The Advanced Encryption Standard, or AES was introduced in 2001 as the replacement for the Data Encryption Standard (more commonly known as DES). AES is a public key, symmetric encryption algorithm. As of the 26 of May 2002, AES formally replaced DES. SLIGHTLY MORE IN DEPTH Unlike it’s predecessor, AES can be utilized in either 128, 192 or 256 bit forms. Unlike DES, AES has been based around the engineering principle of a substitution–permutation network. Block size is set to 128 bits, and it is currently the only cipher which has been approved for both public use and NSA top secret information when deployed in an appropriate cryptographic module. The details of AES definitions can be found as part of FIPS PUB 197: Advanced Encryption Standard (AES)and ISO/IEC 18033-3: Block ciphers. AES is also included under FIPS 140-2 by NIST.
In 2006, distributed.net proved the concept of brute force attacks against AES with a 64-bit RC5 key. Although this showed that brute force attacks are feasible against AES, the large key size makes this more or less not useful. Earlier, in 2002, a version called the XSL-attack was postulated by Nicolas Courtois and Josef Pieprzyk, but this mathematical hypothesis was shown to be infeasible in practice. Side channel attacks, man-in-the-middle attacks and known-distinguishing-key attacks have been all proven to have minimal use. The practicality of each of these is debatable, and currently, these attacks that would work against AES would work against any other form of strong encryption, specifically by taking advantage of artifacts used in the encryption process and user errors.