PEI models towards scalable, usable and high-assurance information sharing

Secure Information Sharing (SIS) or "share but protect" is a challenging and elusive problem both because of its broad scope and complexity ranging right from conception (objective and policy) to culmination (implementation). In this paper, we consider how to solve SIS challenges with three main and conflicting objectives: scalability, usability and high-assurance. In the context of SIS, high-assurance requires strong controls on the client. It is widely accepted that such controls cannot be entirely software-based. In this regard, we consider solutions based on commercially emerging hardware-rooted Trusted Computing Technology. For SIS, we argue super-distribution ("protect once and access wherever authorized") and off-line access are necessary to achieve scalability and usability. We limit super-distribution to occur within a group of Trusted Platform Module [1] or TPM-enabled machine. For simplicity, we assume all content that are distributed to be read-only. Drilling down, we discuss Policy, Enforcement and Implementation (PEI) models for SIS within a group (group-based SIS or g-SIS).