CS 351: Midterm MCQ Practice

The original message or data that is fed into the algorithm is __________.

Plaintext

The __________ is the encryption algorithm run in reverse.

Decription algorithm

__________ is the scrambled message produced as output.

Ciphertext

The most important symmetric algorithms, all of which are block ciphers, are the

DES, triple DES, and the __________.

AES

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 __________ .

Use shorter keys

__________ is a procedure that allows communicating parties to verify that received

or stored messages are authentic.

Message authentication

The purpose of a __________ is to produce a "fingerprint" of a file, message, or

other block of data.

Hash function

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.

Digital signature

Digital signatures and key management are the two most important applications of __________ encryption.

Public-key

A __________ is to try every possible key on a piece of ciphertext until an intelligible translation into plaintext is obtained.

Brute-force attack

Combined one byte at a time with the plaintext stream using the XOR operation, a __________ is the output of the pseudorandom bit generator.

Keystream

There are _____ modes of operation defined by NIST that are intended to cover

virtually all the possible applications of encryption for which a block cipher could be

used.

Five

Cryptographic systems are generically classified by _________.

All of the above (A. The type of operations used for transforming plaintext to ciphertext, B. the number of keys used, and C. the way in which plaintext is processed)

___________ was the first published public-key algorithm.

Diffie-Hellman

The __________ uses an algorithm that is designed to provide only the digital

signature function and cannot be used for encryption or key exchange.

DSS

The following cryptographic algorithm relies on the complexity of the integer

factorization problem:

RSA

The following cryptographic algorithm relies on the complexity of the discrete

logarithm problem:

Diffie-Hellman

Which of the following is a non-linear component of the DES algorithm?

S-box

What is the effective key size used for encryption in the DES algorithm?

56 bits

Which of the following statements is true regarding the key sizes in AES, DES,

and RSA?

AES supports key sizes of 128, 192, and 256 bits, while DES uses a 56-bit key

and RSA supports key sizes of 512, 1024, or 2048 bits.

__________ is a procedure that allows communicating parties to verify that received

or stored messages are authentic.

Message authentication

The purpose of a __________ is to produce a "fingerprint" of a file, message, or other block of data.

Hash function

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.

Digital signature

Digital signatures and key management are the two most important applications of __________ encryption.

Public-key

A __________ is to try every possible key on a piece of ciphertext until an intelligible translation into plaintext is obtained.

brute-force attack

If Richard wants to send an encrypted message to Sue using a public key cryptosystem, which key does he use to encrypt the message?

Sue's public-key

Richard received an encrypted message sent to him from Sue. Which key should he use to decrypt the message?

Richard's private key

Richard wants to digitally sign a message he's sending to Sue so that Sue can be sure the message came from him without modification while in transit. Which key should he use to encrypt the message digest?

Richard's private key

What TCP/IP communications port is used by Transport Layer Security traffic?

443

How many possible keys exist in a 4-bit key space?

16

John recently received an email message from Bill. What cryptographic goal would need to be met to convince John that Bill was actually the sender of the message?

Nonrepudiation

What is the length of the cryptographic key used in the Data Encryption Standard (DES) cryptosystem?

56 bits

What type of cipher relies on changing the location of characters within a message to achieve confidentiality?

Transposition cipher

Which one of the following is not a possible key length for the Advanced Encryption Standard Rijndael cipher?

128 bits

What is the output value of the mathematical function 16 mod 3?

1

Which one of the following cipher types operates on large pieces of a message rather than individual characters or bits of a message?

Block cipher

What is the minimum number of cryptographic keys required for secure two-way communications in symmetric key cryptography?

One

What block size is used by the Advanced Encryption Standard?

128 bits

What kind of attack makes the Caesar cipher virtually unusable?

Frequency analysis attack

How many encryption keys are required to fully implement an asymmetric algorithm with 10 participants?

20