Lightweight Post-Quantum Cryptography for Secure IoT with Engel Isogenies

Last Updated: December 7, 2025By

Breakthrough in Lightweight IoT Security

The explosion of the Internet of Things (IoT) is revolutionizing how we interact with technology, but it also brings heightened security demands. A team at the Walton Institute in Ireland, led by Ilias Cherkaoui and Indrakshi Dey, has developed an innovative cryptographic solution to meet these needs. Their breakthrough involves using Engel expansions over p-adic Laurent series to create incredibly small key sizes—ranging from just 1.1 to 16.9 kilobits. This advancement allows secure communication across IoT devices without burdening their limited processing capabilities.

Key to this innovation is the use of isogeny-based cryptography combined with Engel functions. Isogenies, which map between elliptic curves, are crucial for solid post-quantum security. By integrating Engel functions, the Walton team has crafted a system where encrypted key exchanges are both compact and resilient to cyber threats, significantly enhancing security.

In this system, participants generate a secret key, a sequence of isogenies, to obtain a public key. During exchanges, a special temporary key is used alongside public keys to create a shared secret, robustly encrypted via standard methods. Overcoming the security requires tackling the complex Supersingular Isogeny Diffie-Hellman Problem or the new Engel Inversion Hardness challenge.

Efficient Cryptography for IoT Devices

This research marks a vital step towards protecting IoT devices with streamlined cryptographic methods. By encoding elliptic-curve isogeny data using Engel expansions, the resulting public keys are compact yet computationally efficient on resource-limited devices.

The ESP32 microcontroller serves as a testament to this system’s practicality, efficiently handling key generation, encryption, and decryption under tight memory constraints. Tests reveal stable execution and reduced energy usage, demonstrating the seamless integration of Engel-Laurent arithmetic with physical device capabilities. Constant-time execution counters side-channel attacks, securing consistent operational performance. Innovations in managing ‘zeros’ during calculations further bolster error management.

This project beautifully marries advanced number theory with pragmatic design, unveiling a promising era for lightweight, post-quantum cryptography that protects our interconnected world.

Engel Expansions: A Secure, Lightweight Framework

By harnessing Engel expansions and p-adic arithmetic, this study creates a robust cryptographic framework, balancing compact key sizes with efficient computation. It delivers predictable performance without sacrificing security.

The system performs deterministically, resisting side-channel vulnerabilities while addressing communication delays across multi-node networks. Future developments aim to enhance this framework with multivariate Engel expansions, optimize torsion-point encoding, and employ p-adic isogenies in broader cryptographic applications such as pseudorandom number generation.

This pioneering research exemplifies how abstract mathematical theories can drive real-world security enhancements, paving the way for safer, more efficient connected devices.

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