1 00:00:00,930 --> 00:00:06,900 Now before we wrap up this section I want to spend one more lecture talking about another method to 2 00:00:06,900 --> 00:00:10,810 exchange keys between the sender and the receiver. 3 00:00:10,860 --> 00:00:16,980 So as we learned we can use PDP in order to encrypt the message and make sure that this message will 4 00:00:17,010 --> 00:00:23,350 only be readable by the receiver by encrypting the message with the receiver's public key. 5 00:00:23,880 --> 00:00:29,730 Therefore for this to work for example if David wanted to send a message to John he would have had to 6 00:00:29,730 --> 00:00:34,340 get John's public key then same goes for John. 7 00:00:34,340 --> 00:00:40,800 If John wanted to send something to David he would have had to get David's public key and to exchange 8 00:00:40,800 --> 00:00:42,960 the keys in the previous lectures. 9 00:00:42,960 --> 00:00:47,940 We used email to send the keys from one person to another. 10 00:00:47,940 --> 00:00:50,860 Now we can use any method of communication. 11 00:00:51,000 --> 00:00:57,150 And like I said sometimes if you're using a market or if you're on a forum you might even see the user 12 00:00:57,300 --> 00:01:02,790 including the public key in their signature or in their profile page. 13 00:01:02,790 --> 00:01:07,850 That way you can use that key to encrypt messages and send them to that user. 14 00:01:08,100 --> 00:01:14,230 And you'll be sure that the only person that will be able to read this message is the user. 15 00:01:14,310 --> 00:01:21,840 Now there is another way of sharing the keys which I want to cover in this lecture and that way relies 16 00:01:21,930 --> 00:01:29,970 on using key servers so you can think of this as a computer that's accessible on the Internet or on 17 00:01:29,970 --> 00:01:30,980 the darknet. 18 00:01:31,020 --> 00:01:38,850 It contains a number of keys and then for example if David wanted to share his public key with John 19 00:01:38,910 --> 00:01:44,790 or with anyone else they can upload their key to the server. 20 00:01:44,790 --> 00:01:48,930 Same goes for John if he wanted to share his public key with others. 21 00:01:48,990 --> 00:01:52,220 He can upload his key to the server as well. 22 00:01:53,370 --> 00:02:00,540 And then if David wanted to communicate with John he won't need to ask John for the public key directly. 23 00:02:00,540 --> 00:02:04,960 And John won't need to communicate with David directly and send him the key. 24 00:02:05,460 --> 00:02:11,880 All David has to do is query the server the key server that is accessible like I said on the darknet 25 00:02:11,970 --> 00:02:16,580 or on the internet and download John's public key. 26 00:02:16,590 --> 00:02:20,040 Same goes for John if you wanted to get David's public key. 27 00:02:20,100 --> 00:02:24,450 He can query the server download David's key and that way. 28 00:02:24,450 --> 00:02:32,040 Both David and John have each other's public keys and therefore they can start communicating and encrypted 29 00:02:32,040 --> 00:02:37,010 messages to each other using each other's public keys. 30 00:02:37,050 --> 00:02:42,810 The only thing that you can to keep in mind when doing this is when you upload your key to this public 31 00:02:42,810 --> 00:02:46,720 server anybody can get your public key. 32 00:02:46,740 --> 00:02:50,960 Now like I said the public key cannot be used to decrypt your messages. 33 00:02:51,330 --> 00:02:56,370 But as we've seen before there is an identity tied up to the key. 34 00:02:56,370 --> 00:03:03,200 Now we used fake information but if you're using real information the name will be visible on that key. 35 00:03:03,630 --> 00:03:10,770 And the email associated with that key again like we seen before when we create a key which we set an 36 00:03:10,830 --> 00:03:12,600 email address with that key. 37 00:03:12,870 --> 00:03:16,020 So that email will also be publicly available. 38 00:03:16,350 --> 00:03:24,330 So if you don't want to make this information available then do not upload your keys to these key servers. 39 00:03:24,330 --> 00:03:31,380 Also if the key is associated with other keys or part of a chain of trust these keys will also become 40 00:03:31,410 --> 00:03:34,710 available along with the information tied up to them. 41 00:03:34,950 --> 00:03:42,210 So any contact associated with the key will also become available and public once you upload that key 42 00:03:42,210 --> 00:03:43,560 to the key server. 43 00:03:43,560 --> 00:03:49,170 So again if you don't want this information to be public then do not upload your key to the key server 44 00:03:49,380 --> 00:03:54,200 and just send it directly to the people that you want to share your public key with. 45 00:03:54,210 --> 00:04:01,260 But like I said the main idea remains sound sharing the public key does not compromise the encryption 46 00:04:01,650 --> 00:04:05,250 the public key cannot be used to decrypt the messages. 47 00:04:05,250 --> 00:04:07,310 It can only be used to encrypt them. 48 00:04:07,620 --> 00:04:08,900 Hence the name public. 49 00:04:09,000 --> 00:04:14,100 And that's why we can actually share it with anyone we want and we can just make it publicly available 50 00:04:15,450 --> 00:04:15,860 now. 51 00:04:15,890 --> 00:04:17,090 Let's see how we can do this. 52 00:04:17,150 --> 00:04:23,660 So first of all I'm going to go to John's computer right here and let's say that I want to make my private 53 00:04:23,660 --> 00:04:29,320 key so this key right here available and I want to upload it to a key server. 