1 00:00:01,110 --> 00:00:08,580 All right, let us talk about the metric encryption, although I have told you about symmetric encryption 2 00:00:08,580 --> 00:00:13,020 in one of the previous lectures, but it was just awful. 3 00:00:13,710 --> 00:00:15,630 So what is the symmetric encryption? 4 00:00:15,660 --> 00:00:23,250 Well, from this name, symmetric asymmetric encryption uses the same key to encrypt and decrypt the 5 00:00:23,250 --> 00:00:23,740 message. 6 00:00:24,090 --> 00:00:32,100 So the key that you use to basically generate the plain text to generally decipher text from plain text, 7 00:00:32,310 --> 00:00:37,220 the same key you use to generate the plain text from ciphertext. 8 00:00:37,230 --> 00:00:45,480 So first you generate ciphertext from plaintext, and while decrypting you generate the plain text from 9 00:00:45,480 --> 00:00:46,290 ciphertext. 10 00:00:48,260 --> 00:00:55,340 So basically, symmetric encryption uses a mathematical algorithm, as I said, cryptography is all 11 00:00:55,340 --> 00:01:02,800 about mathematics, it's all about prime numbers, modular arithmetic than a pseudo random numbers, 12 00:01:02,810 --> 00:01:04,510 it's all about mathematics. 13 00:01:04,910 --> 00:01:12,390 So it uses a mathematical algorithm to encrypt and then decrypt the data using a single key. 14 00:01:12,410 --> 00:01:17,960 So what you have to remember when you are asked about symmetric encryption is you have to remember a 15 00:01:17,960 --> 00:01:18,860 single key. 16 00:01:19,790 --> 00:01:26,160 It's a two logarithm, because first you encrypt and then you decrypt. 17 00:01:26,180 --> 00:01:30,340 So first you encrypt, then you decrypt. 18 00:01:30,350 --> 00:01:33,200 That is why it's known as a Dovi algorithm. 19 00:01:34,190 --> 00:01:40,890 It is also referred to as private key encryption or secure key encryption. 20 00:01:41,660 --> 00:01:42,260 Now, why? 21 00:01:42,260 --> 00:01:44,810 It is referred to as private key encryption. 22 00:01:46,070 --> 00:01:51,200 The simple answer here is you have only one key, right? 23 00:01:51,440 --> 00:01:53,900 You have only one key here. 24 00:01:53,900 --> 00:01:57,140 And that key is supposed to be kept private. 25 00:01:57,620 --> 00:02:05,360 As I said, if if you're communicating with the person, that person should also has should also have 26 00:02:05,360 --> 00:02:06,200 the same key. 27 00:02:06,200 --> 00:02:13,180 Because if you're going to unlock a message or unlock a box with one key and if you are using symmetric 28 00:02:13,190 --> 00:02:20,240 encryption, then that person should also have a copy of the same exact same key. 29 00:02:22,220 --> 00:02:31,480 So in that case, if you are traveling or as I as I gave the example of a house and your wife, so those 30 00:02:31,520 --> 00:02:38,450 I give the example in the context of asymmetric encryption because I just wanted you to let me tell 31 00:02:38,450 --> 00:02:42,590 you that if you're unlocking with one key and then you can lock with another key. 32 00:02:42,980 --> 00:02:47,000 But actually that example was off symmetric encryption. 33 00:02:47,000 --> 00:02:49,970 Only the context was different because why? 34 00:02:49,970 --> 00:02:51,380 It is a symmetric encryption. 35 00:02:51,390 --> 00:02:57,410 If you're locking your house with one key, then your wife should also or your wife, your husband should 36 00:02:57,410 --> 00:03:01,520 also have the same copy to unlock the lock. 37 00:03:01,850 --> 00:03:02,400 Right. 38 00:03:03,050 --> 00:03:06,670 So the context, the context was asymmetric encryption. 39 00:03:07,010 --> 00:03:10,820 Now I'm using the same example for asymmetric encryption. 40 00:03:11,870 --> 00:03:13,700 So why does private key? 41 00:03:13,700 --> 00:03:18,430 Because we have seen asymmetric encryption has two types of keys. 42 00:03:18,650 --> 00:03:22,490 Zimet public and private private keys. 43 00:03:22,490 --> 00:03:28,430 The key that you keep to yourself and which you use to encrypt or decrypt the messages and public key 44 00:03:28,430 --> 00:03:30,200 can be of public knowledge. 45 00:03:30,200 --> 00:03:31,290 Anyone can know it. 46 00:03:31,790 --> 00:03:35,550 So do you want the key of your house with everyone? 47 00:03:35,660 --> 00:03:37,910 Do you want everyone to have access to your house? 48 00:03:38,330 --> 00:03:38,940 Well, no. 49 00:03:39,380 --> 00:03:45,590 That is why this key is supposed to be kept private between the communicating parties and hence it is 50 00:03:45,590 --> 00:03:47,930 known as a private key encryption. 51 00:03:48,710 --> 00:03:52,030 Well, again, private and secure are synonymous. 52 00:03:52,070 --> 00:03:54,830 It's also known as a secure key encryption. 