1 00:00:00,130 --> 00:00:06,630 Now, let's have a look at some examples of symmetric encryption in the last lecture, we did talk about 2 00:00:06,630 --> 00:00:13,650 asymmetric encryption and asymmetric encryption has one key, which we used to encrypt the message as 3 00:00:13,650 --> 00:00:15,330 well as decrypt the message. 4 00:00:15,570 --> 00:00:18,210 And that key is known as the security. 5 00:00:19,440 --> 00:00:28,290 So the first example of symmetric encryption is to fish algorithm, not to fish algorithm has 128 bits 6 00:00:28,290 --> 00:00:29,310 of blogsite. 7 00:00:29,640 --> 00:00:31,290 Now, what do I mean by block? 8 00:00:31,290 --> 00:00:42,450 Size is at a time 128 bits of data will get encrypted by using a key off 256 bits. 9 00:00:43,230 --> 00:00:43,670 All right. 10 00:00:43,680 --> 00:00:49,260 Now, you must have a question how 128 and 256 keys work together. 11 00:00:49,480 --> 00:00:51,040 It's twice the value. 12 00:00:51,300 --> 00:00:58,140 So the algorithm has such steps, which reduces the key size, then manipulates the input and then finally 13 00:00:58,140 --> 00:00:59,250 encrypted document. 14 00:00:59,880 --> 00:01:05,100 If we dive deep into the algorithms of each and every example, you will get confused. 15 00:01:05,850 --> 00:01:14,280 So what we are trying to tell you here is at a time 128 bits of data will get encrypted in one block 16 00:01:14,610 --> 00:01:18,690 and using a key of two hundred and fifty six bits. 17 00:01:19,530 --> 00:01:26,370 Similarly, the next standard is data encryption standard, which was developed by the National Institute 18 00:01:26,370 --> 00:01:28,080 of Standards and Technology. 19 00:01:28,530 --> 00:01:32,480 This is very old standard and it is very basic standard. 20 00:01:32,790 --> 00:01:37,850 When the researchers had invented because they thought that it is not unbreakable. 21 00:01:38,340 --> 00:01:38,640 It is. 22 00:01:38,640 --> 00:01:39,620 It is unbreakable. 23 00:01:39,810 --> 00:01:46,610 But some researchers prove that it is breakable and that is why they developed the advance standard. 24 00:01:47,550 --> 00:01:55,590 So for data encryption standard at a time only 64 bits of data can be encrypted and the key size is 25 00:01:55,680 --> 00:01:57,180 fifty six bits. 26 00:01:58,410 --> 00:02:08,190 So as I said, as soon as researchers, you know, they proved that this is not secure and can be attacked, 27 00:02:08,580 --> 00:02:11,340 they developed the advanced encryption standard. 28 00:02:11,710 --> 00:02:12,570 I'm sorry, here. 29 00:02:12,570 --> 00:02:15,330 It must be 86 now. 30 00:02:15,330 --> 00:02:18,990 Eight years has three different versions in place. 31 00:02:18,990 --> 00:02:23,570 So iOS has three different origins. 32 00:02:24,180 --> 00:02:30,650 So the first version has 128 bits of block size and 128 bits of key size. 33 00:02:31,230 --> 00:02:39,360 The second version has 128 bits of block size and 192 bits of key size, and a third version has 128 34 00:02:39,360 --> 00:02:42,590 bits of block size and 256 bits of key size. 35 00:02:43,020 --> 00:02:46,380 So more the key size here, more the key size. 36 00:02:46,530 --> 00:02:48,150 Higher is the security. 37 00:02:48,600 --> 00:02:51,780 But again, time consumption will also increase. 38 00:02:52,050 --> 00:02:57,600 So it depends upon different organizations and programs which encryption they should use. 39 00:02:57,870 --> 00:03:05,070 But nowadays, almost every encryption standard uses the advanced encryption scheme, which is very 40 00:03:05,070 --> 00:03:05,670 helpful. 41 00:03:07,620 --> 00:03:13,050 The next example of symmetric encryption is reversed. 42 00:03:13,050 --> 00:03:23,340 Saiful are C4, which which was very which was invented long ago by one of the scientists and he contributed 43 00:03:23,340 --> 00:03:26,280 to an asymmetric encryption as well. 44 00:03:26,910 --> 00:03:31,310 So Odyssey four has a variable and it's a stream cipher. 