A Verified Information-Flow Architecture

SAFE is a clean-slate design for a highly secure computer sys-tem, with pervasive mechanisms for tracking and limiting infor-mation flows. At the lowest level, the SAFE hardware supports fine-grained programmable tags, with efficient and flexible prop-agation and combination of tags as instructions are executed. The operating system virtualizes these generic facilities to present an information-flow abstract machine that allows user programs to la-bel sensitive data with rich confidentiality policies. We present a formal, machine-checked model of the key hardware and software mechanisms used to control information flow in SAFE and an end-to-end proof of noninterference for this model