How to break a semi-anonymous fingerprinting scheme

Abstract

Fingerprinting schemes are techniques applied to protect the copyright on digital goods. Theyena ble the merchants to identifythe source of illegal redistribution. Anonymous fingerprinting schemes allow the buyers to purchase fingerprinted digital goods anonymously. However, on illegal redistribution the anonymity can be revoked. In this paper we show serious shortcomings of two recent proposals on anonymous fingerprinting schemes. These schemes offer buyers only a weak form of anonymity and allow the merchants to cheat honest buyers. We clarifyt he notations of anonymity and fingerprinting and make several constructive proposals to repair some of the flaws.