Welcome back to the Wireless Village, like most of you ever left.
Contestants, I'm sure you remember by now, but please be quiet.
We're all very glad you're here, and quiet, really quiet.
Because I don't want to have to take points away, or drop this mic.
So, it is my distinct pleasure to introduce two people that, well, if you were playing the dog collar game, you already know.
These are two of our newer friends of the village.
They've managed to ingratiate themselves in a short time.
Tim was one of very few people who said, dog collar challenge, that sounds like fun.
When Russ first introduced it.
No one else would play.
And then after Tim played for about 45 minutes, nobody wanted to play against Tim.
So, yeah, that's been a lot of fun.
He had no idea how software-defined radios worked right up until then.
And then he's been ruined ever since.
I'm sure he does nothing else from the look of it.
And Woody sent me, I cannot even imagine, the most entertaining email I have ever read for the CFL.
So, I'm going to go ahead and read it.
Something to the effect of, I'd like to give this talk, but I need to bring my dog.
Is that okay?
I'm like, just bringing your dog?
Is there any particular reason?
Well, it's a hearing ear dog.
Okay.
Sure.
So, it's actually a service animal.
It's not like a service pony.
It's a dog.
Yeah.
Yeah.
Okay.
Yeah.
You can bring your dog.
No problem.
So, these are some of our newest friends.
And they have done something that the entire Wireless Village team wanted to do.
Which is reverse engineer the bloody GoTenna.
So, I present GoTenna reverse engineering with our new friends, Woody and Tim.
Woo!
So, we're glad to be here.
Actually, we want to thank Wireless Village.
They also gave us a chance last year at DEF CON.
We presented Iris for any of you that have heard of infrared and how that might be a way to track cell phones.
We did.
We did that.
They gave us a chance to do that.
And they brought us back again.
So, pretty happy to be here.
A little bit about me.
I go by Woody.
And I play with Software Defined Radios and RF.
And now, Tim.
Yeah.
I'm Tim.
I came here to the DEF CON for the first time about three years back.
And got really excited when Russ was, like, playing with dog collars.
It's like, man, this is going to be fun.
Not only can we shock people with dog collars.
Like, we can set them up.
We can set this thing up on the Internet.
Like, Japan's going to get really excited about it.
It was...
Anyways.
So, we're going to be working on the Gotenna here.
This is something that came out a couple of years back out of Hurricane Sandy in New Jersey.
There's two people, Daniela and Jorge Perdomo.
They're siblings.
They thought, you know, it would be kind of neat if we could have some way of communicating when cell networks go down.
And so, they made these things.
Do you got one on hand, Woody?
They're about the size of a pack of six pencils.
It's kind of taped together.
They're really small.
And you pair your phone to it over Bluetooth.
And so, once you've got your Bluetooth link up...
Got one over there.
Pretty sick.
Anybody else in the audience got one?
Anybody else?
All right.
Well, we actually have a discount code from them at the end.
We don't work for them.
But we ended up having to contact them about something, which we'll talk about later.
So, anyways, you pair it with your phone or Bluetooth.
You send a little text message to your buddy.
And it goes out over MERS.
Which is sort of similar.
It's similar to push-to-talk radio networks for, like, family radio service, things like that.
And so, some expectation management for the talk.
We're not doing anything with Bluetooth.
We're not doing anything with mobile applications.
It's just not our skill set.
We're going to be focusing on the MERS link and how it communicates.
Also, Goten is coming out with new hardware.
This is not the new hardware that we're studying.
We're studying the older classic hardware, if you will.
So.
Now.
We have ordered the new hardware.
And hopefully it will be arriving within the next few weeks.
But Goten is a fund-me thing.
So we're waiting for the new stuff to come out.
So a couple of things we're going to talk about.
We've all heard of this OSI model.
What became interesting as we did this, a lot of things we do with software-defined radios.
Key fobs, entering vehicles, bypassing your home alarm system, being able to open your garage door.
I don't need to worry about the OSI model as much.
Pretty much, I have the hardware, I'm able to collect some stuff, I can replay, make a couple of changes, make things happen.
That wasn't the way that this worked.
This actually has networking, this actually has the physical model, this actually has presentations, sessions, and applications.
So, I had to read.
But fortunately I had Tim and he reads much better than I do.
Screen's blank.
Okay.
So here's how we got started.
As he pulls up the presentation.
So, this is what we did as we first started out.
I got excited because I'm a big fan of using software-defined radios.
And let me caveat with saying that if you broadcast on the MERS network without permission, that is an FCC violation.
So I'm making sure to tell you, don't ever do it.
And if you do it, only do it in the casino with a yogi.
But.
But.
But, with that being said, in my own home, on my own large piece of property, inside of a RF-free Faraday environment, I might have played with this.
So, as I did that, one thing I noticed is I could replay a message from a GoTenant device hours later and have another GoTenant device still accept the message.
So I was like, oh, that's kind of interesting.
That would be something.
That would be something that could be of use if I had done that.
In a perfectly Faraday cage with no RF environment or anything else.
Yeah.
My Faraday cage was good to go.
So I was fine.
So the first thing I did was I started looking at a spectrum analyzer.
Because I called Tim.
I said, hey, this is pretty cool.
We need some really high-end, expensive equipment to be able to move further with this.
So we used Osmocon FFT.
