WEBVTT 00:00.000 --> 00:03.840 >> Cryptography. The learning objectives for 00:03.840 --> 00:05.520 this lesson are to define 00:05.520 --> 00:07.575 hashing and its role in security, 00:07.575 --> 00:10.260 to explore message authentication codes, 00:10.260 --> 00:13.215 and to differentiate the types of symmetric algorithms. 00:13.215 --> 00:15.480 Let's get started. Well, 00:15.480 --> 00:16.830 before we really get started, 00:16.830 --> 00:18.810 one thing I'd like you to understand is we're not 00:18.810 --> 00:21.135 going to be doing any math on this lesson. 00:21.135 --> 00:23.610 The exam doesn't expect you to understand 00:23.610 --> 00:26.640 the mathematics that are behind these complex algorithms. 00:26.640 --> 00:27.960 What they really want to make sure 00:27.960 --> 00:29.070 is that you know the difference 00:29.070 --> 00:31.604 between symmetric and asymmetric algorithms, 00:31.604 --> 00:33.540 hashing and what are used 00:33.540 --> 00:36.145 cases for these types of technologies. 00:36.145 --> 00:38.595 Think about a professional race car driver. 00:38.595 --> 00:40.170 They are expected to get the 00:40.170 --> 00:42.385 most out of their car on the track. 00:42.385 --> 00:44.120 But they're not the ones that are tuning 00:44.120 --> 00:46.760 the engines or making any repairs to the car. 00:46.760 --> 00:48.290 Also, cryptography is 00:48.290 --> 00:50.570 a very complex subject and there's a lot of areas 00:50.570 --> 00:52.325 on the tests that are 00:52.325 --> 00:54.215 covered by the cryptography subjects. 00:54.215 --> 00:56.930 I've broken it into three lessons and each of 00:56.930 --> 00:58.070 these lessons will cover 00:58.070 --> 01:00.930 different aspects of the cryptography. 01:01.370 --> 01:04.900 What are some common uses of cryptography? 01:04.900 --> 01:07.485 The first is encrypting data at rest. 01:07.485 --> 01:09.200 This is data that is stored on 01:09.200 --> 01:11.930 computers or in databases or other areas. 01:11.930 --> 01:14.510 The key point is that the data isn't moving. 01:14.510 --> 01:16.370 Usually this data will be encrypted with 01:16.370 --> 01:19.300 a symmetrical algorithm like AES. 01:19.300 --> 01:21.830 Full drive encryption or file level encryption 01:21.830 --> 01:23.630 would be examples of this. 01:23.630 --> 01:27.275 Data in transit is sometimes called data in motion. 01:27.275 --> 01:30.290 This is when data is moving from one place to another. 01:30.290 --> 01:33.815 Think of it when you're accessing an HTTPS web site, 01:33.815 --> 01:35.810 the data is moving from the web server to 01:35.810 --> 01:38.815 you across that encrypted channel. 01:38.815 --> 01:41.990 Also TLS and IPsec are methods 01:41.990 --> 01:45.660 that we can use to secure data while it's in motion. 01:45.860 --> 01:48.725 Finally, we have data in use. 01:48.725 --> 01:50.150 This is the data that is in 01:50.150 --> 01:52.415 volatile memory such as the system RAM, 01:52.415 --> 01:54.380 CPU registers, and cache. 01:54.380 --> 01:57.140 An example would be fields in a database that are being 01:57.140 --> 01:59.030 modified or event logs 01:59.030 --> 02:01.340 that are being created while the system is running. 02:01.340 --> 02:04.475 When he data goes from rest to in use, 02:04.475 --> 02:08.550 it will be decrypted and then read or modified. 02:09.710 --> 02:13.580 Hashing. Hashing is a mathematical function 02:13.580 --> 02:14.900 that will take input 02:14.900 --> 02:17.120 from data and then transform that into 02:17.120 --> 02:19.730 a fixed-length hexadecimal output. 02:19.730 --> 02:22.610 The keys to remember about hashing are 02:22.610 --> 02:25.520 that the output is always of a fixed length. 02:25.520 --> 02:29.065 The same input will always produce the same output. 02:29.065 --> 02:31.490 If I were to hash a file, 02:31.490 --> 02:32.885 it will give me an output. 02:32.885 --> 02:35.030 If I hash it 10 minutes later or a week later, 02:35.030 --> 02:36.170 if it's the same file, 02:36.170 --> 02:37.520 I will get the same output. 