Q13

MCQ1 mark, −0.33

Using public key cryptography, $X$ adds a digital signature σ to message $M$ , encrypts $\langle M, \sigma \rangle$ , 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

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