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
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.
(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.
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.
Scytale derrives from the greek word "σκυτάλη" which was basically a stick that olympic runners use to hand to each other during a race. The one who got the scytale stopped running and the receiver of the scytale continued the race.
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.
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?
It is important to note that Utopia is not a whitepaper, some abstract idea or statement of intent. This is a fully functional software product ready to be used.
Just about every military message starts with a classification. Such as SECRET. TOP SECRET, etc, etc. Then there are consistent headers and footers with who the message is to, who the message is from, subject line, date, time ect. So you can always try to crack the message buy using that info.
Cryptanalysis is still possible, but of no value if one doesn't recognize the plaintext. USA used code-talkers during WWII, for example. I believe it was members of the Navaho Nation who spoke their native language over radio circuits in the clear. The axis powers didn't know the language, so the method was secure.
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.
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.
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.
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
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.
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.
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
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.
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.
(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.
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.
@mandawra08 There are three other lectures in the series that get into more details.
Thanks for posting it. I hope to see more to come. Next week I will have presentation about Applied Cryptography by Bruce Scheier.
Scytale derrives from the greek word "σκυτάλη" which was basically a stick that olympic runners use to hand to each other during a race. The one who got the scytale stopped running and the receiver of the scytale continued the race.
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.
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?
It is important to note that Utopia is not a whitepaper, some abstract idea or statement of intent. This is a fully functional software product ready to be used.
Just about every military message starts with a classification. Such as SECRET. TOP SECRET, etc, etc.
Then there are consistent headers and footers with who the message is to, who the message is from, subject line, date, time ect.
So you can always try to crack the message buy using that info.
The slide where he mentions the code I see evict is there more?
@TheDoctorJohnShow It also looks like "he riso" is part of the code. But "Evict Heriso" doesn't quite sound right...
Google chrome beta / chromium wasn't released until 2008 and this talk was given in 2007, if thats what you're refering to.
Stephen -- in future lectures, please repeat audience questions before answering them so those of us not present can know what was asked.
Hey, you work at Google...
How about publishing your slides on Google docs?
I see you are already using it...
Great Tech Talks btw.
when will gmail inherently support SMIME (not through 3rd party apps)?
Very interesting stuff! I was inspired to watch this as I am reading Digital Fortress by Dan Brown.
Cryptanalysis is still possible, but of no value if one doesn't recognize the plaintext. USA used code-talkers during WWII, for example. I believe it was members of the Navaho Nation who spoke their native language over radio circuits in the clear. The axis powers didn't know the language, so the method was secure.
The slides and links to the video are posted on my web site: saweis.net / crypto.html
how to get rest parts of lecturers?
great presentation, good work!
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.
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.
apologies... just got to the end of the lecture where it was brought up.
How does one figure out what lecture comes next?
looks like they only posted the first lecture :c
Thank you for proving my point Gnamp
@PH5221 You might be interested in Dan Boneh's free Stanford crypto class online at crypto-class . org
@StephenWeis Thank you for this lecture! It's a very interesting topic for an undergrad student in the CS field like me to look into. :]
cryptography is a very interesting subject and it's amazing what's possible. What about encrypting videos for example :-)
Had a good beat, one can dance to it....
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.
If I wanted to move North and tell people I'd spell it like Zmdddefads. Now how would you dechiper that as North? Doesn't even stop there.
Course materials: saweis.net/pdfs/CryptoL1.pdf
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
Diffie-Hellman didn't invent it. They re-discovered what Malcolm J. Williamson had already invented.
Agreed
And thank you for proving mine.
That's true. Or you for that matter.
How cryptography would never work is if the practicer of cryptography was trying to break in to a word where they aren't/don't know the language
I'm not the one picking on people
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.
Cryptography.
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.
I did
you know :D
LMAO WHO ELSE WATCHING IN 2k20?!?!?!? 😂😂😂😂😂😂😂😂😂😂
ASASSHAHSHSAHHHSASH BRO I AM THE WATCHING!!!!!!!! 🤣🤣🤣🤣👌👌👌👌👌😛😛😛😛😛😛😍😍😍
er... no. It's a speech impediment.
dude...i know, i know...
srsly, nice talk though
Q,,,lull beware