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The next talk is going to be by
Yizkor, who's working at
the university in Darmstadt as
a PhD student and
mainly working on physical layer
security, and you might also know
her from
embroidery, embroidery machines,
difficult work and past
C.C.C. game shows.
But today she's talking about
building and breaking wireless security.
Give her a warm welcome.
Welcome to my talk about bidding and
breaking Violet's security,
so I have five section
first, I will show you some hardware
and then I will talk about wireless
tenants, because this is a very
physical focused talk and
we will need to speak around them to
understand how to break and build
wireless security.
And in the end, I will give you some
hints on how to get started during the
Congress.
So first, the hardware.
So for a long time,
the only way to do such things
that I'm going to show you today was very
expensive hardware like spectrum
analyzers or oscilloscopes.
And the problem is that private
people cannot afford this and you have
to go to university or big labs.
But many of you got the radio
badge during the camp.
And there's also
another thing that you can buy called
Karif. And they go up
to six gigahertz or four gigahertz
for the radio bitch, and it has the same
rate of 20 percent less per second,
which means you can even transmit
and receive Wi-Fi with it.
So very cool hardware
and you can also buy it if you don't have
one. The hacker.
If so, but some
of you might say, well, 200 years, it's
still too much because
I'm just a student.
And there's another option, which is
Stevie Nicks, and you can still
do great things with them.
So they are in a range
where you can do things like
decoding car keys, decoding
bus transmissions, decoding
GSM, for example.
And then there is a
cheap option for transmissions.
The Raspberry Pi, where you can just
connect one of the GBI options to a long
antenna wire, and then
you just modulate a signal on the CPI
open and you get the low frequency
signal.
However, it's not the nicest signal.
So if you want to have something
cheap, yeah, OK.
But it's not the best option to do this.
So just to get a short
imagination, how many of you have any of
this hardware just mentioned to you?
Wow, great.
So now I'm going to talk about
the concept of violence, it's
so violent, Chenna can
be imagined as fun.
So you have Alice and she is transmitting
a sine wave and
towards the receiver, Bob
or Charlie or whoever,
this amplitude first gets lower.
So the signal power is not that much
anymore.
And over distance,
you also get within the sine wave
a phase shift.
So the channel between Ellerson
Pop basically is the amplitude
and phase change.
And now the next thing is
that there is even more than
just a line of sight.
So there is, for example,
on walls, you have absorption, but
also you might get a reflection on a
wall. And at this
point in time, you have two paths
which might hit a receiver
and at a receiver.
This happens with the time offset and
this looks like a very strong
signal, first
in the time domain, and then you might
get a lower copy of the signal
from the second path and so on.
So you get the impulse response
in a time domain.
And the next part is that
you also get
a frequency response,
which means dispatch, the effects
are different per frequency.
So, for example, if you have a prism,
then, you know, let's just test different
frequency components which break in a
prism and you get the same
effect for different frequencies and
objects.
So you also get a frequency response
because you have different parts per
frequency and
even worse transmitters and receivers
and objects in between.
They all might move.
And you can think of a moving
transmitter of shrinking like
a shrink, a sine wave in one direction
and in the other direction.
That is. So you have a frequency offset
just from moving objects in between.
And all these things are path effects,
which you can measure.
And now the question is, OK, we have all
these measurements, but how can we use
this to break wireless security?
So typically network security
is done as follows.
So you have an upper layer and you have
some cryptography there.
And on the upper layer, the problem is,
well, you have, for example, tearless
or repair to and whatever you do
there, you always get some bits
and output and these
bits. Then I just transferred into a
form.
And the waveform in the end
is the thing that leaves the antenna
and nobody really cares about this.
So first of all, cryptography
has a big problem, which is
eavesdropping.
And you can assume if you eavesdrop
something today, you can decrypt
it in 20 years for very, very
sure just because of computation power.
And if there is some other flaw
in the implementation, maybe even
earlier, and everybody in a
wireless transmission range can
just eavesdrop without being noticed
and decode the signal later.
The next problem is that if
you have multiple eavesdroppers,
they can locate the signal source.
And the problem there is
that the signal source then is
no more. And it's just, you
know, the position and privacy is gone.
And also multiple or better antennas can
enhance the transmit the reception
range for the eavesdropper.
And you can also
inject signals, which means
normally at a receiver
or signals just add up.
And if there is a low and a high signal
that just adds up and the receiver
just has an automatic gain, control
takes the strongest signal and is happy.
So whatever you have,
the one who is sending, let's say the
loudest, is the one who will be
interpreted
and maybe many, many people.