You're going to find out throughout this talk, we want to promote you to the next level.
We want you to use basic tools and be able to use simple tools to do complex tasks.
Osmocon FFT.
So I invite Tim over, and I'm like, hey, I know that you can do some rebroadcasting with this.
So let's figure out how this thing works.
And Tim is really good at software-defined radios, and he can write some really cool code.
So he said, okay, well, let's start playing.
And then, boom, things start hitting.
So can anyone tell me what's happening right here?
The biggest thing you take out of seeing here?
Exactly.
There's a command channel, obviously.
So you see where it spikes right here?
No, hold on.
How long did someone, did someone say command channel?
That took me like 20 minutes to figure out.
I didn't believe him.
Yeah, so here's what happens.
We sent about that many packs, and I go, hey, Tim, look, they got a command channel.
And he's like, no, what is, we're going to have to do some more tests.
I said, no, no, that's a command channel.
So Tim can write really well, and I can kind of look at weird things and say, hey, this is really cool.
And sometimes they pick up.
So I was like, I think there's a command channel at the highest end.
Because we knew there were five channels.
Why?
Because FCC is our friend, and we knew there were five channels in the MERS band.
You're going to find more out about that later.
So Tim doesn't believe me.
You'll find out if you talk, if you were here for our Iris talk.
Tim's a firm believer that I hunt unicorns.
He does.
I will tell you, unicorns are real.
So what happened after we started testing this out?
We realized that they're bouncing around.
But one thing stayed consistent.
So being a little bit more of a scientific man, I thought, hey, how can we test this and actually prove somehow that there's a command channel?
So if there's a command channel, what would that mean?
That means there's some sort of trunked radio network.
And I said, well, let's do something that I think will help Woody and I understand this problem.
So I said, Woody, let's start role playing.
And so I put on my robe and wizard hat.
All right.
I'm going to be, yeah, he's really into this, by the way.
He made a character, maxed out the stern in, and I maxed out my wiz.
So it's just kind of, yeah, there you go.
Lightning bolt.
Anyways, so I'm going to pretend like I'm trying to talk to Woody.
I'm one Gotenna.
I'm the other.
I'm going to start on channel four.
That's the control channel.
I'm going to say, hey, Woody, I want to talk to you.
Let's meet on channel two.
Now, Tim didn't do this to try to make it prove that I was right.
Tim was like, well, I'm going to show you how to do this.
I'm going to show you why this doesn't work.
So Tim said, we're going to do this.
And you'll find out, if it still bounces around, Woody, you're wrong.
Because it's FreeCop, and I don't think there's a command channel.
I was fortunate enough to be able to say, well, I think there is.
So we did it.
What happens if you're on channel two?
Yeah.
So what happens if we start sending it to where one channel, one radio is off, and we send, and that radio doesn't authenticate?
If there's truly a command channel, it should only send from one channel over and over and over.
So let's reset our control channel.
And we're going to shut down all other radios, except the one we want to, except the one who's sending.
And if what we're sending, oh, by the way, we're doing this live demo, because if we're not willing to go live, should we really be here?
We have backups, but I think there should be some principles.
All right.
So we're totally, we're all the way off.
We've only got, I've got my phone on.
And I've got my Gotenna on.
And I'm going to try and transmit to a Gotenna that's currently turned off.
If Woody was right, and I was wrong.
What we should see is on channel four.
That's the one all the way on the right.
We should see it talking and never hopping over to channel two.
To finish off the conversation, what was supposed to happen is, hey, Woody, let's meet on channel two.
And Woody was supposed to go, okay, Tim, I'm ready to receive a message.
But he never did that.
So if it doesn't have a command channel on channel four, it will bounce all over the screen.
So, huh, huh, huh.
God dang it.
I'm sorry, Tim.
I'm right.
So now I might be right, but he can script.
So he wins.
But still.
So as we started to look at this, we were like, dang it.
This could be something to look at.
Because remember, if I know where you start, what are you probably going to tell me when you start?
Who you want to talk to and where we're going.
Woohoo.
So we start working.
So let's go.
Let's go ahead and tell us why the FCC is our good friend.
We were able to find the actual board on the FCC.
Why?
Because they have to be there.
Now as we look at this, remember I told, Tim told you we're not doing Bluetooth exploit.
Not even going to attempt it.
However, in the lower left-hand corner, that is the Wi-Fi antenna.
I'm sorry, Bluetooth.
We're not using Wi-Fi.
Please, okay.
Got it.
Understood.
Now, as we move up on that whole side, we look at the protocol and we realize that we move over all the way to the right.
That is going to be the MERS antenna.
And if we come just between everything else, that is the actual radio antenna for the Gotenna.
Now, this is the antenna, which for MERS is fairly small, but it's one of those things they're working on.
So, at this point, we're like, okay, we're looking at this board, we're able to find some information.
So, what kind of modulation do you think we're going to use, Tim?
So, this is going to be on the MERS channel.
So, if you're familiar with push-to-talk radios and that whole plethora of frequencies that the FCC allocated for unlicensed people to use,
everyone's using frequency modulations.
So, pretty sure about that.
It's frequency modulation.
And also, on top of that, it's probably going to be within a 12.5 kilohertz channel,
because if you're using a 12.5 kilohertz channel,
each of the little push-to-talk radios,
every time you go to the next channel,
12.5 kilohertz.
