Now that we understand how signing works in PDP and this lecture I want to show you how to encrypt messages
and sign them as the sender and how to verify the signature as a receiver and then decrypt the message.
So right here I have Jones computer and let's go ahead and send a message to David.
So as we seem before the first thing you want to do is open up a text editor and we're going to type
the content of our message.
So I'm just going to say this is a secret side message from John to David.
Now like we've seen before I'm going to select all of this.
I'm going to copy it.
I'm going to go to my PDP clipboard and I'm going to click on sign encrypt clipboard with public keys.
Next we want to select the public keys that we want to encrypt the message with.
And like I said I'm sending this message to David.
So I'm going to take him.
You can also take John if you want to be able to decrypt your own message.
And unlike what we did in the previous lecture before clicking on OK I'm going to go to sign message
as if you click on this list you will see a list of all of the private keys that you have on this computer.
So this is John's computer.
And as you can see the only private key that we have is John Wilkes.
So I'm going to select that and I'm going to click OK it's showing a warning about the key.
It's my own key so I trust it.
So I'm going to click.
Yes and then it's going to ask you to enter the passphrase that you selected when you created this key
I'm going to hit.
OK.
And as you can see right here the icon of the clipboard changed to a log which means that now in my
clipboard I have the encrypted message along with the signature.
So I know in my diagrams in here when we were sending the message I said we're going to send a message
with its signature but in reality both the message content and the signature is all going to be one
block of text.
So if I'm back here at my text editor and just paste wherever that is in my clipboard You'll see we'll
just get one block of text that contains the content of the message and the signature.
So as we did before I'm going to go to my email.
I'm going to compose a new message and I'm sending this to David Smith
and I'm going to piece the message along with its signature.
Like I said and I'm going to click on send to send the message now let's go to David's computer refresh
our inbox and click on the new email.
We have the message contents.
So again we're going to select all of it right click copy.
And as you can see right here we can see the log on the PDP upload one click on this and we're going
to click on decrypt verify clipboard so the steps are very very similar to what we did in the previous
lecture.
Now it's going to ask me to enter the passphrase for my own key for David Smith Skip
and as you can see we see the content of the message again very similar to what we've seen in the previous
lecture but at the same time you can see at the bottom in here it's telling us that this message has
been signed with a good signature of John Wick we can also see the key I.D. And the key fingerprint.
So right now we're sure that the person that encrypted this message the sender is actually John week
and it's not someone else that is pretending to be John wake.
Not only that but we're also sure that the contents of this message was not modified as it was transmitted
to us because like I said when data is sent over the Internet or over a lot of methods of communications
it passes through a number of hubs and each one of these hubs could be modified.
Not only that it can also be intercepted by a number of methods.
And when hackers or agencies intercept them they can modify them implant data or remove some data.
Therefore when the signature checks out as we can see in here if it's verified that means that the message
was not modified since it was signed by John's private key.
No can also see that there is a warning say saying the key is not certified with a trusted signature.
This is fine.
You can actually ignore the message.
It's just because the key is not set to be trusted.
But what's really important in here is to see if this is a good signature because like I said if it
says it's a good signature that means that the message was signed by John's private key and it did not
get modified since it got signed by his key.
So right now we have a method to send data anyway so that even if it gets intercepted by any party they
won't be able to read it.
The only person that will be able to read it is the receiver.
Not only that but the receiver will be able to verify that this was sent from the person that they want
the message from.
So they can verify the sender and verified that the message did not get modified as it was being sent.