WEBVTT 00:00.290 --> 00:06.480 What we talk about cryptography we tend to only think about one part of the CIA of security. 00:06.550 --> 00:11.110 There remember CIA stands for confidentiality integrity and availability. 00:11.130 --> 00:15.490 So when we talk about cryptography we tend to concentrate on confidentiality. 00:15.510 --> 00:16.830 Right we're encrypting stuff. 00:16.940 --> 00:18.870 Well that's not always the case. 00:18.870 --> 00:25.710 Well I want to talk about right now something called hashing a hash provides integrity when it comes 00:25.710 --> 00:27.290 to the CIA of security. 00:27.290 --> 00:33.580 Now we don't encrypt with the hash we make things in Taggerty a fight. 00:33.600 --> 00:37.040 I'm going to stick to that word because that's now part of the Webster's dictionary. 00:37.320 --> 00:40.080 So let me explain how a hash works. 00:40.080 --> 00:42.620 The idea behind a hash is that it is an algorithm. 00:42.620 --> 00:47.910 That's why I got my algorithm machine here and it doesn't encrypt what it will do is it will take a 00:48.030 --> 00:57.010 arbitrarily large amount of data and you take that data and you run it through and it comes out in a 00:57.010 --> 00:59.650 fixed value every time. 00:59.650 --> 01:03.610 So if I have a five letter input it's going to come out. 01:03.670 --> 01:11.140 However whatever size the hash is if I have a 300 billion byte input it's always still going to come 01:11.140 --> 01:12.610 out this size. 01:12.610 --> 01:15.160 Now at first glance he'd say Well Mike what am I going to do with that. 01:15.160 --> 01:17.500 Well there's a couple of things about hashes that are cool. 01:17.500 --> 01:20.200 Number one hashes are one way. 01:20.200 --> 01:27.400 If I generate this and I create a hash there is no way it is impossible to figure out what the actual 01:27.400 --> 01:29.050 original data was. 01:29.050 --> 01:32.240 The other thing that's cool about a hash is that it's deterministic. 01:32.270 --> 01:35.590 So look at this he starts with 1 a 6. 01:35.590 --> 01:36.410 Got it. 01:36.730 --> 01:42.100 So I take this document and it doesn't have to be a document it could be a image it doesn't matter as 01:42.100 --> 01:43.580 long as it's ones and zeros. 01:43.630 --> 01:50.710 And if I could take all knowledge known to man from the beginning of mankind and put it into a big word 01:50.710 --> 01:58.300 document and I could go to page $405 and in twenty seven thousand six hundred twenty two and I could 01:58.300 --> 02:04.030 go in there and change one letter one letter change so this upper case could change it to a lower case 02:04.030 --> 02:11.590 c and if I take that value and I run it through a hash algorithm it's going to come out with a completely 02:11.740 --> 02:13.330 different value. 02:13.330 --> 02:19.530 So hashes are a very good way to say this is the data from which I got. 02:19.540 --> 02:25.480 So for example if I'm downloading a big executable file I can run a hash on it and compare it to the 02:25.480 --> 02:29.980 hash value that's up on the Web site and then that way if it didn't come down right or something I could 02:29.980 --> 02:37.960 clearly and very explicitly know that this is the right values so hashes are something we use all over 02:37.960 --> 02:43.410 the place within the world of cryptography so that's the basics of a hash. 02:43.400 --> 02:49.180 Now for the security plus there are lots of hashes hashes have been going around for a long long time 02:49.450 --> 02:51.820 and we have a lot of different versions of them. 02:51.850 --> 02:57.010 They all have different size outputs or what we call a message digest they're all the same word. 02:57.010 --> 03:02.890 And what I want to do right now is just take a minute and let's run through the different types of hashes 03:02.890 --> 03:09.420 that you're going to see on security plus there are a zillion types of hashes out there but luckily 03:09.420 --> 03:14.390 for us we can break down what you need to know for the security plus into three groups. 03:14.520 --> 03:21.750 First is called Message Digest version 5 better known as M.D 5 and 5 is the grandpa of hashes. 03:21.750 --> 03:23.750 It's been around since the early 90s. 03:23.790 --> 03:29.940 It was invented by Ron Rivest of RSA fame and it's been used for years and years and years and years. 