So, I'll show you the modulation.
We should probably go to a live demo at this point.
So,
while we talk about this a little bit,
and we wait for this to pop up,
which, oh, there we go.
Weight's over.
We looked at this, and we're like, okay, it's probably,
well, Tim's like, hey, you know what, I bet they're using FM.
We'd seen a few things that made us feel that way.
And then we looked at the FCC stuff,
and he said, hey, let's really sketch this out
and see how it works.
So, let's go ahead and send something
and see what it looks like.
Now,
there we are.
So, we have a good amount of data here.
For those of you that are familiar with
FM, or, you know,
frequency modulation stuff,
you realize it's a little different than on-off keying,
and it can be a little more difficult to demodulate
and see what's going on.
So,
we need to figure out where all the packets start.
There's questions coming at the end, sir,
but I appreciate your enthusiasm.
That is a great question,
and please remember at the end
that we're willing to answer those.
It's okay.
Yep.
One of the interesting things about this one
is if you look at these bits
that are being transmitted,
they're not square.
If you're looking at a wireless fan remote,
they're going to be square because they're pure FM.
They're hopping right between two frequencies.
As soon as that bit changes,
boom, just hops right over the other bit.
The problem with that is it makes your
frequency content really wide,
and if you were here for Balint's excellent talk,
when you start increasing your bit rate,
you start increasing your bandwidth,
and this is something that we're under a constraint
from the FCC.
So, what you do is instead of hopping instantaneously
between frequencies,
you slide between frequencies.
That lowers your spectral content.
As you can see in the bottom,
that's only about nine kilohertz wide.
Easily fits within 12 kilohertz.
So as you look at this,
and remember Tim's the person who taught me
software-defined radios,
so anything I say incorrectly falls on him,
but Guzman modulation is what we're looking at,
and we're, oh wait, is that,
oh, I'm sorry, Gaussian.
But the way this works is it helps us know
that it's something else that we need.
We need that because we need clock recovery.
We need to be able to figure out the timing,
the sequence of these bits,
to be able to turn them into ones and zeros,
and then from those ones and zeros,
we need to be able to make real information.
This part of the packet's called the preamble,
and it's something that most radios
like to do to start out.
It's kind of like, ahem,
it kind of gets everybody's attention,
but it also lets the clock recovery algorithm
sync to each bit.
So what you're looking at here,
let's see if this is going to break everything,
stem plot.
Alright, those are the actual samples,
so if you had an array inside your programming language,
each of those would be a sample.
The problem is we've got to figure out
which one is the one, which one's the zero.
So this is where something that really handy
came in from Andy Walls.
Andy Walls, the stuff that he did,
oh, by the way, this is all GNU radio based,
which means everybody has a chance to play with this.
You don't have to be high end or anything else.
You don't have to be some guru.
Everybody has an opportunity to play with every piece
of this and it will be released so everyone will be able
to do exactly what we do up here.
Even noobs.
Now, we got bad clock recovery.
So Tim, tell us what that means.
So if we have bad clock recovery,
it means we're not going to know what bits
are correct inside our packet.
So you can see here we had 10101010
in the preamble.
We shouldn't see that sloping.
This was the stock clock recovery block
in GNU radio.
Don't make me say that again.
So it didn't do a very good job.
The one that Andy, no.
The one that Andy Walls wrote was much better.
You see how each of those points are
pretty much perfectly on plus or minus one?
That's great clock recovery.
And for these longer packets, these variable length packets,
we really needed to have something
that would be good on that.
So thank you to Andy Walls if you're hearing this.
Now one of the other things that needed to be done
was a way to actually look at this
and spit it out into something that was readable
where you could actually start and stop
where you wanted to.
So Tim came up with this
really cool module for GNU radio
called GR Revenge.
Now let me give you a caveat.
You're going to have to use that
when we release this.
You're going to have to add that to your repositories
and everything from GitHub.
When you look up GR Revenge, what's going to pop up
is girlfriend revenge over and over
because that's apparently the number one search
for Google under GR.
That is not what he wrote.
It is GR Revenge
without an E.
So please find that on GitHub.
It will be an issue.
I promise you when you search it that's what's going to pop up.
Now what we're able to do here
is take the information,
start with a radio,
move it over,
and as we set it up,
because we know there's five channels in the MERS, right?
We break it into five channels.
Not we, him.
Now we break it into that and we make virtual syncs.
The virtual syncs give us the ability
to now continue working our progresses
that each channel does individually.
So if we can look at
all five channels individually,
we can start figuring out
how they work together.
And because we've already started to figure out
there's a command channel,
the command channels tell me where the next place
I need to look at anyway.
And once that happens,
I can ignore the other channels altogether.
So just to run through the
this really quickly.
It looks really complicated
until you start doing FMD modulation enough.
And once you do it enough,
this becomes like this design pattern
that you do over and over and over again.
On the far left,
demodulate it from a radio signal
into something that you can plot out on an oscilloscope.
After that,
you do a low pass filter on it
to make sure there's less noise.
Clock recovery.
Turn it into a bit, one or zero.
And then after that,
look for the packet.
So we had to figure out what the sync word is.
This is a stream of information coming through.
It's a bit of information.
So as far as radios are concerned,
they have to know when a packet begins.
So what they do is they shift
every bit they think they're receiving
into a shift register.
And they look to see when the shift register
equals a magic value.
