When block chaining cryptography is used, what type of code is calculated and appended to the data
to ensure authenticity?
A.
Message authentication code.
It operates on fixed-size blocks of plaintext
B.
Ciphertext authentication code
This is incorrect as cipthertext is the result not an authentication code. “If meaningful plaintext is
not automatically recognizable, a message authentication code (MAC) can be computed and
appended to the message. The computation is a function of the entire message and a secret key; it is
practically impossible to find another message with the same authenticator. The receiver checks the
authenticity of the message by computing the MAC using the same secret key and then verifying
that the computed value is the same as the one transmitted with the message. A MAC can be used
to provide authenticity for unencrypted messages as well as for encrypted ones. The National
Institute of Standards and Technology (NIST) has adopted a standard for computing a MAC. (It is
found in Computer Data Authentication, Federal Information Processing Standards Publication (FIPS
PUB) 113.)” http://www.cccure.org/Documents/HISM/637-639.html from the Handbook of
Information Security Management by Micki Krause
QUESTION 762
Which of the following statements pertaining to block ciphers is incorrect?
It is more suitable for software than hardware implementations
C.
Cyclic redundancy check
Plain text is encrypted with a public key and decrypted with a private key
D.
Electronic digital signature
Block ciphers can be operated as a stream
B.
Ciphertext authentication code
This is incorrect as cipthertext is the result not an authentication code. “If meaningful plaintext is
not automatically recognizable, a message authentication code (MAC) can be computed and
appended to the message. The computation is a function of the entire message and a secret key; it is
practically impossible to find another message with the same authenticator. The receiver checks the
authenticity of the message by computing the MAC using the same secret key and then verifying
that the computed value is the same as the one transmitted with the message. A MAC can be used
to provide authenticity for unencrypted messages as well as for encrypted ones. The National
Institute of Standards and Technology (NIST) has adopted a standard for computing a MAC. (It is
found in Computer Data Authentication, Federal Information Processing Standards Publication (FIPS
PUB) 113.)” http://www.cccure.org/Documents/HISM/637-639.html from the Handbook of
Information Security Management by Micki Krause
QUESTION 762
Which of the following statements pertaining to block ciphers is incorrect?
It is more suitable for software than hardware implementations
A.
Message authentication code.
It operates on fixed-size blocks of plaintext
B.
Ciphertext authentication code
This is incorrect as cipthertext is the result not an authentication code. “If meaningful plaintext is
not automatically recognizable, a message authentication code (MAC) can be computed and
appended to the message. The computation is a function of the entire message and a secret key; it is
practically impossible to find another message with the same authenticator. The receiver checks the
authenticity of the message by computing the MAC using the same secret key and then verifying
that the computed value is the same as the one transmitted with the message. A MAC can be used
to provide authenticity for unencrypted messages as well as for encrypted ones. The National
Institute of Standards and Technology (NIST) has adopted a standard for computing a MAC. (It is
found in Computer Data Authentication, Federal Information Processing Standards Publication (FIPS
PUB) 113.)” http://www.cccure.org/Documents/HISM/637-639.html from the Handbook of
Information Security Management by Micki Krause
QUESTION 762
Which of the following statements pertaining to block ciphers is incorrect?
It is more suitable for software than hardware implementations
C.
Cyclic redundancy check
Plain text is encrypted with a public key and decrypted with a private key
D.
Electronic digital signature
Block ciphers can be operated as a stream
Explanation:
The original Answer was“Strong and efficient block cryptosystems use random key values so an attacker cannot find a
pattern as to which S-boxes are chosen and used.” Pg. 481 Shon Harris CISSP Certification All-in-One
Exam Guide Not A: “When a block cipher algorithm is used for encryption and decryption purposes,
the message is divided into blocks of bits. These blocks are then put through substitution,
transposition, and other mathematical functions, on block at a time.” Pg. 480 Shon Harris CISSP
Certification All-in-One Exam Guide Not B: “Block ciphers are easier to implement in software
because they work with blocks of data that the software is used to work with.” Pg 483 Shon Harris
CISSP Certification All-in-One Exam Guide Not D: “This encryption continues until the plaintext is
exhausted.” Pg. 196 Krutz The CISSP Prep Guide.