# Test Bank for Network Security Essentials: Applications and Standards, 6th Edition

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Network Security Essentials Applications and Standards, 6th Edition, by William
Stallings
CHAPTER 2: SYMMETRIC ENCRYPTION AND MESSAGE CONFIDENTIALITY
TRUE OR FALSE
T
F
1. Public-key encryption is also referred to as conventional
encryption, secret-key, or single-key encryption.
T
F
2. The advantage of a block cipher is that you can reuse keys.
T
F
3. Ciphertext is the scrambled message produced as output.
T
F
4. The security of symmetric encryption depends on the secrecy of
the algorithm, not the secrecy of the key.
T
F
5. The ciphertext-only attack is the easiest to defend against because
the opponent has the least amount of information to work with.
T
F
6. The Feistel structure is a particular example of the more general
structure used by all symmetric block ciphers.
T
F
7. Smaller block sizes mean greater security but reduced
encryption/decryption speed.
T
F
8. The essence of a symmetric block cipher is that a single round
offers inadequate security but that multiple rounds offer
increasing security.
T
F
9. Triple DES was first standardized for use in financial applications
in ANSI standard X9.17 in 1985.
T
F
10. The most commonly used symmetric encryption algorithms are
stream ciphers.
T
F
11. The principal drawback of 3DES is that the algorithm is relatively
sluggish in software.
T
F
12. AES uses a Feistel structure.
T
F
encryption
13.
Random numbers play an important role in the use of
ยฉ 2017 Pearson Education, Inc., Hoboken, NJ. All rights reserved.
Network Security Essentials Applications and Standards, 6th Edition, by William
Stallings
for various network security applications.
T
F
14. The primary advantage of a stream cipher is that stream ciphers
are almost always faster and use far less code than do block
ciphers.
T
F
15. One desirable property of a stream cipher is that the ciphertext be
longer in length than the plaintext.
MULTIPLE CHOICE
1. A symmetric encryption scheme has _________ ingredients.
A. three
B. six
C. five
D. four
2. _________ is the original message or data that is fed into the algorithm as input.
A. DES
B. Plaintext
C. Encryption key
D. Ciphertext
3. _________ mode requires only the implementation of the encryption algorithm
and not the decryption algorithm.
A. CBC
B. DKS
C. ECB
D. CTR
4. A __________ processes the input elements continuously, producing output one
element at a time, as it goes along.
A. block cipher
B. cryptanalysis
C. keystream
D. stream cipher
ยฉ 2017 Pearson Education, Inc., Hoboken, NJ. All rights reserved.
Network Security Essentials Applications and Standards, 6th Edition, by William
Stallings
5. If both sender and receiver use the same key the system is referred to as
_________ encryption.
A. asymmetric
B. two-key
C. symmetric
D. public-key
6. If the sender and receiver each use a different key the system is referred to as
__________ encryption.
A. secret-key
B. conventional
C. single-key
D. asymmetric
7. A _________ approach involves trying every possible key until an intelligible
translation of the ciphertext into plaintext is obtained.
A. triple DES
B. brute-force
C. block cipher
D. computational
8. With the ________ mode if there is an error in a block of the transmitted
ciphertext only the corresponding plaintext block is affected.
A. CTS
B. CBC
C. ECB
D. TSR
9. The most common key length in modern algorithms is ________ .
A. 64 bits
B. 128 bits
C. 32 bits
D. 256 bits
10. A ________ takes as input a source that is effectively random and is often
referred to as an entropy source.
A. PRNG
B. PRF
ยฉ 2017 Pearson Education, Inc., Hoboken, NJ. All rights reserved.
Network Security Essentials Applications and Standards, 6th Edition, by William
Stallings
C. PSRN
D. TRNG
11. A symmetric block cipher processes _________ of data at a time.
A. two blocks
B. one block
C. four blocks
D. three blocks
12. In _________ mode a counter equal to the plaintext block size is used.
A. CTR
B. CFB
C. ECB
D. CBC
13. The _________ algorithm performs various substitutions and transformations
on the plaintext.
