- Let's go over what are ciphers and keys
in public key cryptography.
And basically a cipher is a set of rules
which can actually be called an algorithm, right?
They're also called algorithms.
And basically there are rules on how to perform encryption,
or decryption of packets, or decryption of emails,
or, you know encryption or decryption of files as well.
Now, there are hundreds of encryptions of algorithms
that actually available out there, right?
And there are likely many more that are proprietary
and used for special purposes, such as, you know,
government and national security.
But some of the common methods that's actually ciphers use
as a whole is the method of substitution.
Another method called polyalphabetic,
and transposition as well, right?
Now, there are also keys,
and a key is a piece of information,
or parameter, that actually specifies
the output of a cryptographic algorithm.
So you actually have a concept of a public
and private key just as we actually mentioned
in the previous lesson.
However, let's actually go over how
that works in practice, right?
So in this screen, I actually have two entities,
or two users.
One is called Ben and the other one is Pete, right?
Typically in examples of cryptography,
you will hear, you know, the word,
or the name, Bob and Alice, right?
So I wanted to be a little bit more creative
and just change names and this is Ben and Pete.
And then you actually may have
an attacker in between, right?
Let's just call that Eve.
And Eve, and you will learn,
you know, what eavesdrop attacks are.
Eve will actually try to eavesdrop
the conversation between Ben and between Pete, right?
There are many different ways
on what you can encrypt traffic between these two entities.
One is by actually using VPN, right?
Things like site-to-site VPN.
You may actually have two different routers,
actually configure for IPv6,
but in this case, it's actually looking
at how Ben can actually send an encrypted email, right?
Specifically using a protocol, or implementation,
called Pretty Good Privacy,
just as we mentioned before, so PGP.
Now Ben will actually have a private,
and a public key.
And also Pete will actually have a private and a public key.
And Ben and Pete will actually change,
or share, their public keys to each other.
That means that for Ben to be able to actually encrypt
an email to Pete, he will actually use his public key
to encrypt that email.
And then Pete will actually use his private key
to decrypt that email, right?
So that's actually the main purpose
of the public and private keys.
Again, you actually keep your private key
all the time with you.
If that key is actually compromised,
you actually have to regenerate your key pair once again
and revoke your keys.
So that's the process of revocations
and you will learn about revocation
once we actually cover digital certificates later
in this course.