Quantum computing threatens current cryptographic methods, with the capability to break widely used algorithms like RSA and ECC, which secure today's digital infrastructure (Chen et al., 2025). As these threats grow, exploring Post-Quantum Cryptography (PQC), i.e. cryptographic algorithms designed to be secure against the potential threats posed by quantum computers, becomes urgent to secure smart city data and services. Implementing Post-Quantum Cryptography in smart city systems is vital to counter future quantum threats while also ensuring compatibility with existing technologies, especially resource-constrained IoT devices.

Recognizing the threat quantum computing poses to classical cryptography, the National Institute of Standards and Technology (NIST) initiated a standardization process to identify and evaluate PQC algorithms. We implemented a “PQC-Smart-City-Data” benchmarking system based on i) the PQClean library (Kannwischer et al., 2022), a C-based library that provides implementations of all PQC algorithms currently considered by NIST, and ii) on a Rust-based library that provides an implementation of the Kyber Post-Quantum key encapsulation mechanism (Argyle-Software, 2025). Our testing system consist of two Raspberry Pi devices (Pi3 and Pi2W), which each can act as either a client or as a server in a particular experiment. The data being sent cryptographically protected from client to server consists of 100 real-world temperature measurements from actual IoT sensors, encoded in JSON format. Our experimental results show the time needed for each individual cryptographic operation at the client and at the server, respectively.