In this case, it was 2DD4.
And when we found that,
we weren't actually sure if we found that correctly.
So we googled it and we found the data sheet
for the Silicon Labs radio,
which turned out to be really good.
Now one thing,
as you look at this and realize,
spitting the data out and being able to see it,
one of the interesting things that really came out
that Tim found,
which should really go on his counter,
but he didn't put it on here,
is the fact that as he comes through
and he's able to spit this data out
and be able to see what's going on,
he does a great job because initially
we didn't know the full length.
Remember, we've got a lot of information.
We've got back and forth, back and forth
and back and forth.
Initially we didn't realize
we actually have to be able to segregate
the length of the packets
for every step of that communication.
So now, we start looking at this.
And initially we're like,
oh, 11, we're good to go.
We know how long this packet is, right?
Yeah, so we had some issues with that.
That may not have been correct.
So then we come down here like,
oh, well, things are looking a little bit better.
Now,
I want to start figuring something out.
I know that I have a protocol that uses encryption,
but I also know that the same protocol
can be used without using encryption.
What's the first thing we do
to start checking ourselves?
We send information unencrypted
and can we find it inside the packet?
Oh,
so there's 41,
which would be a capital A,
62, which is actually a lower case b,
and then 63, which is c.
And we had just sent that exact same message.
And right next to it in red
it actually gave us the length
of the message.
So if we can transfer this over to the encrypted side,
we can start developing how long
the packets they're sending are.
Now we start looking at everything else
and we start realizing we can count how far it goes
to start figuring out a little bit more information.
Yep.
Eat the elephant one bite at a time.
Now,
you see the one e up there?
So as we looked at one e,
what we realized when we
upped the size of the packet by one
it now became one f.
And Tim informed me that means
it went up by one size.
So I was pretty happy.
Because we had now done a, b, c, and d.
I also watch Sesame Street a lot
so I was like this is probably the
system we should use
because that's what I watch every day.
Alright.
So, um,
I had to tell Woody though that
the next thing after one f was not one g.
It was actually 20.
Alright.
Um, alright.
This is another one of Woody's wins.
I'll have him run the slides for a little bit here.
Um,
so one of the things he called me up on the phone
he was really saying, Tim, Tim,
I just found the next channel they're transmitting on.
It's this bit right here.
It says two.
And then the next channel it transmits on is two.
And I'm like, they could have put those bits anywhere.
This could have been anywhere inside the packet.
And he was just so dang sort of,
and I'm starting to try and learn from my mistakes
of telling Woody he's wrong every time he's actually right.
That's how I remember it going.
Anyways,
if you look at that one that's highlighted right there
in green, the two tells you
that the next packet is going to go on channel two.
And on the second one down here
the three says it's going to be on channel three.
We turned out, turns out we didn't need to know that.
Um, in a single receiver system
that can only look at one channel at a time
it's really important for it to tell the next radio
hey, I'm going to be talking to you over here
you need to go there.
But we're looking at all five channels simultaneously.
So although we found that,
it's just a, you know,
interesting thing to know.
So yeah, I'll give Woody another point for that one.
And so once we've,
so we found the length of the packet,
this is starting to tread into like layer two territory.
So an Ethernet frame,
a lot of times it has this is who it's going to,
it's got a length, it's got a payload,
and then the checksum.
So we're starting to step into layer two territory.
We found, pardon me, we found the synchronization,
we found the length byte
where it's located in the packet,
and then we found out,
just about enough to start trying to find checksums.
This was really hard.
And without a checksum,
we're just going to be looking at a bunch of bits on the screen.
And this is really hard to look at
and figure out who's talking to who.
I don't even know which radio it is,
we have no checksum, if there's any noise,
we're screwed.
So that was kind of me.
And I came in one day
and I found Woody just sitting there with a screen
with packets scrolling across them.
And I'm like, oh hey,
did you dremel the thing apart
and solder down onto the debug wires
and write some thing to analyze the packets?
And he's like,
no, I just plugged into the USB port
and it showed up as TTYUSB.
I mean,
I don't even know why I wrote this whole radio thing.
It's...
Yeah, so he also introduced me to Dumb and Dumber.
I'm a nerd, I don't get out,
I don't watch movies a lot,
so this movie's actually really funny.
Yeah.
So one point for Woody.
We actually got full packets here coming through,
which meant we didn't have to worry about the checksum yet.
That was just something we pushed off
into the back burner while we worked on it later.
I'm gonna pass this off and let you talk.
Okay.
So what was interesting about that is
Tim had been working this clock recovery piece
and he's like, man, I think I really got this,
but I can't confirm it.
Well, now we were able to actually
from the radio see what it said
and then compare his radio to it.
And he's pretty good at writing.
Tim was right.
We're gonna keep that low though
because then he'll put it on his column.
So as we start looking at this,
we start figuring more things out
and we keep getting this Gotenna ID
when we start getting into the serial port.
They call it a GID,
which would basically be the equivalent
of a unique identifier.
Think of anything else.
So as we start looking at unique identifiers,
we keep having these numbers pop up.
Now, as we look at these numbers,
up here where it says TRX
and you see ODB9,
we kept seeing that and we're like,
hey, every time I send to somebody,
it says that first where it says,
hey, you on this channel,
I wanna talk to you.
Okay.
Well, that works.
