Block Modes practice questions

Question: What is the length (in bits) of a SHA hash output?

Answer Options:
40
80
160
320

Answer: 160

Question: Which mode of encryption encrypts each block independently?

Answer Options:
CTR
CFB
ECB
OFB

Answer: ECB

Question: How does ECB mode encryption function?

Answer Options:
Converts from block to stream, then uses a counter value and a nonce to encrypt the data
Uses an initialization vector (IV) to encrypt the first block, then uses the result of the encryption to encrypt the next block
Encrypts each block with the same key, where each block is independent of the others
Uses a self-synchronizing stream on the blocks, where the initialization vector (IV) is encrypted and XORed with the data stream

Answer: Encrypts each block with the same key, where each block is independent of the others

Question: Which cryptographic operation has the fastest decryption process?

Answer Options:
Asymmetric
Hashing
Padding
Symmetric

Answer: Symmetric

Question: Which key is used to decrypt a hash in a digitally signed message?

Answer Options:
Recipient’s private key
Sender’s private key
Sender’s public key
Recipient’s public key

Answer: Sender’s public key

Question: A security analyst is using human interactions as data points to generate numbers for a program. Which type of number generator is being used?

Answer Options:
Prime
True random
Pseudorandom
Sequence

Answer: True random

Question: Which encryption algorithm uses an 80-bit key and operates on 64-bit data blocks?

Answer Options:
Twofish
Camellia
Blowfish
Skipjack

Answer: Skipjack

Question: How does a rainbow table crack stored passwords?

Answer Options:
Matches hash values back to the original plaintext
Takes a list of the most common words and tries each entry
Looks at the mathematical probability of paired values being used
Factors the prime numbers used within an RSA algorithm

Answer: Matches hash values back to the original plaintext

Question: Which attack maps hashed values and original data?

Answer Options:
Rainbow table
Brute-force
Birthday
Dictionary

Answer: Rainbow table

Question: Which mode of encryption uses an initialization vector (IV) for the first part of plaintext and then, to encrypt each subsequent part of plaintext, leverages the outcome from each preceding operation?

Answer Options:
CFB
CBC
ECB
OFB

Answer: CBC

Question: What is the correlation between a block algorithm key size and its performance and security?

Answer Options:
The key size is directly proportional to security, but performance is unaffected
As the key size increases, performance and security also increase
As the key size increases, performance decreases, and security increases
The key size is directly proportional to performance, but security is unaffected

Answer: As the key size increases, performance decreases, and security increases

Question: What does the LM hash do to passwords that are fewer than 14 characters before using the DES?

Answer Options:
Rotates characters with a Caesar cipher
Adds null characters to the end
Converts characters to lowercase
Concatenates the characters

Answer: Adds null characters to the end

Question: Which secret key algorithm is used in the Clipper chip?

Answer Options:
Blowfish
Skipjack
IDEA
DES

Answer: Skipjack

Question: Which component is used to verify that a data entity was created?

Answer Options:
TSP
AES
NTLM
HMAC

Answer: TSP

Question: Which type of encryption uses CFB mode?

Answer Options:
Stream
Hash
Salt
Block

Answer: Stream

Question: What is the maximum key size of the Blowfish cipher?

Answer Options:
128
192
256
448

Answer: 448

Question: Why should a forensic investigator create a hash on a victim’s hard drive and the bitstream copy of the hard drive?

Answer Options:
To verify that the drives are identical
To establish who created the files on the drives
To identify if someone opened the drive
To certify the information on the drive is correct

Answer: To verify that the drives are identical