Computer Security Midterm CH3

cryptanalytic

A _________________ attack exploits the characteristics of the algorithm to attempt to deduce a specific plaintext or to deduce the key being used.

stream cipher

A _________________ processes the input elements continuously, producing output one element at a time.

block cipher

A _________________ processes the plaintext input in fixed-size blocks and produces a block of ciphertext of equal size for each plaintext block.

T

A message authentication code is a small block of data generated by a secret key and appended to a message. True or False

symmetric encryption

Also referred to as single-key encryption, the universal technique for providing confidentiality for transmitted or stored data is _______________________ .

F

Cryptanalytic attacks try every possible key on a piece of ciphertext until an intelligible translation into plaintext is obtained. True or False

use longer keys

If the only form of attack that could be made on an encryption algorithm is brute-force, then the way to counter such attacks would be to __________ .

T

Modes of operation are the alternative techniques that have been developed to increase the security of symmetric block encryption for large sequences of data. True or False

half

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

Diffie and Hellman

Public-key encryption was first publicly proposed by _________________ in 1976.

T

Symmetric encryption is used primarily to provide confidentiality. True or False

decryption algorithm

The __________ is the encryption algorithm run in reverse.

decryption

The ________________ algorithm takes the ciphertext and the secret key and produces the original plaintext.

F

The advantage of a stream cipher is that you can reuse keys. True or False

AES

The most important symmetric algorithms, all of which are block ciphers, are the DES, triple DES, and the __________.

plaintext

The original message or data that is fed into the algorithm is __________.

hash function

The purpose of a __________ is to produce a "fingerprint" of a file, message, or other block of data.

T

The secret key is input to the encryption algorithm. True or False

uniform distribution

The two criteria used to validate that a sequence of numbers is random are independence and _________ .

brute-force

There are two general approaches to attacking a symmetric encryption scheme: cryptanalytic attacks and _______________________ attacks.

F

Triple DES takes a plaintext block of 64 bits and a key of 56 bits to produce a ciphertext block of 64 bits. True or False

T

Two of the most important applications of public-key encryption are digital signatures and key management. True or False

Message authentication

__________ is a procedure that allows communicating parties to verify that received or stored messages are authentic.

Ciphertext

__________ is the scrambled message produced as output.