WEBVTT 00:00.330 --> 00:08.040 Symmetric algorithms are fantastic ways to encrypt and decrypt data but symmetric algorithms have one 00:08.040 --> 00:09.120 big problem. 00:09.120 --> 00:12.500 You use the same key to encrypt that you do to decrypt. 00:12.630 --> 00:16.760 And in the real world that can cause some very serious issues. 00:16.770 --> 00:18.950 Now in order to show you what those issues are. 00:19.110 --> 00:22.380 Let me introduce you to my friends Alice and Bob. 00:22.510 --> 00:27.840 Now Alice and Bob what to send each other encrypted data of some form or another. 00:27.840 --> 00:30.440 Now it doesn't matter at this point what they're sending. 00:30.540 --> 00:35.880 Alice could be a web server and Bob could be a web browser or Allison Bob could be sending each other 00:35.880 --> 00:38.540 encrypted e-mail or they could be talking on Skype. 00:38.550 --> 00:41.100 I don't care what they're actually doing. 00:41.160 --> 00:44.060 They simply want to send each other encrypted data. 00:44.220 --> 00:49.470 Now if we were to use a symmetric algorithm like eight Yes that's a great algorithm. 00:49.470 --> 00:55.980 The only downside to ABSs is that the same key that Alice is going to use to encrypt has to be used 00:55.980 --> 00:57.440 by Bob to decrypt. 00:57.450 --> 00:59.970 So how does Alice get the key to Bob. 00:59.970 --> 01:07.320 And that's where the problem comes in asymmetric decryption are vulnerable to people like Eve here who 01:07.320 --> 01:12.540 are listening in if elsewhere to send the key via an e-mail or something like that than Eve could get 01:12.540 --> 01:16.110 a copy of it and she could decrypt our encoded information. 01:16.110 --> 01:22.330 So this is always a big problem with symmetric types of encryption. 01:22.380 --> 01:28.890 The secret to getting around this problem is to not just use one key to both encrypt and decrypt. 01:28.920 --> 01:38.310 The secret is is to use two keys one key can only encrypt and one key can only decrypt and this key 01:38.610 --> 01:45.120 can only encrypt in such a way that only this key can decrypt it so you can have a bunch of other keys. 01:45.150 --> 01:50.130 But if you don't have this key pair and you don't have them set up the right way you're not going to 01:50.130 --> 01:51.150 be able to do anything. 01:51.150 --> 01:57.930 So this is a very powerful idea and we call this asymmetric encryption so asymmetric encryption will 01:57.930 --> 02:00.480 always consist of what we call a key pair. 02:00.510 --> 02:03.830 Now one key is one key we just give out to anybody who wants it. 02:03.830 --> 02:09.090 You know even the bad guys go ahead have a copy of the bad guy because the only thing that this can 02:09.090 --> 02:13.180 do is encrypt data that can only be decrypted by this one. 02:13.320 --> 02:18.660 So this one that we send out to everybody we call this the public key so we send this out to whoever 02:18.660 --> 02:19.900 wants it now. 02:19.920 --> 02:21.480 That way somebody could go out there. 02:21.480 --> 02:27.570 If I give them my public key they can encrypt and then send me something or if I've got a web page they 02:27.570 --> 02:31.220 can encrypt it and send it to me or whatever it is they can send it to me. 02:31.230 --> 02:38.610 And the only person who can decrypt from this public key is me with what we call the private key. 02:38.610 --> 02:45.190 So when we talk about asymmetric we're talking about two keys a public key and a private key. 02:45.210 --> 02:50.230 Now there's a whole bunch of ways to do this and I want to go through some of the examples right now. 02:50.220 --> 02:53.430 Let's start with probably the grandad of all good old RSA 02:57.910 --> 03:05.320 RSA stands for Rivest Shamir and Edelman three guys who got together and back in the late 1970s came 03:05.320 --> 03:10.080 up with a whole bunch of algorithms and protocols which are collectively known as RSA. 03:10.090 --> 03:12.870 Now in this point I want to cover the most basic parts. 03:12.970 --> 03:15.810 So RSA is an asymmetric algorithm. 