The Advanced Encryption Standard (AES) was published as Federal Information Processing Standard (FIPS) 197 on November 26, 2001 (and updated May 9, 2023). The standard specifies the Rijndael block cipher family, designed by Belgian cryptographers Joan Daemen and Vincent Rijmen, which NIST announced as the winner of the AES competition.
NIST ran AES as an open, public competition rather than a closed government process. Candidate ciphers from around the world were submitted, analyzed publicly by the cryptographic community, and judged on security and efficiency. This transparency was a deliberate response to the way DES had been developed and was a major reason AES earned broad trust.
AES transforms data in 128-bit blocks and is defined for three key lengths: AES-128, AES-192, and AES-256, indicated by their numerical suffixes. Larger keys provide greater resistance to brute-force attack. The cipher uses a substitution-permutation network structure applied over multiple rounds.
AES replaced DES as the U.S. government standard for symmetric encryption and went on to become the de facto worldwide standard. It is used to secure web traffic, disk encryption, virtual private networks, wireless networks, and countless other systems, and is widely implemented in hardware for high performance.