Cryptography: Crash Course Computer Science #33

[@crashcourse]

Hey guys, there’s been a ton of news the past week about a vulnerability in the WPA2 protocol that protects our Wi-Fi networks, and since we say that AES is secure in this video, we thought it would be helpful to explain how it all relates. In October of 2017, researchers released a viable hack against WPA2, known as KRACK Attack, which uses AES to ensure secure communication between computers and network routers. The problem isn't with AES, which is provably secure, but with the communication protocol between router and computer. In order to set up secure communication, the computer and router have to agree through what's called a "handshake". If this handshake is interrupted in just the right way, an attacker can cause the handshake to fault to an insecure state and reveal critical information which makes the connection insecure. As is often the case with these situations, the problem is with an implementation, not the secure algorithm itself. Our friends over at Computerphile have a great video on the topic: kzbin.info/www/bejne/o4rXp52fn6aHl5Y

[@disorganizedorg]

I very much appreciate that posted this update; it again demonstrates that you're more into education than simply getting clicks.

[@SSGranor]

Those expression should really have another "mod M".

[@DreadKyller]

+Axyron That was a typo, it should have been "(B^Y mod M)^X mod M" it was missing the second modulus.

[@DavidChipman]

Useless? How so?

[@DavidChipman]

You can slow the playback down, can't you? It's not too fast for me. But I have heard others mentioning changing the speed of playback of youtube videos in general.

[@samuelisaac2984]

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.

[@zikomo8913]

I was confused due to being color blind and had to re watch that part, lol.

[@sam-yx8fr]

Comrade Dyatlov hows it going so far

[@MrKydaman]

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

[@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.

[@Megamen8x]

*_COME ON BRAIN!!!!_*

[@ThBlindElephant]

_404 Page not found_

[@rodneynayo5779]

Overload!.... HAHAHAHA!!!

[@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.

[@ChungusAm0ngus]

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

[@MisokoFukumoto]

I fell for it too

[@that_goofballrightthere5668]

Tbh that whole intro and stuff is from complexity ssooo COPYRIGHT

[@ProfessorSyndicateFranklai]

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

[@Baxtexx]

We have to invent quantum cryptography then :D

[@DharmaJannyter]

Actually, we already did a long time ago.^^ en.wikipedia.org/wiki/Quantum_cryptography

[@nibblrrr7124]

Actually, the most devastating quantum attack (Shor) only breaks asymmetric encryption (RSA, DH key exchange). Grover can weaken AES, but that isn't nearly as bad (speedup by at most the square root). Other algorithms, including some asymmetric ones, might not be affected at all. djb & Tanja Lange have a 32C3 talk kzbin.info/www/bejne/Y33PnH2Qf5p3g7M and a mostly readable 2017 paper, "Post-quantum cryptography".

[@sneakupakashgaur9935]

No it won't

[@christianalbertjahns2577]

If quantum computer come to existence, then One-time Pad will be feasible to use

[@ignaciocorrea6594]

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!).

[@sneakupakashgaur9935]

Ignacio Correa there is error in video

[@davidporowski9512]

Ignacio Correa NSA (no such agency) spends serious taxpayer money to preserve email encryption/decryption using the Cypher Chip ( ironically, iirc, proposed by Bill & Hillary Clinton while in White House to preserve emails securely ) Sharing Key Info with NSA (WTF?)

[@BlueFlash215]

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

[@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 paint.....insane and amazing, i thank you ALSO finally understanding the math that's behind these encryption techniques thank you so much

[@banderi002]

Having a blue day? Keep Calm and Carrie Anne!

[@JM-us3fr]

Seriously, she always cheers me up

[@Pfhorrest]

They should sell this on a T-shirt.

[@microbuilder]

When I read that in my brain, I suddenly realized Carrie Anne does sound like carry on, if you live in the north as I do...soooo Minnesotan, dontcha know eh?!

[@kyoung21b]

Banderi - OK OK you get a big ughhhhh ! for that...

