this scada
telecontrol data and remotely operate
your
sites um and that's a that's kind kind
of a sensitive use case and more on that
later
so a common misconception is that Tetra
is a is an open standard it's not really
an open standard it's a public standard
um large parts of it are indeed U
publicly available so you can dig
through these thousands of pages of
documentation explaining many many
aspects of the Tetra radio technology
but when it gets uh to cryptography and
security you will typically see stuff
like this you will see some some some
charts and you will see some boxes with
labels and these labels correspond to A
cryptographic Primitive a secret
cryptographic primitive and if you would
want to know how such a primitive works
you would need them to get those from
Etsy under a non-disclosure agreement
and Etsy determines whether you are
eligible to receive those they only
provide these uh specifications to Bona
parties whatever that is in their
eyes also as a manufacturer if you
obtain the specifications you are bound
by the terms of the NDA to protect these
algorithms against extraction from your
Hardware so either you could implement
the Tetra cryptography in Silicon which
makes it well quite hard to to reverse
engineer this using electron mic
microscopes and stuff or if you would
want to consider a software
implementation you need to add counter
measures that protect the secret
algorithms from
extraction now a problem is that by now
there is a lot of bonafide vendors um
almost any geopolitical block of any
influence has its own vendor on its own
soil there is vendors in the United
States uh in the UK in France in U
Russia in China so in these countries
there are manufacturers that possess
these specifications and if for instance
an nation state would like to
investigate the security of this they
can just demand their local manufacturer
to hand over the the specifications and
they would not have to jump through all
the Hoops that we had to jump through um
also an attacker could probably just
choose a small one from this list hack a
SharePoint get the specifications of
there but in all these cases you would
not be able to have a public discussion
on the security of
tetra now Tetra security is based on two
parts there is the taa1 suite which
implements authentication and key
distribution as well as identity
encryption and then there is a multiple
algorithms for actual encryption so
error interface encryption which is the
tea Suite you have ta1 which is readily
exportable and free for uh for any use
case there's ta2 which is intended for
emergency services within Europe then
there is ta3 which is also for emergency
services but for countries outside of
the EU with which the EU has good
relationships so our allies so to speak
uh and then there is ta4 which has a
similar uh designation as ta1 but isn't
actually used in
practice um
so optionally you could augment the
security of your Tetra Network by adding
endtoend
encryption this is not actually part of
the Tetra standard but they do provide
some guidelines and some ways of
integrating endtoend encryption into a
Tetra network but the actual
implementation is left to the
manufacturers so in practice this has um
caused that these Solutions are
exceedingly expensive uh quite hellish
with regards to Key Management and once
again very very
opaque so uh with that in mind let's uh
let's talk about the retra project we
undertook so I assume that most of you
will be familiar with kof's principle
but I'll I'll explain it to you briefly
uh the kirkov principle states that the
crypto system should be secure if
everything about the system except for
the key would be public knowledge and
why do we want to adhere to this
principle well because violators don't
farewell in the past we have seen
numerous examples of proprietary secret
cryptography that have been broken or
even turned out to be backdoored as soon
as the secrecy was no longer there and
the specifications became public so to
mind comes the the old GSM ciphers uh
the gmr and ga uh ciphers the
counterparts but also your decked phones
which use encryption which turned out to
be quite weak once we figured out how it
actually
worked now Etsy seems to have a
different opinion on this matter uh in
an interview with Kim zeter the Tetra
chairman of the technical committee
stated that to them obscurity is also a
way of maintaining security and we will
figure out whether that is actually the
case
here so our project motivation uh has
probably become clear now we disagree
with these statements we want to open up
Tetra make it available to anyone to be
able to assess the actual security of uh
of this technology
we approached the Nelnet Foundation
which often provides funding for this
kind of research in open Technologies
and uh with that with that funding we
were able to pursue this research uh
Carlo will tell us more about that all
right thank you very much
[Applause]
wter so uh we needed a way to extract
the algorithms from a radio because
obviously we didn't want to sign an NDA
uh so in order to do that we first had
to explore the landscape of available
radios um and in the end we stumbled
upon this MTM 5400 from Motorola and we
basically just bought it off eBay
secondhand uh then we analyzed the
firmware uh we identified where the
algorithms could be within the firmware
obviously in a nonclear form uh and then
we developed a bunch of reverse
engineering tools um we had to find
multiple zero days in this radio in
order to extract the algorithms from
them then we analyze them and then we
validate uh then we we looked into them
validate their security and see if
there's weaknesses and then uh see if we
could make proof of concepts for those
so that would be the end goal right so
um how do we get to the algorithms given
that we have this radio so um this is a
simplified form on a diagram like this
whole thing is pretty much a talk on its
own I'd love to tell you about it but we
only have 50 minutes here so I'd like to
refer you to the CCC camp talk earlier
this year um so the thing is the MTM
5400 it has a baseband chip uh from
Texas Instruments it's the tiap l138 it
has a arm core and a DSP
core um obviously the arm core does high
level uh application stuff and the DSP
cord well Digital Signal processor it
processes
signals um and within the DSP there's a
trust's execution environment so what we
did is first we found a vulnerability in
