WEBVTT 0 00:01.230 --> 00:08.640 All right, so we've taken a look at level one encryption, which is basically just storing the password 1 00:08.640 --> 00:11.220 as plain text in our database. 2 00:11.370 --> 00:18.770 So maybe it'll be a little bit difficult for people to get access to our server and access our database. 3 00:18.810 --> 00:20.160 At least you can't just simply 4 00:20.160 --> 00:20.490 right- 5 00:20.490 --> 00:25.690 click on a website to view page source and be able to see it in the HTML. 6 00:25.710 --> 00:30.140 At least it's stored at server level. But that's not really good enough. 7 00:30.150 --> 00:37.150 So let's go ahead and see what we can do to improve the security for our users on our website. 8 00:37.470 --> 00:47.710 So let's increase to level two authentication. And level two authentication involves the use of encryption. 9 00:48.480 --> 00:50.520 So what exactly is encryption? 10 00:50.550 --> 00:57.900 Well, basically all it is is just scrambling something so that people can't tell what the original 11 00:57.900 --> 01:02.890 was unless they were in on the secret and they knew how to unscramble it. 12 01:03.240 --> 01:08.610 This is exactly the same as if you and your friend were sending each other secret messages and you had 13 01:08.610 --> 01:14.010 a key to encode the message that you both knew that so that you could decode the message. 14 01:14.970 --> 01:21.480 Now, on a bigger scale, if you've ever watched The Imitation Game or read about the Enigma machine, 15 01:21.690 --> 01:24.750 well, that is basically a form of encryption. 16 01:25.230 --> 01:31.320 And the Enigma machine, if you don't know, is just simply a machine that was used during World War 17 01:31.320 --> 01:34.890 2 when the Germans would send each other messages, 18 01:35.100 --> 01:41.280 they would use the machine to encrypt those messages so that when the messages are intercepted, say, 19 01:41.280 --> 01:50.220 over the radio, unless you had the same Enigma machine and you knew what the decoding key was or what 20 01:50.220 --> 01:54.660 the settings were for the machine, then you wouldn't be able to tell what it is that they were trying 21 01:54.660 --> 01:56.000 to communicate with each other. 22 01:56.310 --> 02:03.660 If you're interested, I really recommend watching two videos that were done by Numberphile on YouTube and 23 02:03.660 --> 02:06.210 I've linked to it in the course resources list. 24 02:06.540 --> 02:14.310 But it explains the Enigma machine and it talks about the flaw in the Enigma machine that led Alan Turing 25 02:14.310 --> 02:20.760 and other people at Bletchley Park to be able to crack the code and create what was very much a specialized 26 02:20.760 --> 02:25.920 computer to be able to decode those messages and helped the allies win the war. 27 02:26.310 --> 02:32.010 And if you ever visit London, be sure to go and check out Bletchley Park and they have a computer museum 28 02:32.010 --> 02:34.230 next to it as well, which is super fascinating. 29 02:34.740 --> 02:36.020 Anyways, I digress. 30 02:36.030 --> 02:36.810 So back to 31 02:36.810 --> 02:43.590 ciphers and encryption, one of the earliest ways of encrypting messages that we know about is the Caesar 32 02:43.590 --> 02:44.120 cipher. 33 02:44.610 --> 02:50.850 And this comes from Julius Caesar, who was one of the generals in the Roman Empire. 34 02:51.000 --> 02:57.770 And what he did is he would send messages to his generals and he would encrypt it 35 02:58.020 --> 03:03.330 so if his messenger got murdered along the way, then his messages would be kept secret. 36 03:03.990 --> 03:09.090 And this is one of the simplest forms of encryption we know about 37 03:09.360 --> 03:10.550 and it's very simple. 38 03:10.560 --> 03:16.080 Let's say we have the alphabet, right? ABCDEFG. All that the Caesar Cipher does 39 03:16.080 --> 03:18.540 is a letter substitution cipher. 40 03:18.660 --> 03:24.820 And the key for the cipher is the number of letters that you would shift by. 41 03:24.870 --> 03:31.900 So if you knew what the shift pattern was, then you could really quickly decipher the message. 