Attack Resilience and Recovery using Physical Challenge Response\n Authentication for Active Sensors Under Integrity Attacks

摘要

Embedded sensing systems are pervasively used in life- and security-critical\nsystems such as those found in airplanes, automobiles, and healthcare.\nTraditional security mechanisms for these sensors focus on data encryption and\nother post-processing techniques, but the sensors themselves often remain\nvulnerable to attacks in the physical/analog domain. If an adversary\nmanipulates a physical/analog signal prior to digitization, no amount of\ndigital security mechanisms after the fact can help. Fortunately, nature\nimposes fundamental constraints on how these analog signals can behave. This\nwork presents PyCRA, a physical challenge-response authentication scheme\ndesigned to protect active sensing systems against physical attacks occurring\nin the analog domain. PyCRA provides security for active sensors by continually\nchallenging the surrounding environment via random but deliberate physical\nprobes. By analyzing the responses to these probes, and by using the fact that\nthe adversary cannot change the underlying laws of physics, we provide an\nauthentication mechanism that not only detects malicious attacks but provides\nresilience against them. We demonstrate the effectiveness of PyCRA through\nseveral case studies using two sensing systems: (1) magnetic sensors like those\nfound wheel speed sensors in robotics and automotive, and (2) commercial RFID\ntags used in many security-critical applications. Finally, we outline methods\nand theoretical proofs for further enhancing the resilience of PyCRA to active\nattacks by means of a confusion phase---a period of low signal to noise ratio\nthat makes it more difficult for an attacker to correctly identify and respond\nto PyCRA's physical challenges. In doing so, we evaluate both the robustness\nand the limitations of PyCRA, concluding by outlining practical considerations\nas well as further applications for the proposed authentication mechanism.\n