Internet of things and cyber-physical systems requiring security functionality has pushed for the design of a number of block ciphers and hash functions specifically developed for being implemented in resource constrained devices. Initially the optimization was mainly on area and power consumption, but, nowadays the attention is more on the energy consumption. In this paper, for the first time, we look at energy consumption of lightweight block ciphers implemented in reconfigurable devices, and we analyze the effects that round unrolling might have on the energy consumed during the encryption. Concentrating on applications that require a number of parallel encryptions, we instantiate several designs on the target FPGA and we analyze how the energy consumption varies in each algorithm when changing the amount of unrolled rounds. Our results, obtained on the Xc6slx45t device of the Spartan6 family, demonstrate that Present is the most energy efficient algorithm and that the relation between the energy consumption and the number of unrolled rounds measured on FPGA is similar to the one measured on dedicated hardware.
International Conference on ReConFigurable Computing and FPGAs, ReConFig 2015