Abstract: A payment card system uses a static payment card identifying number and generates, for each attempted transaction, an authentication cryptogram based at least upon a seed value stored within the payment card and further based upon a temporal signal value that changes for each attempted use of the payment card. The authentication cryptogram may be alpha-numerically encoded, preferably using a radix-32 coding to provide 5-bits of information for each character or symbol, and may be communicated in a 26-character payment card account name field instead of communicating a payment account name in said payment card account name field, to thus convey up to 130-bits of information while maintaining compatibility with existing point-of-sale equipment and payment system infrastructure.