Exam 2: Classical Encryption Techniques

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

On average,half of all possible keys must be tried to achieve success with a brute-force attack.

The process of converting from plaintext to ciphertext is known as deciphering or decryption.

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 __________ .

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.

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

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

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

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.

Restoring the plaintext from the ciphertext is __________ .

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.

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

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

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.

The most widely used cipher is the Data Encryption Standard.

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.

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

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.

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

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