Exam 2: Classical Encryption Techniques

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

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

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 ___________ .

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

The earliest known and simplest use of a substitution cipher was called the __________ cipher and involved replacing each letter of the alphabet with the letter standing three places further down the alphabet.

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

The __________ consist of a set of independently rotating cylinders through which electrical pulses can flow.Each cylinder has 26 input pins and 26 output pins with internal wiring that connects each input pin to a unique output pin.

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.

The __________ was used as the standard field system by the British Army in World War I and was used by the U.S.Army and other Allied forces during World War II.

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

With the use of symmetric encryption,the principal security problem is maintaining the secrecy of the key.

Joseph Mauborgne proposed an improvement to the Vernam cipher that uses a random key that is as long as the message so that the key does not need to be repeated.The key is used to encrypt and decrypt a single message and then is discarded.Each new message requires a new key of the same length as the new message.This scheme is known as an)__________ .

_________ refer to common two-letter combinations in the English language.

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

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 __________ .

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

As with Playfair,the strength of the Hill cipher is that it completely hides single letter frequencies.

The most widely used cipher ever is the __________ .

All encryption algorithms are based on two general principles: substitution and ____________ .

The one-time pad has unlimited utility and is useful primarily for high-bandwidth channels requiring low security.