Advanced Encryption Standard
In 1997 NIST requested proposals for a new advanced encryption standard. Three years later they officially announced that Rijndael was selected as the AES as can be seen in FIPS-197. It is expected to be the standard for approximately 20-30 years, unless an exploit is published before then.
In 2009 there have been a series of attacks on AES, .
AES-256 has a block size of 16 bytes.