RSA Computation

Using public key P = (e, n) to transform messages M:

$$P(M) \;=\; M^e (mod \;n)$$

Using secret key S = (d, n) to transform ciphertext C:

$$S(C) \;=\; C^d (mod \;n)$$

Use Modular-Exponentiation:

If = O(1),
Then Public Key requires O(1) modular multiplications, bit operations
Secret key requires modular multiplications
bit operations.