An automated transaction system employs a card maintaining an account balance and a terminal for dispensing an article of value and debiting the card's balance. The card has a secure, resident microprocessor which executes an interactive handshake recognition procedure with a secure, resident microprocessor in the value dispensing section of the terminal prior to actuating a requested transaction. In the preferred form, the handshake procedure operates by an exchange of encrypted words between the card microprocessor and the dispenser microprocessor using corresponding encryption algorithms and a secret key number, and the card microprocessor providing a command signal to the dispenser microprocessor only upon successful completion of the procedure.
The automated transaction system is particularly suitable as a postage metering terminal having a postmark printer as the value dispensing section. Postage is printed only if the handshake procedure is executed between the card microprocessor and the printer microprocessor. The postal terminal also receives a rate card for computing postage automatically, and prints an invisible authentication mark along with the postmark to discourage counterfeiting. The terminal can be configured to print standard form waybills for postal and private carrier services by loading waybill information from an IC ROM services card. The balance in the user card is refilled in a refilling terminal using a master card which maintains a master account balance and a supervisor card which is in the custody of an authorized person.