02:37.520 --> 02:40.280 The reason we do this is that this allows 02:40.280 --> 02:43.565 us to ensure that no changes have been made to that file. 02:43.565 --> 02:47.390 Also, there is no way for us to take that hash and 02:47.390 --> 02:48.410 reverse it to find 02:48.410 --> 02:50.870 the input or find out the contents of the file. 02:50.870 --> 02:52.820 For example, hashing is irreversible. 02:52.820 --> 02:54.940 It's considered one-way encryption. 02:54.940 --> 02:59.550 Finally, the output of a hash is known as a digest. 02:59.770 --> 03:02.590 Let's talk about a practical example. 03:02.590 --> 03:04.040 Many of you have probably 03:04.040 --> 03:06.080 downloaded ISO files from the Internet. 03:06.080 --> 03:08.885 Most of these ISOs will also have 03:08.885 --> 03:12.455 a sum provided where you download on the site. 03:12.455 --> 03:14.495 You'll see the long string of numbers, 03:14.495 --> 03:16.895 and that is the hash of this file. 03:16.895 --> 03:18.590 After you've downloaded the file, 03:18.590 --> 03:21.170 you can make a hash of it on your own system and then 03:21.170 --> 03:24.020 compare it to the one that's provided by the site. 03:24.020 --> 03:26.570 If they match, you know that you've got an exact copy. 03:26.570 --> 03:28.620 If they don't, then something happened along the way, 03:28.620 --> 03:30.440 maybe the file is incomplete or 03:30.440 --> 03:32.420 it got corrupted and you'll have to download it again. 03:32.420 --> 03:34.790 But this is a way for you to verify that yours is 03:34.790 --> 03:36.050 an exact duplicate of 03:36.050 --> 03:39.300 what they are supplying from the website. 03:39.700 --> 03:43.460 Now there are some potential problems with hashing. 03:43.460 --> 03:46.625 If we're using this to monitor file changes, 03:46.625 --> 03:47.825 like I mentioned earlier, 03:47.825 --> 03:50.625 we have to make sure that we are certain and 03:50.625 --> 03:53.600 have no doubts about the original hash that we took. 03:53.600 --> 03:55.310 If for some reason we are 03:55.310 --> 03:57.770 doubtful about it then any hashes we make of 03:57.770 --> 04:00.575 it after that are pretty much useless because 04:00.575 --> 04:02.420 our baseline that we are using to compare 04:02.420 --> 04:04.940 everything to is no longer solid. 04:04.940 --> 04:07.640 In addition, older hashing algorithms 04:07.640 --> 04:09.274 can allow for collisions. 04:09.274 --> 04:11.600 A collision is when we can take 04:11.600 --> 04:14.090 two completely different inputs but they will 04:14.090 --> 04:17.005 both produce the same output hash. 04:17.005 --> 04:20.435 This happens more often in our older algorithms, 04:20.435 --> 04:23.370 and we're going to cover some of those on the next slide. 04:23.740 --> 04:26.480 Here are some hashing algorithms. 04:26.480 --> 04:28.715 The most famous and most widely used 04:28.715 --> 04:31.584 is the Message-Digest Algorithm or MD5. 04:31.584 --> 04:34.425 It creates a 128-bit output, 04:34.425 --> 04:36.385 but it's easily brute-forced 04:36.385 --> 04:38.420 and it has a high chance of collisions. 04:38.420 --> 04:41.780 I say it's the most widely used because it's 04:41.780 --> 04:45.365 still in use for things where no security is concerned. 04:45.365 --> 04:49.630 For example, for downloading ISO files, MD5 is fine. 04:49.630 --> 04:53.120 But it's long since been considered 04:53.120 --> 04:55.040 insecure and has been replaced by 04:55.040 --> 04:57.380 other far stronger algorithms. 04:57.380 --> 05:00.380 Next, we have the Secure Hash Algorithm or SHA. 05:00.380 --> 05:02.135 We have several variants for this one. 05:02.135 --> 05:06.700 The first is SHA-1 and it produces a 160-bit output, 05:06.700 --> 05:08.180 but it has also successfully 05:08.180 --> 05:09.500 been cracked and it should not 05:09.500 --> 05:12.640 be used for anything that needs to be considered secure. 