And we start realizing that we start seeing these packets.
Oh, and now let me tell you,
you know how you start figuring this out
when you just have a whole bunch of numbers
and letters on the screen?
Anyone in here ever heard of a little program called Vim?
Yeah, well, I don't know how to use it.
So we use Get It.
So,
Get It, control F.
So if you're reverse engineering something
and you really wanna have a quick,
easy way to do it, and I'm not insulting anyone on Vim
because I can't spell Vim.
What I use is Get It.
I take Get It, I use control F,
I highlight what I'm looking for
because part of this talk is we wanna help you
learn how to use the basic tools to be able to do this
for the basic person to be able to do it
and for the advanced person then be able to add it
to their advanced systems.
By doing that, we start searching
and seeing where this pops up in all the packets
and man, we keep seeing this
58570D
fecdb, we keep
seeing the hash 16
equals db9
and I keep looking at that and I'm like,
damn, I think I know what that is.
So we found some other stuff.
There's cryptography, so
it's public key cryptography
public key cryptography as well.
So at some point I'm gonna have to exchange my key
So I found this in a message, public key
and it told me what it is
and then I control F for it
and lo and behold it's sitting somewhere down here
in a transmission message.
So we know they're transmitting the Gotenna ID
we know they're transmitting public keys
and that actually helped us even understand
the format of the protocol
because this is 49 byte long
public key, this is a 49
anyways
if you turn 49 into hexadecimal
it turns into 31.
And so we're understanding
even more of this.
A pretty common paradigm for sending
variable length packets is you say
this is what it is, that's the first byte
the next byte's the length, then you have your data
and maybe a checksum.
If you go back to this previous slide
you see where it says 0109
and then the Gotenna ID
01 means Gotenna, there's 9 bytes to it
and you keep going on to find the end of the packet there.
So this helped us really understand
having this debug port
like the, what's it called?
The clock that they found in the desert
that helped them understand Greek.
Thank you.
So I'm also bad with history.
So I wrote a script that would
let you plug two Gotennas in
to the same computer
and it would interleave the serial port streams
and what this meant is
beforehand in the wireless domain
I didn't know which radio was transmitting what
I just got all these packets
I didn't know who was talking
but now I know this radio started the transmission
and the next radio responded to it.
That's Woody's 2.
He's really excited about that.
And
this is kind of
a little obtuse to look at.
So I translated it into English.
So it starts out, the first radio is transmitting
it says, hey I'm looking to talk to a guy
odb9, that's like the short name
for the whole Gotenna ID.
It lets them get away with not transmitting so much
on the control channel.
The next thing that happens, just like Woody and I
sort of hypothesized in the beginning
it meets over on the message channel
this is me, what do you want to say?
Well, here's the problem, if I say
I'm looking to talk to W, how many people in this room
have a name that starts with W?
Alright, we got a couple people.
Woody included.
Everyone's got to meet, I actually have to disambiguate that
and say, okay I actually wanted to talk
to this guy, is that you?
And also, I might need your public key.
Further, the radio goes and responds
here's your key
and then you end up transmitting the data
which, here's the data from this
user and then finally an acknowledgement
so this is a pretty stereotypical
paradigm for transmitting
stuff over a lossy medium
where you're going to lose a packet somewhere
or get a byte corrupted and it's like
I need you to send this again.
Fortunately we're working really close to each other
we didn't have to worry about that.
So now we start looking at this
and we start going wow
so we can see
using the serial port
when each person talks
when they want to send something
it's almost like a golden egg
given by the person that designed the protocol
that it goes 1, 0, hold on a second
even I can figure this one out
remember Sesame Street?
2, 3, 4, 5
4, 5, 6, 7
they start following it into a
sequential order as they start working the packets out
and that was pretty nice to be able to figure out
what's going on.
And as we move to the end of it
we're actually able to see
they start designing out
the packets they're going to use
how big they're going to be
and what sequence they're going to fall into
and yeah header versus payload
so we're like wow
we can work with that
and then we come up
to one of the funner nights of the entire project
this is called
the GID
which we've already said is
the Gotenna identifier
who in this room has ever used a Gotenna?
Anybody?
Can anyone tell me what the default protocol is
for using a Gotenna?
