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Now that we understand how signing works in PDP and this lecture I want to show you how to encrypt messages

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and sign them as the sender and how to verify the signature as a receiver and then decrypt the message.

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So right here I have Jones computer and let's go ahead and send a message to David.

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So as we seem before the first thing you want to do is open up a text editor and we're going to type

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the content of our message.

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So I'm just going to say this is a secret side message from John to David.

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Now like we've seen before I'm going to select all of this.

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I'm going to copy it.

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I'm going to go to my PDP clipboard and I'm going to click on sign encrypt clipboard with public keys.

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Next we want to select the public keys that we want to encrypt the message with.

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And like I said I'm sending this message to David.

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So I'm going to take him.

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You can also take John if you want to be able to decrypt your own message.

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And unlike what we did in the previous lecture before clicking on OK I'm going to go to sign message

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as if you click on this list you will see a list of all of the private keys that you have on this computer.

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So this is John's computer.

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And as you can see the only private key that we have is John Wilkes.

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So I'm going to select that and I'm going to click OK it's showing a warning about the key.

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It's my own key so I trust it.

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So I'm going to click.

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Yes and then it's going to ask you to enter the passphrase that you selected when you created this key

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I'm going to hit.

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OK.

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And as you can see right here the icon of the clipboard changed to a log which means that now in my

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clipboard I have the encrypted message along with the signature.

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So I know in my diagrams in here when we were sending the message I said we're going to send a message

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with its signature but in reality both the message content and the signature is all going to be one

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block of text.

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So if I'm back here at my text editor and just paste wherever that is in my clipboard You'll see we'll

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just get one block of text that contains the content of the message and the signature.

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So as we did before I'm going to go to my email.

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I'm going to compose a new message and I'm sending this to David Smith

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and I'm going to piece the message along with its signature.

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Like I said and I'm going to click on send to send the message now let's go to David's computer refresh

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our inbox and click on the new email.

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We have the message contents.

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So again we're going to select all of it right click copy.

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And as you can see right here we can see the log on the PDP upload one click on this and we're going

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to click on decrypt verify clipboard so the steps are very very similar to what we did in the previous

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lecture.

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Now it's going to ask me to enter the passphrase for my own key for David Smith Skip

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and as you can see we see the content of the message again very similar to what we've seen in the previous

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lecture but at the same time you can see at the bottom in here it's telling us that this message has

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been signed with a good signature of John Wick we can also see the key I.D. And the key fingerprint.

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So right now we're sure that the person that encrypted this message the sender is actually John week

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and it's not someone else that is pretending to be John wake.

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Not only that but we're also sure that the contents of this message was not modified as it was transmitted

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to us because like I said when data is sent over the Internet or over a lot of methods of communications

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it passes through a number of hubs and each one of these hubs could be modified.

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Not only that it can also be intercepted by a number of methods.

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And when hackers or agencies intercept them they can modify them implant data or remove some data.

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Therefore when the signature checks out as we can see in here if it's verified that means that the message

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was not modified since it was signed by John's private key.

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No can also see that there is a warning say saying the key is not certified with a trusted signature.

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This is fine.

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You can actually ignore the message.

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It's just because the key is not set to be trusted.

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But what's really important in here is to see if this is a good signature because like I said if it

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says it's a good signature that means that the message was signed by John's private key and it did not

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get modified since it got signed by his key.

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So right now we have a method to send data anyway so that even if it gets intercepted by any party they

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won't be able to read it.

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The only person that will be able to read it is the receiver.

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Not only that but the receiver will be able to verify that this was sent from the person that they want

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the message from.

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So they can verify the sender and verified that the message did not get modified as it was being sent.