Cryptography

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) : Incorrect, this is an incorrect number of keys for a Caesar Cipher.
- (D) : Incorrect, this is another incorrect number of keys.

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

Step 1: Understanding the attack types.
A Ciphertext Only Attack is when a cryptanalyst has only the ciphertext and not the corresponding plaintext. This is the type of attack where only the encryption algorithm and ciphertext are known.

Step 2: Analysis of options.
- (A) Known Plaintext Attack: This requires the cryptanalyst to have both ciphertext and the corresponding plaintext.
- (B) Ciphertext Only Attack: This attack uses only the ciphertext, which fits the given conditions.
- (C) Chosen Plaintext Attack: This requires the cryptanalyst to choose the plaintext and encrypt it.
- (D) Chosen Text Attack: This is similar to the Chosen Plaintext Attack, but involves the cryptanalyst choosing both plaintext and ciphertext.

Step 3: Conclusion.
The correct answer is (B) Ciphertext Only Attack.