So just a quick review about symmetric versus asymmetric as far as the keys themselves and symmetric cryptography. There's one key.
The same key that is used to encrypt is also used to decrypt
in asymmetric cryptography. Everybody gets a key pair, Ah, public key and a private key, the two keys for mathematical related in such a way that anything encrypted with one can only be decrypted by the other.
All right, so in symmetric cryptography, there's no good, easy way to distribute the key in symmetric cryptography. But when we use asymmetric cryptography, the symmetric key can be encrypted with the receivers public key.
Remember, if I encrypt something with the receivers public, he only the receivers Private key, which only they should have, will be able to decrypt
speed. Symmetric is much, much, much, much faster, thousands of times faster. Where's asymmetric algorithms air slower and more complex. The number of keys in the symmetric environment in times in minus one, divided by two.
The formula for asymmetric is simply two times the number of users. Be careful here because they're gonna ask you, what's the formula for a number of keys in an asymmetric environment? Because They're counting on you being so proud of yourself that you memorize that in times in minus one. But it by two.
They're so sure that you're gonna be so proud of that, that you're gonna answer it
with asymmetric the formula simply too in right now. Ah, what do we use them for? Primarily for symmetric cryptography. We think of bulk encryption
for asymmetric. We want to do it for key exchange.
We get confidentiality with symmetric cryptography, but with asymmetric, we get confidentiality, we get authenticity and we also get non repudiation. And then when you throw in hashing, which is neither symmetric or asymmetric, we can have the full set of Security Service's.
Now there are various algorithms that are symmetric end asymmetric
symmetric algorithms. There are many of them, and we'll talk about some of these. Dez tripled as a s. Those were the ones that are the standards that we would focus on again A s being the one we would prioritize. That's the de facto standard today.
Algorithms just default to using eight Yes, for encryption
previous years and stares and then tripled. As the exception to that remember idea is used by PGP PGP is a good idea, but there are many other algorithms out there blow fish to fish cast and we could go on and on.
Um and I do expect a reasonable amount of questions. Which of the following algorithms are symmetric? Which is the following is asymmetric. So I've got these and their many other symmetric out rhythms to think about.
And then I've got six asymmetric algorithms. What I would suggest is memorizing the asymmetric algorithms. And if they're not asymmetric, well, then they're symmetric. Now, I'm not saying these were the only six asymmetric algorithms in the world, but these are the only six that would be testable.
And it's gonna be much easier for you to memorize six asymmetric out rhythms.
And if it's not in that list, then it's gotta be symmetric, okay? And here's a cheapo easy way for you to memorize symmetric or I'm sorry, asymmetric algorithms. So this is a little trick we're gonna use, and we're gonna use the buddy system.
The first and most important thing about this little trick is you have to remember it's for asymmetric algorithms. Otherwise you will get every question exactly backwards. So it's for asymmetric and teach this little trick. And before you start your exam, you need to just jot down the six asymmetric algorithm.
I'm gonna use the buddy system. Every algorithm has a buddy. The 1st 2 buddies air the essay Brothers R S A N D s If you can remember those go together R S A N D s a.
The essay brothers All right, the second to both Start with E E C. C in El Gamal
E C. C In El Gamal. They go together because they start with ease and then the last to defeat Hellman and knapsack.
Now it may not seem immediately obvious why the two of them go together, but a friend of mine used to refer to D H, which is have defeat Hellman's often abbreviated. He would refer to it as the Dukie Hauser algorithm for those of you that have missed this fine piece of quality American programming,
Neil Patrick Harris was a 13 year old brain surgeon
in the TV show Doogie Howser. And in the opening credits and everyone, he always had his knapsack that he put in his locker. So Doogie Howser has a nap sec, Diffie, Hellman and knapsack go together. This is strictly a trick to remember just writing down which algorithms are asymmetric.
Diffie, Hellman, Knapsack really have nothing to do with each other. As matter of fact, El Gamal was based on different helmets. So there's no reason that they're buddies.
Other than just it's an easy way to remember them.
when you sit down for the test
before you get started on your scratch sheet of paper, write down your buddies R S A N D s a E C, C and El Gamal,
Diffie Hellman and knapsack. So then I'm gonna ask you some questions. You tell me if the algorithm is symmetric or a Smith.
it's not on the list. So it symmetric idea. Symmetric knapsack. Asymmetric
Moore's symmetric to fish symmetric
eight. Yes, symmetric
rs A asymmetric. So if you'll just remember this this silly little trick, right? These algorithms down on your sheet before you get started, that'll get you three or four questions just easily done. Okay, I expect easily three or four questions on which of the following is symmetric or asymmetric.