You thought this is the main topic
of this talk, which is protocol, reverse
engineering, but it is not.
However, I'm just shortly telling
you about it because this might be your
expectation.
So normally you
just see some wireless transmissions
going on.
You are eavesdropping, and
then you try to find out the bits in
the signal, which is most of the time
not that complicated because there are so
many popular modulation schemes
and you just try some popular things
and then you try to make up some bits
to the actual
content that you are expecting.
So, for example, you say this thing
might be a bust up display
and, you know, names of bus stops and
then you try to map it and just see
what I did two years
ago. And she did it with a simple device,
pietistic, nothing else, and she
decode at the bus stop display.
So another thing is
what I'm holding, which is also still a
little bit upper layer.
So you might have an electronic passport
and you might have a server
in between and then a
reader. And even if they have some
signatures, you can still forward
everything and
it's working and you can eavesdrop on
transmission between the passport
and the reader.
However, this takes some milliseconds
and some milliseconds with speed
of light, with just the speed of wireless
vaisse.
Transmissions would be thousands
of kilometers, so you might
want to measure the time and now
the idea of measuring the time becomes
more physical.
But there has been some cryptographic
protocols and people say, wow, it's so
secure, we proved it.
For example, you just have
big challenges and you say
a receiver is
has to first read a bit before
you can spoof the bit again.
And what you can also do
on wireless face the bit
actually less of a form.
And you might just read the
first few percent of the waveform,
let's say the first 20 percent of the
waveform.
And then you can say for pretty sure
it might be a one or a zero.
And this means you can shorten
the time of interpreting a bit and
spoofing it again, which means you can
shorten the distance or actually
travel in time and predict something
before you actually should be able to
predict it.
And this is a very
big problem. For example, if you have a
car key and you can shorten the distance
and the distance measurement, it's a big
issue.
And another thing that I wanted to show
you is reactive Chien-Ming.
Reactive Chien-Ming means you have
multiple participants
in the network and you want to jam
certain things in this network.
For example, you might only want to Jim
Ellis. And whenever you see Elissa's
make a dress, you jam into
her frame and
break it.
And the nice thing about wi fi
is that wi fi actually
tries to avoid collisions.
And the more collisions happen
and the more packets don't get through
the network, the worse the situation
gets because it just things well, there's
much contention.
And then she has a off time and increases
the time slots in which she tries to
send again.
And she's even sending less often and
less often because all her transmissions
fair and you take just
test them less often and gets all the
bandwidth.
And you can do this, for example.
Also, if you just break some wi fi
firmware and you can get
all the bandwidth for just fifteen
dollars. Great.
And you might also be some security
jamming. And there is the idea
of just jamming everything around you.
So you just have a communication
and then you can say if
this jam signal
is sort of random generated
by a key, then
everybody who has the key can substract
the sort of random signal again because
he or she can calculate
it and then subtract it and just
subtractive to sickness a zero.
And you have no more noise in
the transmission from the data source,
which is overlapped by the jamming
signal.
However, it's an attack for
this. So actually this was used
to build authorization and
confidentiality. But there is an attack
because if you have two ecovillage
channels towards the chamar,
then you get two times the same jamming
signal on both antennas.
We have the same face and amplitude
in the signal.
However, the data source, which you can
see there, has two different distances,
which means two different channels.
So you have
a slight face offset
in this. And when you not
subtract the two received
eavesdropping signals from each other,
then the jamming signal just gets zero
again.
But the data
signal adds up because of the Festschrift
so you can reconstruct
everything even though there was
a jamming signal.
And another scary thing is
actually seeing through walls with Wi-Fi.
So normally you would build a radar
system which scans
through
different positions and then you get
reflectance.
However, you can also do this with a
single antenna, like on your radio, a
bitch. And from
then then you get reflections from
objects and objects
are moving. There is stable.
There is everything is not moving.
Only people are moving in the building
and they have reflections.
And you can think of this the same
way as off a radar system
because of the symmetric channel,
because the channel is valid in both
directions.
And by this you can actually
identify and track movements and you can
even do something like just the
communication through voice.
So, you know, that's a person and the
person is sitting on a couch.
And it gets even more scary because
something is that you can do as you can
with more antennas, even direct
live lip movements approval's
or loud speaker movements, because the
membrane is vibrating and
even more scary on your phone,
the audio chip and the Wi-Fi
chip are located very close
to each other. And when you have Wi-Fi
transmissions via you
have a phone call, then the
audio of the phone call cost us the Wi-Fi
chip to vibrate.
And these vibrations can be measured
to reconstruct your audio.
