1 00:00:06,360 --> 00:00:07,410 - [Instructor] In this segment, 2 00:00:07,410 --> 00:00:09,690 we're gonna look at creating hash values, 3 00:00:09,690 --> 00:00:12,330 also called fingerprints, message digest 4 00:00:12,330 --> 00:00:15,090 and sometimes just hashes. 5 00:00:15,090 --> 00:00:18,300 And we use hashing algorithms to create unique, 6 00:00:18,300 --> 00:00:22,680 one-way fixed length output from variable length input. 7 00:00:22,680 --> 00:00:26,460 Now to create a hash value, you use a hash calculator. 8 00:00:26,460 --> 00:00:28,680 So let's take a look at a hash calculator. 9 00:00:28,680 --> 00:00:30,570 The cryptographic hash algorithms 10 00:00:30,570 --> 00:00:31,950 which is what we're going to use 11 00:00:31,950 --> 00:00:34,950 produce irreversible and unique hashes. 12 00:00:34,950 --> 00:00:37,530 Unique means that two different pieces 13 00:00:37,530 --> 00:00:40,860 of data can never produce the same hash 14 00:00:40,860 --> 00:00:44,520 which is why hashing can be used to prove integrity. 15 00:00:44,520 --> 00:00:47,280 Now this particular hash calculator offers a variety 16 00:00:47,280 --> 00:00:49,020 of hashing algorithms. 17 00:00:49,020 --> 00:00:53,010 The current US government standard is the SHA algorithm. 18 00:00:53,010 --> 00:00:56,250 SHA stands for secure hashing algorithm. 19 00:00:56,250 --> 00:00:58,710 Now, there are three families, SHA-1 20 00:00:58,710 --> 00:01:03,710 which was effectively retired in 2015, the SHA-2 family 21 00:01:03,870 --> 00:01:08,700 which includes SHA-256, SHA-384, and SHA-512 22 00:01:08,700 --> 00:01:10,953 and the emerging SHA-3 family. 23 00:01:12,150 --> 00:01:13,410 So let's select all 24 00:01:13,410 --> 00:01:16,380 of these just so we can have a comparison. 25 00:01:16,380 --> 00:01:20,070 So I'm gonna choose the message digest family, 26 00:01:20,070 --> 00:01:22,770 the SHA family, then RIPEMD, 27 00:01:22,770 --> 00:01:25,923 PANAMA, TIGER, MD2 and Adler. 28 00:01:27,780 --> 00:01:29,820 And I'm going to put in a text string. 29 00:01:29,820 --> 00:01:31,530 It was a bright cold day in April 30 00:01:31,530 --> 00:01:33,693 and the clocks were striking 13. 31 00:01:34,710 --> 00:01:37,350 And now I'm gonna choose calculate. 32 00:01:37,350 --> 00:01:38,610 And you can see that each one 33 00:01:38,610 --> 00:01:43,050 of these created a different hash value. 34 00:01:43,050 --> 00:01:44,160 Now there are different lengths 35 00:01:44,160 --> 00:01:46,410 depending upon the number of bits 36 00:01:46,410 --> 00:01:48,063 and different construction. 37 00:01:49,290 --> 00:01:51,120 So does length matter? 38 00:01:51,120 --> 00:01:53,010 Well, technically, yes. 39 00:01:53,010 --> 00:01:56,580 You know, a bit has two possible values, zero and one. 40 00:01:56,580 --> 00:01:59,670 So the possible number of unique hashes can be expressed 41 00:01:59,670 --> 00:02:03,600 as a number of possible values raised to the number of bits. 42 00:02:03,600 --> 00:02:05,340 So a SHA-256, well, 43 00:02:05,340 --> 00:02:10,260 there are 2 to 256 possible combinations. 44 00:02:10,260 --> 00:02:11,820 That would be 2 of 384. 45 00:02:11,820 --> 00:02:14,070 It would be 2 to the 384th. 46 00:02:14,070 --> 00:02:16,740 512 would be 2 to the 512. 47 00:02:16,740 --> 00:02:18,660 Those are huge, huge numbers. 48 00:02:18,660 --> 00:02:21,240 Matter of fact, 2 to the 256. 49 00:02:21,240 --> 00:02:23,070 Well, the example you often hear 50 00:02:23,070 --> 00:02:25,320 is that it exceeds the number of grains 51 00:02:25,320 --> 00:02:27,540 of sand that there are in the world. 