This thesis explores the security of intermittent devices, embedded systems designed to retain their state across periods of power loss, for cases both when the device has an excess of available energy and when power loss is unavoidable. Existing work with intermittent systems has focused on the problems inherent to the intermittent paradigm and ignored the security implications of persistent state across periods of power loss. The security of these devices is closely linked to their unique operational characteristics and are addressed here in two studies. First, the presence of an energy harvester creates an opportunity to use excess energy, available when additional energy is harvested after the local energy reservoir is filled, to precompute security related operations. Precomputation powered by this excess energy can reduce the cost of expensive tasks during periods of energy scarcity, potentially enabling the use of expensive security operations on traditionally unsecured devices. Second, when energy is limited and intermittent operation is required, the secure storage of checkpoints is a necessity to protect against adversary manipulation of the system state. To examine the secure storage of checkpoints a protocol is implemented to ensure the integrity and authenticity of a device's checkpoints, and evaluated for its energy overhead and performance. The cost of properly ensuring the integrity and authenticity of these checkpoints is examined to identify the overhead necessary to execute intermittent operations in a secure manner. Taken together, these studies lay the groundwork for a comprehensive view of the current state of intermittent device security. / Master of Science / This thesis explores two unique aspects of the intermittent computing paradigm, the precomputation during periods of excess energy and the security of system checkpoints. Intermittent systems are a class of embedded device that lack a classic, consistent, energy source and instead rely on transient energy collected from their surroundings. This removes the need for connection to a power grid or battery management, but introduces challenges in operation since the device can lose power at any time. Additionally, excess energy is available to these systems when they have filled their local energy reservoir, a capacitor or small rechargeable battery, and additional energy can still be collected form the environment. In this case, it is possible to begin precomputing energy intensive operations to enable more operations at a later time on a limited energy budget. Since their power source is inconsistent, intermittent systems checkpoint their current state to allow execution to resume at the beginning of the next power cycle. The security ramifications of saving the current system state into a checkpoint have not been considered in the state of the art. This thesis implements a protocol to properly secure system checkpoints and evaluates its performance to identify the energy overhead required for a secure checkpointing scheme. The results demonstrate the need for the development of more efficient solutions within the domain. Together, the two approaches presented in this thesis provide case studies on the behavior of intermittent devices when provided with either an excess or a dearth of energy. The optimization and improvement of modern intermittent devices will need to address both of these extremes as the field is further improved.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/83376 |
| Date | 22 May 2018 |
| Creators | Suslowicz, Charles Eugene |
| Contributors | Electrical and Computer Engineering, Schaumont, Patrick R., Michaels, Alan J., Patterson, Cameron D. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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