Advanced Encryption Standard encryption. A Federal Information Processing Standard (FIPS), described in FIPS publication 197. AES has been adopted by the US government for the protection of sensitive, nonclassified information. The algorithm was developed by Dr. Joan Daemen and Dr. Vincent Rijmen and was named the Rijndael algorithm. It is a symmetric-key algorithm that can use key sizes of 128, 192, or 256 bits. Apple has adopted the 128-bit version of AES for FileVault. There are approximately 3.4 x 10**38 possible 128-bit keys.