Simon,
you are right.
Ok so I have gone ahead and used a Xor encryption method which works fine.
My problem now is trying to pinpoint when and how to decrypt it for display to the admin. Basically on a member signup a field is encrypted and it needs to be visible to the admin only.
For example when I push the field through to a the member detail popup how am I able to access that info before it is displayed?
eg. $fields->push(new TextField("PromoCode", "Promo Code"));
How would I decrypt PromoCode if it was encrypted?
thanks, hope you can help.