Explanation/Reference:
Explanation:
After DES was used as an encryption standard for over 20 years and it was cracked in a relatively short time once the necessary technology was available, NIST decided a new standard, the Advanced Encryption Standard (AES), needed to be put into place. In January 1997, NIST announced its request for AES candidates and outlined the requirements in FIPS PUB 197. AES was to be a symmetric block cipher supporting key sizes of 128, 192, and 256 bits. The following five algorithms were the finalists:
MARS Developed by the IBM team that created Lucifer

RC6 Developed by RSA Laboratories

Serpent Developed by Ross Anderson, Eli Biham, and Lars Knudsen

Twofish Developed by Counterpane Systems

Rijndael Developed by Joan Daemen and Vincent Rijmen

Out of these contestants, Rijndael was chosen. The block sizes that Rijndael supports are 128, 192, and
256 bits.
Rijndael works well when implemented in software and hardware in a wide range of products and environments. It has low memory requirements and has been constructed to easily defend against timing attacks.
Rijndael was NIST's choice to replace DES. It is now the algorithm required to protect sensitive but unclassified U.S. government information.
Incorrect Answers:
A: RC6 was a finalist; however, Rijndael was selected by NIST as the AES algorithm.
B: Twofish was a finalist; however, Rijndael was selected by NIST as the AES algorithm.
B: Blowfish was not selected by NIST as the AES algorithm.
References:
Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, 2013, p. 809