Theory and Practice of Cryptography

[Gayathrib002]

how to get rest parts of lecturers?

[Nevyle]

dude...i know, i know...

srsly, nice talk though

[jbochi]

Course materials: saweis.net/pdfs/CryptoL1.pdf

[wolfricacc]

dunno who copied off who (or perhaps the order of content is quite familiar) but that's almost EXACTLY the same an in order of what a lecture of steganography. I can't link but just search "Lecture 32: Steganography" in youtube

[TheDoctorJohnShow]

The slide where he mentions the code I see evict is there more?

[RominZadi]

Thank you so much for this awesome lecture!! One of the very few informative cryptography videos I could find; loved the combination of history and cryptography.

[JorgeRamio]

Very interesting video Steve. You can also watch videos of the on-line free educational project intypedia, the Information Security Enciclopedia. Just search in Google for intypedia.

Best regards,

The intypedia Team

[mandawra08]

this video is good but

i think you should involve more technical and advance level of cryptography then history.....

we are not here to attain history classes.

[StephenWeis]

@mandawra08 There are three other lectures in the series that get into more details.

[scout6686]

@mandawra08 speak for yourself dirty indian

[silverblue73]

comments should be disabled as most of the people who happen upon this vid are unlikely to understand or care to understand its contents, resorting to senseless blurbs mirroring their frustration

[kanajlo]

"Sta[s]tistical"?

[gnamp]

I think I've managed to decypher the way this man talks- He just uses a load of redundant 'G' sounds and he simply substitutes many of his 'Ts' for 'Gs'-:-

00:30 "thanks for legging me know, I'm the director of google universigy and I'd like welcome you to wong of the first...

agmingistragive = administrative. I think.

[ktasda]

He's nervous so stfu

[gnamp]

er... no. It's a speech impediment.

[ktasda]

Even if he has a speech impediment, Doesn't make gnamp any less of a ass

[gnamp]

That's true. Or you for that matter.

[ktasda]

I'm not the one picking on people

[gnamp]

look, get stuffed man. I'm not picking on anyone. If a man who is introducing a talk on cryptography speaks in a most unusual or cryptic fashion, expect it to be noticed. It's funny. I'm sure he's a lovely chap etc. etc. but it's an amusing observation- it's as simple as that. Besides, you thought I meant the other guy anyway. He was just nervous.

[ktasda]

Considering the content of the video it is not so much out of the norm considering this is a very interesting topic I certainly frown upon your comment it is neither constructive , productive or even relevant it is just some low brow remark makes me question your age keep it on point this video is to do with the content not the manner in which is was presented.

[gnamp]

I tried with you, you awkward blighter ~really, I did. You wouldn't know 'relevant' if it bit you on the arse (which it probably would). You talk rubbish. You are a curmudgeon and a dullard; apparently devoid of any real sense of humour or fun. Just Get bgack tgo ygour worgk direcging G-g-oogle [ahhh...] Universigy, you silly bugger. Good day, sir.

[ktasda]

Thank you for proving my point Gnamp

[gnamp]

And thank you for proving mine.

[ZirconCode]

Agreed

[jonboy700]

Had a good beat, one can dance to it....

[Drahcir14]

Very interesting stuff! I was inspired to watch this as I am reading Digital Fortress by Dan Brown.

[Abduction09]

a lovely book! i really enjoyed it.

[TheMexicanLoser]

can someone break this down for me?.. what exactly are they talking about?

[lithiumdeuteride]

Cryptography.

[nfest8]

Fun stuff! WW2 cryptography, esp. is fun stuff to learn about. I believe "the bombe" was the mechanical device used to crack "the Enigma". Also, it's interesting to learn about "JN-25",particularly, because it was decoded using only pen and paper. The Enigma, on the other hand, utilized an electro-mechanical device. Anyway, I really enjoy listening to the wide variety of lectures provided by Google. Keep up the great work!

[PoWerExcesS]

Great lecture. I read a few thing about cryptography and this lecture mentions many of them, in a very easy to understand way.

Thanks for posting.

