Asymmetric Key Cryptography: The RSA Algorithm by Hand

This video demonstrates the underlying principles of the RSA cryptosystem. It shows how the public and private asymmetric keys can be calculated from a pair of prime numbers. It also shows how to encrypt a message using the public key, and decrypt it using the private key. For ease, the calculations are performed with a spreadsheet, because the numbers involved in the process can be very large. The video points out that once a pair of asymmetric keys has been generated, the selection of which key should be made public and which key should be private, is arbitrary because RSA is a trap-door process.

[@eveninrose]

Enjoying this little series from you, as it’s particularly well timed for my needs. :) love the range of content as always~

[@d.w.714]

That is MIND BLOWING! bravo

[@HandsomeOrHandy]

Thank you for the explanation that I could understand.

[@inarisound]

Mr. Kevin, thank you *very much* for putting together such beautiful tutorials!

[@ComputerScienceLessons]

You are very welcome. Thanks for the lovely comment. Your channel is fascinating :)KD

[@inarisound]

@@ComputerScienceLessons Hahaha xD I saw notification for my email first, that Mr.Kevin subscribed. I chuckled since my content is 'a bit' off from Computer Science subject (no pun intended). It's a great honor for me. And once again, I want to say how I can't thank you enough for your hard and invaluable work

[@egornashilov5449]

thank you so much for this video - I really like the demonstration!

[@ComputerScienceLessons]

You are very welcome

[@MrDhawal29]

Amazingly explained, is it posssible for you to share excel sheet

[@mustaffaqasim]

Nice series next time pls do make a video on PERT Chart for cambridge Alevel calculating slacktime etc etc

[@chaemelion]

Excellent overview. It seems as though the ciphertext is vulnerable to frequency analysis and more, however. I'm assuming RSA is normally used in conjunction with other algorithms and techniques that effectively prevent such attacks?

[@williamsmith255]

Hashing

[@chaemelion]

@@williamsmith255 Hashing the plaintext prior to encryption or the ciphertext post encryption would help prevent frequency analysis of the ciphertext, but it would also render the decryption theoretically impossible. Hashing is largely used for proofs as I understand it, not direct encryption. Care to elaborate?

[@superpb600]

Isaac cypher

[@fredjenkins5069]

I don't know if I missed something or what, but I was able to decrypt the message without the private key by simply taking the publicly known information and generating a lookup table.
If my analysis is correct, then this encryption method is little more than a keyed Ceasar Cipher?
Can someone enlighten me?

[@mikelwrnc]

In practice, the rsa keys are used to transmit a truly random one-time-pad, which has no frequency content to attack with frequency analysis. Once both sender & receiver have the one-time-pad, they use that to encrypt a real message, and frequency analysis has no leverage against the resulting encrypted message

[@mikelwrnc]

Do you have a video on what is done to use larger primes and not encounter the representation errors you hit at the end of this one?

[@ComputerScienceLessons]

I'm afraid not. Typically, you would not do this on a spreadsheet (I wanted to lay it out visually). Rather, you would do it programmatically. Most high level programming languages support very big numbers one way or another. :)KD

[@mikelwrnc]

@@ComputerScienceLessons after some digging it seems the key is en.m.wikipedia.org/wiki/Modular_exponentiation

[@Wolfeur]

So, if I get it right, the difficult part to break it is to find the totient of n, which requires to find the factors of n.

[@GodIsEverPowerful]

nice

[@MrDhawal29]

can you share the excel sheet

[@ComputerScienceLessons]

I'll see if I can track it down :)KD

[@KamiK4ze]

@@ComputerScienceLessons did you manage to track it down?

[@jamesmatthews2751]

he picked 7 because it was cool ig