53 00:03:55,250 --> 00:04:02,090 So if anyone asks you, hey, please explain me about security encryption, you shouldn't confuse the 54 00:04:02,330 --> 00:04:05,540 security, security, security. 55 00:04:05,940 --> 00:04:06,590 Right. 56 00:04:07,100 --> 00:04:08,810 Symmetric encryption. 57 00:04:11,090 --> 00:04:18,800 So let us have a look at the examples of asymmetric encryption blobfish algorithm to fish algorithm. 58 00:04:19,190 --> 00:04:27,740 Advanced encryption standard data encryption standard reversed Saiful four, five and six versions are 59 00:04:27,740 --> 00:04:30,740 a few examples of symmetric encryption. 60 00:04:31,580 --> 00:04:36,950 Well, one of the drawbacks of asymmetric encryption is a secure sharing of keys. 61 00:04:36,950 --> 00:04:39,620 How are you going to exactly share those keys? 62 00:04:40,190 --> 00:04:44,030 Because even you have to share a key over email. 63 00:04:44,030 --> 00:04:46,430 You have to keep that key confidential. 64 00:04:47,000 --> 00:04:48,880 So again, you have to encrypt that key. 65 00:04:48,890 --> 00:04:54,950 But if you're using asymmetric encryption again and again and again, again, the keys need to be shared. 66 00:04:54,950 --> 00:05:02,460 So secure sharing of keys is a tough problem, but nothing is tough for people who are curious. 67 00:05:02,480 --> 00:05:06,740 So there were two people, Diffie and Helmond together. 68 00:05:07,130 --> 00:05:15,350 They solve this problem and they proposed a new solution to this, which was difficult Hellman key exchange 69 00:05:15,350 --> 00:05:24,110 algorithm in which this key is shared securely without using or without using some other factors. 70 00:05:25,550 --> 00:05:28,580 Well, what is the advantage of symmetric encryption? 71 00:05:28,590 --> 00:05:34,010 You must ask if there are two keys and if that is more secure, why have symmetric encryption in place? 72 00:05:34,520 --> 00:05:43,130 Well, the most fundamental advantage of symmetric encryption is speed. 73 00:05:43,790 --> 00:05:46,700 Symmetric key encryption is much. 74 00:05:46,810 --> 00:05:55,870 Faster than asymmetric encryption, it's it's much faster, although you think that the asymmetric is 75 00:05:55,870 --> 00:06:03,430 much secure, it's not used that much because of its extreme consumption of power, symmetric encryption, 76 00:06:03,430 --> 00:06:05,410 since it uses the same key. 77 00:06:05,470 --> 00:06:07,600 It has a predefined process to do. 78 00:06:07,960 --> 00:06:16,090 That is why the task of encryption and decryption requires, you know, it's a speedy task. 79 00:06:16,090 --> 00:06:20,050 Less time is required in order to carry out the entire process. 80 00:06:21,280 --> 00:06:23,670 So drawback is secure sharing of keys. 81 00:06:23,680 --> 00:06:29,520 But again, there were two brilliant people out there, Diffie and Helman, who proposed the development 82 00:06:29,530 --> 00:06:30,130 algorithm. 83 00:06:31,390 --> 00:06:38,910 So to sum up what you have to remember when it comes to symmetric encryption is the same keys used. 84 00:06:39,160 --> 00:06:41,050 OK, I'll just mark it again. 85 00:06:42,610 --> 00:06:52,930 So same keys used, mathematical algorithm, single key to be private, key encryption. 86 00:06:53,590 --> 00:06:56,340 And these are a few examples. 87 00:06:56,740 --> 00:07:05,410 And again, you have to remember, as for speed, as for symmetric encryption, the only drawback is, 88 00:07:05,410 --> 00:07:08,800 again, as that is secure sharing of keys. 89 00:07:09,850 --> 00:07:16,870 In the next lecture, we'll talk about a few examples of asymmetric encryption will see different algorithms, 90 00:07:17,330 --> 00:07:18,520 the key size. 91 00:07:18,520 --> 00:07:20,850 What is the key size for those algorithms? 92 00:07:21,190 --> 00:07:25,320 What is the input and what is the exact output? 93 00:07:26,430 --> 00:07:31,350 OK, I have I have got this question a couple of times, what is the input? 94 00:07:31,380 --> 00:07:36,180 Well, you cannot give a word document at random, right? 95 00:07:36,190 --> 00:07:42,990 That is fixed input size for each of different algorithms and inline that algorithms. 96 00:07:42,990 --> 00:07:44,420 The data is encrypted. 97 00:07:44,730 --> 00:07:50,080 You cannot give 2000 characters to encrypt, uh, as a single block. 98 00:07:50,100 --> 00:07:57,120 So there are different various block sizes in case of symmetric encryption, which we will be seeing 99 00:07:57,120 --> 00:07:58,320 in the next lecture. 100 00:07:58,740 --> 00:07:59,190 All right. 101 00:07:59,520 --> 00:08:00,900 Keep the momentum going. 102 00:08:01,220 --> 00:08:02,460 You're doing a great job. 103 00:08:02,730 --> 00:08:07,550 If you have any questions, do let us know and I'll be happy to solve them for you.