52 00:02:27,540 --> 00:02:30,150 Now the larger the number of possible hashes, 53 00:02:30,150 --> 00:02:31,350 the smaller the chance 54 00:02:31,350 --> 00:02:34,440 that two values will create the same hash. 55 00:02:34,440 --> 00:02:37,290 Now, a large bit length doesn't automatically, however, 56 00:02:37,290 --> 00:02:40,770 mean that a hashing algorithm produces more secure hash. 57 00:02:40,770 --> 00:02:41,603 The construction 58 00:02:41,603 --> 00:02:44,400 of the algorithm is also incredibly important 59 00:02:44,400 --> 00:02:46,470 which is why we use hashing algorithms 60 00:02:46,470 --> 00:02:49,713 that are specifically designed for cryptographic security. 61 00:02:50,820 --> 00:02:51,930 Now let's look at what happens 62 00:02:51,930 --> 00:02:54,870 if I make even the slightest change. 63 00:02:54,870 --> 00:02:59,250 I want you to focus in on any one of those outputs 64 00:02:59,250 --> 00:03:02,100 and just look at maybe the last three or four characters. 65 00:03:02,100 --> 00:03:03,840 Choose any one you want. 66 00:03:03,840 --> 00:03:06,120 And what I'm gonna do is I'm gonna come back up 67 00:03:06,120 --> 00:03:09,930 to my data input, and I'm gonna change that last period 68 00:03:09,930 --> 00:03:14,220 to an explanation point, and we're gonna calculate it again. 69 00:03:14,220 --> 00:03:19,170 And what you should see now is a different output, right? 70 00:03:19,170 --> 00:03:23,010 Because if we make the slightest change, we add a space, 71 00:03:23,010 --> 00:03:26,040 we change the punctuation, we add a letter, 72 00:03:26,040 --> 00:03:29,160 we take a letter away, we take a letter that's lowercase 73 00:03:29,160 --> 00:03:33,180 and make it uppercase, and it will change the output, right? 74 00:03:33,180 --> 00:03:34,950 And it's absolutely critical 75 00:03:34,950 --> 00:03:38,493 that the output is unique to that input. 76 00:03:41,280 --> 00:03:44,220 Now you also see we have an option of doing an HMAC. 77 00:03:44,220 --> 00:03:49,220 Now, a HMAC is when we add a symmetric key to the input. 78 00:03:50,220 --> 00:03:51,510 Now, why would we do that? 79 00:03:51,510 --> 00:03:54,420 Well, that means that both parties have to be communicating 80 00:03:54,420 --> 00:03:57,330 because symmetric key means single key or a shared key. 81 00:03:57,330 --> 00:04:00,600 So both parties are going to have to be in possession 82 00:04:00,600 --> 00:04:03,960 of that key, and they'll take the input 83 00:04:03,960 --> 00:04:07,440 as well as the key to produce the hash 84 00:04:07,440 --> 00:04:09,090 and then they'll compare that. 85 00:04:09,090 --> 00:04:13,050 So I'm just gonna show you how we're going to do an HMAC. 86 00:04:13,050 --> 00:04:15,060 I've got that same data string. 87 00:04:15,060 --> 00:04:19,923 I'm just gonna add a key and then I'll calculate. 88 00:04:22,080 --> 00:04:25,230 So all the calculator's doing is it's taking the data 89 00:04:25,230 --> 00:04:29,283 plus the key in order to produce the output. 90 00:04:31,350 --> 00:04:32,430 Very straightforward. 91 00:04:32,430 --> 00:04:35,100 You can find hash calculators online 92 00:04:35,100 --> 00:04:37,980 or you can bring down a local application. 93 00:04:37,980 --> 00:04:42,060 But understanding that we use hashing to prove integrity 94 00:04:42,060 --> 00:04:43,920 that the uniqueness is important 95 00:04:43,920 --> 00:04:47,460 that if we don't have uniqueness, it's called a collision. 96 00:04:47,460 --> 00:04:50,730 And once we start having collisions, we can no longer depend 97 00:04:50,730 --> 00:04:54,810 upon that hashing algorithm to prove integrity. 98 00:04:54,810 --> 00:04:57,480 And that my friends is a closer look 99 00:04:57,480 --> 00:04:59,013 at creating hash values.