[@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 :)

[@mehdibounya]

Xappreviews yeah they didn't cover a really important part, the man in the middle attack, they should've mentioned certificates

[@FakeButt]

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

[@watchit387]

"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

[@dcstone]

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

[@drewlyton]

It is uncanny how much this series is aligning with what I'm learning in my Defense Against the Dark Arts class haha! Sharing all of these with my professor! Keep 'em coming!

[@GKS225]

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

[@donsample1002]

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

[@ducksoop.x]

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

[@eriksatterqvist6027]

In practical modular exponantiation you don't calculate the B^n before taking mod m since this number would be stupidly big and probably wont fit into memory. Instead you divide it into a series of taking power 2. If n = 2k is even, then B^n = (B^2)^k. If n = 2k+1 is odd, then B^n = B(B^2)^k. If B^2 > m, let C = B^2 mod m, then and (B^2)^k mod m = (B^2 mod m)^k = C^k (Also B(B^2)^k mod m = B(B^2 mod m)^k = BC^k). It is quite easy to code this if you want to give it a try.

[@jeaniebeanie6]

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!

[@ratgreen]

I have learnt more from a few Crash course videos than I did my entire XX years spent at school. Just goes to show education is not education its just there to make you pass tests, not to learn. Thanks CC. Thanks Alan Turing

[@Hofftari]

It's not that simple. Sure, this is explained in an easy way, but our brains aren't capable of storing this information in a way that you can remember it easily in the future. These videos should in my opinion instead be seen as a support for the subject which you then learn through a more conventional way.

[@lutze5086]

ratgreen no, you just don't recognise the skills you learnt in school

[@user-qj9gj5cw3b]

The videos give you a taste of these subjects, just a scratch on the surface. You need education to learn how to study properly and get as much knowledge as you need. Don't hate school, it's normal to feel that way, but it's a lot more important than you think :)

[@alwync3253]

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

[@flopped3419]

"so now you know all the _key_ parts of modern cryptography" , this woman makes me crease omg im dying thanks cryptography for bringing this woman to me the puns are fantastic

[@starryk79]

Fantastic Video. I finally understand how key exchange works. i always wondered how it can be secure if the keys need to be known to both parties. Now i know that! Thank you Carie-Anne!

[@VitorVelosoSA]

Finally I understand the key exchange, thanks to your color explanation. Very nice :)

[@shalop5614]

B^Y mod M to the X is not equivelent to B^X mod M to the Y. You have to take the modulo afterwards, and it only works for very specific bases and modulos.

[@RichyMaths]

I did a course on Cryptography and Information Security in my degree. I remember we touched upon DES and AES, and other advanced topics such as elliptic curves.

[@Lycz]

An interesting addition: The first version of Enigma, the one which had only 3 rotors has been cracked even before the beginning of WWII by 3 Polish mathematicians. Unfortunately their methods became obsolete the moment the 2 additional rotors have been added to the machine, making it again impossible do decipher Enigma until the Turing's breakthrough. (A commemorative memorial of the Polish input was placed in 2002 at Bletchley Park).

[@hokageenergy9599]

Tip: if you want to learn something, change the speed to .75

[@christomapher]

I love the flying toasters! Obscure reference that brings me back to the 90s PC computing world!

[@gasquakestudios]

Really good explanation of how the fact that no secret key needs to be exchanged!

[@jackkraus6948]

I'm taking a software engineering technical interview and wanted to brush up quickly on this stuff, thanks Crash Course 👍

[@Mr_Creasy_]

Very informative video!

[@sedthh]

wow this is the first time I got my head around how public keys work, please do more videos on the subject!

[@yuvaldolev7969]

Something you should have mentioned is that cryptography is only perfectly secure in theory - in the real world there are side channel attacks. Id explain it but I think that people who read this comment will have more fun researching this themselves ;)

[@shalop5614]

Yep and side channel attacks are the only crypanalysis attacks out there. There isn't a single other more common attack.

