Which encryption standard replaced DES as the U.S. federal standard in 2001?

The Advanced Encryption Standard replaced DES as the U.S. federal encryption standard in 2001.

AES was selected by the U.S. National Institute of Standards and Technology after an international competition that began in 1997. The winning algorithm, designed by Belgian cryptographers Joan Daemen and Vincent Rijmen, was originally called Rijndael. NIST announced the selection in 2000, and the standard was published as FIPS 197 in November 2001.

AES is a symmetric block cipher, meaning the same secret key is used to encrypt and decrypt data. It processes 128-bit blocks and supports 128-, 192-, and 256-bit keys. AES-128, AES-192, and AES-256 differ mainly in their key lengths and number of transformation rounds.

A common mix-up is treating AES as a hashing algorithm or a public-key system. It is neither: AES is reversible encryption for protecting data confidentiality. DES used a much shorter effective key and became vulnerable to exhaustive search as computing power increased; Triple DES extended its useful life but was slower and has since been deprecated for many applications.