1 00:00:00,540 --> 00:00:03,330 Welcome to this section on cryptography. 2 00:00:03,330 --> 00:00:04,690 What is cryptography? 3 00:00:04,690 --> 00:00:06,139 Well cryptography is the practice 4 00:00:06,139 --> 00:00:07,550 and study of writing 5 00:00:07,550 --> 00:00:09,470 and solving codes in order to hide 6 00:00:09,470 --> 00:00:11,650 the true meaning of the information. 7 00:00:11,650 --> 00:00:12,550 Now most commonly, 8 00:00:12,550 --> 00:00:13,720 we're going to use cryptography 9 00:00:13,720 --> 00:00:15,410 as a form of encryption. 10 00:00:15,410 --> 00:00:16,600 Encryption is the process 11 00:00:16,600 --> 00:00:18,350 of converting ordinary information 12 00:00:18,350 --> 00:00:19,337 known as plaintext, 13 00:00:19,337 --> 00:00:21,450 into an unintelligible format 14 00:00:21,450 --> 00:00:22,860 known as ciphertext. 15 00:00:22,860 --> 00:00:24,410 So if I take some plain words 16 00:00:24,410 --> 00:00:26,590 and I encrypt them into some gobbledygook. 17 00:00:26,590 --> 00:00:28,960 Nobody else can read it unless they have the key 18 00:00:28,960 --> 00:00:31,490 and they can turn it back into that plaintext. 19 00:00:31,490 --> 00:00:33,490 That's the concept of encryption. 20 00:00:33,490 --> 00:00:36,670 Now encryption is used to provide us data at rest, 21 00:00:36,670 --> 00:00:37,670 data in transit 22 00:00:37,670 --> 00:00:39,630 and data in use protection 23 00:00:39,630 --> 00:00:41,010 and this is the three areas 24 00:00:41,010 --> 00:00:42,310 that we've talked about previously, 25 00:00:42,310 --> 00:00:43,240 that we want to make sure 26 00:00:43,240 --> 00:00:44,980 we're securing our information. 27 00:00:44,980 --> 00:00:45,940 By using encryption, 28 00:00:45,940 --> 00:00:47,020 we can do that. 29 00:00:47,020 --> 00:00:48,900 Now what exactly is data at rest? 30 00:00:48,900 --> 00:00:51,350 Well it's inactive data that is archived, 31 00:00:51,350 --> 00:00:52,540 such as data that's resident 32 00:00:52,540 --> 00:00:53,690 on a hard drive. 33 00:00:53,690 --> 00:00:55,600 So in data is just sitting there in a file, 34 00:00:55,600 --> 00:00:57,630 that is known as data at rest. 35 00:00:57,630 --> 00:00:59,760 Now when we start moving that data around, 36 00:00:59,760 --> 00:01:02,110 that becomes known as data in transit. 37 00:01:02,110 --> 00:01:03,840 That's data that's crossing the network 38 00:01:03,840 --> 00:01:06,940 or data that's residing inside the computers memory, 39 00:01:06,940 --> 00:01:08,100 the random access memory, 40 00:01:08,100 --> 00:01:08,933 the RAM, 41 00:01:08,933 --> 00:01:10,580 as it's waiting to be processed. 42 00:01:10,580 --> 00:01:11,909 Now if data is in use, 43 00:01:11,909 --> 00:01:13,170 that means that data 44 00:01:13,170 --> 00:01:15,480 is currently undergoing constant change, 45 00:01:15,480 --> 00:01:17,400 so there's data inside your processor 46 00:01:17,400 --> 00:01:18,940 and calculations are being done. 47 00:01:18,940 --> 00:01:20,208 That's data in use. 48 00:01:20,208 --> 00:01:23,320 Encryption can be used in all three of these places 49 00:01:23,320 --> 00:01:24,153 and so it's important 50 00:01:24,153 --> 00:01:25,960 to understand how you're going to use it. 51 00:01:25,960 --> 00:01:27,120 Now let me go back 52 00:01:27,120 --> 00:01:29,780 and explain how encryption works a little bit. 53 00:01:29,780 --> 00:01:30,760 Let's say I have something 54 00:01:30,760 --> 00:01:32,270 like you see here on the screen. 55 00:01:32,270 --> 00:01:33,810 This is gobbledygook. 56 00:01:33,810 --> 00:01:35,640 You have no idea what it means, right? 