[@gnollins]

Hands down the best video on cryptography on KZbin. 12 minutes for expert level 😀

[@davidsweeney111]

the wife has got the best cryptography, I dont understand her at all!

[@the80386]

don't they all?

[@chasepablo5222]

The real question is, who is she encrypting it for? 😏😏😏

[@NeedForMadnessSVK]

She is hashing, not encrypting

[@rickh3714]

Well a brute force attack will get you divorced I think so I don't recommend that! How about taking her on a phishing​ trip with you- If you promise to cook the catch and clean the dishes afterwards you may net that critical algorithm!

[@markzucc3277]

Boomer humor

[@moritzmakowski9422]

9:43 That is not mathematically equivalent... See for example: b = 4, x = 3, y = 7, m = 18 You need to take the modulo M of the result to get the same key. In the wikipedia article about that topic they say, that b needs to be a generator of the group of m , but I haven't tried it out yet.

[@fabiomarsiaj8172]

I just love the way you explain everything!! Amazing course.

[@jeremybailey262]

Hot oil in the medieval ages wasn't used like you see it in Hollywood. Oil was an expensive resources so what they would actually do is pour boiling water or extremely hot sand. Yes there was some occasions where it happened but that's an exception not the norm as it's portrayed.

[@tenow]

Finally! An understandable explanation how prime numbers work in cryptography with color metaphor.

[@collinsmilgo8869]

The amount of times hank has been attacked lmao

[@theblinkingbrownie4654]

Hey may need to go to -Hotel- Healthcare Trivago.

[@What_was_wrong_w_jst_our_names]

The paint analogy was very useful

[@SoulDragonWithFlow]

Wow, I knew a few basics of encryption but was always quite hazy on the details. This was so informative! Thanks! :D

[@k54ltyd28]

You forgot to show the part where John has to call Daniel Biss and ask what an exponent is.

[@DavidChipman]

Now that's *harsh* LMAO

[@tellingfoxtales]

The bit about key exchange was very informational.

[@FedJimSmith]

We can more appreciate this by citing non-electronic ciphering/deciphering.. Good job mentioning Ceasar and Columnar

[@Ni7ram]

ive watched a GAZILLION videos on cryptography... and i always had the sensation that some part was missing, that it didnt make total sense.. i thought i was just dumb, but FINALLY someone explained it completely and clearly! best explanation EVER. all other videos forget to tell the public key is used in conjunction to the private to create something new. thats key! (pun intended) awesome job! this crash course is truly a masterpiece

[@TravelTrivia]

I love this channel! Awesome videos

[@dabay200]

With the modular exponent example if somebody in the middle intercepts both sides of the communication they get the same value for the shared key - i'm sure the NSA is already doing this, they already compromised RSA security and functions with backdoors to decrypt without using brute force.

[@gustavlarsson1785]

I really liked both the video's content and the narrator - She's great! Good job! :)

[@tgeo2880]

great video!

[@NickShvelidze]

Awesome video, thank you! I can finally understand a little bit of cryptography.

[@milestone2852]

thanks for the awesome videos. this is one of my favourite channels on youtube. can you please do a series on Criminology and also Linguistics? thanks :)

[@max500k]

I love simple explanations of complicated things, awesome video

[@LeO-hm3tj]

I fall in love at the end of the video~

[@AJVainio]

If my understanding is correct, it is crucial to the color-analogy that even if an eavesdropper has the shared color, and could theoretically "subtract" it from the two transmitted mixed colors to get the two secret colors, this subtraction-process is what would be prohibitively cumbersome?

[@wilfredevertsz1915]

I have this same question in mind. It seems simple enough to solve. Let me know if you find the answer to your question.

[@phantomapprentice6749]

I'm pretty bad at math and could understand this , well done. Although it does beg the question of why people consider math a requirement when the principles have more to do with logic than mathematics.

