Question

If it is known that a given ciphertext is Caesar Cipher, then a brute-force cryptanalysis requires \(\underline{\hspace{1cm}}\) keys to try.

• A. 25
• B. 26
• C. $2^{25}$
• D. $2^{26}$

Hint:

In Caesar Cipher, there are 26 possible shifts (keys), corresponding to the 26 letters of the alphabet.

Answer 1

The Correct Option is B

Step 1: Caesar Cipher Fundamentals.
The Caesar Cipher operates by cyclically shifting each letter of the plaintext by a fixed number of positions within the English alphabet. Given the 26 letters in the alphabet, there exist 26 distinct keys, each corresponding to a unique shift value.

Step 2: Evaluation of Choices.
- (A) 25: This is incorrect. The number of possible keys is 26.
- (B) 26: This is correct. There are 26 possible shifts for the Caesar Cipher.
- (C) $2^{25}$: This is incorrect. This value does not represent the number of keys for a Caesar Cipher.
- (D) $2^{26}$: This is also incorrect. This value does not represent the number of keys.

Step 3: Determination.
The accurate response is (B) 26.