05:12.640 --> 05:16.640 SHA-3 is a replacement and it has fundamentally 05:16.640 --> 05:18.680 changed the way the algorithm 05:18.680 --> 05:21.990 works compared to the previous SHA-1 or even MD5. 05:21.990 --> 05:24.550 We also have the Race Integrity Primitives 05:24.550 --> 05:27.295 Evaluation Message Digest or RIPEMD. 05:27.295 --> 05:29.900 This was developed completely independently from 05:29.900 --> 05:31.820 the US government and it has 05:31.820 --> 05:34.270 versions that allow for 128, 05:34.270 --> 05:38.705 160, 256 and 320 bit outputs. 05:38.705 --> 05:41.730 This is used for bitcoin addresses. 05:43.060 --> 05:46.045 Message authentication codes. 05:46.045 --> 05:48.050 Remember when I said in previous lessons that 05:48.050 --> 05:49.790 you would see MAC several times throughout 05:49.790 --> 05:51.590 the course and they would almost always 05:51.590 --> 05:54.990 be different meanings, 05:54.990 --> 05:56.980 this is another example of that. 05:56.980 --> 05:59.120 Message authentication codes allows 05:59.120 --> 06:01.925 us to validate messages. 06:01.925 --> 06:05.875 These are hash-based message authentication codes, 06:05.875 --> 06:08.915 HMAC, and this is a specific usage 06:08.915 --> 06:11.150 of MAC, message authentication codes. 06:11.150 --> 06:13.760 With HMAC, both the source and the message 06:13.760 --> 06:17.015 content can be verified without needing anything else. 06:17.015 --> 06:18.770 MAC is created through hashing 06:18.770 --> 06:20.365 and then it becomes an HMAC. 06:20.365 --> 06:22.280 HMACs have two parameters, 06:22.280 --> 06:24.080 the message and a secret key that is 06:24.080 --> 06:27.060 known by the sender and the receiver. 06:27.410 --> 06:30.995 Here's a flow of how HMAC works. 06:30.995 --> 06:34.489 The sender creates a message which is then concatenated 06:34.489 --> 06:38.120 with a symmetric key that the receiver also has. 06:38.120 --> 06:41.630 The message and the key are hashed using a MAC algorithm. 06:41.630 --> 06:42.965 This could be SHA-2, 06:42.965 --> 06:45.245 SHA-3 or SHA-256, 06:45.245 --> 06:47.315 and that is sent to the receiver. 06:47.315 --> 06:50.000 The receiver can use the MAC algorithm to check 06:50.000 --> 06:53.405 the hash and then confirm the integrity of the message, 06:53.405 --> 06:55.760 and then decrypt it using the key with 06:55.760 --> 06:59.010 a reasonable certainty that it came from the sender. 07:02.750 --> 07:05.900 Poly1305 is a MAC that is 07:05.900 --> 07:08.945 focused on speed and efficiency. 07:08.945 --> 07:11.510 If functions were on devices that do not have 07:11.510 --> 07:14.375 hardware acceleration for crypto like AES, 07:14.375 --> 07:17.990 and when used with algorithms like ChaCha20 or Salsa20, 07:17.990 --> 07:19.970 it is much faster and has 07:19.970 --> 07:22.980 better performance than traditional algorithms. 07:24.040 --> 07:26.585 Symmetric algorithms. 07:26.585 --> 07:29.540 These are used to encrypt data or messages. 07:29.540 --> 07:32.620 They can only be unlocked with a single key. 07:32.620 --> 07:34.780 Encryption isn't like hashing as you 07:34.780 --> 07:37.045 can view the data once it's been decrypted. 07:37.045 --> 07:38.680 That's a key thing to keep in mind 07:38.680 --> 07:40.675 between hashing and encryption. 07:40.675 --> 07:43.375 The weakness for symmetric algorithms is the 07:43.375 --> 07:46.855 creating and distributing the keys in a secure way. 07:46.855 --> 07:48.750 This is similar to, 07:48.750 --> 07:51.310 imagine you have a file and you 07:51.310 --> 07:52.540 right-click on it and select 07:52.540 --> 07:54.295 encrypt and it asks you for a password. 07:54.295 --> 07:56.530 You type the password. Now the file is encrypted. 