the arm core like in the software that
runs on the arm core uh so you can talk
to this thing through the peripheral
connector and we found a format string
vulnerability there which we exploited
which got us code execution on the arm
core then we pivoted to the DSP through
uh shared memory misconfiguration and
then we finally we extracted uh a secret
key from The Trusted execution
environment which allowed us to decrypt
uh the secret algorithms and we got that
key through cach timing sent analysis so
again um hopefully this sounds appealing
and you'll watch the talk okay so given
that we have those algorithms uh let's
have a look at them and see what we
found so uh first we'll talk a little
bit about the
authentication uh the taa1 suite is used
for again authentication and uh overd a
re keing um so again the standard
specifies some diagrams but not the
actual Primitives uh so we recovered all
of them and we figured that all of the
Primitive prefix with ta um have
something to do with encryption and TB
are just simple transformation or like
expansion and uh compression
functions um right okay so during the
authentication uh what happens is that
you have a long-term shared secret
between the the infrastructure and the
radio uh it's called key K and they both
do a a handshake they combine it with a
random seat RS um and that results in KS
uh the infrastructure then authenticates
the radio to the uh to the
infrastructure and then uh the radio
authenticates the uh the uh the
infrastructure authenticates the radio
and the radio authenticates the
infrastructure uh by taking these KS
values and combining them with random
numbers Rand one and Rand two and and in
the end uh shared secret key dck it's a
session key uh is
produced now um this in itself doesn't
look awfully insecure but when you uh
dive deeper you figure out that one some
of these boxes are actually the same or
very related so for example uh ta uh uh
21 is just ta 11 with the random seat in
Reverse bite order and ta22 is just ta12
it's just the exact same thing and um
tb4 turns out to be an
xor okay uh now assume that we
impersonate the infrastructure towards a
radio and then we send a seed RS which
is justes like whenever you reverse it
in order it will be the same so a
palindrome let's say and and um if we
then can predict the challenge sent out
by the radio uh which is in our case for
the MTM 5400 that was actually the case
because it has a weak random number
generator which is quite typical in
embedded devices uh then we would find
that if we then just use the predicted
random number in the infrastructure uh
as as an infrastructure random it turns
out that uh you get you end up with an X
or between two identical Parts which
results in the key that's all zero uh so
this will give you a partial man in the
middle attack so you get uh you can
intercept all the Uplink traffic from a
radio OB obviously you cannot just send
it onto the actual infrastructure
because that has a different key uh but
you do get some nice uh position you can
access post authentication uh attack
surface if you will so um somewhat uh
nice okay so there's also identity
encryption so um Tetra do doesn't have
strong anonymity but it has a
pseudonymity scheme uh so every
subscriber identity is uh 24-bit number
and that is obfuscated with a key and it
turns out that due to some um that is
actually easily breakable and then you
can actually recover the the the the
plain text identity and due to some
serious stakeholder concerns uh that
that primitive that we decided to we we
decided to hold back that primitive back
in the day uh which we are going to make
public today so you'll find the code on
GitHub if you if you're
interested so the way the anonymization
scheme works is you get an intermediate
secret C which is based off of a key
using the hurdle block Cipher and the
hurdle block Cipher is used in such a
fashion that it's it's sort of resembles
a hash
function um so the details again can be
found on
GitHub um and the so you get you get a
custom transformation scheme like sort
of in between cryptography and uh um
cpto um so you get uh on the right side
you get this key um you it it gets X or
into the the the pl Tex identity then
there's a transformation function which
also public since as of today it applies
a transformation then more bits are exor
in and another transformation and then
you end up with a encrypted
identity now it turns out that this um
this scheme is actually vulnerable to a
med and midle attack um so you need like
some modest amount of computing power
and then you can actually uh recover the
secret C which doesn't give you the
actual network key but it does give you
the ability to De anonymize all the all
the traffic immediately so what does it
give
you um so uh picture the following
scenario um you get there's there's uh
subscriber identities those are
encrypted you manage to decrypt them
then you get you find out that like
there's certain ranges right it's like
like between Z and 10 there's police
forces between 11 and 20 it's covert
operation uh 21 till 30 that's fire
brigade you name it like you you can
easily spot those patterns and this will
give you an interesting counter
surveillance
capability this can be done very
conveniently uh with a Raspberry Pi and
some rtlsdr so very cheap you just
scatter them around uh and it's also uh
a passive attack so nobody will notice
so let's uh let's have a little
demo in order to protect against traffic
pattern analysis Tetra provides an
identity encryption scheme which
transforms plain text subscriber
identities into pseudonymous
versions however as part of our Research
into Tetra security we uncovered that
t61 the Primitive responsible for
identity encryption suffers from an
easily exploitable weakness allowing
attackers to instantly de anonymize
Tetra
traffic the attacker needs to identify
three pairs of identities with their
encrypted equivalents these can be
obtained by observing unencrypted
authentications in which both a user's
encrypted and unencrypted identity are
used this can be done fully
passively by analyzing which key fits
the observed identity pass the attacker
May recover an identity encryption key
in about 2 minutes on a 5-year-old
laptop using this key an attacker can
now instantly decrypt identities and use
them for subsequent analysis for example
an attacker could use this to correlate
subscriber identity ranges to specific
user groups such as undercover police or