03:15.940 --> 03:21.780 So that means we have to have a public private key the public key encrypts and the private key decrypts. 03:21.850 --> 03:28.420 So RSA number one specifies how do you as an individual host generate your own public and private key 03:28.420 --> 03:29.100 pair. 03:29.290 --> 03:34.480 And then secondly how we go about sending public keys to people that we want to talk to. 03:34.720 --> 03:40.900 Now I don't know about you but I find it utterly fascinating that somebody can use groovey math to take 03:40.900 --> 03:43.480 one algorithm and you take that one algorithm. 03:43.570 --> 03:47.990 You show in a public key you take some plaintext and outcome ciphertext. 03:48.010 --> 03:53.500 Now you take the same algorithm you pull out your public key put in your private key and you take that 03:53.500 --> 03:57.550 ciphertext and it comes out as plaintext Well it absolutely works. 03:57.550 --> 04:04.010 Now the math behind RSA is pretty advanced and you don't need to know it for the exam. 04:04.120 --> 04:08.520 But I want to give you at least a little bit of a tease to get an idea of how all this works. 04:08.530 --> 04:14.300 So what I'd like you to do is talk about factoring a little bit so let's take the number 12 for example. 04:14.320 --> 04:18.370 Now the factors are all the numbers that can be multiplied together to come up with 12. 04:18.370 --> 04:22.590 So just from experience we know three times four equals 12. 04:22.720 --> 04:24.620 We know two times six equals 12. 04:24.760 --> 04:27.070 And of course one times 12 equals 12. 04:27.070 --> 04:32.650 So it's fairly trivial for us for a small number like this to come up with all the factors for the number 04:32.650 --> 04:33.660 12. 04:33.670 --> 04:39.550 Now there are lots of numbers out there that can only be divided by themselves like for example the 04:39.550 --> 04:47.560 number 11 is a number that can only be divided by itself we call that a prime number so a prime number 04:47.650 --> 04:53.410 like a lead that is fairly easy to look at and we can say well we can only multiply that times 1 and 04:53.410 --> 04:54.250 11. 04:54.310 --> 05:01.510 But if you take two prime numbers and you multiply them together so 11 and 17 say we get what's known 05:01.510 --> 05:05.650 as a send the prime number which is in this case 187. 05:05.650 --> 05:10.910 Now if I had taken 11 and 17 away and I said go ahead and factor that. 05:10.990 --> 05:12.680 How long do you think it would take you to do it. 05:12.700 --> 05:14.190 It would take you a while. 05:14.200 --> 05:22.260 There is no easy groovey mathematical way to do factoring all factoring is basically done by brute force. 05:22.270 --> 05:27.260 Now again because 187 is a relatively small number you can figure that out. 05:27.310 --> 05:30.900 But how about if I generate a slightly larger 70 prime number like. 05:31.090 --> 05:32.070 How about that. 05:33.560 --> 05:38.000 I'll take a minute in fact I'll take 15 minutes right now on the video and let you go ahead and try 05:38.000 --> 05:39.360 to figure that one out. 05:39.590 --> 05:41.090 No I'm kidding I'm kidding. 05:41.090 --> 05:43.750 Let me go ahead and generate those answers for you. 05:43.760 --> 05:46.640 The bottom line is that it's very very hard to factor. 05:46.730 --> 05:55.400 So in the world of RSA we start off with values that can be oh so like forty thousand ninety six bits 05:55.400 --> 05:56.160 long. 05:56.240 --> 06:00.090 So how about a number like this and that isn't even 40 96 bits worth. 06:00.110 --> 06:02.060 Do you think you could factor that one easily. 06:02.060 --> 06:06.410 Why don't you go ahead and get your best supercomputer and take a couple of hundred years and you tell 06:06.410 --> 06:09.530 me what the two prime numbers are that generate this value. 06:09.830 --> 06:15.140 That's the cornerstone of our s a is to be able to take two large prime numbers multiplied together 06:15.140 --> 06:17.050 to generate a semi prime number. 06:17.090 --> 06:20.240 The actual math behind this is wildly complicated. 