Btw could someone tell me wich universities have worth-doing post-studies programmes on cryptography?

[ranlr]

when will gmail inherently support SMIME (not through 3rd party apps)?

[StephenWeis]

I don't think S/MIME is well suited for web-based clients. You generally don't want your private keys to live on a remote server, so would want to store them locally.

Regardless, it is possible to support S/MIME in a web-based client with JavaScript and something like Google Gears for key storage. But, I think you'd be better off just using a S/MIME compatible email client with Gmail IMAP/POP access.

[motionthings]

Hey, you work at Google...

How about publishing your slides on Google docs?

I see you are already using it...

Great Tech Talks btw.

[StephenWeis]

Hi. I plan to post the slides soon. They are internal-only Google Docs for now. I will export them all to my personal web page when I get a chance.

[tedtdu]

Thanks for posting it. I hope to see more to come. Next week I will have presentation about Applied Cryptography by Bruce Scheier.

[speedy314]

Stephen -- in future lectures, please repeat audience questions before answering them so those of us not present can know what was asked.

[speedy314]

apologies... just got to the end of the lecture where it was brought up.

[StephenWeis]

Hi everyone. I am the lecturer in the video. Thanks for watching. I plan to post all the materials from this course on the web when I get a chance. Keep an eye out for a link that I'll post here.

[PH5221]

@StephenWeis Thanks for this lecture :) I'm only 15 but I am learning about cryptography, this was very helpful. I like the maths side of it surprisingly enough :) Good job.

[StephenWeis]

@PH5221 You might be interested in Dan Boneh's free Stanford crypto class online at crypto-class . org

[PH5221]

@StephenWeis Thanks man :) Appreciate it.

[nsantha2]

I see a HUGE problem with Diffie-Hellman. Suppose someone on the the channel, say Eve is eavesdropping (sincerely, I didn't intend to be punny), and they have G, g, g^x and g^y. Given this information, how hard is it to figure out x & y? And with some brute-force cracking, it should be easy to find g^xy.

Am I the only one that sees this, or am I making a mistake?

[tommoyer324]

The problem is that calculating x (or y) from  g^x (or g^y) is "thought" to be very hard (what is known as the Computational Diffie-Hellman problem or the discrete log problem). Also these groups are usually very large which makes brute-force unfeasible.

[nsantha2]

Yes, that is very hard, I agree. But that doesn't seem to be the problem here. An eavesdropper has G, g, g^x & g^y, right? Or is that where I'm making the mistake? If you have g, g^x & g^y, calculating x & y should be trivial, right?

Of course, if you didn't have g, it would be an excellent method, since, as you say, figuring out x & y from g^x & g^y would be really difficult.

[tommoyer324]

Not really since you would have to calculate the x^th (and y^th) root of g which in the case of using groups (and modular arithmetic) is highly non-trivial, and there isn't a method of manipulating g^x and g^y to give g^(x*y). There is a good book on "modern" crypto called "Introduction to Modern Cryptography" by Jonathan Katz and Yehuda Lindell which goes into great detail proving that Diffie-Hellman is secure against an eavesdropper.

[nsantha2]

I'll definitely check out the book. Thanks for your time!

[StephenWeis]

Hi. First off, thanks for your interest in the lecture.

One thing to note is that we're talking about operations in what are formally known as "multiplicative groups". If we were taking logarithms over all integers, then you're right -- it would be very easy and you could do it on a pocket calculator.

A common multiplicative group that is used in practice are numbers modulo a large prime, denoted Z_p. If p=7, g=3, and x=2, then: g^x = 3^2 mod 7 = 9 mod 7 = 2 mod 7

[StephenWeis]

(Continued) Asking what the base-3 logarithm of 2 is in Z_p is asking "What value of x do I raise 3 to such that the remainder after dividing by 7 is 2?"

In this example, it's trivial for us to figure out that x=2 by trying all possible values. But if p is very large, it becomes more difficult.

[nsantha2]

Oh, I see. The larger the prime, the harder it is to brute-force the algorithm. Thanks very much for the clarification.

[rudyiking]

Very interesting talk.

Thanks for putting it up.