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SIMON is a block cipher developed to provide flexible security options for lightweight hardware applications such as the Internet-of-things (IoT). Safeguarding such resource-constrained hardware from side-channel attacks poses a significant challenge. Adiabatic circuit operation has recently received attention for such applications due to ultra-low power consumption. In this work, a charge-based methodology is developed to mount a correlation power analysis (CPA) based side-channel attack to an adiabatic SIMON core. The charge-based method significantly reduces the attack complexity by reducing the required number of power samples by two orders of magnitude. The CPA results demonstrate that the required measurements-to-disclosure (MTD) to retrieve the secret key of an adiabatic SIMON core is 4× higher compared to a conventional static CMOS based implementation. The effect of increase in the target signal load capacitance on the MTD is also investigated. It is observed that the MTD can be reduced by half if the load driven by the target signal is increased by 2× for an adiabatic SIMON, and by 5× for a static CMOS based SIMON. This sensitivity to target signal capacitance of the adiabatic SIMON can pose a serious concern by facilitating a more efficient CPA attack. 

A novel framework and related methodologies are described to leverage RF power for building intelligent and battery-free devices with communication and computation capabilities. These passive devices are envisioned to make significant impact for the popular vision of smart dust due to extreme low power operation. The communication framework relies on tag-to-tag backscattering with very limited energy resources. The computing framework relies on a novel AC computing methodology that facilitates local data processing with an order of magnitude less power consumption. These enabling technologies, as described in this paper, revitalize the concept of smart dust with significant impact on various application domains such as smart spaces, implantable devices, and environmental/structural monitoring. 

Hardware security is a critical challenge for various emerging applications in the massive deployment of IoT devices due to lack of computing resources. In this paper, an energy- efficient AC computing methodology is proposed to facilitate lightweight encryption in RF powered devices such as RFIDs. Contrary to conventional methods that rely on rectification and regulation, the wirelessly harvested AC signal is directly used to drive the data processing circuity by leveraging charge- recycling mechanism. To quantify the advantages of the proposed framework, SIMON block cipher, a lightweight cryptography al- gorithm, is implemented in both AC computing and conventional methods. The simulation results demonstrate that the proposed methodology achieves up to 34 times reduction in power and enables a relatively powerful encryption core to be embedded within resource-constrained IoT devices. 

Charge-recycling based AC computing has recently been proposed to significantly increase energy efficiency in wirelessly powered devices. The power consumption is reduced by 1) eliminating the rectification and regulation stages of traditional DC computing and 2) recycling charge through AC computing. An alternative charge-recycling mechanism is proposed in this paper that does not require a phase shifter or peak detector, thereby reducing the overhead power consumption. Simulation results in 45 nm technology demonstrate that an additional 60% reduction in power consumption can be achieved while operating at the same frequency. As compared to the traditional case, power consumption is reduced by more than an order of magnitude.