Using public key cryptography, X adds a digital signature s to message M, encrypts , and sends it to Y, where it is decrypted. Which one of the following sequences of keys is used for the operations?...

Using public key cryptography, X adds a digital signature s to message M, encrypts , and sends it to Y, where it is decrypted. Which one of the following sequences of keys is used for the operations?

A) Encryption: X's private key followed by Y's private key; Decryption: X's public key followed by Y's public key

B) Encryption: X's private key followed by Y's public key; Decryption: X's public key followed by Y's private key

C) Encryption: X's public key followed by Y's private key; Decryption: Y's public key followed by X's private key

D) Encryption: X's private key followed by Y's public key; Decryption: Y's private key followed by X's public key