Syntax:
AES_ENCRYPT(str,key_str)

AES_ENCRYPT() and AES_DECRYPT() enable encryption and decryption of
data using the official AES (Advanced Encryption Standard) algorithm,
previously known as "Rijndael." Encoding with a 128-bit key length is
used, but you can extend it up to 256 bits by modifying the source. We
chose 128 bits because it is much faster and it is secure enough for
most purposes.

AES_ENCRYPT() encrypts a string and returns a binary string.
AES_DECRYPT() decrypts the encrypted string and returns the original
string. The input arguments may be any length. If either argument is
NULL, the result of this function is also NULL.

Because AES is a block-level algorithm, padding is used to encode
uneven length strings and so the result string length may be calculated
using this formula:

16 * (trunc(string_length / 16) + 1)

If AES_DECRYPT() detects invalid data or incorrect padding, it returns
NULL. However, it is possible for AES_DECRYPT() to return a non-NULL
value (possibly garbage) if the input data or the key is invalid.

You can use the AES functions to store data in an encrypted form by
modifying your queries:

URL: http://dev.mysql.com/doc/refman/5.5/en/encryption-functions.html

