Cryptography: Crash Course Computer Science #33

Today we’re going to talk about how to keep information secret, and this isn’t a new goal. From as early as Julius Caesar’s Caesar cipher to Mary, Queen of Scots, encrypted messages to kill Queen Elizabeth in 1587, theres has long been a need to encrypt and decrypt private correspondence. This proved especially critical during World War II as Allan Turing and his team at Bletchley Park attempted to decrypt messages from Nazi Enigma machines, and this need has only grown as more and more information sensitive tasks are completed on our computers. So today, we’re going to walk you through some common encryption techniques such as the Advanced Encryption Standard (AES), Diffie-Hellman Key Exchange, and RSA which are employed to keep your information safe, private, and secure.

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[samuelisaac]

I loved cryptography as a kid so much that I actually used to entertain myself with frequency analysis. I had a lot of books on cryptography, and I used to try to crack the examples before the book explained them, the way people try to solve mystery books before they reach the end. Now I'm falling in love with cryptography again, but with a more modern, computerized version. Thanks Crash Course!

[KikomochiMendoza]

As a total n00b in programming or encryption for some reason I understood the Debbie Hellman explanation over the paint trading analogy. Thanks.

[MrKydaman]

The "Thanks cryptography" 👍👍 at the end was pure gold.

[ChungusAmngus]

"Adding another level of... complexity" #trolled

[vezokpiraka]

This is probably one of the best Crash course videos ever made. Really great explanation and somehow more detailed than other ones while still explaining the concepts easily. This videos deserves praise.

[ProfessorSyndicateFranklai]

Just waiting for that quantum computer to mess all of our encryption up.

[banderi]

Having a blue day? Keep Calm and Carrie Anne!

[brocksprogramming]

I look forward to watching this every week. You guys at crash course are keen on the idea of the feynman technique. Making things as simple as possible. I find these videos on computers to be basically an overview of all the things I've studied over the years. It's a very complete and timely piece. Perhaps you guys may choose to go into more depth on some of these topics in the future. Anyway, these are a great introductory learning tool for those who are interested. Power to male and female programmers and tech nerds! While we ride the wave of the future.

[watchit]

"For a 128-bit keys, you'd need trillions of years to try every combination, even if you used every single computer on the planet today. So you better get started" XD

[donsample]

I've always thought there was something shifty about that Hank guy.

[BlueFlash]

Wow, this was actually the exact right speed to follow, awesome graphics and amazing good comparisons. I'm actually a little happier now!

[GKS]

This is the best asymmetrical cryptography analogy I've seen so far! It makes so much sense to me. Thanks CC!

[day_saram]

i've been cracking my head open to understand how keys function for the past few weeks since uni started and you just explained it all very clearly with some and amazing, i thank you ALSO finally understanding the math that's behind these encryption techniques thank you so much

[ignaciocorrea]

I love this course, and I'd like to add a little more information (due to the fact that CC cannot cover everything in just 15 minutes).

First, when Carrie Ann says that one-way functions are "easy to do in one direction, but hard to reverse", "easy" and "hard" refer to computational complexity, specifically polynomial time problems. This means that the time needed to apply a one-way function must be small (a polynomial in the length of the argument of the function), but the time needed to reverse the computation must be awfully big.

Second, the existence of one-way functions is an open problem in computer science. Modular exponentiation is a candidate for being a one-way function: indeed, computing the function is easy, even for huge numbers, but the reverse (the modular discrete logarithm) is believed to be difficult (but it has not been proved!).

[FakeButt]

This is one of the best simple explanations of criptography ! Great work!

[dcstone]

I did not realize there was so much to a secure connection... Amazing! Thanks for the explanation!

[ducksoop.x]

Your Public/Private key explanation was the best I have ever seen, now I understand it! Thank you so much.

[Xappreviews]

I think it would be a great idea to make a second video where you talk about vulnerabilities of cryptography!
For example, Diffie-Hellman is only secure against passive attacks; however you can fool both sides into thinking that a secure connection is established by a man-in-the-middle attack. There are different ways to eliminate this problem.
Also public keys need to be stored in a secure source. If an attacker is able to distribute his own public key, it will lead to problems.

There are many more examples, which could easily fill another video.

I loved this one, it was a great introduction, but I wish you would go into more detail, especially since it might give the impression that these algorithms have no flaws :)

[jeaniebeanie]

This was such an amazing explanation. Perfectly paced, great graphics, fun analogies, easy to understand, and very well spoken. Thank you so much for this!

[alwync]

That's by far the best explanation of asymmetric encryption (in particular, Diffie–Hellman key exchange) I've come across.