chapter2

Question 1

Symmetric encryption is used primarily to provide confidentiality

Answer 1

T

Question 2

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

Answer 2

T

Question 3

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

Answer 3

F

Question 4

The secret key is input to the encryption algorithm

Answer 4

T

Question 5

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

Answer 5

F

Question 6

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

Answer 6

T

Question 7

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

Answer 7

F

Question 8

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

Answer 8

T

Question 9

Like the MAC, a hash function also takes a secret key as input.

Answer 9

F

Question 10

The strength of a hash function against brute-force attacks depends
solely on the length of the hash code produced by the algorithm.

Answer 10

T

Question 11

Public-key cryptography is asymmetric

Answer 11

T

Question 12

Public-key algorithms are based on simple operations on bit patterns

Answer 12

F

Question 13

The purpose of the DSS algorithm is to enable two users to securely
reach agreement about a shared secret that can be used as a secret key
for subsequent symmetric encryption of messages

Answer 13

F

Question 14

An important element in many computer security services and
applications is the use of cryptographic algorithms.

Answer 14

T

Question 15

Some form of protocol is needed for public-key distribution

Answer 15

T

Question 16

The original message or data that is fed into the algorithm is __________.
A. encryption algorithm B. secret key
C. decryption algorithm D. plaintext

Answer 16

plaintext

Question 17

The __________ is the encryption algorithm run in reverse.
A. decryption algorithm B. plaintext
C. ciphertext D. encryption algorithm

Answer 17

decryption algorithm

Question 18

__________ is the scrambled message produced as output.
A. Plaintext B. Ciphertext
C. Secret key D. Cryptanalysis

Answer 18

Ciphertext

Question 19

On average, __________ of all possible keys must be tried in order to achieve success with a brute-force attack.
A. one-fourth B. half
C. two-thirds D. three-fourths

Answer 19

half

Question 20

The most important symmetric algorithms, all of which are block ciphers, are the DES, triple DES, and the __________.
A. SHA B. RSA
C. AES D. DSS

Answer 20

AES

Question 21

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 __________ .
A. use longer keys B. use shorter keys
C. use more keys D. use less keys

Answer 21

use longer keys

Question 22

__________ is a procedure that allows communicating parties to verify that received or stored messages are authentic.
A. Cryptanalysis B. Decryption
C. Message authentication D. Collision resistance

Answer 22

Message authentication

Question 23

The purpose of a __________ is to produce a “fingerprint” of a file, message, or other block of data.
A. secret key B. digital signature
C. keystream D. hash function

Answer 23

hash function

Question 24

__________ is a block cipher in which the plaintext and ciphertext are integers between 0 and n-1 for some n.
A. DSS B. RSA
C. SHA D. AES

Answer 24

RSA

Question 25

A __________ is created by using a secure hash function to generate a hash value for a message and then encrypting the hash code with a private key. A. digital signature B. keystream C. one way hash function D. secret key

Answer 25

digital signature

Question 26

Transmitted data stored locally are referred to as __________ . A. ciphertext B. DES C. data at rest D. ECC

Answer 26

data at rest

Question 27

Digital signatures and key management are the two most important applications of __________ encryption. A. private-key B. public-key C. preimage resistant D. advanced

Answer 27

public-key

Question 28

A __________ is to try every possible key on a piece of ciphertext until an intelligible translation into plaintext is obtained. A. mode of operation B. hash function C. cryptanalysis D. brute-force attack

Answer 28

brute-force attack

Question 29

Combined one byte at a time with the plaintext stream using the XOR operation, a __________ is the output of the pseudorandom bit generator. A. keystream B. digital signature C. secure hash D. message authentication code

Answer 29

keystream

Question 30

A _________ protects against an attack in which one party generates a message for another party to sign. A. data authenticator B. strong hash function C. weak hash function D. digital signature

Answer 30

strong hash function