54 00:04:29,430 --> 00:04:34,450 Now before uploading it to a key server I need to enable this feature and to do that. 55 00:04:34,460 --> 00:04:42,320 We're going to go to edit preferences and in here when it says publish keys too I'm going to click on 56 00:04:42,320 --> 00:04:46,340 the drop down menu and select the server right here. 57 00:04:46,340 --> 00:04:48,880 Now as you can see this is an online service. 58 00:04:48,920 --> 00:04:55,650 Therefore whoever is going to download this key needs to be connected to the TOR network. 59 00:04:55,670 --> 00:05:02,360 Now I'm going to close this and the next thing that I'm going to do is upload this key to the key server. 60 00:05:02,540 --> 00:05:07,790 So to do that we're going to go to remote and sync and publish keys. 61 00:05:07,910 --> 00:05:12,980 This is telling us that one key is selected and it's going to be synchronized and uploaded to the key 62 00:05:12,980 --> 00:05:15,160 server that we selected. 63 00:05:15,230 --> 00:05:23,330 We're going to click on sync and this will upload my key to the key server that we selected. 64 00:05:23,360 --> 00:05:26,970 Now anyone who wants to communicate with me will join week. 65 00:05:27,080 --> 00:05:36,080 They can query this key server and find my public key and use that to encrypt messages for me. 66 00:05:36,080 --> 00:05:40,030 So in our example it's David that wants to communicate with John. 67 00:05:40,160 --> 00:05:47,480 We have his computer right here and all he needs to do is open his passwords and keys from the utilities. 68 00:05:47,480 --> 00:05:56,700 As we've seen before and he is going to first select the G and you PGE keys go to remote and click on 69 00:05:56,700 --> 00:05:58,350 find the remote keys. 70 00:05:58,350 --> 00:06:05,850 So these are the steps that you need to use if you want to pull a key from a key server when you click 71 00:06:05,850 --> 00:06:06,290 on this. 72 00:06:06,300 --> 00:06:12,270 You'll get a search box as you can see in here which you can use to search for your contact. 73 00:06:12,300 --> 00:06:17,490 You can search using the name associated with the key as we know that's John wake. 74 00:06:17,520 --> 00:06:27,090 You can also use the e-mail or the I.D. I'm just going to use the email which is G N C K 7 at a blue 75 00:06:27,090 --> 00:06:36,800 dot in and I'm going to click on Search now as you can see I have the result right here. 76 00:06:36,800 --> 00:06:43,430 Now you can right click and look up the properties of this contact and you can see this is for a person 77 00:06:43,430 --> 00:06:44,660 named John wake. 78 00:06:44,690 --> 00:06:46,180 You can see the e-mail. 79 00:06:46,310 --> 00:06:48,080 You can see the key I.D.. 80 00:06:48,500 --> 00:06:54,350 And if we click on details you'll also be able to see the key fingerprint. 81 00:06:54,350 --> 00:07:02,450 Now ideally you'd want to confirm the key I.D. and the fingerprint with your contact before adding this 82 00:07:02,450 --> 00:07:08,870 key because as we seen anyone can publish a key to the key server and claim to be anybody. 83 00:07:08,870 --> 00:07:14,640 So we're not sure that this John Wick is actually the John Wick that we need to communicate with. 84 00:07:14,690 --> 00:07:21,110 Therefore you should communicate with your contact use in another method of communication for example 85 00:07:21,110 --> 00:07:25,910 by e-mail by phone or by a text message and confirmed the fingerprint. 86 00:07:25,910 --> 00:07:32,030 And the idea that you're about to add to make sure that this is the correct fingerprint and the correct 87 00:07:32,120 --> 00:07:39,880 I.D. for the key that you want to add now obviously John can get this information again by going to 88 00:07:39,880 --> 00:07:45,610 his passwords and keys right click his own key click on properties and he can get his own fingerprint 89 00:07:45,850 --> 00:07:50,270 and use that to help you confirm that this is the right contact. 90 00:07:50,500 --> 00:07:57,280 Once you're sure this is the right contact you can click it in here and click on import to add to your 91 00:07:57,280 --> 00:08:06,670 keys and as you can see it got added in here into my keyring and then as we've seen before you can start 92 00:08:06,670 --> 00:08:13,540 typing messages and encrypt them from the applet in here or encrypt files by right clicking the files 93 00:08:13,570 --> 00:08:15,840 and encrypting them. 94 00:08:16,020 --> 00:08:21,810 So basically I just wanted to show you another method of key exchange how you can upload a key to a 95 00:08:21,810 --> 00:08:29,130 key server and how your contact can download it or how you can download a key from the key server. 96 00:08:29,130 --> 00:08:35,610 Now keep in mind when you upload a key to the key server it might not become immediately available. 97 00:08:36,000 --> 00:08:44,340 I actually posed the video and resumed recording after several hours after uploading the John Key because 98 00:08:44,340 --> 00:08:47,980 usually there are more than just one key server. 99 00:08:48,030 --> 00:08:53,520 So when you upload your key to one of the servers it actually takes some time for the key to be shared 100 00:08:53,520 --> 00:08:54,850 with all of the servers. 101 00:08:54,930 --> 00:09:02,190 And to become available for everybody to download so if you uploaded a key and your contact tried to 102 00:09:02,190 --> 00:09:06,200 download it within the same hour and couldn't find it then that's fine. 103 00:09:06,210 --> 00:09:10,920 Just tell them to wait for a few hours and then they should be able to download it.