new encrypted_text field

I just modified text.module to make encrypted_text.module. This module
encrypts when inserting and updating, using MySQL function AES_ENCRYPT.
It decrypts this text value on loading the field, using AES_DECRYPT function. It stores the encrypted text in BLOB columns.

Admin must specify the encryption key to use in settings.php as in

$conf = array(
      'encrypted_text_key' => 'my encryption key'
);

Works in my testing.

Please advise changes, and how to contribute this module. Thanks