ANONYMOUS CREDIT CARDS AND THEIR COLLUSION ANALYSIS

Communications networks are traditionally used to bring information to gether. They can also be used to keep information apart in order to pr otect personal privacy, A cryptographic protocol specifies a process b y which some information is transferred among some users and hidden fr om others. We show how to implement anonymous credit cards using simpl e cryptographic protocols, We pose, and solve, a collusion problem whi ch determines whether it is possible for a subset of users to discover information that is designed to be hidden from them during or after e xecution of the anonymous credit card protocol.