An RSA public key is a pair of numbers (e, n) where e is an exponent and n = pq where p and q are large prime numbers. The original RSA paper said choose a private key d and compute e. In practice now we choose e and compute d. Furthermore, e is now almost always 65537 for reasons given here. So the public key is essentially just n. The relationship between the exponent and the private decryption key in the original RSA paper was ed = 1 mod φ(n). It is easy to compute e given d, or d given e, wh...