An Optimization of Credit - Based Payment for Electronic Toll Collection Systems ∗

Credit-based electronic payment systems are considered to play important roles in future automated payment systems. Like most other types of payment systems, however, credit-based systems proposed so far generally involve computationally expensive cryptographic operations. Such a relatively heavy computational load is preventing credit-based systems from being used in applications which require very fast processing. A typical example is admission-fee payment at the toll gate of an expressway without stopping a vehicle that travels at a high speed. In this article, we propose a very fast credit-based electronic payment protocol for admission-fee payment. More specifically, we propose a payment system between a high-speed vehicle and a toll gate which uses only very simple and fast computations. The proposed system makes use of an optimized Key Pre-distribution System (or KPS) to obtain high resistance against collusion attacks. key words: credit-based payment, electronic toll collection sys-