57 00:01:35,640 --> 00:01:37,120 Do you know what this message is? 58 00:01:37,120 --> 00:01:38,580 Well I don't the way it's written 59 00:01:38,580 --> 00:01:42,470 but if I told you that I used a ROT13 cipher, 60 00:01:42,470 --> 00:01:43,720 then that might tell you 61 00:01:43,720 --> 00:01:45,340 that you could figure out how to get back 62 00:01:45,340 --> 00:01:47,070 to the original plaintext. 63 00:01:47,070 --> 00:01:48,760 What a ROT13 cipher is, 64 00:01:48,760 --> 00:01:50,898 it stands for rotate 13 spots. 65 00:01:50,898 --> 00:01:53,670 So if I start with something like the letter C 66 00:01:53,670 --> 00:01:56,010 and I count 13 letters to the right, 67 00:01:56,010 --> 00:01:57,300 that gets me to P. 68 00:01:57,300 --> 00:01:58,480 If I go with R, 69 00:01:58,480 --> 00:02:00,980 13 letters to the right goes around past Z, 70 00:02:00,980 --> 00:02:02,280 A, B, C, D, E 71 00:02:02,280 --> 00:02:03,430 and it gets me to E. 72 00:02:03,430 --> 00:02:06,310 So I know have P and E is C and R. 73 00:02:06,310 --> 00:02:07,660 Do you know what this says yet? 74 00:02:07,660 --> 00:02:08,810 Well let me help you. 75 00:02:08,810 --> 00:02:10,210 Instead of me making you do all the math 76 00:02:10,210 --> 00:02:11,350 and figuring it out on your own, 77 00:02:11,350 --> 00:02:12,320 I'm going to show it to you. 78 00:02:12,320 --> 00:02:14,280 It stands for cryptography is fun. 79 00:02:14,280 --> 00:02:17,060 Now that you know what that key is, 80 00:02:17,060 --> 00:02:18,440 that 13 places, 81 00:02:18,440 --> 00:02:20,720 it makes it really easy for you to figure out 82 00:02:20,720 --> 00:02:22,630 how to convert things forward and back. 83 00:02:22,630 --> 00:02:24,220 That's the idea with encryption. 84 00:02:24,220 --> 00:02:26,520 It's not the fact that we have some algorithm 85 00:02:26,520 --> 00:02:27,740 that's very complicated. 86 00:02:27,740 --> 00:02:29,110 It's knowing the key. 87 00:02:29,110 --> 00:02:30,841 If I told you everything was a rotation, 88 00:02:30,841 --> 00:02:33,470 you can figure it out if you know what the key is 89 00:02:33,470 --> 00:02:35,550 and the key here is 13 numbers. 90 00:02:35,550 --> 00:02:38,490 Now our encryption is going to be much more complicated 91 00:02:38,490 --> 00:02:39,370 than that in a computer 92 00:02:39,370 --> 00:02:41,550 but that's the same basic principle 93 00:02:41,550 --> 00:02:43,600 and I wanted you to understand how it works. 94 00:02:43,600 --> 00:02:45,460 Now that ROT13 that I talked about, 95 00:02:45,460 --> 00:02:46,500 that rotation, 96 00:02:46,500 --> 00:02:47,870 that's known as an algorithm. 97 00:02:47,870 --> 00:02:49,330 It's the cipher we're going to use 98 00:02:49,330 --> 00:02:51,180 and a cipher is simply an algorithm 99 00:02:51,180 --> 00:02:53,828 which performs the encryption or decryption function. 100 00:02:53,828 --> 00:02:55,290 In my example, 101 00:02:55,290 --> 00:02:57,420 when you added 13 you encrypted, 102 00:02:57,420 --> 00:03:00,270 when you subtracted 13 spots you decrypted 103 00:03:00,270 --> 00:03:01,660 and that's the way we're going to use it 104 00:03:01,660 --> 00:03:03,400 in a ROT13 cipher. 105 00:03:03,400 --> 00:03:05,810 We're going to use much more complicated ciphers than that 106 00:03:05,810 --> 00:03:06,822 when we get into the ciphers 107 00:03:06,822 --> 00:03:09,310 and we'll talk about all of the different algorithms, 108 00:03:09,310 --> 00:03:11,140 both symmetric and asymmetric, 109 00:03:11,140 --> 00:03:12,099 block and stream. 110 00:03:12,099 --> 00:03:15,110 We'll talk about all of that in this section of the course. 