CHAPTER 2: CLASSICAL ENCRYPTION TECHNIQUES

TRUE OR FALSE

T F 1. Symmetric encryption remains by far the most widely used of the

two types of encryption.

T F 2. Rotor machines are sophisticated precomputer hardware devices

that use substitution techniques.

T F 3. Symmetric encryption is a form of cryptosystem in which

encryption and decryption are performed using different keys. It is

also known as non- conventional encryption.

T F 4. With the use of symmetric encryption, the principal security

problem is maintaining the secrecy of the key.

T F 5. The process of converting from plaintext to ciphertext is known as

deciphering or decryption.

T F 6. The algorithm will produce a different output depending on the

specific secret key being used at the time. The exact substitutions

and transformations performed by the algorithm depend on the

key.

T F 7. When using symmetric encryption it is very important to keep the

algorithm secret.

T F 8. On average, half of all possible keys must be tried to achieve

success with a brute-force attack.

T F 9. Ciphertext generated using a computationally secure encryption

scheme is impossible for an opponent to decrypt simply because

the required information is not there.

T F 10. Monoalphabetic ciphers are easy to break because they reflect the

frequency data of the original alphabet.

T F 11. As with Playfair, the strength of the Hill cipher is that it

completely hides single letter frequencies.

T F 12. A scheme known as a one-time pad is unbreakable because it

produces random output that bears no statistical relationship to

the plaintext.

T F 13. The one-time pad has unlimited utility and is useful primarily for

high-bandwidth channels requiring low security.

T F 14. The most widely used cipher is the Data Encryption Standard.

T F 15. Steganography renders the message unintelligible to outsiders by

various transformations of the text.