AES was announced by National Institute of Standards and Technology ( NIST ) as U.S. FIPS PUB 197 ( FIPS 197 ) on November 26 , 2001 after a 5-year standardization process in which fifteen competing designs were presented and evaluated before Rijndael was selected as the most suitable . AES was announced by National Institute of Standards and Technology ( NIST ) as U.S. FIPS PUB 197 ( FIPS 197 ) on November 26 , 2001 after a 5-year standardization process in which fifteen competing designs were presented and evaluated before Rijndael was selected as the most suitable ( see Advanced Encryption Standard process for more details ) .