How to Encrypt with RSA (but easy)

A simple explanation of the RSA encryption algorithm. Includes a demonstration of encrypting and decrypting with the popular algorithm.
Enjoy :)

[Iba-jn]

I usually never comment on videos but you’re an absolute legend mate, you exactly know how a student thinks and you know exactly what to teach, please upload more videos, i would love to learn coding from you, cheers

[amihart]

The constraints for e is just {2 < e < r; gcd(e, r) = 1}, and it has to follow those constraints so that the encryption is one-to-one rather than many-to-one, where in the latter case it would not be reversible. More recent versions of RSA use the Carmichael's function, in this case λ(n), (which simplifies to lcm(p - 1, q - 1)) in those constraints rather than r (which is just the Eurler's totient function of n). It achieves the same results but has the benefit of faster decryption.

[linamoussadek]

Why doesn't this have more views??? Thank you so much !!

[Moocow]

Thank you so much for this tutorial! I could not wrap my head around turning the concepts behind encryption into code before this.

[michaiahf]

How does D = 7? I don't understand that part. Is 7 just a random number that you are using as the message to send?

[pedropago]

this dude just saved my finals, awesome video thank lord i found it

[thegreatpugtato]

Holy shit this was actually huge for an assignment, made it so much easier and less stressful

[rudraprasad]

Bro you have only one video and a great one.

[SirArghPirate]

I don't get it; how does 3^(-1) % 20 equal 7 and not 0.33..

[Its_Me_Butters]

Simple AF, come back with more stuff dude!

[zachahmad]

Really nice video....definitely simple and yet makes a lot of sense!

[bumpsy]

the whole modulo stuff is not possible, because when calculating d, the first mod value is always smaller than the second, which gives a syntax error

[lucinali]

I love it! I'm looking forward to learn programming with python with your video.

[Листочек-чк]

Thank you so much! The best explanation!!!

[cagnozkut]

I don't understand how we find d=7 ??

[ReikiMaulana]

*patiently waits for the python program implementation*

[daddyhollow]

Hey I dont think there's a gaurentee that e can always be 3. If totient n is 72 then 3 is not relatively prime and does not fit the. requirements

[khadijahalhayder]

Awesome!! well-explained thank you so much

[FriedMonkey]

At the end of both encryption and decryption we're doing mod n making it within the range of n

Meaning our initial messsage CANT be higher than n?

[Kwatch]

your d formula is different to what i have in my course material. what i have is d = e^-1 mod( λ(n) )

now λ(n) = lcm(p-1, q-1)
the way you do the d also gets the right answer but answer must be divided by 1 but in your example i get 3 not 7.

i think the right d formula is d = 1 / e^-1 mod(r)


ok so i found out a shortcut. to find d just try this formula first because if numbers are small enough you can just get the d directly. e * d ≡ 1 mod(r)

so here e = 3 and r = 20
so 3 * d ≡ 1 mod(20)
if you know how to mod words we can see by putting d=7 we get 21 ≡ 1 mod(20)
if you dont know how mod words then it just means 21 remove as many 20 as you can until you have remaining 1. ya when i first learned mod the notation was going above my head but trick is not to look at is a equality. its triple bar not equal sign. so 21 ≡ 1 mod(20) this expression would be same even if i wrote it as 41 ≡ 1 mod(20) because that just means if i did 41 - 20 - 20 i would have 1 remaining.

r = (p-1)(q-1)