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Today’s computer users receive few assurances that their software executes as expected. The problem is that legacy devices do not enable personal verification of code execution. In addition, legacy devices lack trusted paths for secure user I/O making it difficult to ensure the privacy of data. We present PRISM, a software-only human-verifiable code execution system that temporally separates a legacy computer system into a trusted component and an untrusted component. PRISM enables a user to securely interact with applications by establishing a trusted path and enables personal verification of untampered application execution. PRISM enables the development of a new class of applications which we term personally verifiable applications (PVAs). PVAs have the property that a user can both securely interact with and execute these applications even in the face of a kernel-level compromise. We develop a personally verifiable digital signature application that assures the user that the password-protected private key is not misused and that neither the private key nor the password are disclosed to malware on the device. We describe an implementation of this application on a personal device, and evaluate the usability of our approach with a user study.
Franklin et al. (Fri,) studied this question.