42 03:32.340 --> 03:38.210 So if we were to encrypt the word hello, there's a really neat tool online that can help us do that. 43 03:38.220 --> 03:41.850 It's called cryptii.com and it's got two 'i's at the end. 44 03:42.300 --> 03:47.760 And you can basically choose the kind of cipher or encryption that you want to use 45 03:48.120 --> 03:52.550 and then you can specify the shift and we're going to say a shift of three, let's say. 46 03:52.800 --> 04:00.930 So if my text was hello, then it becomes shifted into khoor. And to an unknowing person and a non-cryptographer, 47 04:01.200 --> 04:07.950 it can be quite difficult to see at a glance what exactly this is trying to say. Now in modern days and 48 04:07.950 --> 04:14.010 with modern cryptography, this is overly simplistic and it's very, very easy to crack. 49 04:14.460 --> 04:20.550 But there are other forms of encryption which are a little bit more complicated and it involves a lot 50 04:20.550 --> 04:25.380 more math to make it more time consuming for somebody to crack. 51 04:25.770 --> 04:29.760 But essentially all encryption works exactly the same way. 52 04:30.150 --> 04:38.730 You have a way of scrambling your message and it requires a key to be able to unscramble that message. 53 04:39.450 --> 04:39.930 All right. 54 04:39.930 --> 04:44.520 So now it's time to level up to the next level of security. 55 04:44.760 --> 04:48.630 And in this lesson, we're going to cover something called hashing. 56 04:49.620 --> 04:56.910 Now, previously, we've already looked at encryption, so taking the user's password and securing it 57 04:56.910 --> 05:00.120 using an encryption key, and then 58 05:00.140 --> 05:06.560 using a particular cipher method, be it a Caesar cipher or the Enigma cipher, no matter which way 59 05:06.560 --> 05:12.440 we chose, we always had a password, a key, and we ended up with some ciphertext which will make it 60 05:12.440 --> 05:16.940 hard for people to be able to immediately guess what our user's password is. 61 05:17.120 --> 05:23.390 So, for example, if we took a password like qwerty and we use the Caesar cipher method and we decided to 62 05:23.390 --> 05:27.440 shift it by one, then our encryption key is the number one. 63 05:27.860 --> 05:32.880 And that creates the ciphertext where every single letter is shifted up by one. 64 05:33.350 --> 05:39.110 Now, in order to decrypt this, all you have to do, as long as you know what the key is, then you 65 05:39.110 --> 05:45.980 can simply shift all of the ciphertext down by one and you end up with the original password. 66 05:46.340 --> 05:51.650 Now, the Caesar cipher is a very, very weak encryption method. 67 05:51.650 --> 05:58.310 It's incredibly easy to figure out what the original text was, even if you didn't have a key. 68 05:58.880 --> 06:04.790 And just to illustrate what bad things can happen when you have a weak encryption system, I'm going 69 06:04.790 --> 06:11.110 to tell you a story from history that tells us why we should not be using a weak encryption system. 70 06:11.690 --> 06:18.770 So back in the 1500's on this island that we now call the United Kingdom, there used to be two large 71 06:18.770 --> 06:19.400 areas. 72 06:19.670 --> 06:23.810 One was Scotland and the other was England. 73 06:24.320 --> 06:27.080 And they were ruled over by two Queens. 74 06:27.380 --> 06:33.860 Scotland was ruled by Mary Queen of Scots, who was a Catholic, and England was ruled over by Queen 75 06:33.860 --> 06:35.210 Elizabeth the first. 76 06:35.630 --> 06:41.330 Now, these two ladies between them controlled the land that we now call the UK, but they each wanted 77 06:41.330 --> 06:43.790 to have more power and more land. 78 06:44.300 --> 06:45.990 So what did they do? 79 06:46.010 --> 06:53.870 Well, Mary Queen of Scots who ruled over Scotland decided to plot with her friend, Lord Babington, 80 06:54.200 --> 06:56.800 to try and assassinate Queen Elizabeth. 81 06:57.260 --> 07:02.720 That way, she would be the legitimate heir to both the English and Scottish throne, 82 07:03.050 --> 07:06.920 and it was kind of a Game of Thrones kind of situation going on back then. 83 07:07.460 --> 07:13.910 But in order to mobilize their forces or try to come up with some sort of secret plan, they decided 84 07:13.910 --> 07:17.800 to send letters to each other using ciphertext. 85 07:18.020 --> 07:25.850 So they came up with a system to encrypt their letters to each other such that if it fell into the wrong 86 07:25.850 --> 07:32.800 hands, the subject of the letter wouldn't be revealed and they wouldn't end up being tried for treason. 