03:29.940 --> 03:35.920 The important thing to remember about M.D 5 is that it uses a 128 bit hash. 03:36.090 --> 03:41.140 Now M.D five is a great one but they found a little problem with an ox plane that in just a moment. 03:41.340 --> 03:47.110 The second type of hash I want you to be aware of is the secure hash algorithm better than the Shah. 03:47.160 --> 03:51.930 And this is a family of hashes that were developed by the National Institute of Standards here in the 03:51.930 --> 03:57.230 U.S. technically they're still being developed the earliest version of Shaw that you're going to see 03:57.300 --> 04:00.410 on the security plus is called Shaw Dash 1. 04:00.420 --> 04:04.350 Now Shaw one has a 160 bit hash. 04:04.350 --> 04:05.490 Now here's the problem. 04:05.490 --> 04:12.000 Both M.D 5 and Shaw 1 have the ability to generate what we call collisions. 04:12.000 --> 04:13.400 Let me explain that. 04:13.860 --> 04:19.470 A collision simply means when you take two different types of data and generate the same hash. 04:19.680 --> 04:27.070 If you can force a hash to make occasional collisions it can often be figured out how the hash works. 04:27.180 --> 04:28.460 And that is a naughty naughty thing. 04:28.470 --> 04:29.500 We don't like that. 04:29.760 --> 04:34.560 So neither end D5 nor shot want or use that commonly anymore. 04:34.620 --> 04:41.070 If you're talking about hashes that are being used today for websites and all kinds of stuff we're talking 04:41.070 --> 04:48.200 about shot to now shot to is not just one type of hash shot two is broken down into different types. 04:48.200 --> 04:49.870 Based on the length of the hash. 04:49.980 --> 04:56.740 So we don't see a shot to what we will say though is shot 256 or shot 512. 04:56.820 --> 05:01.120 So you could see that these big long hashes are much less prone. 05:01.170 --> 05:03.300 In fact no one's made a collision with them yet. 05:03.300 --> 05:05.530 Knock on wood. 05:05.680 --> 05:07.780 The last type of hash I want to talk about. 05:07.960 --> 05:09.480 It's mentioned on security plus. 05:09.500 --> 05:11.420 Let me bring it up is right. 05:11.440 --> 05:16.620 EMT and that stands for race integrity primitives evaluation message digest. 05:16.840 --> 05:20.220 Now this is not a real common hashing algorithm. 05:20.230 --> 05:25.690 It's nice because it's open standard that everybody can check it out but it's just not used that much. 05:25.690 --> 05:30.010 Nothing really wrong with it it just that everybody like shot to these days but do be aware for the 05:30.010 --> 05:40.000 test that right BMD comes in 128 160 256 and 320 bit versions and you will be tested on every one of 05:40.000 --> 05:46.700 these on the security plus Yep that is a lot of hashes you need to memorize my friends. 05:46.700 --> 05:53.000 Not only do you need to memorize the different names of each hash but make sure you know the size of 05:53.000 --> 05:59.470 the hash because the security plus loves to hash on that sorry OK I'll keep my day job. 05:59.510 --> 06:04.520 Now people will ask me especially just been exposed to this. 06:04.520 --> 06:06.260 What do we do with hashes. 06:06.260 --> 06:11.300 The easier answer is within the world occurred toggery you would be hard pressed to find a place where 06:11.300 --> 06:13.240 we don't use hashes. 06:13.250 --> 06:14.300 Some great examples. 06:14.300 --> 06:16.870 Example Number one password storage. 06:16.940 --> 06:23.450 Most operating systems never store your passwords so you type in a password at it at it and you hit 06:23.450 --> 06:28.550 enter and the password is saved onto the hard drive only as its hash. 06:28.550 --> 06:34.460 So when you type in your password to log into something it goes ahead and hashes it and compares it 06:34.460 --> 06:36.700 and says oh you type in the right password. 06:36.890 --> 06:44.780 We use hashes on virtually every type of encryption and authentication known to man we use hashes everywhere. 06:44.780 --> 06:49.350 So what I'm on right now is you only need to memorize the different types of hashes. 06:49.460 --> 06:54.170 Starting from here and going through the rest of this course we're going to be seeing hashes over and 06:54.200 --> 07:02.200 over again.