Requirements For Public Key

• It is computationally infeasible for an opponent, knowing the public key KUb to determine the private key KRb

• It is computationally infeasible for an opponent, knowing the public key KUb and a ciphertext, C, to recover the original message, M

• Either of the two related keys can be used for encryption, with the other used for decryption M = DKRb[EKUb(M)]= DKUb[EKRb(M)]