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: Understanding Caesar Cipher.
In a Caesar Cipher, each letter of the plaintext is shifted by a certain number of positions in the alphabet. Since there are 26 letters in the English alphabet, there are 26 possible keys, one for each possible shift.

Step 2: Analysis of options.
- (A) 25: Incorrect, as there are 26 possible keys (shifts).
- (B) 26: Correct, there are 26 possible shifts for the Caesar Cipher.
- (C) $2^{25}$: Incorrect, this is an incorrect number of keys for a Caesar Cipher.
- (D) $2^{26}$: Incorrect, this is another incorrect number of keys.

Step 3: Conclusion.
The correct answer is (B) 26.