WEBVTT 00:00.600 --> 00:07.200 Now that we understand how signing works in Pjp and this lecture, I want to show you how to encrypt 00:07.200 --> 00:14.580 messages and sign them as the sender and how to verify the signature as a receiver and then decrypt 00:14.580 --> 00:15.360 the message. 00:16.350 --> 00:21.820 So right here I have John's computer and let's go ahead and send a message to David. 00:21.840 --> 00:28.170 So as we've seen before, the first thing you want to do is open up a text editor and we're going to 00:28.170 --> 00:29.880 type the content of our message. 00:29.880 --> 00:35.910 So I'm just going to say this is a secret side message from John to David. 00:36.450 --> 00:39.620 Now, like we seen before, I'm going to select all of this. 00:39.630 --> 00:41.190 I'm going to copy it. 00:41.610 --> 00:48.690 I'm going to go to my BGP clipboard and I'm going to click on Sign Encrypt Clipboard with public keys. 00:49.260 --> 00:53.420 Next, we want to select the public keys that we want to encrypt the message with. 00:53.430 --> 00:57.410 And like I said, I'm sending this message to David, so I'm going to take him. 00:57.420 --> 01:01.470 You can also take John if you want to be able to decrypt your own message. 01:01.920 --> 01:08.340 And unlike what we did in the previous lecture before clicking on, okay, I'm going to go to sign message. 01:08.340 --> 01:14.640 As if you click on this list, you will see a list of all of the private keys that you have on this 01:14.640 --> 01:15.330 computer. 01:15.330 --> 01:17.130 So this is John's computer. 01:17.130 --> 01:21.210 And as you can see, the only private key that we have is John works. 01:21.210 --> 01:24.330 So I'm going to select that and I'm going to click. 01:24.330 --> 01:25.080 Okay. 01:26.320 --> 01:28.190 It's shown a warning about the key. 01:28.210 --> 01:29.910 It's my own key, so I trust it. 01:29.920 --> 01:30.730 So I'm going to click. 01:30.730 --> 01:31.330 Yes. 01:32.440 --> 01:38.110 And then it's going to ask you to enter the passphrase that you selected when you created this key. 01:39.460 --> 01:40.900 I'm going to hit oak. 01:41.940 --> 01:47.940 And as you can see right here, the icon of the clipboard changed to a lock, which means that now in 01:47.940 --> 01:52.740 my clipboard, I have the encrypted message along with the signature. 01:52.740 --> 01:57.900 So I know in my diagrams in here, when we were sending the message, I said, we're going to send a 01:57.900 --> 01:59.490 message with its signature. 01:59.490 --> 02:06.630 But in reality, both the message content and the signature is all going to be one block of text. 02:06.720 --> 02:13.140 So if I'm back here at my text editor and just paste whatever that is in my clipboard, you'll see. 02:13.140 --> 02:19.500 We'll just get one block of text that contains the content of the message and the signature. 02:20.340 --> 02:27.210 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 02:27.210 --> 02:28.670 this to David Smith. 02:31.120 --> 02:36.700 And I'm going to paste the message along with its signature, like I said, and I'm going to click on 02:36.700 --> 02:38.740 Send to send the message. 02:39.820 --> 02:44.260 Now let's go to David's computer, refresh our inbox. 02:46.310 --> 02:48.440 And click on the new email. 02:48.860 --> 02:50.450 We have the message content. 02:50.450 --> 02:54.590 So again, we're going to select all of it right click copy. 02:54.830 --> 03:01.070 And as you can see right here, we can see the lock on the BGP applet one. 03:01.070 --> 03:05.270 Click on this and we're going to click on Decrypt Verify Clipboard. 03:05.270 --> 03:09.770 So the steps are very, very similar to what we did in the previous lecture. 03:11.170 --> 03:15.340 Now it's going to ask me to enter the passphrase for my own key. 03:15.340 --> 03:16.900 For David Smith's key. 03:20.080 --> 03:24.910 And as you can see, we see the content of the message, again, very similar to what we seen in the 03:24.910 --> 03:26.080 previous lecture. 03:26.200 --> 03:32.740 But at the same time, you can see at the bottom in here, it's telling us that this message has been 03:32.740 --> 03:36.370 signed with a good signature of John Wick. 03:36.760 --> 03:41.530 We can also see the key ID and the key fingerprint. 03:42.540 --> 03:49.680 So right now we're sure that the person that encrypted this message, the sender is actually John Wick 03:49.680 --> 03:53.790 and it's not someone else that is pretending to be John Wick. 03:53.820 --> 04:01.740 Not only that, but we're also sure that the contents of this message was not modified as it was transmitted 04:01.740 --> 04:02.250 to us. 04:02.250 --> 04:08.400 Because, like I said, when data is sent over the Internet or over a lot of methods of communications, 04:08.460 --> 04:13.990 it passes through a number of hubs, and each one of these hubs could be modified. 04:14.010 --> 04:20.790 Not only that, it can also be intercepted by a number of methods, and when hackers or agencies intercept 04:20.790 --> 04:24.930 them, they can modify them, implant data or remove some data. 04:25.440 --> 04:31.920 Therefore, when the signature checks out, as we can see in here, if it's verified, that means that 04:31.920 --> 04:37.950 the message was not modified since it was signed by John's private key. 04:39.330 --> 04:46.180 Now you can also see that there is a warning sign saying the key is not certified with a trusted signature. 04:46.200 --> 04:47.130 This is fine. 04:47.130 --> 04:49.100 You can actually ignore the message. 04:49.110 --> 04:52.610 It's just because the key is not set to be trusted. 04:52.620 --> 04:57.330 But what's really important in here is to see if this is a good signature. 04:57.330 --> 05:04.260 Because like I said, if it says it's a good signature, that means that the message was signed by John's 05:04.260 --> 05:09.870 private key and it did not get modified since it got signed by his key. 05:10.810 --> 05:17.650 So right now we have a method to send data in a way so that even if it gets intercepted by any party, 05:17.650 --> 05:19.330 they won't be able to read it. 05:19.360 --> 05:22.750 The only person that will be able to read it is the receiver. 05:22.780 --> 05:29.140 Not only that, but the receiver will be able to verify that this was sent from the person that they 05:29.140 --> 05:35.980 want the message from so they can verify the sender and verify that the message did not get modified 05:35.980 --> 05:37.900 as it was being sent.