Which Security Policy for Multiplication Smart Cards?

In this paper, we aim to clarify some issues regarding the deployment context of multiapplicative smart cards. We especially deal with the trust relationships between the involved parties and the resulting constraints from a security point of view. We highlight a new security threat in a multiapplicative context and propose a new multilevel security model which allows to control precisely the information flows inside the card, and to detect illegal data sharing. Finally we illustrate all the proposed concepts on an multiapplicative example involving three applications.