Electromagnetic Enclosure PUF for Tamper Proofing Commodity Hardware and other Applications

Johannes Tobisch, Christian Zenger, Chris­tof Paar

TRUDEVICE 2020: 9th Workshop on Trustworthy Manufacturing and Utilization of Secure Devices, Grenoble, France, March 13, 2020


Abstract

In this paper, we introduce a novel approach for verifying the authenticity, integrity and/or physical condition of an item. We examine this construction as a tamper resistance mechanism for computer systems, which are located within an electromagnetic measurable dedicated environment. Our approach forms an Algorithmic Tamper Proof (ATP) to protect secret information, such as keys, without circuit-level sensors, which is a known difficult and imperfect undertaking. The approach also allows tamper evidence for larger structures, e.g., off-the-shelf computers and its periphery. To this end, we build a confined and shielded space around the system of interest, together with an RF measurement system, consisting of antennas and sealing material. The RF channel between the antennas is uniquely influenced by the environment, including computer system and sealing. Channel State Information (CSI), which captures the influence of the physical environment, represents the basis for a digital fingerprint. CSI is used to extract cryptographic keys that are directly tied to the integrity of the whole system.We use an experimental setup for verifying the applicability of our idea. The setup enables us to demonstrate the three core requirements: uniqueness, sensitivity and reliability. We show how the channel measurements allow constant real-time tests of the integrity and, by analyzing raw CSI values, we demonstrate that the keys can only be recovered if the physical structure remains undisturbed. The derived cryptographic keys can, for example, be used for memory encryption or remote attestation to ensure the integrity and confidentiality of any stored data within the device.

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