RSA

   TODO

   generating keys:

    1. p := large random prime
    2. q := large random prime
    3. n := p * q
    4. f := (p - 1) * (q - 1) (this step may differ in other versions)
    5. e := 65537 (most common, other constants exist)
    6. d := solve for x: x * e = 1 mod f
    7. public key := (n,e)
    8. private key := d

   message encryption:

    1. m := message encoded as a number < n
    2. encrypted := m^e mod n

   message decryption:

    1. m := encrypted^d mod n
    2. decrypted := decode message from number m