L13 - Intro to Cryptography

Question 1

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 a longer key length
b) Use a shorter key length
c) Use a more complex algorithm
d) Use a harder to guess key

Answer 1

a) Use a longer key length

A longer key length means the attacker has to search more keys

Question 2

What weaknesses can be exploited in the Vigenere Cipher?

a) It uses a repeating key letters
b) It requires security for the key, not the message
c) The length of the key can be determined using frequency analysis

Answer 2

A and C

a) It uses a repeating key letters
c) The length of the key can be determined using frequency analysis

Question 3

Which of the following characteristics would improve password security?

a) Use a one-way hash function
b) Should not use the avalanche effect
c) Should only check to see that the hash function output is the same stored output

Answer 3

A and C

a) Use a one-way hash function
c) Should only check to see that the hash function output is the same stored output

Question 4

Select the correct definition for the following attack:
known-plaintext attacks

a) A method to determine the encryption function by analyzing know phrases and their encryption
b) Analyzing the effect of changes in input on the encrypted output
c) Compare the ciphertexts with its known plaintext
d) A method where a specific known plaintext is compared to its cipertext

Answer 4

d) A method where a specific known plaintext is compared to its cipertext

Question 5

Select the correct definition for the following attack:
chosen-plaintext attack

a) A method to determine the encryption function by analyzing know phrases and their encryption
b) Analyzing the effect of changes in input on the encrypted output
c) Compare the ciphertexts with its known plaintext
d) A method where a specific known plaintext is compared to its cipertext

Answer 5

c) Compare the ciphertexts with its known plaintext

Question 6

Select the correct definition for the following attack:
differential cryptanalysis

a) A method to determine the encryption function by analyzing know phrases and their encryption
b) Analyzing the effect of changes in input on the encrypted output
c) Compare the ciphertexts with its known plaintext
d) A method where a specific known plaintext is compared to its cipertext

Answer 6

b) Analyzing the effect of changes in input on the encrypted output

Question 7

Select the correct definition for the following attack:
linear cryptanalysis

a) A method to determine the encryption function by analyzing know phrases and their encryption
b) Analyzing the effect of changes in input on the encrypted output
c) Compare the ciphertexts with its known plaintext
d) A method where a specific known plaintext is compared to its cipertext

Answer 7

a) A method to determine the encryption function by analyzing know phrases and their encryption

Question 8

Check all tasks for which asymmetric encryption is better:

a) Provide confidentiality of a message
b) Securely distribute a session key
c) Scalability

Answer 8

B and C

b) Securely distribute a session key
c) Scalability

Question 9

Symmetric encryption can only be used to provide confidentiality

a) True
b) False

Answer 9

b) False

Can be used for other security services such as authentication

Question 10

Public-key encryption can be used to create digital signatures

a) True
b) False

Answer 10

a) True

We can first hash a message then encrypt a message using our public key. The encrypted hash value becomes the digital signature of message

Question 11

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

a) True
b) False

Answer 11

b) False

What is describe here is Brute Force.

Question 12

The secret key is input to the encryption algorithm

a) True
b) False

Answer 12

a) True