87 07:32.990 --> 07:39.260 But the problem was that the encryption method that they used, which was a letter substitution method 88 07:39.410 --> 07:44.510 similar to the Caesar cipher, was a very weak form of encryption. 89 07:45.110 --> 07:54.230 And Queen Elizabeth had a chief decoder who ended up deciphering their letters and figuring out what 90 07:54.230 --> 07:56.220 their encryption key was. 91 07:56.420 --> 08:04.400 So he decided to take this encryption key and write a letter back to Lord Babington to try and get him 92 08:04.400 --> 08:07.490 to reveal all of the co-conspirators. 93 08:07.880 --> 08:11.330 And what was the end result of having their weak encryption system? 94 08:11.720 --> 08:19.250 Well, Queen Elizabeth decided to accuse Mary Queen of Scots of treason, and hence she ended up having 95 08:19.250 --> 08:20.360 her head chopped off. 96 08:20.750 --> 08:25.420 So this is not what you want to happen to you or your website. 97 08:25.940 --> 08:33.320 So weak encryption systems can end up putting user passwords at risk and your company might end up metaphorically 98 08:33.320 --> 08:39.230 decapitated, such as in the case of companies like TalkTalk or Equifax, where they ended up getting 99 08:39.230 --> 08:42.200 hacked and lost a lot of the trust of their users. 100 08:42.440 --> 08:48.410 Now, if you're interested in more stories like this and to learn more about cryptography and encryption, 101 08:48.590 --> 08:52.820 there's a really great book recommendation I would make called The Code Book by Simon Singh. 102 08:53.000 --> 08:56.480 It contains stories like the one that I just told you and more. 103 08:56.540 --> 08:59.380 So if you're interested in this, go ahead and read more about it. 104 08:59.720 --> 09:03.500 Now, how can we make our password more secure Now, 105 09:03.530 --> 09:09.920 at the moment, the biggest flaw in our authentication method is the fact that we need an encryption 106 09:09.920 --> 09:14.450 key to encrypt our passwords and decrypt our passwords. 107 09:14.870 --> 09:22.040 And chances are that if somebody is motivated enough to spend time and hack into your database, then 108 09:22.040 --> 09:29.150 it's probably not that difficult for them to also be able to get your encryption key, even if you've 109 09:29.150 --> 09:33.480 saved it in environment variable or somewhere secure on your server. 110 09:33.950 --> 09:38.880 So how can we address this weakest link, the need for that encryption key? 111 09:39.140 --> 09:45.380 Well, here is where hashing comes into play. Whereas previously with encryption we needed that encryption 112 09:45.380 --> 09:52.560 key, hashing takes it away and no longer requires the need for an encryption key. 113 09:53.180 --> 09:59.450 Well, then you might ask, well, if we don't have an encryption key, how can we decrypt our password 114 09:59.450 --> 09:59.990 back into 115 10:00.060 --> 10:08.520 plain text? Well, the secret is you don't. Let's say a user registers on our website and they enter 116 10:08.520 --> 10:16.560 a password to register with, we use something called a hash function to turn that password into a hash 117 10:16.560 --> 10:19.500 and we store that hash in our database. 118 10:20.160 --> 10:29.700 Now, the problem is that hash functions are mathematical equations that are designed to make it almost 119 10:29.700 --> 10:32.280 impossible to go backwards. 120 10:32.560 --> 10:38.910 So it's almost impossible to turn a hash back into a password. 121 10:39.150 --> 10:41.130 How is this possible, you might ask? 122 10:41.160 --> 10:48.690 How is it possible that you can turn a password into a hash very quickly and easily, but make it almost 123 10:48.690 --> 10:52.080 impossible to turn that hash back into a password? 124 10:52.800 --> 10:53.880 Well, here's a question. 125 10:54.600 --> 11:01.710 Let me ask you, what are the factors of 377 other than one and 377? 126 11:02.040 --> 11:05.650 So basically, I'm saying 377 is not a prime number. 127 11:06.090 --> 11:14.490 Not only can you divide 377 by 1 and 377, but there's also two other numbers that you 128 11:14.490 --> 11:15.450 can divide it by. 129 11:15.870 --> 11:19.260 Now it's your job to figure out what those numbers are. 130 11:20.130 --> 11:21.420 So, what might you do? 131 11:21.450 --> 11:23.130 Well, you might divide it by two. 132 11:23.490 --> 11:26.090 OK, so that becomes 188.5. 