Now that we understand the theory behind signatures in BGP.
In this lecture, I want to show you how to practically verify the integrity of the message by checking
the signature.
So right here, I'm in John's computer and as you can see, his entry is in bold because we have the
public and the private key for John.
And in here for David, I have the public key of David.
And that's why it's not bold.
It's like all of the other public keys that we have, because as mentioned in the theory lecture, we
need the public key of the sender in order to verify the integrity of the message.
And obviously our own private key to decrypt the message.
Now, right here, I have a message that is sent from David and signed by them using their own private
key and encrypt it for me, for John, using my own public key.
I'm not covering this in this lecture because previously when I showed you how to encrypt messages,
I also covered how to sign them.
As you can see in this flashback right here.
So right now, I have the message.
It's already signed using David's private key and encrypted using my own private key, using John's
private key.
So all I have to do in here is simply copy the message.
And go to my notepad.
Paste the message and we're going to click on Decrypt Verify Notepad.
Now it's going to ask me for my own private key in order to decrypt the message, just like we seen
earlier, because the message is actually encrypted using my public key, using John's public key.
So I'm going to put the passphrase.
And again, as we saw earlier, we can see the message decrypted in here.
But that's not what we're here for.
What we're here for is the signature.
We want to make sure that David is actually the person that sent this message.
And we should be able to do this, because this time, unlike the last time we actually imported David's
public key in Cleopatra.
So all I have to do now is click on the audit log in here.
And as you can see, it's telling us that we have a good signature from David Smith.
This means that whoever sent this message has the private key for David Smith.
Therefore, we can be sure that David Smith is the person that actually sent this message so we can
verify the integrity of the message and we can verify that the sender is actually the sender that they
are claiming to be.
Not only that, but we're also sure that the content of this message was not modified since it was created
or composed by David or by the sender.
Because as mentioned earlier, if the message gets modified, then this signature will not check out,
the verification will fail.
And knowing that the message did not get modified is very, very important because as mentioned earlier,
when data is sent, it passes over a number of points where it can be modified.
It can also be intercepted and modified by hackers or agencies.
Therefore, checking the signature like this is really, really important to make sure that the message
did not get modified since it was created.
You can also see in here that it's saying the key is not certified with a trusted signature.
This is fine.
This is just because the key is not set to be trusted within Cleopatra.
But the main thing is you want to make sure that it's saying that you got a good signature from the
sender, that you're expecting this message to be sent from.
So now, as a result, we are able to send encrypted messages that can only be read by the receiver.
The receiver, on the other hand, can make sure that this message is actually sent from us, and they
can also make sure that the message did not get modified since it was written or created or composed
by us.