The Role of Energy in the Lightweight Cryptographic Profile

NIST’s Lightweight Cryptography Project ties selected crypto­ graphic algorithms to a profile, which captures the physical, performance and security characteristics of the target devices that run these algorithms. This contribution investigates the role of energy in the profile. For many of the important application domains of Lightweight Cryptography, the opera­ tion is intermittent, rather than continuous. Examples include devices with a low duty cycle, devices running on an energy-harvested energy source, and RFID. In this context, energy consumption becomes as important as power dissipation. We analyze recently published lightweight cryptographic algo­ rithms from the energy perspective. We highlight a unique opportunity that exists between energy harvesting and cryptography. The bulk of the opera­ tions in a cryptographic algorithm, such as the key schedule or key-stream generation, can be completed off-line when a secure nonvolatile memory is available. This decreases the latency and complexity of the online phase, and it spreads out the energy needs of the algorithm more evenly in time. We describe how such energy-harvesting friendly operation can be captured in the profile of the algorithm, and provide several examples of this concept to symmetric-key and public-key primitives.