The Advanced Encryption Standard is the U.S. National Institute of Standards and Technology proposed replacement for the DES cipher. See US FIPS PUB 197 [L1 ]
AES is a block cipher once known as Rijndael which supports variable key and block sizes. As part of the NIST standardization the block size in AES is fixed at 128 bits and the permitted key sizes limited to 128, 192 or 256 bits. AES should be used in preference to DES in all new protocol designs.
A pure-Tcl implementation of AES is now included in tcllib and will be present in the 1.8 release.