1 00:00:01,280 --> 00:00:07,800 Well, in today's world, you cannot sign the document then, you know, you send it to your postman 2 00:00:07,820 --> 00:00:11,330 and the postman will transfer overseas, you don't do that anymore. 3 00:00:11,360 --> 00:00:12,780 It will take a lot of time. 4 00:00:13,560 --> 00:00:17,420 That's why the concept of digital signatures is introduced. 5 00:00:17,720 --> 00:00:21,560 And cryptography is again to the rescue of security. 6 00:00:22,100 --> 00:00:31,130 So digital signatures are basically it's a kind of authentication that, you know, tells the receiver 7 00:00:31,130 --> 00:00:37,670 that, OK, the sender has signed and he is he's agreeing with what is present in the document. 8 00:00:38,960 --> 00:00:44,030 So it helps in a secure transmission of information. 9 00:00:44,030 --> 00:00:52,940 And it validates and instead of a real signature, a digital signature is also a proof that the document 10 00:00:52,940 --> 00:00:54,620 is a legitimate document. 11 00:00:55,730 --> 00:00:58,890 Every digital signature works on Piqué. 12 00:00:59,090 --> 00:01:01,480 That is the public key infrastructure. 13 00:01:02,180 --> 00:01:10,310 Now, public key infrastructure is a unique set of requirements that help in the working of digital 14 00:01:10,310 --> 00:01:11,110 signatures. 15 00:01:11,420 --> 00:01:19,640 So it's basically a framework of cryptography that employs many such things like digital signatures, 16 00:01:19,640 --> 00:01:23,470 private keys, public key certificate, the authority. 17 00:01:23,870 --> 00:01:25,760 Well, what is certificate authority? 18 00:01:26,990 --> 00:01:35,780 So Certificate Authority is a third party organization that have been widely accepted as reliable for 19 00:01:35,780 --> 00:01:39,340 ensuring security in the same way. 20 00:01:39,350 --> 00:01:40,460 Let's consider this. 21 00:01:40,790 --> 00:01:48,590 All of you might have heard of the University of Harvard or Stanford or M.I.T. or Oxford game, but 22 00:01:48,770 --> 00:01:51,000 these are some of the known institutes. 23 00:01:51,380 --> 00:01:58,760 Now, if there is a YouTube channel of a person who is, you know, who's teaching some things which 24 00:01:58,760 --> 00:02:05,750 are taught in the scene, the exactly same fee in the Harvard University, and he says that I'll give 25 00:02:05,750 --> 00:02:06,920 you a certificate. 26 00:02:06,920 --> 00:02:09,620 And, you know, this is a valid certificate. 27 00:02:09,620 --> 00:02:12,560 You can show this certificate and you'll get a job. 28 00:02:13,310 --> 00:02:19,230 And let's say there's a guy who already has a certificate from the Harvard University, OK? 29 00:02:19,280 --> 00:02:25,670 He doesn't have the certificate from this guy who's teaching on YouTube, but he has the university 30 00:02:25,670 --> 00:02:26,450 from Harvard. 31 00:02:26,450 --> 00:02:27,720 He has that degree. 32 00:02:28,550 --> 00:02:36,260 So what do you think people will trust which degree the most, even though both the persons of same 33 00:02:36,260 --> 00:02:42,770 knowledge, would the people have some knowledge of which degree is more trusted, but obviously the 34 00:02:42,770 --> 00:02:50,690 one from Harvard, because they are established universities, which have been widely accepted by many 35 00:02:50,690 --> 00:02:58,610 students in giving this certificate in the same the certificate authorities are entities or organizations 36 00:02:59,180 --> 00:03:03,940 which have been widely accepted as the status quo. 37 00:03:03,950 --> 00:03:11,630 For example, if Howard says this guy is a legitimate engineer, then that guy is a legitimate engineer. 38 00:03:12,020 --> 00:03:18,470 In the same way, if certificate authorities give certificate to Alice, then she is alleged to have 39 00:03:18,470 --> 00:03:20,480 verified her identity. 40 00:03:20,480 --> 00:03:28,010 And no one is going to doubt that because these certificate authorities are very highly functioning 41 00:03:28,010 --> 00:03:28,880 organizations. 42 00:03:28,880 --> 00:03:30,980 They have detailed processes. 43 00:03:31,050 --> 00:03:34,640 Then there is no wrongdoing in those organizations. 44 00:03:34,640 --> 00:03:38,000 No process is just a simple process. 45 00:03:38,000 --> 00:03:47,090 They all have a detailed framework and many operations and processes take place to make certificate 46 00:03:47,090 --> 00:03:48,650 authorities work. 47 00:03:49,730 --> 00:03:58,160 So it is a combination of all such things which makes the working of digital signatures possible. 48 00:03:58,580 --> 00:04:03,980 So you can consider digital signatures as actual signatures just sent over the email. 49 00:04:04,020 --> 00:04:10,790 So instead of you signing the document and then posting it to overseas, you have to just attach your 50 00:04:10,790 --> 00:04:11,790 digital signature. 51 00:04:13,040 --> 00:04:19,460 Now, the next obvious question in mind would be, well, what is a digital signature? 52 00:04:19,460 --> 00:04:26,120 What exactly does it look like or how do I see a document has a digital signature? 53 00:04:27,080 --> 00:04:30,350 Then obviously I have a new lecture on that. 54 00:04:30,710 --> 00:04:37,520 So without wasting any time in the next lecture, will straight talk about will have a good talk about 55 00:04:37,520 --> 00:04:40,310 the working of digital signatures. 56 00:04:40,820 --> 00:04:48,920 So and it's a warning for you that if you have forgot about if you have forgotten about public encryption, 57 00:04:49,460 --> 00:04:56,300 which is asymmetric encryption and harshing, I would request you to please revise those topics because 58 00:04:56,690 --> 00:05:00,590 digital signatures do make use of asymmetric encryption. 59 00:05:00,980 --> 00:05:02,000 And has. 60 00:05:02,720 --> 00:05:03,260 All right. 61 00:05:03,560 --> 00:05:07,490 In the next lecture, we'll see the working of digital signatures.