45 00:03:31,710 --> 00:03:38,990 We have seen the difference between a stream cipher and a block, so variable length of stream cipher 46 00:03:39,060 --> 00:03:42,530 in which the data input is in the form of stream. 47 00:03:42,540 --> 00:03:50,490 It's a continuous stream of data input and the key size can be 64 bits or 128 bits. 48 00:03:51,330 --> 00:03:56,250 Similarly, Odyssey five Volgin was there are different types of block. 49 00:03:56,250 --> 00:04:02,340 Now RC five starts with a block, but Odyssey four is streamside four. 50 00:04:02,910 --> 00:04:04,860 And the key again is variable. 51 00:04:04,860 --> 00:04:07,110 It can be zero to 255 bits. 52 00:04:07,420 --> 00:04:14,670 And finally, Odyssey's six has 16, 32, 64 bits of block size and zero to two. 53 00:04:14,710 --> 00:04:18,100 Now, what's the difference between these two here? 54 00:04:18,120 --> 00:04:19,840 What is the difference there? 55 00:04:20,250 --> 00:04:25,680 Here, only two bit registers were used while performing the operations. 56 00:04:25,680 --> 00:04:30,840 But here, Forbert registers are used for its advanced version of Odyssey five. 57 00:04:31,290 --> 00:04:36,690 Here in BIJA, multiplication was not done, whereas here integer multiplication is performed. 58 00:04:37,140 --> 00:04:45,780 So you can see that Odyssey six is much advanced version of Odyssey five, not algorithms of all these 59 00:04:45,780 --> 00:04:48,630 encryptions are very difficult to understand. 60 00:04:48,960 --> 00:04:51,660 That is why we haven't included the lectures. 61 00:04:52,170 --> 00:04:56,040 So I tell you how exactly these encryption algorithms work. 62 00:04:56,430 --> 00:05:03,090 If we do so, if we plan to do a course on cryptography, will surely include everything in detail. 63 00:05:03,090 --> 00:05:09,310 But for timing, we are not going to dive deep into how exactly these numbers play. 64 00:05:10,320 --> 00:05:15,660 So if you if you have any exams or interviews, you have to make sure that you have to remember these 65 00:05:15,840 --> 00:05:17,340 numbers right here. 66 00:05:18,680 --> 00:05:25,280 So now how what is the main drawback of symmetric encryption? 67 00:05:25,640 --> 00:05:30,410 Well, according to the definition, symmetric encryption has only one key. 68 00:05:30,860 --> 00:05:35,030 And suppose we have Bob here and we have Alice. 69 00:05:35,850 --> 00:05:39,770 So how exactly are you going to share the key to Bob? 70 00:05:39,980 --> 00:05:43,430 And I mean, how exactly are you going to share the same key? 71 00:05:43,430 --> 00:05:48,380 Because even if the attacker gets to know the key, he gets to know everything. 72 00:05:48,680 --> 00:05:54,700 So secure sharing of keys is the drawback of asymmetric encryption. 73 00:05:55,040 --> 00:06:02,210 So how exactly will Bob share the key which he used to decode, encrypt the message so that Alice can 74 00:06:02,210 --> 00:06:02,860 decrypt? 75 00:06:03,260 --> 00:06:08,300 Now, some of you may say that we can again encrypt the key, but again, for that encryption, you 76 00:06:08,300 --> 00:06:09,650 will also have one key. 77 00:06:10,100 --> 00:06:17,510 So this process is very tedious and that is why there is one algorithm, Diffie Helmond Key Exchange 78 00:06:17,510 --> 00:06:26,000 algorithm, which was founded out by two people, outstanding brains that overlap the algorithm, which 79 00:06:26,000 --> 00:06:28,840 we will be seeing in later part of this code. 80 00:06:29,540 --> 00:06:35,420 So that that algorithm actually gives us a V in order to share a security. 81 00:06:35,780 --> 00:06:40,200 I will be showing you true graphics, how you actually can achieve that. 82 00:06:40,850 --> 00:06:41,320 All right. 83 00:06:41,540 --> 00:06:48,260 In the next lecture, we will be talking about asymmetric encryption where we will be having a look 84 00:06:48,920 --> 00:06:52,580 versus asymmetric and asymmetric encryption. 85 00:06:52,850 --> 00:06:53,350 All right. 86 00:06:53,480 --> 00:06:54,480 Stay tuned. 87 00:06:54,500 --> 00:06:55,760 Keep moving forward. 88 00:06:56,030 --> 00:06:58,400 I will see you in the next lecture.