(AES) The NIST's replacement for the Data Encryption Standard (DES). The Rijndael /rayn-dahl/ symmetric block cipher, designed by Joan Daemen and Vincent Rijmen, was chosen by a NIST contest to be AES. AES is Federal Information Processing Standard FIPS-197. AES currently supports 128, 192 and 256-bit keys and encryption blocks, but may be extended in multiples of 32 bits.