Encryption

Hi, I am trying to do a simple encryption on a credit card number to store in a mysql text field. I also have to de-crypt the number after exporting to an access db. I tried to use xor encryption, but it seems to only work half the time, the other half, I can't seem to de-crypt the # properly, some of the numbers end up screwed. Is this because of the way mysql is storing the field? Mabye it can't recognize some of the characters that are generated from the xor encryption? Ex: 123456789123 may end up 1 YdR
 and then de-crypts to 1234(*$8912# Is it the  that are the problem? Or is the the access database that isn't properly storing the  ? Is there a better way to do this? Thanks, Chris