special intervention units and build a
powerful Counter Intelligence and early
warning
capability while while this issue cannot
be resolved by a firmware upgrade it is
addressed in the new non-b backwards
compatible Tetra algorithm set
B all
right all right so let's let's cut to
the chase let's talk about the actual
air interface encryption the turro users
uh we found a protocol level issue that
applies to all the encryption algorithm
regardless uh of of strength um so on
the slide you can see signaling
message uh the contents are encrypted
but uh the Mac header at the left that's
actually unencrypted and it and it
contains like basic stuff like the
length of the message and the who the
message is intended for and um what's
like from starting from the LLC header
it's going to be encrypted so what's
important to realize here that Tetra
messages have no cryptographic in
Integrity or authentication checks uh
there's a checkm but that only goes over
the cipher text so it's not really
relevant here for an
attacker so um the way key stream
generator uh works is that um it needs
fresh information for every frame right
because uh otherwise it will generate
the same keyst stream every single time
so that's uh being uh facilitated by
frame numbers or let's say Network time
uh so those frame numbers are unique for
every message you send so therefore uh
unique keyst streams generated for every
message which is then exord with the
actual message right uh so the problem
is like suppose that you're a radio and
you want to subscribe you want to
register to the network which uh which
network time will you be using well it
gets told to you by uh the
network so um how does that work well
the network actually tells you in an
unauthenticated and unencrypted fashion
so as an attacka you can use that to
force the use of a certain keyst
stream so imagine that an attacker
overpowers a signal um can be done many
ways like just put more transid power in
or just be closer to your victim or just
use a directional antenna or a
combination of those um and so if you
then decide to tell the radio like hey
this is the network time it will just
start using that Network time uh and
that that means that the key will be
generated that corresponds to that
Network time in
past um so this isn't uh this this this
works regardless of the tea Cipher
you're using and it's also not prevented
by Network authentication that we
discussed
earlier so the way you attack Works uh
is like you get a message you passively
capture a message and turns out that
you're interested in what that message
contained so the plain text of that
message so that the time that you
capture this message let's say that's
called time
T um then later on you just go back to
that same location where you caught it
or a different one it doesn't really
matter you can go anywhere as long as
the radio that you're targeting shares
key material with the one that sent out
the message okay so now now then at some
point you tell this victim radio like
hey this the time is now the time that
it was in the past at time T and that
radio will start generating keystream
for that time and then you do a little
dance with that radio and it will
gradually tell you what the key stream
is um so I go into that more deeply
now so in order to recover the keystream
assume that we already have n Bits of
keystream and we want to extend that
knowledge uh so we construct a message
that is exactly of length n + one bits
and we make sure that it has a checkm in
there and it we make sure that the
message has to be acknowledged whenever
it's received in good order um so what
do we encrypt that additional key stream
bit with well we just pick zero say Okay
um now if we if we encrypt that and we
send it off to our victim radio the
radio will probably will see what
happens but if the zero bit was uh
guessed correctly it will acknowledge
the message if our guess was wrong and
it was actually a one it will just silly
drop the message in our the case we
learn what the value of this key stream
bit is and we could just repeat this
over and over and over again and then we
get the entire key stream okay so how do
we get like this first couple of bits of
keystream well it turns out that you can
just brute force a four bit message uh
so you just try all 16 of them and turns
out that just one of them will be
acknowledged and then you know what the
keyst stream for that for those four
bits will be well in the end we need 40
bits of keystream so four won't do so
how do we get from four to
40 uh well we turns out that we can
leverage Mac layer uh fragmentation for
that so we can just like use 10 slots uh
of four bits of keyst stream in a row
and we can just use fragmentation and
then uh layer our messes on top of that
and then have the radio Stitch back all
those pieces together and if the check s
turns out to be correct then it will
just happily acknowledged that it
received the message in good order so
that means you could just pick any of
those slots and then extend the keyst
stream for that and therefore we have
our magic key stream recovery
capability okay so that's the attack in
full so when we presented this to Etsy
they also had something to
say um they well they found it a nice
theoretical find uh but not practical at
all like how are you going to overpower
signal blah blah blah um so like okay we
uh we gave them a friendly gesture and
asked them like hey could you just hand
us a base station so we could just like
figure this out for you and they said ha
well no
LOL so um yeah so so we also were in uh
in contact by by those days uh with with
several stakeholders and they pretty
much uh set the same me they gave us the
same message uh and we really wanted to
verify this so H how do you go about
this well obviously uh we didn't want to
spend time developing a full Tetra stack
on our own because like as things
currently stand we kind of like our life
so um so yeah well we just went ahead
and bought one off eBay
so
so this so this is a Motorola base
station from
2004 uh yeah it's really old it's uh
it's very bulky it's 75 kilos it's in my
house and um well well at first it
didn't want really want to cooperate but
then again it doesn't really check
firmare signatur so like it's very easy
to persuade uh we found some
vulnerabilities in there and we built
our attack platform on top of this so uh
theis recovery attack looks kind of like
this hi we are M Night blue we have
