ENERGY EFFICIENCY OF A LIGHTWEIGHT CRYPTOGRAPHIC STACK FOR LPWAN DEVICES: COMPARATIVE ANALYSIS ON 32-BIT AND ARM64 PLATFORMS

Abstract

The article presents the results of a comparative analysis of energy efficiency and computational performance of a lightweight cryptographic stack combining X25519, HKDF, Ascon-128a, and TESLA primitives on two classes of hardware platforms: 32-bit ARM Cortex-M4 microcontrollers and the 64-bit ARM Cortex-A53 (ARM64) platform. The study builds upon a previously developed cross-layer security architecture for IoT devices in LPWAN environments and extends it with quantitative assessment of resource costs at each layer. Experimental measurements were performed on a hardware-software testbed with Arduino Uno R4 WiFi (Renesas RA4M1, Cortex-M4) and Raspberry Pi 3 Model B+ (ARM Cortex-A53), which simultaneously acts as the LoRa receiver, the Go-based edge server, and the platform for cryptographic microbenchmarks. Power consumption measurements were conducted using a USB power analyzer with real-time current, voltage, and power logging. Results confirm that lightweight cryptographic primitives achieve two to four orders of magnitude lower latency compared to traditional DTLS protocols on resource-constrained platforms, with power consumption during radio packet transmission increasing by 78 % above the baseline, while the gateway's electrical duty cycle (54.9 %) substantially exceeds that of the client (12.7 %) due to background workload. The proposed stack occupies 48 KB of Flash and 6 KB of SRAM, leaving sufficient resources for IoT application logic. For the first time, precise microsecond-level cryptographic latency metrics are captured directly on the Cortex-M4 microcontroller: Ascon-128a executes in 337 us (n=1104, aggregated across three independent field runs), TESLA MAC in 1.464 ms, and X25519 operations require 93–95 ms. The energy cost of symmetric cryptographic operations (Ascon, TESLA) on the Raspberry Pi 3 is 4.95–26.9 uJ per operation at an average power consumption of 1.93 W. An extended reliability analysis across four independent runs (1104 transmitted packets in total) plus an additional run with an elevated reconnection rate (PDR 99.3 %) confirmed correct protocol degradation and recovery under realistic link conditions without a single missed attack.

Keywords: lightweight cryptography, energy efficiency, LPWAN, IoT, Ascon, X25519, TESLA, microcontroller, ARM Cortex-M4, ARM64.