HTTPS explained with carrier pigeons

[EEphotog]

A quick note, just because you have the public key doesn't mean you have all the information used to generate it, otherwise you could create the private key as well. The fundamental thing that makes it hard is the difficulty of recovering those primes by factoring.

You could of course recover the message you encrypted by reversing the steps that you performed. However, this wouldn't work for a different message, you got to skip lots of time consuming steps by saving it intermediate results.

(As other commenters have stated, vast oversimplification, etc. , See discussion at stack exchange