uncovered several serious
vulnerabilities in the Tetra radio
standard. Tetra burst we will first
demonstrate a decryption Oracle attack
to recover a text message but the attack
can also be applied to voice
communication and data the demonstration
takes place on our lab
setup the radio receives an encrypted
message which is also captured by the
attacker we see the message says
secret the attacker now needs to Target
a radio and impersonate the
infrastructure and carry out the attack
to decrypt the previously captured
message we have sped up this
process
the attacker has now recovered all he
needs to decrypt the message this attack
applies to all tatra configurations but
can be resolved with a firmware update
further details will be disclosed on
August
[Music]
9th all right uh on to the next issue uh
we'll dive into the keym generators a
bit so they all have a very similar
structure consisting of several linear
feedback shift registers uh some nonl
linear function uh and some sboxes and
this picture is a diagram of tea2 like
the the European police one um and it
seems pretty robust we weren't able to
really pinpoint any like graph uh issue
with it but then again I have to admit
that I'm not a real uh a hardcore
cryptographer
um well when it gets really serious is
with
da1 uh when we took a look at that well
basically the first thing it does is uh
it will grab that 80 bit key and just
push it through a function which output
outputs a 32-bit key and then based does
everything based on that um so yeah
that's pretty that's pretty awful we
could now like just brot force that
32bit key that takes about a minute on
the laptop and uh then you can just
basically intercept and and uh traffic
and inject uh some whatever you like uh
this ta1 as you as I as should probably
remind you that's used in critical
infrastructure and not just outside of
Europe but within Europe as well because
critical infrastructure isn't uh public
it's it's private usually uh and it's
also not police so like as a critical
infrastructure asset owner you typically
uh have the choice between no crypto no
cryptography or ta1 which turns out to
be like sort of equivalent to no
cryptography all right
um so uh what was etsy's response to
this so like within the in the interview
that wter also referred to with Etsy te
technical committee chairman uh they
they claimed that our proof of concept
attack is used on a very high-powered
graphics card uh which which is a
stretch because like it was consumer
Hardware in 2016
uh like I have to to be fair it's
probably very uh very powerful 25 years
ago when these things were uh were
invented um and then he goes on to claim
that 32 bits have would might may or may
not have been sufficient back in those
days so how about we just put this
discussion to rest let's not assume uh
let's not use reasonable equipment let's
see what this boy can
[Music]
do
hi we night blue about 2 weeks ago we
announced the Tetra burst
vulnerabilities consisting of five
vulnerabilities in the Tetra radio
standard two of which are deemed
critical since then Etsy the
standardization body responsible for
Tetra has made public statements in
which they downplay the seriousness of
the
vulnerabilities in these statements they
resorted to a semantic discussion not
calling a spade a spade or more
specifically not calling a backd door a
backd door furthermore they made a
number of of evidently false statements
such as claiming packet injection and
ta1 encrypted networks would be
impossible and that 32 bits of
cryptographic strength would have been
sufficient in the late '90s to any
information security expert it's pretty
clear that this is not the case but to
help remove those few remaining doubts
we decided to take on the challenge of
cracking tea1 on this beautiful machine
produced in 1998 running good old
Windows
95
go frankly the hardware is so old that
it wasn't easy to get our hands
on when we run the cracking tool we see
it reports that it needs about 13 hours
to go through the entire search
space after 12 and 1/2 hours the key is
found demonstrating the feasibility of
cracking ta1 on '90s consumer
hardw all right Etsy now that we've
cleared up this issue please let us know
if you'd like us to demonstrate Becket
injection as
well
hello hi we are my
[Music]
blue all right thanks for that so um
surely this is a terrible back door but
it shouldn't be a problem for Europe
right it should only be a problem for
all those big bad countries outside of
Europe surely nobody would design a back
door and then end up shooting themselves
in the foot um in the interview with
with Brian mergatroid the chairman of
the Etsy technical committee on Tetra he
said well I would expect that anybody
who would need a lot of protection would
not just be using ta1 within Europe I
would suggest that anyone who needed
high security would be using ta to so
luckily crisis averted no real problem
here
right except it's
[ __ ] so we went through several rfps
and tenders and public documents
and found that there are multiple
countries in Europe that are part of the
European Union where police and military
units are actually using ta1 so the
first example that you can see on the
slide is from Poland which has been a
European Union member since 2004 where
the Municipal Police were sold tea1
radios as shortly recently as 2019 or
2020 and this is in cities like warau
and kraco and Lutz um and they're using
ta1 there
a second example is Bulgaria they're a u
Au member since 2007 and there the
ministry of Defense has been procuring
ta1 radios as recently as 2020 for
various
systems a third example is Slovenia also
a EU member since 2004 and they've
recently already had a bit of a Tetra
Scandal where an independent researchers
showed that actually they weren't
encrypting anything at all um contrary
to what they thought H he went to the
media with this um got jail time for it
um and then shortly after that Scandal
they started procuring police
helicopters announcing that they were
Now using ta1 which is also no
encryption
so fourth example is Montenegro they're
a candidate EU member since 2010 um
they've really been struggling with
International organized crime and drug
cartels especially in the city of bar um
and there the police has been procuring
ta 1 radios as recently as 2018 and and
given the use and lifetime of these
radios you know all of this stuff is
still in use and 32 bits of cryptography
