Secure over-the-air firmware update mechanism for embedded IoT devices using lightweight cryptographic authentication

Abstract

Securing over-the-air firmware updates for resource-constrained IoT devices remains challenging, as existing solutions either rely on memory-intensive cryptographic algorithms or provide only basic integrity checks. This study aims to address this gap by developing a resource-efficient yet cryptographically comprehensive OTA update mechanism for commercial microcontrollers. A four-stage cryptographic authentication pipeline is proposed and evaluated on the ESP32-S3 microcontroller, integrating Ed25519 signature verification, ASCON-AEAD128 authenticated decryption, ASCON-Hash256 integrity verification, and monotonic version counter-based rollback protection within the ESP-IDF A/B partition scheme. The mechanism employs chunk-level authenticated encryption with power-loss recovery and was benchmarked against AES-GCM/RSA-2048 and AES-GCM/ECDSA-P256 configurations on identical hardware. Functional validation across 100 update trials demonstrated a 100% success rate under stable conditions, with full recovery in all 20 power interruption trials. Security evaluation through 200 adversarial tests confirmed complete detection of all attack categories with zero false negatives. The pipeline completed in 350 ms, consuming 18.2 KB RAM and 12.4 KB code space, representing 34% and 50% reductions compared to the ECDSA-P256 baseline. Ablation analysis revealed that Ed25519 verification contributed the greatest efficiency gain, reducing latency by 99.3% over RSA-2048. These results demonstrate that NIST-standardized lightweight cryptographic primitives can be practically deployed in end-to-end OTA pipelines for commercial microcontrollers.