試題詳解

13. RSA (Rivest–Shamir–Adleman) is one of public-key cryptosystems and is widely used for secure data transmission. In RSA, if public key (e, N) = (5, 21), private key (d, N) = (5, 21), and ciphertext is 11, what is the corresponding plaintext?
(A) 7
(B) 4
(C) 9
(D) 5
(E) 2