Presence Attestation: The Missing Link in Dynamic Trust Bootstrapping

Many popular modern processors include an important hardware security feature in the form of a DRTM (Dynamic Root of Trust for Measurement) that helps bootstrap trust and resists software attacks. However, despite substantial body of prior research on trust establishment, security of DRTM was treated without involvement of the human user, who represents a vital missing link. The basic challenge is: how can a human user determine whether an expected DRTM is currently active on her device? In this paper, we define the notion of "presence attestation", which is based on mandatory, though minimal, user participation. We present three concrete presence attestation schemes: sightbased, location-based and scene-based. They vary in terms of security and usability features, and are suitable for different application contexts. After analyzing their security, we assess their usability and performance based on prototype implementations. KEYWORDS trusted computing, attestation, dynamic root of trust, human-inthe-loop, device I/O * The work was mainly done when the author visited SMU as a student intern. 1 We slightly expand the notion of DRTM as TrustZone functions differently from the TXT and SVM.