isn't just terrible for State actors
it's terrible for organized crime as
well the fifth example just to you know
continue the trend um is mdova mdova is
a candidate EU member since 2022 for
obvious reasons um they're
geopolitically very sensitive currently
because of tensions with Russia and
there the mova police and Carabiner have
been procuring ti1 radios between 2017
and 2020 including with United Nations
Aid so this really goes to show that
geopolitical relations might change over
time um but technology Stacks don't
really so you might think these people
need to have ta1 they need to have a
back door and then your relationship to
these countries changes and now you end
up shooting yourself in the foot which
also happened outside of Europe with
United States local local allies we
found various uh procurement documents
describing that local allies of the
United States were handed ta1 radios and
not ta3 radios such as the entire Iraqi
police Network um the entire Lebanese
police Network um the combined Joint
Task Force in the Horn of Africa which
is in Somalia with the United States
Department of Defense um and the United
Nations in Afghanistan when they still
were there they were all using ta1
equipment 32 bits of cryptography there
but on top of that and far worse in my
opinion is the use of ta1 in critical
infrastructure like Carlo already
mentioned um there's two options if
you're critical infrastructure either
you use plain text Communications or you
use
da1 um and to understand the impact of
this you need to have a little bit of
background about Tetra usage in critical
infrastructure so there's multiple ways
to do networking you can have radio to
radio communications um you can have a
Gateway where all the radios communicate
with a Gateway and on top of that you
have two main modes of communication
there's the short data service which is
a little bit like SMS but for Tetra and
then there's packet data where you have
an IP subnet that gets extended over a
Tetra Network and then on top of these
communication modes you have a data
carrier um and that can be serial
communication serial over IP or pure IP
networks over these Tetra Communications
and in critical infrastructure they
carry The Usual Suspects the IC 101 104
dmp3 modbus protocols which as you may
or may not know are all insecure by
Design so these these protocols have no
security features of themselves and rely
on the layers below that now an example
of that is transportation so the slide
you can see here is based on real world
systems the documentation of which we
found online um and there's many cases
of Transportation um in in the United
States United Kingdom Here in Germany
Spain Greece South America Eastern
Europe where buses and Light Rail are
communicating over Tetra and that can be
as simple as the security Personnel on a
train but it can also be the control of
the breaking of the doors of the
passenger information system of the
Railside safety signaling and all of
this might go over Tetra now the first
scenario where that could go horribly
wrong is an instance of Passenger
deception so at the top of the slide you
can see um anonymized slides that we
found online from a real world Tetra
system where they are controlling the
passenger information systems that you
see inside the trains um as well as on
the the uh stations through SDS messages
over Tetra as well as audio um if you
are able to inject traffic into a Tetra
Network as you will be able to do once
you crack a ta1 key you can send fake
messages and that way you could for
example call a bomb alert you could
disrupt the the passenger information
systems and something very similar
happened a few years ago in Iran where
the passenger information systems were
hacked um they put fake delays on there
and they said well if you have trouble
with the train call this phone number
and it turned out to be a private phone
number of the iatola um this caused this
caused some serious delays for a for a
very long time so just because you're
not immediately attacking the railway
signaling systems themselves just this
kind of disruption can already have a
serious impact
a second scenario would be dispatcher
deception so one of the things that you
can do in transportation systems that
are managed of aetra is you can have the
GPS coordinates of a bus or a trm or you
know anything like that uh transmitted
over an SDS message and have the
dispatcher that sits in in a command
center tell a certain vehicle where it
needs to go now obviously if you can
fake these messages you can tell the
dispatcher that vehicles are where they
aren't or you can tell the vehicles to
go where they shouldn't be going and
something similar happened at the start
of the invasion in in Ukraine where
Yandex tuxi was hacked and hundreds of
taxis were sent to the same place in
Moscow causing a grit lock that takes a
long time to resolve so a scenario like
this could potentially be possible too
thirdly and and wor more worryingly um
as you can see on the slides some
Transportation Systems over Tetra allow
for remote control of the trains
switching a train on or off doing
emergency braking disabling the service
Brak uh messing with the fire detection
and if you're able to trigger an
emergency breake on a train this might
not immediately lead to a safety impact
that depends on on how these systems are
engineered but it will certainly cause
disruption especially when you're doing
this at scale and something similar
happened this year in Poland uh where a
other analog radio system um they
injected a message that caused emergency
braking and several trains were halted
in 2008 a Polish team did a replay
attack on an emergency breaking message
uh on a tram and that caused derailment
so the potential impact of this stuff is
very serious and to leave that up to 32
bits of encryption is absolutely
mind-blowing so uh finally there is a
little bit to be told about ta3 that's
the third algorithm and a very
interesting case because it's not the
one that is meant for you know the
countries where they have bad
relationships with it's also not meant
for Europe it's meant for allies outside
of Europe
and we found an interesting thing there
that the sbox a crucial cryptographic
component had a duplicate entry and I
won't go into the details of what that
means but this is certainly something
that you don't do if you want to
strengthen an algorithm um it's also
unlikely to be accidental because all