06:20.240 --> 06:25.130 There are wonderful resources on the Internet that you can look at if you really want to get into the 06:25.130 --> 06:30.140 math but that is the process we use to generate our initial key pair. 06:30.140 --> 06:31.860 Now once we had that key pair. 06:31.970 --> 06:37.160 Let's go ahead and use Alice and Bob and show you how an RSA key exchange takes place. 06:37.160 --> 06:41.830 Now Allison Bob want to communicate via RSA asymmetric encryption. 06:41.990 --> 06:46.250 So the first thing they're going to do is generate each of their own key pairs. 06:46.400 --> 06:50.380 And this is done through whatever software is supplied for that particular application. 06:51.110 --> 06:55.160 And then they go about the process of exchanging their public keys. 06:55.160 --> 07:00.500 Now keep in mind if each grabs one of these public keys it doesn't really make any difference because 07:00.770 --> 07:05.540 the only thing Eve could do would be encrypt something and then send it to somebody else for them to 07:05.540 --> 07:06.320 decrypt. 07:06.590 --> 07:13.160 But there is a problem and that is what if Eve pretends to be Alice or Bob. 07:13.400 --> 07:20.030 Well the RSA guys thought about that stuff ahead of time and s a includes all kinds of protocols that 07:20.030 --> 07:24.020 do things that include what we call authentication. 07:24.020 --> 07:30.050 Now we have entire episodes that cover all of this stuff in fact boils down to digital signatures and 07:30.050 --> 07:32.000 certificates just to give you an idea. 07:32.120 --> 07:36.100 But that even goes beyond the basics of what I want to cover in this episode. 07:36.110 --> 07:41.690 So go ahead and check out those episodes if you really want to get into the details of what makes this 07:41.690 --> 07:43.500 a very very powerful. 07:43.640 --> 07:47.870 Now RSA is great but it's been around for a long long time. 07:47.900 --> 07:57.080 When RSA first came out it had very short keys 256 bit keys 512 bit keys 1024 bit keys and in the last 07:57.080 --> 08:03.560 few years the Internet folks have said if you're going to use RSA use at least a 2048 bit key as your 08:03.560 --> 08:09.050 absolute minimum size because computers are getting better and people are figuring out how to crack 08:09.230 --> 08:10.730 the smaller keys. 08:10.790 --> 08:16.420 So even though RSA goes up to 40000 ninety four thousand ninety six. 08:16.490 --> 08:22.430 The problem that we run into is that these become big keys and people have to keep copies of keys and 08:22.700 --> 08:30.080 it becomes kind of a bit of a pain and that's why we came up with a new type of methodology called ECAC 08:35.000 --> 08:41.420 elliptic curve cryptography or ECAC is probably about the hottest thing that's going right now in terms 08:41.420 --> 08:43.220 of asymmetric algorithms. 08:43.490 --> 08:52.550 The power of ECAC is that it can provide us very very small keys that we can transfer around that have 08:52.550 --> 08:55.820 the same robustness as much larger RSA keys. 08:55.830 --> 09:02.160 So write down don't hold me to this because there's differences of opinion but basically a three thousand 09:02.160 --> 09:09.130 seventy two bit are as a key can now be replaced with roughly a 256 bit ECAC key. 09:09.140 --> 09:15.500 So that is one of the biggest benefits of A.S.C. also generated these keys and going through the encryption 09:15.500 --> 09:20.690 decryption process is a lot faster than an RSA even That's arguable though. 09:20.900 --> 09:25.110 The bottom line is that ECAC is based on an elliptic curve formula. 09:25.130 --> 09:26.820 It looks basically like this. 09:27.810 --> 09:30.780 So this formula when plotted on a graph. 09:30.870 --> 09:35.190 Well look well in one of many iterations will look something like this. 09:35.460 --> 09:42.090 So you can actually do as you can plot a point on the curve and through a lot of fascinating mumbojumbo 09:42.300 --> 09:49.770 can generate a key pair that is extremely robust extremely fast and extremely small compared to RSA 09:50.580 --> 09:54.340 A.S.C. is only now starting to come out in a big big way. 09:54.360 --> 09:58.900 But we're seeing it take over more and more everyday.