Hello and welcome this video titled Introduction to the RSN framework.
And if you're wondering what is RSN, don't worry, I'll explain the acronym
in just a moment.
So let's talk a little bit about keys and how they pertain to Wi-Fi security.
So if you know anything about security, you're probably familiar with
this term key. So the key is a numeric construct.
It's a series of 1s and 0 bits, usually quite long, that is applied against
some data with some algorithm, like for example, an encryption algorithm.
And when you pair the data with this string of bits, call this key and
your encryption algorithm, you're able to encrypt and then using the same
algorithm and key, you can decrypt your data.
But keys are used for a lot more than just encryption and decryption,
or less the most common way that people think of keys.
Now in the world of wireless LANs or Wi-Fi, all security revolves around
keys. If you want to obviously protect your data via encryption and decryption,
you're going to need some keys to do that.
If you want to validate the integrity of the data to ensure it hasn't
been modified or changed in transit, you're going to need some keys to
do that. So it's a complete basis of wireless confidentiality, which is
encryption, the foundation for integrity, and it also stops replay and
impersonation attacks.
So as you can see here, there's several different kinds of keys which
are used for different purposes.
And as we go through this video, I'm going to give you a really quick
introduction to the names of some of these different types of keys.
And then in subsequent videos, we'll talk about how they are derived and
what specifically they're used for.
Now, the derivation and distribution of keys is defined by the RSN.
We're going to say what the RSN is in just a second.
But this thing called the RSN that we're going to look at in the next
slide really dictates things like, all right, how is a key formed?
What's the procedure for creating this string of bits that we're going
to call a key? How long is this key going to be?
What exactly is it going to be used for?
If this key is going to be used as a foundation to build other keys, how
does that process work?
So RSN dictates all of that.
And also, how do we distribute the keys in a secure manner so that some
eavesdropper can't see it while it's being distributed and use it?
So RSN stands for the robust security network.
And this was technically introduced in the 802.11i amendment back in 2004.
So if you remember a little bit about Wi-Fi history, you remember that
when Wi-Fi first came out, the earliest forms of data confidentiality
was called WEP, Wired equivalent privacy.
And that was built right into the 802.11 standard.
But very quickly, it became realized that it was insecure.
So then several years elapsed between WEP and the next thing in order
for them to make Wi-Fi a lot more secure.
And that thing that finally came out, which said, okay, we're redoing
the whole landscape of Wi -Fi security was 802.11i.
So there's a lot of stuff in 802.11i.
And one of the main components of that was the robust security network.
Now, what is RSN?
So RSN is really a framework.
Now remember, in the world of networking and stuff, when we talk about
something being a framework, like the RSN framework, or we'll talk about
something called the EAP framework, we're really talking about like a
blueprint or a scaffolding that describes how something works.
Like what at a high level are the components that are needed to make this
work? How do these components interact?
But a framework many times doesn't go into the nitty-gritty implementation
details. It says, well, we're going to need these processes and these
particular orders and the things that do these are going to have to have
these characteristics.
But we're really going to leave it up to individual manufacturers and
ventures to come up with the specific details of how that stuff works.
So RSN is a framework.
So what does it include?
So it includes things like we talked about how are keys derived and managed.
It talks about cipher suites.
Like when we talk about cipher suites, we're talking about like the specific
algorithms for figuring out how to encrypt and decrypt data.
So for example, a very common cipher suite that you see in the world of
Wi-Fi is AES, CCNP.
That was very first included in the 802.11i robust security network.
How the four-way EAP over land handshake works.
Now, I'm not sure where you're watching this video in the context of anything
else. You may not have heard of that yet, but I will be talking about
what that is. But just at a real quick level, the EAP over land handshake,
it's a four-way handshake.
So it's one, two, three, four.
Four messages are exchanged back and forth between a Wi-Fi client and
the access point that helps derive the final set of keys that the client
and the access point need to encrypt things, decrypt things, manage data
integrity, and so forth.
So it also defines in the remote security network a particular field in
Wi-Fi management frames that actually say, okay, what are my capabilities
as far as Wi-Fi security is concerned?
So if you capture a beacon from an access point and you want to see, okay,
what encryption algorithms is this access point supporting?
What authentication key mechanisms is he supporting?
Then you would look for a particular information element within the beacon
called the robust security network or the RSN information element.
It actually looks like this.
So you can see here, here's a beacon frame and you've got all sorts of
information elements in there such as SSID parameter traffic indication
map. And right there, RSN information.
And without going into the gory details of all the stuff here, you can
see that the 802.11i amendment said, well, we're going to structure this
RSN. For example, you can see here the cipher suite is listed as the advanced
encryption standard.
AES, you can see authentication key management.
It says we can actually do two different ways on this particular wireless
LAN of managing authentication.
We can actually do pre shared key right there and we can do the simultaneous
authentication of equals right here.
So this is actually a wireless LAN that's in transition or offers transition
capabilities of both WPA two and WPA three.
That's why we have two different authentication key management methods.
You can see how can we actually protect some of the group frames like
broadcast and multicast that the access point wants to send to all the
clients? Well, we can use BIP to do that.