111 00:03:15,110 --> 00:03:17,240 Now when we talk about these algorithms, 112 00:03:17,240 --> 00:03:19,760 this is a mathematical function. 113 00:03:19,760 --> 00:03:21,150 Something gets input, 114 00:03:21,150 --> 00:03:22,480 some things get changed 115 00:03:22,480 --> 00:03:25,280 and out the other side comes some value. 116 00:03:25,280 --> 00:03:26,550 So when I input the C 117 00:03:26,550 --> 00:03:28,310 and it went through my ROT13 cipher, 118 00:03:28,310 --> 00:03:30,440 it came out the other side as a P 119 00:03:30,440 --> 00:03:32,687 because it moved 13 spots to the right. 120 00:03:32,687 --> 00:03:33,990 That's the idea. 121 00:03:33,990 --> 00:03:35,420 All an algorithm is, 122 00:03:35,420 --> 00:03:36,970 is a mathematical formula 123 00:03:36,970 --> 00:03:38,950 that tells you how we're going to encrypt 124 00:03:38,950 --> 00:03:40,038 or decrypt something. 125 00:03:40,038 --> 00:03:42,140 Now as we move through this 126 00:03:42,140 --> 00:03:44,420 we have to think about what gives us 127 00:03:44,420 --> 00:03:46,890 the security inside our cryptography 128 00:03:46,890 --> 00:03:48,210 and our encryption. 129 00:03:48,210 --> 00:03:49,619 What is really the strength here? 130 00:03:49,619 --> 00:03:52,287 Is it that ROT13 that I told you? 131 00:03:52,287 --> 00:03:54,050 Well it wasn't the ROT part. 132 00:03:54,050 --> 00:03:55,197 The ROT was the algorithm. 133 00:03:55,197 --> 00:03:57,149 It was the 13 which was the key 134 00:03:57,149 --> 00:03:59,460 because all encryption strength comes 135 00:03:59,460 --> 00:04:01,270 from the key not the algorithm. 136 00:04:01,270 --> 00:04:03,700 In fact almost all of the algorithms 137 00:04:03,700 --> 00:04:04,610 we're going to talk about, 138 00:04:04,610 --> 00:04:06,840 in probably all of the algorithms we're going to talk about, 139 00:04:06,840 --> 00:04:08,900 have undergone public review, 140 00:04:08,900 --> 00:04:11,030 meaning the people who have designed them 141 00:04:11,030 --> 00:04:12,630 have opened up their code and said 142 00:04:12,630 --> 00:04:14,480 here is how we've done it. 143 00:04:14,480 --> 00:04:15,520 If you can do that, 144 00:04:15,520 --> 00:04:17,630 you have a good encryption algorithm 145 00:04:17,630 --> 00:04:19,529 because it's not the algorithm that's secure. 146 00:04:19,529 --> 00:04:21,830 It's the key that makes it secure 147 00:04:21,830 --> 00:04:23,740 and we're going to talk about that over and over again, 148 00:04:23,740 --> 00:04:25,089 throughout this section as well. 149 00:04:25,089 --> 00:04:26,710 When we talk about a key, 150 00:04:26,710 --> 00:04:28,590 this is that essential piece of information 151 00:04:28,590 --> 00:04:31,140 that determines the output of a cipher. 152 00:04:31,140 --> 00:04:32,950 Going back to my ROT13 example, 153 00:04:32,950 --> 00:04:34,120 what was the key? 154 00:04:34,120 --> 00:04:35,250 It was the 13. 155 00:04:35,250 --> 00:04:37,770 It was telling you to move 13 places to the right 156 00:04:37,770 --> 00:04:40,509 or decrypting by going 13 places to the left. 157 00:04:40,509 --> 00:04:42,730 Now that's the whole idea here 158 00:04:42,730 --> 00:04:44,270 and so it's really important you understand 159 00:04:44,270 --> 00:04:46,249 that the key is the security. 160 00:04:46,249 --> 00:04:49,690 The key is the key to security inside encryption. 161 00:04:49,690 --> 00:04:51,630 So let's get started with this section 162 00:04:51,630 --> 00:04:52,990 and we're going to have a lot of fun 163 00:04:52,990 --> 00:04:54,470 talking about all of the different ways 164 00:04:54,470 --> 00:04:55,663 to secure your data.