Which one of the following statements BEST describes the operation of the Digital Signature
Algorithm (DSA) (National Institute of Standards and Technology, NIST FIPS PUB 186, Digital
Signature Standard,
A.
A message of < 264 bits is input to the DSA, and the resultant message digest of 160 bits is fed
into the Secure Hash Algorithm (SHA), which generates the digital signature of the message.
B.
A message of < 264 bits is input to the Secure Hash Algorithm (SHA), and the resultant message
digest of 160 bits is used as the digital signature of the message.
C.
A message of < 264 bits is input to the Secure Hash Algorithm (SHA), and the resultant message
digest of 160 bits is fed into the DSA, which generates the digital signature of the message.
D.
A message of < 264 bits is input to the Secure Hash Algorithm (SHA), and the resultant message
digest of 128 bits is fed into the DSA, which generates the digital signature of the message.
Explanation:
The correct answer describes the proper sequence of operating on the message and has the correct
value of 160 bits for the SHAmessage digest. At the receiving end, the message is fed into the SHA,
and the result is compared to the received message digest to verify the signature. *Answer “A
message of < 264 bits is input to the DSA, and the resultant message digest of 160 bits is fed into the
Secure Hash Algorithm (SHA), which generates the digital signature of the message” is incorrect
since the order of the DSA and SHA are in reverse sequence from the correct order of their
application. * Answer “A message of < 264 bits is input to the Secure Hash Algorithm (SHA), and the
resultant message digest of 128 bits is fed into the DSA, which generates the digital signature of the
message.” is incorrect since it has the incorrect value of 128 bits for the message digest produced by
the SHa. * Answer “A message of < 264 bits is input to the Secure Hash Algorithm (SHA), and the
resultant message digest of 160 bits is used as the digital signature of the message” is incorrect since
the message digest has to be fed into the DSA to generate the digital signature of the message.