Exam 3: Classical Encryption Techniques

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

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

An encryption scheme is __________ secure if the ciphertext generated by the scheme does not contain enough information to determine uniquely the corresponding plaintext, no matter how much ciphertext is available.

the simplest transposition cipher is the _________ technique, in which the plaintext is written down as a sequence of diagonals and then read off as a sequence of rows.

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

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

A technique for hiding a secret message within a larger document or picture in such a way that others cannot discern the presence or contents of the hidden message is __________ .

techniques used for deciphering a message without any knowledge of the enciphering details is ___________ .

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.

Symmetric encryption remains by far the most widely used of the two types of encryption.

the task of making large quantities of random keys on a regular basis and distributing a key of equal length to both sender and receiver for every message sent are difficulties of the __________ scheme.

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.

__________ attacks exploit the characteristics of the algorithm to attempt to deduce a specific plaintext or to deduce the key being used.

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.

One of the simplest and best known polyalphabetic ciphers is _________ cipher.In this scheme, the set of related monoalphabetic substitution rules consists of the 26 Caesar ciphers with shifts of 0 through 25.Each cipher is denoted by a key letter which is the ciphertext letter that substitutes for the plaintext letter A.

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

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.

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.

the ___________ takes the ciphertext and the secret key and produces the original plaintext.It is essentially the encryption algorithm run in reverse.

A __________ attack involves trying every possible key until an intelligible translation of the ciphertext is obtained.