Classical Cryptography

What is the weakness of a Caesar cipher?

• It is vulnerable to brute-force attacks

• It is impossible to decrypt

• It requires a large key space

• It is too slow for practical use

Caesar encryption is a form of Transposition Cipher.

• True

• False

What is the encryption algorithm used in a Caesar cipher?

• Transposition

• Substitution

• Permutation

• Asymmetric

What is the maximum number of keys that need to be tried in a brute-force attack to crack Caesar encryption?

• 1

• 13

• 25

• 26

How does Playfair cipher handle repeated letters in the key?

• Dropping any repeated letters

• Add an "x" letter to the end of the word

• Add an extra bogus letter between the two repeated letters

• All are correct

The ciphertext is:

• The algorithm used to encrypt a message

• The secret key used to encrypt a message

• The encrypted message

• The original unencrypted message

What is the purpose of encryption?

• To make a message more readable

• To increase the size of a message

• To decrease the size of a message

• To protect the confidentiality of a message

What is the difference between Symmetric Encryption (SE) and Asymmetric Encryption (AE)?

• SE uses one key to encrypt and decrypt a message, while AE uses two keys.

• SE uses two keys to encrypt and decrypt a message, while AE uses one key.

• AE is faster and more efficient

• SE is more secure than AE.

The plaintext is:

• The encrypted message

• The original unencrypted message

• The secret key used to encrypt a message

• The algorithm used to encrypt a message

What is the key length for the Vigenere Cipher?

• Fixed

• Variable

• 64 bits

• 128 bits