QUESTION 11 The sender signs a message with its private key, is described as O Encryption/decryption O Digital signature Key exchange O None of the above Which from the following is describe Output Feedback mode OFB, where is Pj and Pj-1 are plaintext and previous plaintext, and Cj and Cj-1 ciphertext and previous cipher text, K is a key and E encryption function OC = E(K, Cj-1 XOR Pj]) O Cj = E(K, Pj) O Cj = Pj_E(K, [Cj-1 XOR Pj-1]) O None of above Which from the following is describe Cipher Block Chaining Mode CBC, where is Pj and Pj-1 are plaintext and previous plaintext, and Cj and Cj-1 ciphertext and previous cipher text, K is a key and E encryption function O = E(K, [Cj-1 XOR Pj]) O Cj = E(K, Pj) O G = Pj_E(K, [Cj-1 XOR Pj-1]) O None of above Public key encryption, assume that the A encrypts a Text uses private key and send to B, which one from the following described the process of encryption O B knows its from A and it could decrypt using A public key Even if B knows who sent the text it cannot be decrypted It cannot be decrypted at all as no one knows Private key of A O A should send his public key with text Which of the following threats has not grown over the last decade as a result of increasing numbers of Internet users? O Viruses Hackers O Denial-of-Service attacks O All of these have seen an increase over the last decade