The Audit Logic: Policy Compliance in Distributed Systems

We present a distributed framework where agents can share data along with usage policies. We use an expressive policy language including conditions, obligations and delegation. Our framework also supports the possibility to refine policies. Policies are not enforced a-priori. Instead policy compliance is checked using an a-posteriri auditing approach. Policy compliance is shown by a (logical) proof that the authority can systematically check for validity. Tools for automatically checking and generating proofs are also part of the framework.\u

An Audit Logic for Accountability

We describe and implement a policy language. In our system, agents can distribute data along with usage policies in a decentralized architecture. Our language supports the specification of conditions and obligations, and also the possibility to refine policies. In our framework, the compliance with usage policies is not actively enforced. However, agents are accountable for their actions, and may be audited by an authority requiring justifications.Comment: To appear in Proceedings of IEEE Policy 200

A certified email protocol using key chains

This paper introduces an asynchronous optimistic certified email protocol, with stateless recipients, that relies on key chains to considerably reduce the storage requirements of the trusted third party. The proposed protocol thereby outperforms the existing schemes that achieve strong fairness. The paper also discusses the revocation of compromised keys as well as practical considerations regarding the implementation of the protocol

Extended Privilege Inheritance in RBAC

In existing RBAC literature, administrative privileges are inherited just like ordinary user privileges. We argue that from a security viewpoint this is too restrictive, and we believe that a more flexible approach can be very useful in practice. We define an ordering on the set of administrative privileges, enabling us to extend the standard privilege inheritance relation in a natural way. This means that if a user has a particular administrative privilege, then she is also implicitly authorized for weaker administrative privileges. We prove the non-trivial result that it is possible to decide whether one administrative privilege is weaker than another and show how this result can be used to decide administrative requests in an RBAC security monitor