After solving my first problem with the coin acceptor a new mission comes up.
The plan is to use a RFID reader to identify a chip. The unique chip code should be send to a webserver which checks in a SQL database if the chip still has some credit (if so withdraws "1") and then returns a "Yes" ( - if a credit could be deducted) or a "No" ( - if the rfid chip wasn't recognized or has less then 1 credit).
This seems not the most difficult thing to do, however since it is used as a payment gateway using plain HTML isn't secure. I'm afraid that by reading network information on the local network the arduino is on someone could be able to reproduce an answer and send the "Yes" to the arduino without the script on the webserver even being touched.
Ofcourse SSL/TLS is not available for the arduino uno so what would you do to do this?