Postulates for Revocation Schemes

In access control frameworks with the possibility of delegating
permissions and administrative rights, delegation chains can form. There
are di erent ways to treat these delegation chains when revoking rights,
which give rise to di erent revocation schemes. Hagstr om et al. [11] proposed
a framework for classifying revocation schemes, in which the di erent
revocation schemes are de ned graph-theoretically. At the outset, we identify
multiple problems with Hagstr om et al.'s de nitions of the revocation
schemes, which can pose security risks. This paper is centered around the
question how one can systematically ensure that improved de nitions of the
revocation schemes do not lead to similar problems. For this we propose to
apply the axiomatic method originating in social choice theory to revocation
schemes. Our use of the axiomatic method resembles its use in belief revision
theory. This means that we de ne postulates that describe the desirable behaviour
of revocation schemes, study which existing revocation frameworks
satisfy which postulates, and show how all de ned postulates can be satis ed
by de ning the revocation schemes in a novel way.