07:56.530 --> 07:58.930 You want to send that to someone across the Internet, 07:58.930 --> 08:01.240 but you also have to send the key with them too. 08:01.240 --> 08:03.955 For one-to-one, this is not such a big deal. 08:03.955 --> 08:05.230 You can call someone up, 08:05.230 --> 08:07.270 you can find another way to get the key to 08:07.270 --> 08:08.470 them or maybe it's just something 08:08.470 --> 08:09.820 you agree to ahead of time. 08:09.820 --> 08:12.480 But imagine having to do this with millions of people. 08:12.480 --> 08:15.860 It becomes very cumbersome to use symmetric algorithms in 08:15.860 --> 08:20.425 this way. Stream cipher. 08:20.425 --> 08:23.750 This is where every digit of plaintext data 08:23.750 --> 08:27.080 is encrypted one at a time using a keystream. 08:27.080 --> 08:29.585 This is a stream of pseudorandom values. 08:29.585 --> 08:32.165 It's useful for encrypting data when the amount 08:32.165 --> 08:35.195 or the length of the data isn't known like video. 08:35.195 --> 08:38.570 Key streams are generated by an initialization vector 08:38.570 --> 08:41.585 IV that is combined with a static key. 08:41.585 --> 08:43.850 This creates a unique key stream. 08:43.850 --> 08:47.000 The IV is always changing to ensure that 08:47.000 --> 08:48.320 the unique ciphertext is 08:48.320 --> 08:51.240 created from the same plain text. 08:52.600 --> 08:56.960 Block ciphers. This is where plain texts to separate it 08:56.960 --> 08:58.565 into equal size blocks 08:58.565 --> 09:00.950 and they're usually 128 bits in length. 09:00.950 --> 09:04.550 If there isn't enough data to fill a block, it is padded. 09:04.550 --> 09:06.500 This is where we add additional data to 09:06.500 --> 09:09.290 the end to bring it up to 128 bits. 09:09.290 --> 09:11.540 Each block is then encrypted based on 09:11.540 --> 09:13.690 the mode of operation being used. 09:13.690 --> 09:15.500 We'll go over those modes of operation in 09:15.500 --> 09:17.830 the next slide. Let's do an example. 09:17.830 --> 09:21.140 We have 950 bits of data that we need to encrypt. 09:21.140 --> 09:23.510 The data will be broken into seven blocks that are 09:23.510 --> 09:26.395 128 bits long but we have a leftover, 09:26.395 --> 09:28.270 the block will be 54 bits. 09:28.270 --> 09:30.760 We will add 74 bits to 09:30.760 --> 09:35.770 that to bring that last block up to 128 bits. 09:38.390 --> 09:41.810 This is the cipher modes of operation. 09:41.810 --> 09:43.250 There are quite a lot here. 09:43.250 --> 09:45.050 But the key to remember is 09:45.050 --> 09:47.135 that we're only going to be using 09:47.135 --> 09:50.180 the last three or four because this has 09:50.180 --> 09:51.440 been the evolution of 09:51.440 --> 09:53.635 the different modes of ciphers over time. 09:53.635 --> 09:55.130 The first one we'll go over is 09:55.130 --> 09:57.470 the cipher block chaining or CBC. 09:57.470 --> 10:00.365 This is a very simple mode and it should not be used. 10:00.365 --> 10:03.530 The same is true of the Electronic Code Book or ECB. 10:03.530 --> 10:04.820 Another one that's very simple 10:04.820 --> 10:06.425 mode and shouldn't be used. 10:06.425 --> 10:10.235 Next we have the Galois Counter Mode or GCM. 10:10.235 --> 10:12.470 This is a high performance mode 10:12.470 --> 10:13.730 of operation and it provides 10:13.730 --> 10:19.430 authenticated encryption and it's been widely adopted. 10:19.430 --> 10:21.990 We also have counter or CTR. 10:21.990 --> 10:24.050 This applies an IV and 10:24.050 --> 10:25.880 an incrementing counter value 10:25.880 --> 10:28.390 to the key to create a keystream. 10:28.390 --> 10:30.140 You do not need padding with 10:30.140 --> 10:32.695 the leftover space because it's removed. 10:32.695 --> 10:36.255 Then finally we have the Output Feedback or OFB. 10:36.255 --> 10:39.375 This uses initial chaining vector, ICV, 10:39.375 --> 10:42.065 for the first round and then combines the output of 10:42.065 --> 10:46.320 all previous rounds as input to the next round. 10:48.590 --> 10:52.275 Stream ciphers and block cipher examples. 10:52.275 --> 10:54.885 For stream ciphers, we have RC4. 