The Advanced Encryption Standard or AES is a symmetric block cipher used by the U.S. government to protect classified information and is implemented in software and hardware throughout the world to encrypt sensitive data.
In 1999, after detailed testing and evaluation by leading cryptography experts, the National Institute of Standards and Technology (NIST) selected AES as the successor to the aging Data Encryption Standard (DES), which was becoming vulnerable to brute-force attacks.
The Advanced Encryption Standard became effective as a federal government standard in 2002. It is also included in the ISO/IEC 18033-3 standard which specifies block ciphers for the purpose of data confidentiality.
In June 2003, the U.S. government announced that AES could be used to protect classified information, and it soon became the default encryption algorithm for protecting classified information as well as the first publicly accessible and open cipher approved by the NSA for top-secret information. AES is one of the Suite B cryptographic algorithms used by NSA's Information Assurance Directorate in technology approved for protecting national security systems.