Chapter 6 Cryptography and Symmetric Key Algorithms

Question 1

To encrypt a message, you simply shift each letter of the alphabet three places to the
right

Answer 1

Caesar cipher r .

Question 2

a cryptographic system should be secure

even if everything about the system, except the key, is public knowledge.

Answer 2

The Kerchoff Principle

Question 3

random number that acts as a placeholder variable in mathematical functions.

Answer 3

nonce

Question 4

Zero-Knowledge Proof

Answer 4

zero-knowledge proof

Question 5

When the information or privilege required to perform an operation is divided among
multiple users, no single person has suffi cient privileges to compromise the security
of an environment.

Answer 5

Split Knowledge

Question 6

a minimum number of agents out of the total number of agents work together to perform high-security tasks.

Answer 6

M of N Control

Question 7

cryptographic systems of symbols that represent words or phrases,

Answer 7

Codes

Question 8

always meant to hide the true meaning of a message

Answer 8

Ciphers

Question 9

________ use an encryption algorithm to rearrange the letters of a plaintext message, forming the ciphertext message.

Answer 9

Transposition ciphers

Question 10

use a different substitution alphabet for each letter of the plaintext message.

Answer 10

one-time pad

Question 11

the encryption key is as long as the m r essage itself and is often
chosen from a common book

Answer 11

running key cipher

Question 12

the relationship between the plain text
and the key is so complicated that an attacker can’t merely continue altering the plain
text and analyzing the resulting ciphertext to determine the key.

Answer 12

Confusion

Question 13

a change in the plain text results in multiple changes spread throughout the ciphertext.

Answer 13

Diffusion

Question 14

Advanced Encryption Standard (AES)

Block Size____ bits
Key Size _____ bits

Answer 14

Block Size - 128

Key size - 128, 192, 256

Question 15

Skipjack

Block Size____ bits
Key Size _____ bits

Answer 15

Block Size 64

Key size 80

Question 16

IDEA (used in PGP)

Block Size____ bits
Key Size _____ bits

Answer 16

Block size 64

Key size 128

Question 17

Twofish

Block Size____ bits
Key Size _____ bits

Answer 17

Block size 128

Key size 1 - 256

Question 18

DES
Block Size____ bits
Key Size _____ bits

Answer 18

Block size 64

Key size 56

Question 19

Triple DES (3DES)
Block Size____ bits
Key Size _____ bits

Answer 19

Block size 64

Key size 168

Question 20

_______ was developed in response to complaints about the insufficient key length of the DES algorithm.

Answer 20

International Data Encryption Algorithm (IDEA)

Question 21

International Data Encryption Algorithm key is broken up in a series of operations into __ 16-bit subkeys.

Answer 21

52

Question 22

Which algorithm supports the escrow of encryption keys ?

Rijndael
Twofish
Skipjack
Blowfish

Answer 22

Skipjack

Question 23

Twofish uses two techniques not found in other algorithms

Answer 23

Prewhitening

Postwhitening

Question 24

Involves XORing the plain text with a separate subkey before the first round of encryption.

Prewhitening
Postwhitening

Answer 24

Prewhitening

Question 25

Involves XORing the plain text with a separate subkey after the 16th round of encryption.

Answer 25

Postwhitening

Question 26

Name the three main methods used to exchange secret keys securely.

Answer 26

Diffie-Hellman, Public Key Encryption, Offline Distribution

Question 27

Name two major approaches to key escrow that have been proposed over the past decade:

Answer 27

Fair Cryptosystems, Escrowed Encryption Standard

Question 28

In this escrow approach, the secret keys used in a communication are divided into two or more pieces, each of which is given to an independent third party.
Each of these pieces is useless on its own but may be recombined to obtain the secret key.

Fair Cryptosystems
Escrowed Encryption Standard

Answer 28

Fair Cryptosystems

Question 29

This escrow approach provides the government with a technological means to decrypt ciphertext. This standard is the basis behind the Skipjack algorithm.

Fair Cryptosystems
Escrowed Encryption Standard

Answer 29

Escrowed Encryption Standard

Question 30

Name 6 symmetric algorithms

Answer 30

Data Encryption Standard (DES)
Triple DES (3DES)
 International Data Encryption Algorithm (IDEA)
Blowfish
Skipjack,
Advanced Encryption Standard (AES).