the vendors will need to have the same
implementation for interoperability
reasons and they made some changes to
the cipher that that really put it apart
from taa1 uh and ta2 now the impact of
this is currently unclear to us we we'd
like more public scrutiny of this but if
there turns out to be an additional back
door here that is um very interesting
indeed all right so a little bit about
the coordinated vulnerability
disclosure so as you can see this is a
very long timeline we started working on
this project in uh January of 2021 uh
within four months we had the algorithms
then we spent essentially the rest of
the year perfecting the uh the attacks
writing the reports and in the member of
2021 we first contacted the Dutch
national cyber security Center in uh
January of 2022 we had our um meetings
with the Dutch police with Etsy with uh
intelligence Community to to put this
information outside um and then we had
our advisories throughout 2022 and 2023
um and get everybody informed because
these systems are very hard to patch
very hard to mitigate very hard to work
around so we wanted to give enough
parties ample time to prepare before um
making this public so when it comes to
mitigations um there's different
mitigations possible for for the various
attacks when it comes to the keystream
recovery attack vendors have made
firmware updates available for this a
little bit more about that later for the
ta1 back door um you will most likely
need to either migrate to a new tea
Cipher um if you are able to do that or
you will need to put end to end
encryption on top of that or if you're
in critical infrastructure you will need
to start thinking about Security on the
layers that are put on top of tetra when
it comes to the deanonymization attack
well you can't really do anything you
need to take operational security
measures and you need to wait until the
new Tetra algorithms are available from
a vendor and finally when it comes to
the dck pinning attack uh firmware
updates are available for that as well
depending on your vendor now little bit
of information about misinformation so
we wanted to insert this because
since our disclosures we've had a lot of
contact with a lot of different vendors
a lot of different uh users a lot of
different system integrators and we've
consistently heard vendors and standards
organizations spread
misinformation first of all when it
comes to the official statement by Etsy
and the tcca which is the um the
industry organization of tetra in their
official statement in July of 2023 they
first said well ta1 is not a backdoor
it's you know it's a um a Sur
repetitious weakening semantics nonsense
but then they also didn't make a mention
of any of the other vulnerabilities the
only thing they said about the keystream
recovery attack the deanonymization the
dck pinning is the research uncovered
some general areas for improvement in
the Tetra protocol well you can say that
again um as of December this uh this
year continued statements are being made
by these organizations to the industry
claiming that only the te A1 issue is
relevant and that's simply not the case
so if if you are someone who works with
Tetra if you know someone who works with
Tetra um please push back on
this they also very irresponsibly in my
eyes continue to recommend Tetra as a
highly secure wireless link for scada as
of this year one and a half years after
we disclose these issues to them for
example they say well many train real
Metro and TR transport operators use
Tetra for control and function ity for
their public transport operations the
high security and encryption support of
tetra enables these safety critical
applications and they go on to say that
the same holds for oil and gas pipelines
and whatever so they're trying to stand
up new systems with these
Technologies now when it comes to the
vendors and the system integrators well
the vast majority of responses have been
crickets they have made no public
statement some don't even inform their
customers others just Echo what Etsy
says which makes sense because the
vendor there are Etsy and the other way
around um they just say well it's all
hypothetical there are lab conditions
there's no evidence of real world
attacks and this makes our and ncsc job
a lot more tiresome so please stop doing
this interestingly they also do risk
assessments for their customers they say
well wholly selflessly they say well
we'll do a risk assessment free of
charge which is like grading your own
exm right it's the butcher judging his
own meat um for supposedly hypothetical
vulnerabilities so you already know what
kind of conclusions they're going to
draw and this wouldn't be so terrible if
they didn't fundamentally misunderstand
things for example we saw vendor saying
that the keystream recovery attack is a
man in the middle which means you
haven't understood it um and then they
end end up giving bad advice on top of
that so we've heard of multiple vendors
trying to sell the backdoor ta1
algorithm to multiple European critical
infra parties as late as May of this
year year telling them it was either
fine there was nothing wrong with it or
that it would be patched which is
impossible um also multiple vendors told
critical infrastructure in Europe that
Network authentication would protect
them against message injection which is
nonsense because there's no
cryptographic signing at a message level
for Tetra so this is plain false
information and at least in one case we
saw a vendor deliver a patch that did
absolutely nothing so I'm not saying
it's a bad patch it didn't do anything
anything so these are the people giving
the advice and doing the risk assessment
so please take this with a grain of salt
and maybe get a second opinion and
independent
advice so little bit about the aftermath
of this stuff maybe maybe I'm all
exagerating maybe this is a big nothing
Burger um as Etsy said well our official
position is that at this time we are not
aware of any exploitations on
operational networks which you know two
out of five attacks are passive so how
are you going to notice
but we also did some digging in the
Snowden documents and we found that in
2007 there was a joint NSA in Australian
signals director at operation to collect
the communications of the Indonesian
police during the United Nations climate
change conference in Bali and there they
mentioned that they got the
demonstration routes they got the Bali
