Q1. Given that totient( 527 ) is 480 , what is 526 ∧ 959(mod527) ? Q2. You agreed to use a Caesar cipher with a key of k=5 with a friend. While sitting in a group, the friend hands you over a message that says “QNGWFWD”. Decrypt the message? Q3. Suppose you actually forgot the key. How many decryption computations of

EXPERT ANSWER

Q.2: You agreed to use a Caesar cipher with a key of k = 5 with a friend. While sitting in a group, the friend hands you over a message that says “QNGWFWD”. Decrypt the message?

Here, the encrypted text is “QNGWFWD” and value of the key is 5. So, we need to substitute each letter of the word with the key value.

Q – 5 => L

N – 5 => I

G – 5 => B

W – 5 => R

F – 5 => A

W – 5 => R

D – 5 => Y

So, the encrypted text is LIBRARY.

Q.3: Suppose you actually forgot the key. How many decryption computations of the cipher text “QNGWFWD” do you need to perform to reach to the plaintext?

In Ceaser cipher, the rules of decryption of a encrypted text is to take the first letter of the ciphertext and the first letter of the key, and subtract their value . No, as the number of alphabates is 26. So, we need to perform 26 decryption computations of the cipher text “QNGWFWD” to reach to the plaintext.