An Offline Check System with Reusable Refunds

Abstract

This paper presents a new online check system that solves the reusability problem of refunds in existing systems using the partially blind signature. The clear part of the signature is used to encode the face value of a check. In our system, refunds can be reused in payment in the same way as withdrawn checks without any limitation. We also use a one-time secret key as the serial number of a check to increase the efficiency of payment. The new system provides multiple offline shopping sessions to minimize the number of online messages. During the offline session, we use a one-way accumulator to construct a proof of payment. The security and the atomicity of the system is also discussed.