B for your unique identifier
it starts with phone ends with number
that's right
so
so here's the thing
but Tim and I aren't those guys
like we don't use our phone numbers for stuff
because we both have high levels of paranoia
so we always use randomized
so this actually was a setback
for us at first
so we start looking at this and we're like man
we're never finding this 972210
in any of the data
I don't know how they're sending it
wait a minute
maybe we look into the hex
maybe it's some kind of MAC address formula
because obviously whoever wrote this
is going to make sure it's very secure
and a very high end protocol
nah that ain't working
well let's look at it again
maybe there's some kind of sequential ordering
that goes back and forth
and we start kind of pulling our hair out a little bit
and we start going hey what is that
anyone here ever use a thing called
gnome calculator
well hold on before we get to that
so let's just talk about gnome calculator
so gnome calculator
which is in
most Linux systems
it allows you to take like hexadecimal
and transfer it into
other protocols
but we figured there had to be some high end
things being used
so this is what we did
we just jumped out of presentation mode
and said let's just get it on
and just throw things on the screen
yep
oh
yeah
so what Tim was just saying
because again remember he's the guy that helps teach me
so any mistakes I make are his
so we started noticing
you know that whole 9597 sequence
that's a fairly high number
but then
we decided
you know what we're going to do
we're going to use one of the cell phone numbers
just like the default protocol is in Gotenna
and when we did that we were like wow
that's a really little number
that's a little odd
gnome calculator
again please always use basic tools first
because then you can talk to me
and I can understand it
so we throw the information in there
zero one
zero zero zero one
c three eight nine
wait a minute
own shites a biscuit
that's a phone number
your to and from blocks
we know have been identified
and what we realize is they broadcast
if you use your phone number for Gotenna
your phone number
so if any of you do
open source information or technologies
we can talk on the side
but I'm pretty good with phone numbers and Facebook
to be able to figure out who you are
but that's another conversation
how dangerous could it be
oh
well and then we're sitting there
and I was like man
I'm bored and Tim was working on the presentation
and he's an engineer so he like works on things
like really intensely
and I get bored really easy
and I got tired of shaking my keys
because they weren't shiny enough
so I said huh
I took a couple phones and I just started saying
well if I now there is a fix for this
if you use the Gotenna GID random identifier
you know what's going to happen
you get a random identifier
and you don't have to compromise your phone
so Gotenna has put this in there
I want to add this is not a slam on Gotenna
this whole talk I still like Gotenna
I will use Gotenna and I think for what it's designed to do
I think it's great and I want to make sure I add that in there
and I was like man
hey Tim do you think I could make two Gotenna IDs
that are exactly the same
if they're random at some point they'll cross contaminate
and they'd have to be identical
and he's like what are you
stuff doesn't happen like that
so I said
Tim's poking me again
remember he beats me all the time
so what I did was I took two phones
and at the exact same time
I pressed new random identifier
on both of them
and we realized this is a time sequence
now
and then I was like
well what if we go back to what
nineteen
I don't know maybe 1970
a certain month a certain day a certain time
and see what happens
couldn't do it
we could go back to a certain date
and that's the furthest it led to go back
so we could go back to a certain date
and try to set it at the exact same time
but it actually goes all the way to the milliseconds
so we couldn't get the same one
I was a little bummed but that's okay
what I realized is
the year doesn't matter
that's what the nine does
it stops you from having the year important
but the month the day
the time all the way down to the millisecond
that's how you set these identifiers
so you can from someone's identifier
at least know some rough information
so even if I don't have your phone number
I can still pull some rough information out of this
and I can still do
link analysis
Tim those are your words
not mine
so if you've ever seen a movie
where there's like some guy sitting up
with like this wall with all this stuff
and little red lines going there
it's called a crazy wall
and we made our own crazy wall
sorry if you just give me a second to get it open
pulling open my favorite tool here
I'm going to actually need to move this to my monitor
so I can see what I'm doing
so what we ended up doing is
one of our primary tools like we mentioned earlier
sorry about the disjointedness of this presentation
that's kind of the way we work
you don't find things in a linear manner
that would be really nice
but we didn't
so this is our crazy wall
and I'll just show you a couple of things
this is a lot to process
and I don't want to spend a lot of time here
but what we did first is
we started by organizing our packets
by the way they happen
so each one of these little blocks of text
is a communication
and what we started doing is we just started
to make sure that it made sense to us
so remember we had that 0db9
this is what Woody was talking about
we control F for it
and we found it in another part of the packet
and so we used that to create divisions
within the packet structure
and that helped us break the fields out
outside the packet
moving on down
so these are communications
so again 10 was the hello I'd like to talk to you
62 was I'm there
23 was this is the person I actually wanted to talk to
remember this was the gif
this is the ID coming along here
followed by yup that's me
here's the packet and I got it
thank you very much
when you have it in this structure
you can see some interesting things
but not everything
one of the neat ones if I can find it
yeah here it is
this was a long message that got sent
and so if you have a very long message
it gives you a high probability of a bit error
which means your packet is going to get dropped
so you chop your messages up to smaller packets
so that you have a better chance of getting through
so this is part one
and this was part two of the passage
but what really helped
was when we looked at it from a different perspective
let's gather all the
transmit announcements
on the control channel
let's gather all those together
and look at them again
and that helped us see more things
down here in the packet
haha
alright
so once we started finding that
type length
data
paradigm again
we saw FBOF
oh hey look
there's the Gotenna ID that we found
we control left and that popped out
so within the message FB
that means this is the Gotenna ID
there's lots of little other things
that we didn't particularly understand
here's your message 416263
that's ABC
and then at the beginning this one here
the type 3 wraps the entirety
of the packet
this is my crazy wall
you gotta be careful with crazy walls
enough said
so to break the packet apart
we showed you like all these bytes
and your eyes are probably blurry
so were ours
so to make it simple
you've got a packet header
at the start of every packet
optionally there's a frame
that shows up at the end of the packet
which is again the type, length
and then some checksum at the end of it
and the message has the type, length, whatever
so if I type a message to you
there's several frames that build together
to form some sort of message
which brings us
to this part here
so as we look at this
what we would like to see
versus what we did see
versus how things work
your broadcast messages
are meant for everyone
let's say there's an emergency
you want someone to know where you are
you just send it out, it's not encrypted, everyone can see it
there's a protocol
again, I'm not slamming Goten
I think it's a great thing
and I don't discourage anyone from using them
I just want you to understand the difference
between anonymity and privacy
and security
they're different elements
now, in the broadcast
you can see everything
from who's sending it
to it goes out to everyone
you can see the initials of who's sending the message
you can see GPS coordinates
messages, all that
but there's actually a little bit more I can see too
not just the sender
but I can also see who it's going to
so early in the conversation
I can see who it's going to
and who it's from
how does this bother us?