And it's all working through voice.
You don't see the attacker,
OK?
And because this might have been a bit
scary, I'm also going
now to my second part of the talk, which
is how we can build security
if vapes
so we might have
cryptography or not.
We might have some bits in the end and we
will try to do the magic on
the waveform.
So what can we do?
Something that you might know from
cryptography is different than
one time pet, which basically
means that you have a key, which is as
long as your plaintext and the
key is only used once.
And for example, it has a bug
and it is Bob, a key, which is one
terabyte large, and they exchange
information until they reach the one
terabyte limit and then they need to
exchange another key before they can
exchange more data.
The good thing about this is that an
eavesdropper cannot do any calculation on
this. So if you have an NSA attack,
for example, with unlimited calculation
resources, the attacker will
not be successful.
However, in practice, you would need
to share your key with
all servers that you have contact with.
So it's very impractical
and it's symmetric. So another key for
each server
in the violence domain there, something
similar, Divino
via China, where you have
the assumption that each channel is
different.
And this means that the
channel between Ellyson, Pop and Ellis'
and the eavesdropper might be
different in the way that if
is, for example, 10 percent information
that Bob would get.
And this 10 percent information
advantage can be used for confidential
data transmission.
However, in practice,
the problem is that we don't know the
position of the eavesdropping and you
might have multiple antennas or
a very good antenna and might not
have a disadvantage.
So it's hard to estimate
your advantage over the eavesdropping.
But this doesn't matter if you do
extraction with the same thing.
So you say sheknows are
symmetric or reciprocal,
and this means that you can
generate symmetric keys out of a channel.
So you have to face an empty IT
information and all the other responses
that I told you about.
And you can really build Keest from that
and Houston in upper layer protocols.
The only problem is if you implement
this, for example, with the received
signal strength indicator of which is
propagated by Fed chips to upper layers,
this is just an added value and
it can even be predictive depending
on your distance.
So you shouldn't use the received signal
strength, for example.
But there is good metrics that you can
use for this.
And to build confidentiality, you can
also use covert channels,
which means you are not doing something
like encryption, but you just try to hide
information.
And normally when you have a
transmission, then you have, for example,
different phases and then two or three
presenting bits.
So let's say the yellow
cloud is the thing, which actually
was one point at the transmission
representing the bits 00.
And then at reception
you will get another thing, which
means a cloud
because of the channel, the channel
modified slightly
the the transmission at the receiver.
And you can introduce some
more artificial noise to actually
encode some data in
this and hide it.
And as long as you keep within these
squares, this is not propagated
to any appliance.
No transmission errors occur.
And if you do this in a good
way so that the statistics
are still OK of this
error, then you might even
not be detected by a software defined
radio if this
and something else is just happening.
I already told it for short.
In the time traveling's scenario,
you can use this for authentication and
authorization, but I would only
use it as a second factor because you
never know if someone is there who can
slightly shorten the time for some
reason.
And another thing you can use is
device fingerprinting, because each
device is
when it's filled, manufactured, has
some differences.
And these differences also
will change the transmission behavior.
Everything is still within the standard.
But you can first of all identify
devices so you can track a device
and you can also classify
devices, which means you can say this
device is from this vendor, this device
is from the other vendor, and maybe you
just exclude
some vendors from your network if you
want this.
The only problem here is
that you really need a very good
measurement of this.
Fingerprint, because otherwise
some properties might be easily spoofed,
so you really need a good measurement.
So and there's even more, which I
only will tell in very short,
for example, you can build and
it for pacemakers
and other implantable devices,
which protects you from
terrorists. So it just varied in addition
to sending a signal or you can
build integrity with an of coding
or you can implement
oblivious transfer protocols on the
physical layer. And you can also do
location fingerprinting because of
all these different channels.
And now the question is where to start?
There are people here who are thinking
about these things, at least to some
extent. So there is
one assembling the data, 23
Connellsville, which
is located close to the food.
Then there's the radio assembly from the
radio, which they are in
all three.
And if you are just listening
right now, you can also just get a ham
radio license. And it's not too hard.
It's just a multiple choice test
and it's not expensive.
So you should do it.
And then you are allowed to transmit on
frequencies, on lots of frequencies,
and maybe you just want
to record something like all your cockies
and then share it to experts and ask
them about these things.
Or maybe you are
still a student and then maybe your
university is offering something.
So at least in doubt that we're offering
lectures. And there's also a mailing
list on this topic that I could offer
people. And they are also talking
about which university
is doing ham radio or software defined
radio things.
So thank you for listening.
And now I will take questions.
