Cryptography 101 - The Basics

[@Fre3r]

got really interested in encryption recently. thanks for making this!

[@barrykavanagh5045]

Using HTTPS to securely thank you for this video! :)

[@gsharpshooter80]

Did anybody else think this demonstration should have been used with Spongebob, Patrick, and squidward when they were sending voice messages through bubbles and squidward would hijack the moment with hate bubbles XD

[@Divya-tl6gr]

+gsharpshooter80 very creative thought dude.

[@aughtrycw1009]

You are now my God

[@julianocamargo6674]

It would be great for kids but you would need to talk to Viacom

[@bestbotreview]

im here for the party like its opposite day

[@anonymoustester9472]

Simple Encryption Technique in just 30 sec kzbin.info/www/bejne/h4e3oqtnlq5ribc

[@sujanbaruah3305]

THANK YOU soooo much..... Very intuitive and easy explanation

[@anoncker]

Thank you so much man,you made things MUUUUUUUUCH clear for me. I LOVE YOU :D

[@uwumukizasolange8889]

thank you for providing this understandable video for us

[@DX413RB8]

this is why i learned english; international knowledge

[@punditgi]

A freebie lecture from CMU? Nice! 👍

[@TheMojoPhoto]

Well done, I ended up here by mishap. You have a new Sub. I was look up classical pigpen. FYI.

[@osmanmusse9432]

Thanks for explaining this topic

[@supremeleadersnoke792]

how do i decode your video on Cryptography 101 - The Basics ...the video was obviously made by cicada 3301

[@anonymoustester9472]

Simple Encryption Technique in just 30 sec kzbin.info/www/bejne/h4e3oqtnlq5ribc

[@SantoshBalakrishnanVSL]

Hi David, this is an excellent start. Can you share more or related videos?

[@malluk4127]

Sorry if this is a bit late... But he has more on his channel...

[@Divya-tl6gr]

i really liked the way you explained it.

[@bkzegyptshin1]

Do you have a full course of this , I never had someone explain Somthing do understandable ..

[@Jamie-iv8dp]

How do Alice and bob know the same key without sending a decrypted version first?

[@DannyD1Chung]

Thank you. Well explained.

[@tarannumkhatri5636]

very helpful..easy to understand thanks..

[@BambiOnIce19]

So the exchange of keys is the really important part, right? You can steal the information, but you cannot do nothing with that information unless you have the 'key'. So how do you get your hands on this 'key', that is what i want to know

[@raregear]

very well explained!

[@adithyavikramm3837]

how could eve has access to the cipher text.. Pls explain

[@creamy6680]

Interesting ! I have a question... is online banking considered as asymetric encryption?

[@the17kyd]

Is this helping me crack the Z340 cipher?

[@skitflow5.046]

does Alice use Bobs public key to encrypt the message? then wen she sends the message only bob that can decrypt it with his Private key?

[@julianocamargo6674]

Alice creates a session key to encrypt the message, and she uses Bob's public key to encrypt this session key. Bob uses his private key to retrieve the session key. He now has the same session key that Alice used, as in symmetric cryptography. He uses this key to finally decrypt the message.

[@wildcountryman13]

Hi I enjoyed your video. I was trying to find someone that could possibly make an encryption and decryption program using an old method that ive used on paper.

[@binnypatel7061]

great job.... thanks!!

[@Spudst3r]

If I use Bob's public key to encrypt a message to him, couldn't an adversary just apply Bob's public key to unlock it? How does Alice effectively obscure the message encrypted to bob with his public key, so that an adversary can't open it while Bob can?

[@khan0000007]

Ok I will try to explain. Bob has 2 keys, public and private. Public key can do encryption and is given to everyone. Private key can do decryption and is kept with bob only. So when alice wants to encrypt the message she uses bob's public. Even though eve can eavesdrop the message, she cannot decrypt it because she does not have the private key needed to decrypt it, only bob has that key. So only bob can decrypt alice's message because he has private key with him. Hope this makes you clear. Also remember when you go deeper into subject, you will come to know that these keys can be used alternatively, that is data encrypted with public key is decrypted using private key and that is data encrypted with private key is decrypted using public key.

[@Spudst3r]

Yeah I understand it now. What I didn't understand, and I think is conceptually hard to figure out until you delve into the actual math of public key/private key encryption, is *how* the public key can have properties that make it only possible to be decoded by the private key. Namely, that a *public key* is a number that is a factor of two prime numbers, and that knowing *which two prime numbers* were used to generate this number is critical to figuring out the actual private key. Since it is very mathematically difficult to figure out which prime numbers were used if you only know the public key, encryption works.

[@mboerrigter1]

Spuds7er Bob will generate two keys based on some mathematical operation which is easy to apply in one direction but next to impossible in the other direction. For example, Bob can generate two very large prime numbers and compute the product of those two numbers (easy) but if Bob asks Alice to factor the two prime numbers giving Alice only the product she will need a very, very long time to figure it out. It's not quite impossible but the time involved would be prohibitive. Now, Bob could use this very large number to generate two keys, one public and one private. The public key will be sent to Alice and she can encrypt her message with it. Bob's private key is never disclosed to Alice and it is the only key that is able to decrypt the message. The relationship between the public key and the private key (only known to Bob) allows Bob, and only Bob, to decrypt the message. Of course, anybody can get Bob's public key so this particular scenario only ensures confidentiality and not non-repudiation since Alice can never prove that the message came from her (or not).