well, because maybe some of that
could be protected a little bit better
you don't have to necessarily
give away both ends of the conversation
I want you to think a tour
do we want everyone to know
where we're starting and where we're going?
could be dangerous
so as we move forward and we start looking at this
we start thinking what would our goals be
what would we like to see
we'd like to see a little less information come out of that
and with that
initially the name of the program was called
GoDump
kind of like arrow dump
but then we started realizing
wow, this is a little bit overseeing
it sees everything going on
who's sending something
who's receiving something
what channel they're going to go to next
it lets us know
how big the packet is
so if I know
how much information you sent
where it started from and where it's going to
would that be of any value
to anybody?
if it is, it is
if it isn't, it isn't
I'm going to leave it at that
so now
what we're going to show you is a little bit about
how some of the SCAPI plays into this
so you can see what does it look like
so what we're going to release
we want to kind of show you a little bit
about what it looks like
and how we put this into place
going from what we're initially using to SCAPI
so I'm sure
all of you guys in here are familiar with SCAPI
but to explain it a little bit better
just in case anyone doesn't know
it's a python framework for understanding packets
so you give it
you give it a block of data
so I've got this here
I called this variable m
and you feed that into an object
and SCAPI
will pull apart the fields
as you've told it
and it will let you access them in a really easy programmatic way
so
one of the things you can do here is packet.show
and so what you're looking at
it was type 45 packet
which if you guys remember
here's the data I'm sending to you
so it automatically understands that
it's a message fragment
it pulled apart the
the payload down here
and it separated that
out for us
however the payload remember
it's a multiple step thing
and so you might need more sequences
or more fragments to make the complete payload
I know for a fact that this one was short
so I'm going to pull it out really quickly
I'm going to do packet.fragmenter
you know what
I can't even remember
my own code
so we're not going to do this
we're just going to show you Sauron
whatever
so we're moving to Sauron
alright
so you're going to see
something similar to this in
because what happened was
in the beautiful mind he put all this together
and he actually has it spit it out
so you have to do zero work
so do you see where it says press enter to quit
that's because right now we're live
and we're going to go ahead and just go live with this
okay because again
you probably want to see it
what's that?
alright let's just go live
then we don't have to remember the code
so
oh wait a minute what is that
so Tim just sent a broadcast message
over Gotenna
so this would go out to anyone
so if you had a Gotenna you'd be able to read
and decrypt this too
but the simple fact is we now have a listener
a packet sniffer
that can listen to all of this and make it happen
now on top of that
can't see it?
I'm going to send another broadcast message
they can't see it there's nothing up there
yeah I know
okay
Uncheit's a biscuit
okay
alright
sorry I can't
good enough
spelling errors are okay
yeah you're not in any of it
oh come on Gotenna
you're not there
first the demo guy's right
okay so why he's
putting that back up
does anyone in here have a Gotenna
if you do send a message
go ahead what's the worst that happens
let's go live
everyone with a Gotenna launch as fast as you can
let's go
Tim does not want this to happen but I do
let's see it
oh if you're using your phone number don't do it
unless you really want some things to happen
so Tim
Tim you're not paired with anything
no I sent a message out
I told you
one more time
sorry
sometimes
things crash
kids these days
so hold on
let me get my Gotenna up
alright so here's what we're going to do
we're going to go ahead and look at a couple things
we're going to launch some Gotennas
we're going to make some things talk
and go live with it
okay
there we go now
so again if you have a Gotenna
please feel free to
send whatever messages you want
and we'll just see what happens randomly
oh you're paired
that one right there
okay
we'll send it
alright so now he's going to send a message
Jared is yours up?
alright
so we got Jay Boone in the room
which by the way
if any of you do software defined radio
like just amazing work
he's just incredible
so
oh my goodness
scientific progress going
maybe too many antennas open
one more shot
and then we're going to move on
yeah
say again
what radio are you using? that one
one more shot
no it's
that's not it
is anyone jamming any of the
MERS channels?