[@nthgreen87]

Guys, at 0:35 you used the picture of the monument dedicated to the 3 Polish mathematicians who first broke the Enigma cipher in 1932, making it possible for Turing et al. at Bletchley Park to proceed. Yet you didn't breathe a word of their contribution, nor did you even credit the photo (here it is on Wikipedia, recognizable by the digit order at the top: commons.wikimedia.org/wiki/File:Polish_cryptologists_breaking_Enigma_ciphers_monument_01.JPG ). I can understand that the English speaking world may be unwilling to break their tongues on names such as Różycki, but the complete erasure of the Polish contribution in ANY account of the Enigma-breaking is more than a little unfair.

[@cmilkau]

Amazing video! Can you also make a video on modern cryptography, focusing more on all the cool things not directly related to encryption? Hardly anyone knows there's so much more to cryptography than that. Only one minor objection: please don't reiterate the myth of million-year cryptoanalysis. Assuming Moore's law to continue, even the strongest encryptions in use today can be broken within decades.

[@Danny_Boel]

0:30 Wilhelm scream!

[@vikaskadel3005]

Alan Turing blinking on the bug of engima was hilarious

[@1035TheIce]

I like how Hank is the bad guy here 😂

[@souvikcseiitk]

3:20, nueral network 😅

[@annayapaymah7352]

Perfect description

[@DuluthTW]

Thanks, this episode really helped me.

[@PierreThierryKPH]

OK, managing to get the Wilhelm Scream into a cryptography is an accomplishment in itself… \o/

[@cholten99]

Nice Code Club shout-out - Claire and Linda will be happy :-).

[@kareemrshaidat1794]

Have a good day everyone!

[@philward2098]

Love the Shirts

[@Wielki48]

The first person to break the enigma code was Marian Rejewski and his colleagues, Polish mathematician, and he did it in 1932 ! Before outbreak of WW2 and certainly before Alan Turing. That's sad you don't mention it.

[@ArjunSutar]

This nice explanation you have given. Hope all needs to watch it.

[@jameshoe1750]

big fans of this series of videos, currently pursuing a diploma in IT. 'd to know if there is any plan for making a video about quantum computing?

[@just_jimmy]

You have very good videos, however i suggest you either decrease the amount or info or make a longer video. It’s a bit difficult following you with normal playback speed

[@tommrutherford]

This series is so awesome!

[@SirPetterTheFirst]

Weird, My math teacher was going to show us cryptography tomorrow.(I'm studying in computer programing)

[@michelleschultze4641]

This is so interesting, wow!

[@Tharindusri91]

Thank you very very very much for this great video. It helped me a lot for understanding the fundamentals and history of Cryptography. :)

[@SergioBobillierC]

Great episode!

[@nascomfub]

I love this!

[@hyunjinpark5086]

Cracking open the code book with the bois

[@atticusdeutsch5427]

4:33 LETS GET IT CARIE ANNE IS A GD shout out to the folks rip JOJO

[@tilinapple]

so proud when turing came up :)

[@gavin5861]

Love these videos!

[@electroninja8768]

Nice video, I was really hoping for an illustration of one time pads though.

[@roidrage420]

"There will always be bugs..." (shows jQuery)

[@Utkarshkharb]

So well explained ! Thanks a lot !

[@sneakupakashgaur9935]

There should be one more modulas after the results in getting key.

[@sarielreigns777]

Thank you for making me understand

[@windowsforvista]

This is a great video!

[@AmanSingh-xc6xv]

Great video. Thanks

[@andrewgrebenisan6141]

Absolutely beautiful

[@JavierSalcedoC]

Episode on blockchain pretty please?

[@griffdog8233]

Do you have any plans to do a future of computing video . Maybe have something about AI?

[@loversdiscovers5099]

Great video guys!

[@shitdotnet5405]

You provide great information, high-quality videos, and awesome graphics team. you should’ve brought a better tutor!

[@shitdotnet5405]

Literally, she destroys my poor brain cells whenever I watch her, she has no idea about simplifying complexity!

[@darioaguado5981]

very informative . Good job!