[@jorgejr5876]

***** How does one get the Private key? Is it sent through the first public message. Or is it given to the other party even before communication begins?

[@OmriSama]

Jorge jr I thought the idea was that no one gets the private key?

[@yvfg326]

thank u so much u want video plz about reed solomn

[@markmillenium438]

GHCQ?

[@atulshriwastva3595]

where is the other video after this first ?

[@malluk4127]

Atul, check his channel... He has more videos listed...

[@gaabinubatrafinulifilit122]

Alice ? Who the fuck is Alice ?

[@skateboards3571]

your wife, and she's cheating on you...

[@coldfrostbyte5344]

Decode this if you can- PGZ1Y2s=

[@chrisredmon5494]

Dark Moon I can see the house of black.

[@almicc]

Dark Moon it's a bad word :(

[@greenspringvalley]

outstanding

[@leonardadams2341]

Okay so are these messages sent by email ?!?!?!

[@antochess9749]

prof can plz explain stegnogrphy

[@friscianviales7519]

Hope you bought some bitcoin for yourself, it is really expensive in 2018. Thanks for the info btw

[@TooManyBrackets]

6:58 Oh no! He said GHCQ.....Goodness! Kinda grates the ear like if a security expert called the CIA the IAC :-O (The rest seems okay though)

[@CrazyK64]

But Bob is cheating on Eve and she's 2yrs behind the technology in passing love notes..now what

[@aksahani26]

:( very difficult 'Alice' and bob but very well explained thanks

[@Multigameguy35]

anand sahani I think this may help.www.khanacademy.org/computing/computer-science/cryptography/crypt/v/intro-to-cryptography

[@tomfearnley2354]

"Hate" Wouldn't be bad in that context because he would assume she was joking....

[@BrianFaure1]

What if Bob doesn't have a sense of humor

[@dissaid]

😎😎😎

[@adamwebster1652]

If you give a man with an understanding of calculus/algebra 3 months to create his own cipher for mobile phone numbers what would be the best way to do it? Ciphering text is one thing but to be able to look down at your own mobile phone and in 10 seconds to be able to change a phone book full of 'jibberish' into something that will take a computer a few months to crack... What's the best method? As reward I will link you all to the best XKCD cartoon ever made(most of you will have read it already).

[@schuegrafma]

The most secure way is the so called one-time pad. But its also the least practical.

[@adamwebster1652]

Adam Webster I came up with a vignere cipher. The 'one-time' pad is not something that given a short amount of time a (smart) person would be able to do fairly quickly in their head I think. I'm quick at this Vignere cipher now and it has only been two weeks and about four hours of practice. A mobile phone number is eleven numbers so by coming up with a 11 letter phrase I have been able to commit quickly to doing it but only on paper and I think in a year I will be able to do it without any real cognitive thinking. I think a Vignere is pretty badass and would delay a computer quite a long time. I don't mind even mentioning it here on youtube because without the key nobody can really have a crack at it. A dictionary attack proof type of vignere is nigh invincible I think? My pre-frontal cortex will always outperform a computers GPU huh!

[@adamwebster1652]

Adam Webster My favourite thing to do it use mnemonics to memorise number plates. I'm interested in joining the police force you see and anything like this I can do in my spare time not only proves useful but absolutely fascinating. What is it about the spy stuff that makes it so much fun? I always wanted to be James Bond as a kid but until now the only thing I've had in common with him is his ability with women... I have to work at the math! :)

[@adamwebster1652]

MdK xkcd.com/936/ YOUR REWARD! That was a fascinating read. Thank you!

[@adamwebster1652]

Adam Webster Click the link for your XKCD cartoon reward, here it is again: xkcd.com/936/

[@Sam_Hopkins]

The drawings kinda look like the drawings from the book what if

[@huntertony56]

i dont understand can someone please make it simpler....

[@XUndeadChampionX]

surely you investd in bitcoin

[@karlreimers]

Nice video- easy to follow and understand -devoid of some irritating foreign accent.

[@williamm.9429]

RACIST

[@karlreimers]

Morg'n Freem'n Tea Party Man- get educated!

[@carte0000blanche]

Karl Reimers Super racist

[@cryptojeetu7599]

Bitcoin was $154.20 when this video was published.

[@poisonpotato1]

I just want to solve the cryptoquotes in the paper

[@kennethserrano2661]

BSIT 3B HERE sana atin kung antndiyan

[@vaibhavahuja5849]

good

[@pinruihuang8463]

Alice and Bob look like xkcd characters.

[@andyduly98]

Hmm very helpful, but i still got a long way to go ;)

[@13antawa85]

andyduly98 did you get anywhere?

[@ParadoxUmbra]

Prakash Rajendran is a legend. Thumbs up this comment if you came here from the private group on FB known as "IT UTS".

[@robotslayer9690]

Cool c o d e

[@GamingRading]

this fuckin guy knew about bitcoin in 2013

[@zoeazsss5035]

hey, boss, can u pay me in cryptocurrency so the govt wont know how much money I make

[@HalfTelevision]

i use a secret language, It Would Work Easier

[@dwrldgster3151]

siht devol I

[@ShopperPlug]

I didn't learn anything...