chief of police's mobile phone number
and they were collecting this kind of
traffic now I'm not saying that they
exploited our vulnerabilities we don't
have those technical details um but this
proof of active Tetra targeting by state
sponsored
actors we also found in the Snowden
documents that the United Kingdom's gchq
undertook an effects operation called
operation Kito against Argentina around
the fauland islands um because of
conflicts around oil exploration rights
in 2009 there they were collecting Tetra
Communications of military and
Leadership again showing that Tetra is
being actively targeted so with that
what's next I'll let vder handle that
part
[Applause]
thanks all
right so uh some time ago already Etsy
has released a new version of the
standard uh with an algorithm set B and
uh that includes new encryption
algorithms for the air interface and new
authentication Suite with new uh New
Primitives also new identity encryption
and they were initially going to be
secret egg again so they we're going to
make the same mistake all over again but
following our uh our research they have
discussed among themselves and with the
manufacturers and they have now decided
to make both the Old and the new uh
algorithms public for public uh scrutiny
so that's a big win for open
Technologies thank
you because transparency is at the root
of etsy so yay with a with a small star
because just disclosing cryptographic
Primitives is not really enough like we
talked about tea3 there is some weird
stuff going on we would like to have
full disclosure on design process no
unexplained cont uh uh constants we want
to understand why they devis the
algorithms in that way and then we can
um gain some understanding and some
confidence in the strength of these
ciphers now um also a statement that was
made and it was less widely covered is
that um the tea7 algorithm they admitted
has an effective key length of 56 bits
so it has another reduction function
which reduces the the key length to 56
bits uh as per the wasr
arrangement and well let's let's put
that into perspective a little bit um
let's make some assumptions let's say
that the new keystream generators are
about as fast in generating keystream as
the old ones
um and let's take our fastest
implementation uh of a cracker on ta1 as
a baseline so in that case uh a single
really fat Amazon machine would take 170
days of crunching through all the
possible keys to to find the tea7 key
that corresponds to a
network and if you are using spot
pricing so that's a discounting pricing
model using underutilized servers you
can uh look up uh online which region at
that point has the lowest pricing for a
specific device type uh then we estimate
that this could cost as as little as
5,000 and you could of course speed this
up by getting more machines you could
grab a couple of dozen maybe and we
think it's reasonable to to think that
you could mount an a AWS based uh
attacker platform and for5 6,000 within
a week get your hands on a da7 key and
that is without discussing GPU
implementations or fbga implementation
it's just a a lower bar it's also
excluding the fact that computational uh
cost will go down over the next couple
of decades um so obviously this is an
amount of money that any reasonably or
even somewhat uh motivated adversary
would be able to handle uh it would be
within range for uh for organized crime
and maybe even a board teenager that
just has too much money on his hands at
some point in the future in any case
this is not going to be uh future
proof so we keep hearing that vasar is
the reason that these back doors are are
there and have to be there and while
there is certainly restrictions on uh
the export of strong cryptography there
are also exceptions in lar there are
exceptions regarding public cryptography
exceptions regarding uh civil use like a
mobile civil use and exceptions for what
they call connected civil industry
applications so in many many many cases
um a network would not need to be
restricted to these low levels of
security uh so will critical infra now
be getting tea7 and will we have the
whole ta one debacco again it's possible
let's hope not but at least we now know
on beforehand what we are getting
ourselves
into now ta6 is the counterpart of ta3
it's meant for European allies for law
enforcement and Emergency Services
outside of the EU um should we trust
that yeah well we could just ask Etsy
because in the interview that was cited
before um the chair of the technical
committee said they have no reason to
produce dogy algorithms uh they also say
that there is some
uh well let's say responsibility for the
end user so if you are using we
cryptography then you should probably
have picked something else in the past
this was a ludicrous ludicrous statement
because the algorithms were uh secret uh
but now you can make up your own mind
and probably come to the conclusion that
you do not want a multi- deade um
attachment to a weak cryptog
cryptographic standard in conclusion we
have presented the first public in-depth
uh security analysis of tetra it's a
technology used in over 100 countries in
a lot of different sectors we found
motal vulnerabilities
um we informed manufacturers and
stakeholders who have been working on
patches rolling them out and as of yet
there is still a lot of work to be done
uh but we will get there
eventually last a call to action if your
organization uses thra please be sure to
properly investigate the issues that we
uncovered look into the mitigations uh
spend money on it because it will cost
money and effort don't blindly trust
your vendors uh if you you're in doubt
whether they are telling you the full
story or they understand the full story
please reach out reach out to us it
would be interesting for the
cryptographic community to take a closer
look at the cryptography the the new
variants once they get disclosed or the
current tea3 or hurdle ciphers uh there
is open technology Stacks that uh are
really great but there is a lot of work
to be done there so for the coding
people there is lots of opportunities to
contribute and lastly please stop doing
Secret cryptography
especially Tetra end to end is uh is
very painful because it's reserved for
the most sensitive of of use cases for
Tetra and with that I'm not sure if we
have time left for questions but at the
very least I would like to thank you for
your
[Applause]
attention thank you thank you thank you
thank you it's on okay uh we do some
