Exam 3: Classical Encryption Techniques

A way to improve on the simple monoalphabetic technique is to use different monoalphabetic substitutions as one proceeds through the plaintext Message.the general name for this approach is ___________ .

__________ techniques map plaintext elements (characters, bits) into ciphertext elements.

the two types of attack on an encryption algorithm are cryptanalysis, based on properties of the encryption algorithm, and _________ which involves trying all possible keys.

Restoring the plaintext from the ciphertext is __________ .

Rotor machines are sophisticated precomputer hardware devices that use substitution techniques.

the __________ attack is the easiest to defend against because the opponent has the least amount of information to work with.

the best known multiple letter encryption cipher is the __________ , which treats digrams in the plaintext as single units and translates these units into ciphertext digrams.

An encryption scheme is said to be __________ if the cost of breaking the cipher exceeds the value of the encrypted information and the time required to break the cipher exceeds the useful lifetime of the information.

A scheme known as a one-time pad is unbreakable because it produces random output that bears no statistical relationship to the plaintext.

A technique referred to as a __________ is a mapping achieved by performing some sort of permutation on the plaintext letters.

__________ encryption is a form of cryptosystem in which encryption and decryption are performed using the same key.

the most widely used cipher ever is the __________ .

Ciphertext generated using a computationally secure encryption scheme is impossible for an opponent to decrypt simply because the required information is not there.

Cryptographic systems are characterized along three independent dimensions: the type of operations used for transforming plaintext to ciphertext; the way in which the plaintext is processed; and __________ .

An original intelligible message fed into the algorithm as input is known as _________ , while the coded message produced as output is called the __________ .

Steganography renders the message unintelligible to outsiders by various transformations of the text.

the methods of __________ conceal the existence of the message in a graphic image.

When using symmetric encryption it is very important to keep the algorithm secret.

Monoalphabetic ciphers are easy to break because they reflect the frequency data of the original alphabet.

A __________ cipher processes the input one block of elements at a time, producing an output block for each input block, whereas a stream cipher processes the input elements continuously, producing output one element at a time.