Advanced Encryption Standard

The Advanced Encryption Standard, or AES, is a US government specification for a block cipher to replace the earlier and weaker Data Encryption Standard (DES).

AES encrypts data in 128-bit blocks and can take a 128, 192 or 256-bit key. DES used 64-bit blocks and a 56-bit key.

Starting in the late 90s, the US National Institute of Standards and Technology (NIST) ran a competition to find a block cipher to replace DES. Fifteen candidates were submitted; for descriptions of the criteria used and of all candidates see AES competition.

In October 2002, they announced [1] the winner — Rijndael (pronounced approximately "rhine doll"), from two Belgian designers. That algorithm is now the Advanced Encryption Standard.

The NIST page on AES [2] has much detail, including links to all the Rinjdael design documents, to several implementations, and to the official standard, approved as FIPS 197,