133 11:26.130 --> 11:27.300 That's not a whole number 134 11:27.300 --> 11:28.880 so 2 is not a factor. 135 11:29.280 --> 11:30.610 What if you divide it by three? 136 11:30.630 --> 11:36.290 Well, that becomes 113.3 recurring, which is also not a whole number. 137 11:36.450 --> 11:38.870 So three is not a factor either. 138 11:39.180 --> 11:45.940 And you might go through this process for a long time, tediously going through number by number. 139 11:45.990 --> 11:53.010 Well, then you might arrive at the point where you divide 377 by 13 and you end up with 140 11:53.010 --> 11:53.680 29. 141 11:54.060 --> 12:04.140 So 13 and 29 are the answers to this question. They are the only factors of 377 other than 1 and 142 12:04.140 --> 12:05.000 377. 143 12:05.640 --> 12:12.750 And as you can see, that process of getting to this point of finding those two factors took us a while, 144 12:12.750 --> 12:13.130 right? 145 12:13.140 --> 12:14.400 It wasn't that easy. 146 12:14.910 --> 12:17.400 But consider if I asked you a different question. 147 12:17.400 --> 12:20.990 If I said to you, can you multiply 13 by 29? 148 12:21.330 --> 12:24.900 Well, you would be able to do that really quickly and easily. 149 12:24.900 --> 12:30.050 It would take you almost no time at all to figure out that the answer is 377. 150 12:30.870 --> 12:36.880 So here is a very, very simplified version of a hash function. 151 12:37.350 --> 12:44.790 So going forward, multiplying 13 by 29 is really quick and easy, but going backward, trying 152 12:44.790 --> 12:46.440 to get back those numbers 153 12:46.440 --> 12:52.360 13 and 29 starting from 377 is very, very time consuming. 154 12:52.770 --> 12:56.120 So this is essentially how a hash function works. 155 12:56.520 --> 13:01.340 Just add a little bit more complexity and you end up with a real hash function. 156 13:01.590 --> 13:09.360 So they're designed to be calculated very quickly going forwards, but almost impossible to go backward. 157 13:09.360 --> 13:10.860 And by almost impossible 158 13:11.100 --> 13:19.110 I simply mean that using current levels of computing power, it would take far too long to make it worthwhile 159 13:19.110 --> 13:19.810 for the hacker. 160 13:20.130 --> 13:26.880 So let's say that to calculate the hash going forward, it takes a millisecond, but to go backward 161 13:26.880 --> 13:31.800 it takes two years, then that hacker probably has better things to do with his time. 162 13:31.980 --> 13:38.700 So when a user tries to register on our website, then we ask them for the registration password, which 163 13:38.700 --> 13:44.720 we turn into a hash using our hash function, and then we store that hash on our database. 164 13:45.210 --> 13:52.020 Now, at a later point when the user tries to log in and they type in their password, then we again 165 13:52.110 --> 14:00.330 hash that password that they typed in to produce a hash and then we compare it against the hash that 166 14:00.330 --> 14:02.570 we have stored in our database. 167 14:03.060 --> 14:10.170 And if those two hashes match, then that must mean that the login password is the same as the registration 168 14:10.170 --> 14:11.100 password as well. 169 14:11.400 --> 14:18.810 And at no point in this process do we have to store their password in plain text or are we able to reverse 170 14:18.810 --> 14:22.350 the process to figure out their original password? 171 14:22.710 --> 14:26.480 The only person who knows their password is the user themselves. 172 14:26.760 --> 14:35.400 Now, previously we saw that by using the Enigma machine, as long as we knew what the settings were 173 14:35.400 --> 14:39.030 for the Enigma machine, which is basically the encryption key, 174 14:39.030 --> 14:39.360 right? 175 14:39.690 --> 14:46.800 As long as we knew what that was, then I can decode it by setting it to the same encryption key. 176 14:48.270 --> 14:55.920 And we end up being able to retrieve the original text. Now, however, if I was to go and change this 177 14:56.130 --> 15:04.860 to a hash function instead, then you can see that when we try to decode this using the same hash function, 178 15:04.860 --> 15:06.900 MD5, we get the error 179 15:06.900 --> 15:12.210 that decoding step is not defined for hash function because you can't really go back. 180 15:12.570 --> 15:19.310 That's the whole point of the hash function and this is what will make our authentication more secure.