Secure Intermittent Computing

Sammanfattning: Low-power embedded systems exist in many forms. Using batteries for these devices generally imposes high maintenance costs and there are many applications where a grid connection is not feasible [1]. A solution for powering this class of embedded systems is energy harvesting. This can mean the use of energy from ambient RF-signals to power the device, or another form of ambient energy [2].These batteryless devices are generally unable to harvest enough power for continuous operation and therefore employ some sort of checkpointing mechanism to copy (parts of) the main memory to non-volatile storage. State-ofthe-art checkpointing mechanisms employ no security [3–19], or employ encryption to protect the checkpoints [20, 21].In this thesis, the use of TrustZone to secure the checkpoints is compared to the use of the Advanced Encryption Standard (AES). A model was developed to analyze the energy overhead of different security mechanisms based on a large number of experiments. The results show that securing checkpoints with software based AES-128 encryption has a 2.5 times higher energy overhead than securing these using TrustZone. The level of security for these mechanisms was also evaluated. It is shown that TrustZone security is indeed able to protect the checkpoints while they are stored in non-volatile storage, while the software based AES implementation was not secure against known attacks from previous research [22–24].