Syntax:
AES_ENCRYPT(str,key_str), AES_DECRYPT(crypt_str,key_str)

These functions allow 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 x (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/5.0/en/encryption-functions.html

