TRUE/FALSE QUESTIONS:
T F 1. Symmetric encryption is used primarily to provide confidentiality.
T F 2. Two of the most important applications of public-key encryption are
digital signatures and key management.
T F 3. Cryptanalytic attacks try every possible key on a piece of ciphertext
until an intelligible translation into plaintext is obtained.
T F 4. The secret key is input to the encryption algorithm.
T 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.
T F 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.
T F 7. The advantage of a stream cipher is that you can reuse keys.
T F 8. A message authentication code is a small block of data generated by a
secret key and appended to a message.
T F 9. Like the MAC, a hash function also takes a secret key as input.
T F 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 F 11. Public-key cryptography is asymmetric.
T F 12. Public-key algorithms are based on simple operations on bit patterns.
T 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 F 14. An important element in many computer security services and
applications is the use of cryptographic algorithms.
T F 15. Some form of protocol is needed for public-key distribution.
MULTIPLE CHOICE QUESTIONS:
• The original message or data that is fed into the algorithm is __________.
A. encryption algorithm B. secret key
C. decryption algorithm D. plaintext
2. The __________ is the encryption algorithm run in reverse.
A. decryption algorithm B. plaintext
C. ciphertext D. encryption algorithm
3. __________ is the scrambled message produced as output.
A. Plaintext B. Ciphertext
C. Secret key D. Cryptanalysis
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
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
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
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
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
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
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
11. Transmitted data stored locally are referred to as __________ .
A. ciphertext B. DES
C. data at rest D. ECC
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
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
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
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
SHORT ANSWER QUESTIONS:
• Also referred to as single-key encryption, the universal technique for providing confidentiality for transmitted or stored data is __________ .
• There are two general approaches to attacking a symmetric encryption scheme:
cryptanalytic attacks and __________ attacks.
• The __________ algorithm takes the ciphertext and the secret key and produces
the original plaintext.
• A __________ attack exploits the characteristics of the algorithm to attempt to deduce a specific plaintext or to deduce the key being used.
• A __________ processes the plaintext input in fixed-size blocks and produces a block of ciphertext of equal size for each plaintext block.
• A __________ processes the input elements continuously, producing output one element at a time.
• Public-key encryption was first publicly proposed by __________ in 1976.
• The two criteria used to validate that a sequence of numbers is random are independence and _________ .
• 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.
• In July 1998 the __________ announced that it had broken a DES encryption using a special purpose “DES cracker” machine.
• 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.
• A __________ stream is one that is unpredictable without knowledge of the input key and which has an apparently random character.
• The __________ is a pair of keys that have been selected so that if one is used for encryption, the other is used for decryption.
• __________ is provided by means of a co-processor board embedded in the tape drive and tape library hardware.
• 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.