And we'll talk more about BIP and subsequent videos.
So the whole structure of this information element and how it's put together
and what information it can contain is defined in the robust security
network. All right.
So within the robust security network, it also talks about how there are
a variety of keys that can be used for different purposes.
And a lot of times keys are derived from other keys.
In other words, a bunch of mechanics will take place to derive a string
of bits, which can be used as sort of like a main master key.
And then you'll feed that main master key into a different formula to
come up with other keys.
And the idea here being that, you know, the overall goal of Wi-Fi security,
obviously, is that we want to keep the attackers out, right?
We, there's actually several goals.
One goal might be we want to keep the malicious actors off of our wireless
LAN entirely. We don't want them to be able to associate at all.
Another goal might be, well, if they're just passively sniffing wireless
traffic, maybe they're not associated, but they're sniffing wireless traffic
with their own antenna, we don't want them to be able to read that traffic.
That's another goal.
Another goal might be, well, we don't want them to be able to inject traffic
spoofing somebody else.
So there's a whole bunch of goals with wireless LAN security and keys
are used to implement those particular objectives.
And so now the goal is, well, if we're going to use keys, we want to make
it as difficult as possible for those malicious actors to figure out what
the key is so they can use it themselves for evil purposes.
And there's really sort of two ways of doing that.
Number one, the longer a key is, the more bits it is, the harder it is
to reverse engineer and crack that key.
So you'll see some protocols derive longer keys than others.
Another sort of method of protecting keys is saying, well, why don't we
go through this long complex process to create one key, but then we won't
use that one key.
We'll actually take that one key, feed it into a completely different
process to create a second key.
So as we derive these keys, the more times you take in deriving one key
to another key to another key, that will also make it more difficult for
malicious actor to reverse engineer that process.
So you'll see that the robust security network as we go along here has
different keys are used for different purposes, such as the encryption
of unit cast frames, the encryption of broadcast and multicast frames
and providing integrity verification of some management frames.
And a big thing about the robust security network is that if, let's say
your client, your laptop, your tablet was to associate to your home network,
and let's say that every time you disconnect it from your home network,
like, you know, you drove away from your house and then you come back
and you reassociate again, let's say every time you disconnect and reassociate,
you always ended up using the exact same security keys.
Well, if the key never changed for you, it would be pretty easy for someone
who's sniffing your traffic for hours or days and just passively collecting
it to maybe be able to reverse engineer that key and then be able to break
the code and look at your data and figure out what it was before it became
encrypted. So one of the things of the robust security network in 802
.11i was that a fresh set of keys should be generated for every client
every time they connect to the access point.
So if your laptop, let's say your your smartphone right now is connected
to your access point on the second floor of your house, you move down
to the first floor where there's another access point and now your tablet
or your smartphone connects to that one.
Now you go back to your office on the second floor and you reconnect to
that access point up there.
Guess what? The set of keys that has just been derived will be completely
different than when you're on the second floor like an hour ago.
So every time you connect to a wireless LAN, a fresh set of keys is derived
and that's what makes it more difficult for the malicious hacker to do
their job. Now without going into sort of the gory details here, this
is just a real sort of introduction into the types of the names of the
different keys that the robust security network uses.
And you can see here that they sort of go in an order.
So at the very top, you've got one called a master session key, which
you can see here that's only used if you're doing WPA enterprise, which
uses 802.1x and a back end authentication server doing radius.
So if you're doing WPA enterprise, the first key that will be derived
is the master session key.
And then from that, another key called the pairwise master key will then
be derived. Now, if you're not doing WPA enterprise, if you're just doing
WPA personal, you're just going to start out with the pairwise master
key. And then from the pairwise master key, you can see there are these
other keys that are subsequently derived from those.
And we're going to talk about what are the sort of formulas used to derive
each of these. What are each of these keys actually used for?
For example, you can see here in the box in the left, all these keys are
used for unit cast traffic.
And for the box on the right, these are keys used for multicast or broadcast
traffic. And we'll talk about all of those.
Now, one more thing I want to talk about before I leave this presentation
is notice that there's a lot of keys, for example, here on the left, that
start out with the word pairwise, like pairwise master key, pairwise transient
key. So what does this word pairwise mean?
So this is actually quite important.
So pairwise simply is talking about how this key is for a pair of devices
only. So for example, your laptop and the access point you're connected
to, that is a pair of devices.
So there is a set of pairwise keys just for you, your laptop and the access
point. If Sally's laptop sitting next to you is connected to that same
access point, she's going to get a different set of pairwise keys.
So this also helps maintain per client isolation.
You see, it wouldn't really be very secure if you and Sally, who are on
the exact same wireless LAN, could actually read each other's traffic.
If you could crank up, you know, wire shark, capture all of Sally's Wi
-Fi frames and clearly see in plain text what she was doing.
But because she's got her own set of pairwise keys, you can't do that.
And she can't read your data.
And so that's what is referring to here.
Each client has its own distinct set of keys.
So thank you so much for watching this brief overview and introduction
to the robust security network and how keys fit into the scheme of things.
I really hope this video was helpful for you.