RSA has been invented in 1977 and till that time everyone things that encryption/decryption can be done only with one symetric key. As header says this is public key cryptosystem, so we gonna have two keys for encryption / decryption and that is public key and private key. I know about this setup so lets jump straight to RSA algorithm.

RSA algorithm has these steps:

- choose large primes p,q
- take these two primes and multiply them. n=p.q
- compute eulers phi function of (n)