I see no one running to
the microphones.
Well, maybe I have just been talking
too fast.
The Internet has any questions?
Yeah, sort of.
So does
he do two point one X,
so IAPT less help against
eavesdropping?
Well, not really, because on the physical
layer, you can always eavesdrop,
it's I mean, the question
actually is if there is
decryption or not.
And I mean, of course, encryption helps
you against eavesdropping, but it does
not help you from actually recording
the bits. And you might decode them,
as I said, in 20 years.
So whenever you see a standard which is
older than 20 years, I assume
it is broken and maybe it's just not
published because of some legal reasons.
Now, there's someone on microphone one.
Uh, have you ever played around with the
use up here?
A little bit.
Normally, I'm using another platform,
which is called VoIP, and,
um, but it's about the same
thing.
But is it cheaper?
No, it's seven thousand instead of seven
hundred.
And microphone
four, please.
I was wondering if any of these attacks
do you know if they were already
implemented on open
source firmware or drivers
on nado 211?
Yes. So there is,
for example, in mentation for
just the Wi-Fi protocol for
use up here and RF
and it's working on the radio, which I
already tried it.
You can find it on GetUp
for the attacks.
I mean,
all the things I should have at least
some implementation papers.
So there are some sources on the bottom,
but I don't know which of
them are open source.
So some of them are, but I don't know if
all of them are.
And microphone number three, please.
Thanks.
First, thanks for the talk.
If you have a repeater in your network,
shouldn't shouldn't shouldn't you be able
to locate yourself
better than any other so that you can
exclude any structure?
Why should I be able to exclude
an eavesdropper if I can locate myself?
If it's if it's possible to
to calculate where you are, you
should be able to just give yourself the
signal.
Right.
Yes, but the eavesdropper is passive.
I mean, this is not sending anything,
it's just a receiver.
How should you know if the receiver.
OK, one
microphone, one, please.
Thanks for the talk
as part of an authentication
protocol.
Couldn't we use hardware that implements
directed antennas to provide extra
security by locking out eavesdroppers,
by not providing them with the signal in
the first place?
Yes. So there
has been, for example, the new 60
gigahertz standard.
It has this very narrow
antenna beams,
but you still get reflections.
So, um,
we really did it in experiments
and we measured that.
You get, for example, if you have a cup
in the middle of a transmission, then it
has a surface which is also
bent some some of the rest
like round.
And so you can just put simple
objects in the room, which cause
reflections that you still can eavesdrop
and the Internet again.
So you said something about a receiver
fingerprint. Can you give an example for
that receiver?
I said transmitter fingerprint.
OK, so
they are asking for an example apart from
the Mac address.
How but to make a dress, I mean, to
make a dress is still above
the physical layer.
So a fingerprint would be,
for example, when you switch
your device on when
sending, then you have a certain
characteristic how the signal starts
when turning on the device.
This might be a characteristic.
And microphone one,
I think you have you already tested
the voice eavesdropping and
how complicated it is.
I didn't test it, but
there is a video on YouTube.
So this has been published on maybe
come in this year during September,
I think will become has been and
just Google the
Viper Matri and Moby come
and there's the video.
Thank you.
And microphone for
that. It's naturally trivial to locate
a single omnidirectional source
for an article.
All the fancy things I can do to consume
up and put my position was
was directed or multiple
Sondos.
You mean you want to obfuscate your own
location? Yes.
Where I'm standing from because I was
single.
So yes,
let's say it's possible you can craft
another signal, other locations, but
I would really call it a kind of antenna.
So if you have an eavesdropper having
more antennas, then you can still be
localized and so on.
So it's a question of costs.
Not not really.
So maybe you have more antennas than the
eavesdropper. OK, then you are safe
again, then Detropia as Montanas and so
on.
Thank you.
Um, I see no more questions.
One more question on microphone number
four.
And you briefly mentioned something about
a warm house, probably use
some kind of bridging to connect
devices that aren't supposed
to be connected because they're too far
away.
Do any real world systems actually detect
this kind of attack or can
you just basically use it to
fake your password?
And someone
who actually has the password is somebody
completely different for
that scenario that I showed with the
passport. It's working and
it's also working for our Menza
cards at my university.
So there's lots of things which are
working. There's maybe
also things that do distance bonding and
then it's not working, of course.
And students in our troop implemented
this. So you can really download the
source, install the app on your phone and
do this.
Thank you.
So no,
actually. And does the Internet
have any questions anymore?
No questions in the room anymore.
So why would you want a
finished before the time is over?
Thank you very much.
And give a warm hand to discuss.