alright one more shot
and then we're going to move on with the talk
alright so he got the message
use the old card
this one's not working
use the old card
we're getting the packets
it's just not working
alright scientific progress
we got more time
go again
we don't
no go
try it again
okay so what winds up happening is
wish we had HDMI
go ahead push it
here we go
so we're going to run off the other radio
so when this is working
which typically it was up until earlier
that's why if anyone is
jamming MERS
please don't
so what'll happen is
it'll actually spit out your message
so let me tell you what you're going to be able to see
who sent the message
who's the message going to
and how large is the message
so
oh wait a minute
oh shoot what is
can you go ahead and pull that up a little bit
it pulled up
there we go so now we're up again
so wait what is
757512
oh a phone number
so we're using a burner phone up here
and the burner phone's phone number is
although it's not quad zeros at the end
which we've modified that out
you get to see
where it came from
who it's going to and what it means
and you see where it says DEFCON
that's the individual name of the individual
who has listed that as their name
so if you said Jeff Wilson
it would say
JW
what we did is made a very long name
that the first initial of each name spelled out DEFCON
but
that's a live demo
right there
you're actually able to see it
so
so
sorry that didn't quite work out the way
but it's a live environment
so the metadata circle
this is like a lame thing that I came up with
to try and explain metadata
so there's like five different things
that are being sent out whenever you transmit packets
who, when, where, how much
and then the actual content
with cryptography
you can kind of get rid of the content
you can hide that and make it so that people can't see what you're saying
the who
that's a little tricky to hide
because at some point my Gotenna has to say to someone else's Gotenna
I'm talking to you
the cryptographic protocols
can compensate for that
but it makes it really tough to program
and it makes
what's supposed to be simple
device really complicated
but that being said
who it's going to
we understand why they have that
who it's coming from we definitely think
that should be encrypted
as far as when, where, and how much
you're not going to get away from transmitting energy
you have to use energy to send a signal
there's no getting out of it
and especially since we're constrained in frequency
we've only got a particular
yeah we got it
we've only got a particular bandwidth
we have to put all of our energy in that tiny narrow channel
so we can get a long range
and that just shows up like a thumb tack
on the waterfall
so everyone's going to know when you transmitted
they're going to know where you transmitted
because they were with you when they caught that waveform
and they're also going to know
how much got transmitted just by the length
so it's understandable that you can't get away from that
you can't get away from those things there
also it's on a mobile device
I'm not particularly sure that mobile devices
are the most secure things ever
I'm not convinced but that's just me
so we did contact Gotenna and we said
hey look we'd like to talk to you guys about
this we think this was maybe perhaps a mistake
in your design
and they did come back very
they were very responsive to us
they were very welcoming of our analysis
and our report and they were thankful for it
and they said right now what we're promising our users
is encryption
anonymity
so they said it's kind of like an envelope
you can look at the inside of the envelope
or you can look at the outside of the envelope
and get to and from but the inside is encrypted
we didn't really study their cryptography protocol very much
because we're not cryptographers
but as far as we can tell they are encrypting it
just to wrap up
so
as we wrap this up we're going to go ahead
and just talk a little bit more about this
and we're only going to have a couple questions
haha
nice I love seeing the Gotenna traffic
that's kicking through here right now
so what we want to be able to tell people is hey
as you go through and do this there's a couple key features
that are going to be safe that we want you to think about
do not use your phone number
why?
well that is just going to be a bad day
there we go
now we got it kicking up
so see to and from
a couple of things that I want you to realize
Gotenna I think is still a great product
if I send an encrypted message to somebody
a couple of things that are going to wind up happening is
that you're going to have issues
those issues are
if you use your phone number
I'm going to see your phone number
if you send
hold on
pull down
do you see what that's
do you see right there where it says location
what's that that just came across
somebody just broadcast their actual Latin line
we can see that if they're using broadcast
even if they're using encrypted
we can see who it came from
who it's going to
and the size of the packet
anyone in here that does targeting
I think you understand what that means
they were very receptive
they gave us a code that we can use
if anyone wants to buy Gotennas
they gave us a discount for Defcon
we do not work for Gotenna
we are not salesmen for anything else
but part of the responsible disclosure was to tell them
so they said hey
thank you
if anyone wants 15% off
use this code and you can buy their product
I'm a big fan of it
but as you can see
and we did go live
we had some recorded video
but we figured live was better
because you guys are a pretty impressive crew
any time if you're a person that designs a protocol
and you're using command channels
be careful with exposing
where you're going to be next
who you're talking to
who you are and where it's going to go
if you're a protestor
if you're a government person
if you're anyone that uses this
realize if I'm a celebrity
and I walk down the street with a protective detail
I have security
if I'm that same celebrity
and I disguise myself
and I sit on the corner of the street
like a homeless person that no one looks at
I now have anonymity
but I no longer have security
just like the celebrity surrounded by a bodyguard detail
doesn't have anonymity
the two are not always the same
security is not anonymity
and anonymity is not security
but each can be used to protect
in certain and individual ways
yeah further work
so we have a lot of work
that's still not done
we haven't found the checksum yet
it's kind of embarrassing
we don't know how the cryptography works
if you're a cryptographer
we're going to be putting this online
in a couple days
so we'd love your input
we haven't done anything with group chat or emergency broadcasts
any of these millions of unknown fields
so we've got a lot of work to do still
so I guess
we've got about five minutes left
some things that we wanted to talk about
is just what worked in this project
if you're new to the security research field
you're coming into this
there's some basic skills that are helpful
the first is know your tools
cut, grep, sort
unique, gnome calculator, gedit
we can have the fancy tools
with the hundred dollar equipment
but if you can't use these basic tools
what uses your equipment
just like Zero was saying earlier on
also know your formats
integers, chars, shorts, floats
hexadecimal, binary, strings
know how to convert between the other
move it around
we're finishing up, we're nearly done
automation
you can do this with some of the tools
D-Spectrum
but it's not going to get you too far
you need automation
so again, in conclusion
we appreciate all your time
if you want to communicate
no human patterns
try before you pry
sometimes you might get that serial port
before you have to solder into something
change one thing at a time
and if nothing else
if you're a new person out there
who's never had a chance to speak
or be in front of a crowd
submit to the Wireless Village
because these guys are amazing
they'll put you out there
and they'll let you do it
and they're just good people
thank you