Hi. Welcome back to the course. In the last video, we talked about going to a website and checking their security certificate. So during that, I showed you how to do that. And then we talked about certification authorities, including the route certificate and how to look for that.
So in this video, we're gonna talk about crypt analysis, so we'll cover things like linear differential and integral quick analysis. I want to stress It's a very, very high level video on those topics. We're not gonna get a linear algebra or anything like that at all.
And then we're off Murphy attacks. And also, there's a few new things added in the exam will go over those as we see those. So one of those is the crypt analysis portion of it. So this will be in the new material that should be out there being tested for everyone.
So linear crypt analysis. So basically, he's got two parts, right? So the the first part is it's going to construct linear equations that relate to plain text after text and key bits that are more than likely gonna be close to zero or one,
once it does that is going to use those discover linear equations along with no. One plane Texas cipher text pairs to try and figure out the key bits. So this is used in block and stream cipher attacks
Differential crypt analysis that's gonna basically be founded on non random behavior in the ciphers. So the method is we generally use a chosen plain text. Attacks of the attacker must obtain the cipher text for a set of plain text. And so one of the things here is that separates Differential
um, from the integral is that differential uses pairs of the plain text, so keep that in the back of your head there.
And then those pears are related by constant different. So that's where that's your calculation comes into play.
And then the cipher text were basically looking for patterns in the cipher text so that we can potentially crack it and see what the real messages
So integral crypt analysis. It uses sets or multi sets of the chosen plane takes, and then part of those plain text will be constant and other ones will be variable. So the example here is that you've got 256 plain text and that have all of the same bits except for eight of them. So on those plain text,
the last eight bits, all of them are different from all of them. So that that's kind of where that integral comes into play.
So different types of cryptography attacks. We've got a brute force which we know from the working with the password stuff, but basically weaken brute force passwords. You know, it's gonna allow us to these adult pass phrases. We've got the birthday attack. So
the easiest way to explain that It's like if you in grade school your teacher and ask you like all right, you know, everyone raise your hand if you got a birthday in this month or whatever.
So basically, that concept is this. So let's say their student, 30 students in the class
and you know, of course, we're not gonna worry about leap here. So we're gonna say there's 365 days in the year and, you know, and then you know, what's the probability off a student, you know, sharing a birthday with someone else. You know, I think the numbers around 7% basically take, you know, the one student and then minus
the product of, you know, 364 days, you know, because you're
figuring that they're strangers before other birthdays that aren't were not accounting for and then divide that by the year. So 365 days. So in parentheses you would have 364 divided by 3 65 then that would be to the 30th power. Because there's 30 students, right, and we're not gonna really dive into that. But just know, that birthday attack works on a similar concept.
So it's basically I'm depending on
Mork allusions being found between random attack attempts than the non random attack attempts.
So that's really constant behind that.
You've got me in the middle attack. That's kind of similar to like a man in the middle. So basically, the concept is this. So you're you know, you the thought process would be I include my data
once, you know, I used maybe a hash or something, whatever, you know, and I include my data, and then I encrypt the same data again and the same data again, you know? And so I'm crypt into multiple times, but it really doesn't make it more secure. And so the concept behind this attack is that there's a space, same time tradeoff. So it's basically tryingto
get you at some point in that process, right? So meeting you quote unquote in the middle. I'm not I'm not trying to the very end of trying to get through all this encryption. I'm trying to get somewhere there in the middle. I'm tryingto find a pattern or a similarity, and that'll allow me to get the information that I want.
Oh, the duck attack will talk about injustice. Second here and then the rainbow table attack. So if you just think from the password aspect, we use rainbow tables or charge on the Ripper. Example. We used, uh, password file there to go ahead and try a whole bunch of different combinations of passwords hashes
on DSI. What? What work to crack the password.
So the duck attack stands for Don't use hard quoted keys. Basically effects VP in a web session. So it allows you as an attacker to ah, you know, recover the secret secret encryption keys from different vulnerable implementations and then on. And that's implementations of the random number. Number generator. Excuse me, Rong.
So it allows you to you too.
Basically decrypted data and read the actual communication passing over a VPN or the encrypted web session.
Hola, Online, MD. Five tools out there. No, I did want to mention just backing up a second here that the birthday to attack the duck attack
and then the rainbow table attack those air. All newer things in the new material for the EEC counsel stuff. So you might see those actually tested on the newer again. There's not versions, but I'll just say the newer version of the exam,
Same thing with the crypt analysis tools like online MD five decryption tools. You're going to see that in the official material as well. So that's another new aspect of it. But you can find literally hundreds if not thousands, of MD five tools out there. And basically all you're doing is you're gonna take your hash that you have. So maybe you're
you're hacking something and you take that hash,
you're gonna pop it in one of these and try to decrypt it. So they were basically databases of, you know, hundreds, hundreds of millions, if not billions off already hashed items, you know, so like files or phrases etcetera. So it's the's huge databases, and then you just come in and
put your stuff in and hope that it's already in there.
So just one quick post assessment question before we wrap up our lecture portion of the cryptography module. So, uh, what? Which one of these was retired due to the brutal attack?
All right, so you guessed, answer being That was a pretty easy one. The answer. Be secure sockets, layer. That was basically retired. And now everyone's using transport layer security or tea, less open SSL keys are again. Those are just tools to do. Ah, different type of Christ gives me cryptography
s O. That wraps up our lecture for the cryptography section in the lab that we're gonna get to in just a second here. We're gonna go ahead over a We're gonna look at a couple different photos. I'll show you how to set up the lab first, so it's split up into different sections, and then we're gonna look at a couple of different photos. We're gonna do some hashing, and then we're going to try to see the differences in those photos,
just basically for the lab. You don't have to use the photos I'm using. You don't try to find those, but you can just use, like, any photo that you find or that you have laying around.
All right, so look forward to seeing you in the next video.