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.