E-cash for Intelligent Public Transportation

A public transportation system should move masses of people from one point to another, imposing minimum possible delays for the users. In particular, the payment process for fares should not impact the smooth operation of the system. Hence, a payment needs to be executed quickly. This favors the use of electronic payments, which have further

benefits, including improved throughput, new capabilities (congestion-based pricing etc.) and user convenience. Yet, currently employed electronic transportation payment systems are often not secure and do not preserve a user's locational privacy. E-cash allows for the execution of secure payments without revealing a user's identity. Even though e-cash protocols have been proposed three decades ago, there are relatively few actual implementations. One limiting factor has been the computation complexity, as e-cash schemes are based on public-key cryptography. That makes it challenging to be executed on payment devices, which are usually low-power embedded devices.

We show the applicability of e-cash to the transportation setting, by implementing e-cash schemes for potential payment devices. To achieve the extreme time requirements, we use devices that can communicate with an access point in a contactless fashion. As potential payment devices we chose an NFC-enabled smartphone, as well as a computational RFID tag. We look at several proposed schemes, which differ in their complexity and security. Using advanced implementation techniques, we achieve payment times of less than 400 ms, which is the acceptance threshold for the payment process in the transportation setting.

Award ID: 0964641