ENCRYPT() in MySQL

Hi all, Sorry to be slightly OT, but I've prolly answered 1000 OT posts in the last year, and this IS related for all those without mycrypt, so... I'm on a shared server which does not have mcrypt... not good, since i want to temporarily store credit card numbers in an encrypted manner, either in a MySQL database, or in a text file. So I started google'ing for a class or something that someone may have written for two-way encryption WITH A KEY TO UNLOCK. Couldn't find much, then did a search on MySQL.com, and found the ENCRYPT(), DECRYPT(), ENCODE() and DECODE() functions. Am I barking up the wrong tree, or can these be used for storing sensitive information (credit card, etc etc) in a mysql table? The MySQL manual isn't particularly in-depth about it all: http://www.mysql.com/doc/M/i/Miscellaneous_functions.html I AM running in a linux environment (RedHat I think)... Thanks in advance, Justin French