10:54.885 --> 10:57.115 This was developed in 1984 10:57.115 --> 10:59.075 and it has numerous vulnerabilities. 10:59.075 --> 11:01.115 It really shouldn't be used anymore. 11:01.115 --> 11:02.850 We also have Salsa20. 11:02.850 --> 11:04.760 It was developed in 2005 and it's 11:04.760 --> 11:07.460 well regarded and it's also a fast algorithm. 11:07.460 --> 11:09.255 We also have ChaCha, 11:09.255 --> 11:11.955 which is a variant of Salsa developed in 2008. 11:11.955 --> 11:15.665 It's used in Chrome on Android devices. 11:15.665 --> 11:17.630 It's good for devices that lack 11:17.630 --> 11:19.130 the hardware support that couldn't 11:19.130 --> 11:21.960 use algorithms such as AES. 11:22.090 --> 11:24.320 For block ciphers, we have 11:24.320 --> 11:27.365 the Data Encryption Standard or DES, or triple DES. 11:27.365 --> 11:30.135 This was originally developed in 1977. 11:30.135 --> 11:33.240 This states DES should be replaced with AES. 11:33.240 --> 11:34.455 Being an old cipher, 11:34.455 --> 11:35.835 DES has already been broken 11:35.835 --> 11:38.090 and that was the purpose for AES 11:38.090 --> 11:42.645 being created was to shift everything from DES to AES. 11:42.645 --> 11:44.690 Finally we have AES, 11:44.690 --> 11:46.700 which is the Advanced Encryption Standard. 11:46.700 --> 11:49.070 This is the US Federal Government encryption standard 11:49.070 --> 11:50.719 for symmetric algorithms. 11:50.719 --> 11:53.120 It's very efficient and secure and 11:53.120 --> 11:55.445 it's available in 128 bit, 11:55.445 --> 11:58.190 192 and 256 bit versions. 11:58.190 --> 12:00.910 It's based on the Rijndael algorithm. 12:00.910 --> 12:03.650 Two other examples because you've probably seen them 12:03.650 --> 12:07.745 in your own research online are Twofish and Blowfish. 12:07.745 --> 12:10.170 These are both block ciphers. 12:10.940 --> 12:13.200 Here's some crypto humor. 12:13.200 --> 12:16.410 Like I said, this cartoon always has good stuff. 12:16.410 --> 12:18.500 I really got a kick out of this one 12:18.500 --> 12:20.405 when I was building this lesson. 12:20.405 --> 12:22.770 Hopefully you'd like it as well. 12:24.440 --> 12:27.050 Let's summarize. We went 12:27.050 --> 12:29.165 over hashing and hashing algorithms. 12:29.165 --> 12:31.850 We also discuss symmetric algorithms 12:31.850 --> 12:33.845 and streaming and block ciphers. 12:33.845 --> 12:37.255 We went over the different encryption modes of operation. 12:37.255 --> 12:40.360 Let's do some example questions. 12:40.430 --> 12:43.095 Question 1, true or false. 12:43.095 --> 12:46.490 Symmetric encryption keys can be sent through email so 12:46.490 --> 12:50.815 that the recipient can decrypt any encrypted attachments. 12:50.815 --> 12:56.070 False. Symmetric keys must be shared in a secure manner. 12:56.900 --> 13:00.230 Question 2, blank transforms 13:00.230 --> 13:04.500 data inputs into fixed length output called a digest. 13:05.140 --> 13:09.925 Hashing. Question 3, 13:09.925 --> 13:12.440 this type of symmetric algorithm encrypts 13:12.440 --> 13:13.730 each bit of data 13:13.730 --> 13:15.575 and is ideal for situations 13:15.575 --> 13:18.660 where the amount of data is unknown. 13:19.420 --> 13:24.110 Stream cipher. Remember this is often used for video. 13:24.110 --> 13:25.550 If you keep that in mind 13:25.550 --> 13:27.710 that you don't know how long that video file 13:27.710 --> 13:31.280 is going to be and because it's unknown, 13:31.280 --> 13:33.275 it's being streamed across the Internet, 13:33.275 --> 13:34.835 think stream cipher, 13:34.835 --> 13:36.680 unknown length video that 13:36.680 --> 13:39.540 will maybe help you remember for the test. 13:39.760 --> 13:42.200 Question 4, this is 13:42.200 --> 13:44.210 the current US government encryption standard 13:44.210 --> 13:46.410 and is widely used. 13:46.670 --> 13:50.055 Advanced Encryption Standard or AES. 13:50.055 --> 13:51.470 Hope this lesson was helpful 13:51.470 --> 13:53.880 for you and I'll see you the next one.