A. keystream
B. cipher
C. encryption
D. codebook
14. If the analyst is able to get the source system to insert into the system a
message chosen by the analyst, a _________ attack is possible.
A. ciphertext only
C. chosen plaintext
B. known plaintext
D. chosen ciphertext
15. The _________ key size is used with the Data Encryption Standard algorithm.
A. 128 bit
B. 168 bit
C. 56 bit
D. 32 bit
ยฉ 2017 Pearson Education, Inc., Hoboken, NJ. All rights reserved.
Network Security Essentials Applications and Standards, 6th Edition, by William
Stallings
SHORT ANSWER
1. The _________ algorithm takes the ciphertext and the same secret key and produces
the original plaintext.
2. A _________ cipher processes the plaintext input in fixed sized blocks and produces
a block of ciphertext of equal size for each plaintext block.
3. With the use of symmetric encryption, the principal security problem is
maintaining the secrecy of the _________ .
4. Three broad categories of cryptographic algorithms are commonly used to create
PRNGs: Asymmetric ciphers, Hash functions and message authentication codes,
and ___________ .
5. The process of attempting to discover the plaintext or key is known as _________ .
6. An encryption scheme is __________ if the cost of breaking the cipher exceeds the
value of the encrypted information and/or the time required to break the cipher
exceeds the useful lifetime of the information.
7. The three most important symmetric block ciphers are: triple DES (3DES), the
Advanced Encryption Standard (AES), and the ___________ .
8. The ________ source is drawn from the physical environment of the computer and
could include things such as keystroke timing patterns, disk electrical activity,
mouse movements, and instantaneous values of the system clock.
9. A PRNG takes as input a fixed value called the ________ and produces a sequence of
output bits using a deterministic algorithm.
10. __________ is a stream cipher used in the Secure Sockets Layer/Transport Layer
Security standards that have been defined for communication between Web
browsers and servers and is also used in WEP and WPA protocols.
11. In the _________ mode the input to the encryption algorithm is the XOR of the
current plaintext block and the preceeding ciphertext block; the same key is
used for each block.
12. Also referred to as conventional encryption, secret-key, or single-key
encryption, _________ encryption was the only type of encryption in use prior to
the development of public-key encryption in the late 1970’s.
ยฉ 2017 Pearson Education, Inc., Hoboken, NJ. All rights reserved.
Network Security Essentials Applications and Standards, 6th Edition, by William
Stallings
13. Two requirements for secure use of symmetric encryption are: sender and
receiver must have obtained copies of the secret key in a secure fashion and a
strong __________ is needed.
14. All encryption algorithms are based on two general principles: _________, in which
each element in the plaintext is mapped into another element, and
transposition, in which elements in the plaintext are rearranged.
15. Many symmetric block encryption algorithms including DES have a structure
first described by _________ of IBM in 1973.
CHAPTER 2: SYMMETRIC ENCRYPTION AND MESSAGE CONFIDENTIALITY
TRUE OR FALSE
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
F
T
T
F
T
T
F
T
T
F
T
F
T
T
F
MULTIPLE CHOICE
1.
2.
3.
C
B
D
ยฉ 2017 Pearson Education, Inc., Hoboken, NJ. All rights reserved.
Network Security Essentials Applications and Standards, 6th Edition, by William
Stallings
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
D
C
D
B
C
B
D
B
A
C
C
C
SHORT ANSWER
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
decryption
block
key
Symmetric block ciphers
cryptanalysis
computationally secure
Data Encryption Standard (DES)
entropy
seed
RC4
cipher block chaining (CBC)
symmetric
encryption algorithm
substitution
Horst Feistel
ยฉ 2017 Pearson Education, Inc., Hoboken, NJ. All rights reserved.

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