Physical cash, in the form of coins and notes, is an anachronism in the information age. A newly developed system of cryptographic protocols realizes digital currency so that electronic payments can be done cash without on-line authorization or pre-registration. The user?s electronic wallet contains digital currency, and can be used both at physical and virtual (such as Internet) points of sale. An important goal of the CAFE project1 was to develop a system with significant improvements over existing retail payment systems by developing a truly open system with high standards of multiparty security that can be scaled to international operations. The paper reports on design issues for this type of digital currency systems.