So what we're going to do the rest of this unit is look at 3 particular protocols.
We're going to look at the encrypted key exchange protocol,
we're going to look at SSH for setting up a secure shell,
and we'll look at TLS, which is the most widely used cryptographic protocol today.
That's the protocol that's used every time someone connects to a secure website
using HTTPS.
All these have some things in common.
They all have the goal of authenticating a client and a server.
This could be in either direction or in both directions.
It could be to allow a client to know that they're talking to the right server.
It could be to allow a server to know that they're talking to the right client.
It could be to mutually authenticate both parties.
And they all involve a mix of asymmetric and symmetric techniques.
What I hope you get from seeing the 3 different protocols
is a sense of some of the things that are the same--
that there are techniques that all the protocols have in common at some level,
but there are also differences between the protocols,
the things that led to those decisions and why the protocols have different properties.
We'll start by talking about encrypted key exchange.
