RSA encryption works by creating a public modulus N using two secret primes p and q, and then choosing an encryption exponent e such that gcd(e, (p-1)(q-1)) = 1. In order to encrypt a message, transform it into a number m. Then, use the public key (N,e) to compute c ≡ m^e (mod N), and send the ciphertext c. To decode the message, compute d such that ed = 1 (mod (p-1)(q-1)). Then compute m' ≡ c^d (mod N). The message m' is the same as the original message m.