Chapter 2 - Cryptography - Final
symmetric encryption
1. Also referred to as single-key encryption, the universal technique for providing confidentiality for transmitted or stored data is __________ .
T
1. Symmetric encryption is used primarily to provide confidentiality.
D
1. The original message or data that is fed into the algorithm is __________. A. encryption algorithm B. secret key C. decryption algorithm D. plaintext
A
10. 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. A. digital signature B. keystream C. one way hash function D. secret key
Electronic Frontier Foundation (EFF)
10. In July 1998 the __________ announced that it had broken a DES encryption using a special purpose "DES cracker" machine.
T
10. The strength of a hash function against brute-force attacks depends solely on the length of the hash code produced by the algorithm.
T
11. Public-key cryptography is asymmetric.
electronic codebook (ECB)
11. The simplest approach to multiple block encryption is known as __________ mode, in which plaintext is handled b bits at a time and each block of plaintext is encrypted using the same key.
C
11. Transmitted data stored locally are referred to as __________ . A. ciphertext B. DES C. data at rest D. ECC
pseudorandom
12. A __________ stream is one that is unpredictable without knowledge of the input key and which has an apparently random character.
B
12. Digital signatures and key management are the two most important applications of __________ encryption. A. private-key B. public-key C. preimage resistant D. advanced
F
12. Public-key algorithms are based on simple operations on bit patterns.
D
13. A __________ is to try every possible key on a piece of ciphertext until an intelligible translation into plaintext is obtained. A. mode of operation B. hash function C. cryptanalysis D. brute-force attack
public and private key
13. The __________ is a pair of keys that have been selected so that if one is used for encryption, the other is used for decryption.
F
13. The purpose of the DSS algorithm is to enable two users to securely reach agreement about a shared secret that can be used as a secret key for subsequent symmetric encryption of messages.
T
14. An important element in many computer security services and applications is the use of cryptographic algorithms.
A
14. Combined one byte at a time with the plaintext stream using the XOR operation, a __________ is the output of the pseudorandom bit generator. A. keystream B. digital signature C. secure hash D. message authentication code
library-based tape encryption
14. __________ is provided by means of a co-processor board embedded in the tape drive and tape library hardware.
B
15. A _________ protects against an attack in which one party generates a message for another party to sign. A. data authenticator B. strong hash function C. weak hash function D. digital signature
T
15. Some form of protocol is needed for public-key distribution.
Diffie-Hellman Key Agreement
15. The purpose of the __________ algorithm is to enable two users to securely reach agreement about a shared secret that can be used as a secret key for subsequent symmetric encryption of messages.
A
2. The __________ is the encryption algorithm run in reverse. A. decryption algorithm B. plaintext C. ciphertext D. encryption algorithm
brute-force
2. There are two general approaches to attacking a symmetric encryption scheme: cryptanalytic attacks and __________ attacks.
T
2. Two of the most important applications of public-key encryption are digital signatures and key management.
F
3. Cryptanalytic attacks try every possible key on a piece of ciphertext until an intelligible translation into plaintext is obtained.
decryption
3. The __________ algorithm takes the ciphertext and the secret key and produces the original plaintext.
B
3. __________ is the scrambled message produced as output. A. Plaintext B. Ciphertext C. Secret key D. Cryptanalysis
cryptanalytic
4. A __________ attack exploits the characteristics of the algorithm to attempt to deduce a specific plaintext or to deduce the key being used.
B
4. On average, __________ of all possible keys must be tried in order to achieve success with a brute-force attack. A. one-fourth B. half C. two-thirds D. three-fourths
T
4. The secret key is input to the encryption algorithm.
block cipher
5. A __________ processes the plaintext input in fixed-size blocks and produces a block of ciphertext of equal size for each plaintext block.
C
5. The most important symmetric algorithms, all of which are block ciphers, are the DES, triple DES, and the __________. A. SHA B. RSA C. AES D. DSS
F
5. Triple DES takes a plaintext block of 64 bits and a key of 56 bits to produce a ciphertext block of 64 bits.
stream cipher
6. A __________ processes the input elements continuously, producing output one element at a time.
A
6. 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 longer keys B. use shorter keys C. use more keys D. use less keys
T
6. Modes of operation are the alternative techniques that have been developed to increase the security of symmetric block encryption for large sequences of data
Diffie and Hellman
7. Public-key encryption was first publicly proposed by __________ in 1976.
F
7. The advantage of a stream cipher is that you can reuse keys.
C
7. __________ is a procedure that allows communicating parties to verify that received or stored messages are authentic. A. Cryptanalysis B. Decryption C. Message authentication D. Collision resistance
T
8. A message authentication code is a small block of data generated by a secret key and appended to a message.
D
8. The purpose of a __________ is to produce a "fingerprint" of a file, message, or other block of data. A. secret key B. digital signature C. keystream D. hash function
uniform distribution
8. The two criteria used to validate that a sequence of numbers is random are independence and _________ .
back-end appliance
9. A _________ is a hardware device that sits between servers and storage systems and encrypts all data going from the server to the storage system and decrypts data going in the opposite direction.
F
9. Like the MAC, a hash function also takes a secret key as input.
B
9. __________ is a block cipher in which the plaintext and ciphertext are integers between 0 and n-1 for some n. A. DSS B. RSA C. SHA D. AES
