Date Added: Dec 2009
Design of secure systems can often be expressed as ensuring that some property is maintained at every step of a distributed computation among mutually-untrusting parties. Special cases include integrity of programs running on untrusted platforms, various forms of confidentiality and side-channel resilience, and domain-specific invariants. The authors propose a new approach, Proof-Carrying Data (PCD), which circumnavigates the threat of faults and leakage by reasoning about properties of the output data, independently of the preceding computation. In PCD, the system designer prescribes the desired properties of the computation's outputs. Corresponding proofs are attached to every message flowing through the system, and are mutually verified by the system's components. Each such proof attests that the message's data and all of its history comply with the specified properties.