questions we still have some time uh
we're running over time but we have a
large break please try to be a bit
silent if you're leaving the room now I
know that the signal Angel has some
questions let's start there
yes yes I think that the internet has
been satisfied by the rest of the talk
so there may not be more questions but
I'll let you know if there if there
are
okay here is a question at number one
right side hello um your flag of
Indonesia was upside
down and but I also have a question
actually is it not a gdpr violation if
any officials use this technology and
then talk about suspects Witnesses
patients and so
on um I think with regards to the
Indonesian flag you need to take it up
with the NSA um with regards to the gdpr
I'm I'm not a specialist um on
regulation I I think it might it might
be an issue um but I haven't heard
anyone actually digging into this so if
this is something you're interested in I
think it might be interesting to uh to
poke at that a little bit maybe there
could be just a like a judge decision
that this is illegal to use
it could
be it's definitely murky Waters right
now like the Privacy guarant are
extremely limited that's for
sure all right uh number four you have a
question yeah so um one of the takeaways
of your talk was is that we should use
publicly vetted and standardized
algorithms so um how can we make it
easier to actually build secure
protocols on top of those cryptographic
Primitives and specifically do you have
any recommendations for nist um to take
in on their like ongoing process for
standardizing ascon and for stand for
for their review of the shake standard
which is likely to be used in Tetra
right um so as of things stand of today
there's plenty of publicly available
algorithms that you can just take and uh
and just pick them and put them in as as
a building block as a Lego blocks let's
say uh so you can just use that and then
you build a protocol around those and
typically what you see in practice is
that every uh once in a while these
things just get broken and then they
evolve over time like we now have ipv4
and we have or IPv6 and we have um TLS
1.3 like those didn't those things
didn't come falling out of the sky so
those standards went through a painful
Evolution and they they're sort of
reasonably secure as of today yeah to
add to that the these things need to be
made maintainable which is not the case
with Tetra where updates are very
painful to roll out um and you're
completely dependent on the vendor to
yeah to to basically allow you to do
that so
right number one
please uh thank you for the great talk
uh my question would be uh will you
probe other algorithms uh including
newer Tetra algorithms but also there
are a lot of other protocols and
algorithms from other vendors and
organizations yeah so I mean we're
definitely going to look at the new
tatra algorithms um we chose tatra
because it's one of the last remaining
bastions of proprietary cryptography
outside of the military space um we have
some ideas for future research but um
yeah if anybody has any ideas that
they'd like to shoot our way we yeah
we'd love to have a go at it
so okay I see someone here in front at
number two have you had a look into uh
the cryptography of uh
DMR um no uh but I I know that it used
to be rc4 with 40 bits then there's some
as based versions that nobody's really
looked into but I suspect that at a
protocol implementation level um there
might be some issues there with DMR as
there might be with p25 Phase 2 so
that's that's also interesting potential
research material we have an expert team
here number one um hi how does it work
in the scatter use case for the do those
Industrial devices like use Tetra up to
application layer when you're talking
about like fake messages and stuff or is
it like a network layer or something so
it's used basically as as a a network
and then on top of tetra you carry
serial messages or IP messages over SDS
or over the packet data uh uh mode um
and it's transparent to the ska systems
and the rtus and so on so they don't
know about Tetra um they just treat it
like any other cereal or or IP network
which is also why you need to take the
security layers um above uh the Security
Options above uh Tetra right but usually
they aren't encrypted no no no I mean
usually OT networks and critical
infrastructure are insecure
uh okay a number one yes sir uh how can
the sbox not be symmetric uh what do you
do on the decrypt side do you just guess
I mean sorry how can it not be a
permutation that that doesn't really
matter because uh the sbox is used in
the
key register so the key register is
initialized with an 80-bit key and then
it just uh it just rolls and outputs a
stream of key material which is injected
into the state um so you never have to
go back screener you decrypt by
reapplying the same keyst stream uh
besides that they also made some tweaks
to the design that prevent State
merges and Signal Angel is waving
something from outer
space yes so the internet would like to
know what do you think ets's incentive
his for being deceptive about disclosure
and why do you think they haven't
learned from uh other public
ciphers I didn't quite get that yeah I
didn't fully get that um so what do you
think that etsy's incentive is uh for
deception around the uh
disclosure and uh why do you think they
have not learned from other public
ciphers I I don't think it's a question
of learning I I think it's a question of
as you said
incentive um Etsy continues to choose
and has chosen in the past to keep these
things secret and proprietary they did
it with with GSM they did it with with
satellite phones with GPRS um it's
because there is a conscious choice to
enforce these export controls to have
back door cryptography in other parts of
the world so this is this is not an
oversight it's policy now they're making
these new algorithms open under public
pressure as a result of our our research
but they're still going to uh [ __ ] at
least one of the algorithms and
potentially a second one um so this is
yeah this is a matter of their policy
this is something that's that's
ingrained in the way it they work as an
organization
so whoa we solved quite some questions
here uh thank you guys uh they can reach
on the emails
there um of course you can always reach
out to us seems like there is still a
lot lot of work to be done yeah toally
thank you to Yos wetel Carlo mayor
Walter
[Applause]
[Music]
boar