AES or Advance Encryption Standard is another secret key encryption algorithm. We have DES so why there is need AES? AES is designed because the length of DES key is small. Since 3DES cover/solve the problem of key but the size of 3DES process is small so we need something having bigger key length and process. Therefore, AES is designed. AES is very complex round cipher and specifies that the length of block size must be 128 bit. In this length of key must be 128, 192, 256 bits. AES has 3 distinct configurations with respect to the number of rounds and the key size.

Size of data   Number of rounds     Key Size
128 bits                       10                   128-bits
128 bits                       12                   192-bits
128 bits                       14                   256-bits

There is an XOR operation followed by 10 round cipher. And the last round is slightly different from proceeding rounds. AES is based on the Rijndael cipher. Unlike DES, the algorithm described by AES is a symmetric-key algorithm, meaning the same key is used for both encrypting and decrypting the data. High speed and low RAM requirements were criteria of the AES selection process.