Original title: Lightweight Sensor Data Encryption on ESP32 Using the Pi Number for Dynamic Operations
Manuel Alejandro Cardona-López, Santiago Segura-Romo, Aura Luz Barcenas-Medina, Jaime Robles García +2 · September 2026
Smart devices collect sensor data that can reveal your private daily habits if intercepted. Tiny computer chips need fast, lightweight security that will not slow them down. Researchers built a new lightweight stream cipher called LSEPI to protect electrical sensor data. The system works by blending the AES substitution box with moving mix-ups and secret masks. These masks come from a secret key paired with the digits of the number π. Both an ESP32 chip and an Android phone store the first 20 KB of the decimal expansion of π to avoid slow calculations. As the chip measures electrical readings, it scrambles them quickly. The cipher scored high randomness, achieving an entropy of 7.9971 in just one round. It matches older, slower tools and takes only 135 μs per sensor record, which adds just 0.04% computational overhead to the chip's electrical measurements.
You are packing a suitcase and want to hide the contents from someone who might peek. Normally you would have to shuffle and repack everything many times to make the order unpredictable. Here, you use the digits of π to decide exactly how to rearrange and mask each item in a single pass, achieving the same level of randomness as many shuffles.
IoT devices like smart meters and home sensors constantly transmit data that can reveal your daily routines. LSEPI encrypts this data with almost no extra power or time, using the digits of π to achieve strong security in a single round. This means your privacy is protected without draining the battery or slowing down the device.
The paper only evaluates statistical properties and known-plaintext resistance, not other attacks like differential or side-channel. It is designed specifically for electrical sensor data on ESP32 and Android, so generalizability to other platforms or data types is not shown. The use of pre-stored π digits requires memory and may not be suitable for all constrained devices.
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Lightweight Sensor Data Encryption on ESP32 Using the Pi Number for Dynamic Operations — Manuel Alejandro Cardona-López, Santiago Segura-Romo, Aura Luz Barcenas-Medina et al. — Technologies — doi:10.3390/technologies14100595
Abstract licence: CC BY
Explanation generated by Synthesis from the abstract — it is not the original paper.