Business is moving from face-to-face trading, mail order, and telephone order to electronic commerce over open networks such as the Internet. Even face-to-face payments are more and more conducted digitally, e.g. with smartcards. These developments pose new challenges both for security against fraud and for privacy. This talk gives a systematic overview of existing and proposed digital payment systems, with special emphasis on systems aiming for the cash market, i.e. low-value payments for everyday goods such as newspapers and bus tickets. Functionality, security, and privacy properties are also identified in this talk. From the Series:Grace Hopper Celebration of Women in Computing