   DES_ENCRYPT(str[,(key_num|key_str)])

Encrypts the string with the given key using the Triple-DES algorithm.
On error, this function returns NULL.

Note that this function works only if MySQL has been configured with
SSL support. See also : [Secure connections].

The encryption key to use is chosen based on the second argument to
DES_ENCRYPT(), if one was given:

     Argument 	 Description
   No argument 	
The first key from the DES key file is used.
   key_num 	
The given key number (0-9) from the DES key file is used.
   key_str 	
The given key string is used to encrypt str.
  

The key file can be specified with the --des-key-file server option.

The return string is a binary string where the first character
is CHAR(128 | key_num).

The 128 is added to make it easier to recognize an encrypted key.
If you use a string key, key_num is 127.

The string length for the result is
new_len = orig_len + (8-(orig_len % 8))+1.
