Scalable Remote Attestation with Privacy Protection

Assurance of fulfillment of stakeholder's expectations on a target platform is termed as remote attestation. Without such an assurance, there is no way of knowing whether the policies of the remote owner will be enforced as expected. Existing approaches toward remote attestation work at different levels of the software stack and most of them only measure binary hashes of the applications on the remote platform. Several dynamic attestation techniques have been proposed that aim to measure the internal working of an application. As there can be more than one application running on a target system, we need to have mechanisms to remotely certify the internal behavior of multiple applications on a single system. Similarly in TCG-based attestations we use Platform Configuration Register (PCR) for storing and advocating the platform configuration to the remote party. Currently a single PCR is used to capture the behavior of one application/purpose. In this paper we propose the idea of using a single PCR for multiple instances of a target application, while preserving the privacy of other application instances. Moreover, our technique also keeps the trusted status of each application intact. We propose a protocol for measurement and verification of a single instance by its respective stakeholder. Further, the mechanism proposed in this paper can be applied to different attestation techniques that work at different levels of the software stack. We develop a proof-of-concept implementation of our idea and provide future implications of this research.