ESAT Forouzan - Chapter 29: Cyrptography

Question 1

Before a message is encrypted, it is called _______.
a. Plaintext
b. Ciphertext
c. Cryptotext
d. Cryptonite

Answer 1

a. Plaintext

Question 2

After a message is decrypted, it is called _______.
a. Plaintext
b. Ciphertext
c. Cryptotext
d. Cryptonite

Answer 2

a. Plaintext

Question 3

A cipher is _______.
a. An encryption algorithm
b. A decryption algorithm
c. A private key
d. (a) or (b)

Answer 3

d. (a) or (b)

Question 4

In the symmetric-key method of cryptography, which key is publicly known?
a. Encryption key only
b. Decryption key only
c. Both
d. None of the Above

Answer 4

d. None of the Above

Question 5

If 20 people need to communicate using symmetric-key cryptography, ____ symmetric keys are needed.
a. 19
b. 20
c. 190
d. 200

Answer 5

c. 190

Question 6

The _______ is an example of polyalphabetic substitution.
a. P-box
b. S-box
c. Product block
d. Vigenere cipher

Answer 6

d. Vigenere cipher

Question 7

The _________ is a block cipher.
a. P-box
b. S-box
c. Product block
d. All the above

Answer 7

d. All the above

Question 8

We use a cryptography method in which the character Z always substitutes for the character G. This is probably ___________.
a. Monoalphabetic substitution
b. Polyalphabetic substitution
c. Transpositional
d. None of the Above

Answer 8

a. Monoalphabetic substitution

Question 9

We use a cryptography method in which the plaintext AAAAAA becomes the ciphertext BCDEFG. This is probably ____________.
a. Monoalphabetic substitution
b. Polyalphabetic substitution
c. Transposition
d. None of the Above

Answer 9

b. Polyalphabetic substitution

Question 10

One way to encrypt and decrypt long messages is through the use of the _______.
a. ECB mode
b. CBC mode
c. CFM
d. All of the Above

Answer 10

d. All of the Above

Question 11

An initialization vector is needed in the _____________.
a. CSM
b. CBC mode
c. CVF
d. a and b

Answer 11

d. a and b

Question 12

In the __________, the encryption of each 8-byte block is independent of the other
a. ECB mode
b. CBC mode
c. CVF
d. CSM

Answer 12

a. ECB mode

Question 13

In the public key method of cryptography, which key is publicly known?
a. Encryption key only
b. Decryption key only
c. Both
d. None of the Above

Answer 13

a. Encryption key only

Question 14

In the public-key method of cryptography, only the receiver has possession of the __________.
a. Private key
b. Public key
c. Both keys
d. None of the Above

Answer 14

a. Private key

Question 15

The RSA algorithm uses a __________ cryptography method.
a. Public-key
b. Private-key
c. Symmetric-key
d. Denominational

Answer 15

a. Public-key