640 the transaction processor decrements the escrow amount of the vmo by the pin amount sold in the current transaction it is possible that the amount by which the escrow amount is decremented is less than the pin amount due to any commissions the prepaid service provider may give to the vmos next in step 650 the pin digits are sent to the vending machine for security in communications well known methods of encryptions and decryption may be adopted to transmit the pin to the vending machines the vending machine then generates in step 660 a digital signature based on information unique to the current transaction and the vending machine for example vending machine identification number and date and time of issuance of pin may be used to produce the digital signature next in step 670 the vending machine imprints the pin on a receipt as well as the digital signature and other relevant information useful to the user a typical receipt 700 is shown in fig7 the user collects the receipt and change amount if any in step 680 from the vending machine it is also possible to print the pin on a separate card and issue the receipt with the digital signature separately after the pin is obtained the user can at any time enter the pin number via the keyboard of a vending machine and get the information about the available balance amount also amounts from two or more pins may be consolidated into a single pin at the.