I think no one has mentioned the base for all the cryptographic functions.
A mathematical operation which is simple in one direction but very hard in the the other (backwards). The factorisation of large prime numbers is one example.
I'm satisfied with the answers and insights I got so far. But if you may add I'd be happy to know why factorization of prime numbers is so crucial in cryptography. I heard about this a lot before but don't know anything. I know quite well about Prime number and theorems about them on math, but not their applications
Calculating primes is fairly straightforward so you calculate a few large prime numbers, and do some math to them.
Now you have a strong key that didn't require a supercomputer to create but taking that final number and turning it back into those original primes is a much more computationally expensive proposition.
In fact, it's one that's not viable with current technology.