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TPM-Based Post-Quantum Cryptography: A Case Study on Quantum-Resistant and Mutually Authenticated TLS for IoT Environments

The prospect of large-scale quantum computers necessitates the design, development, and standardization of post-quantum cryptography (PQC). Industrial control systems (ICS) and critical infrastructures are expected to be among the first industrial environments to adopt PQC. As their components have a long life span (≥ 10 years) and are increasingly interconnected to form an Industrial Internet of Things (IIoT), they require strong and long-lasting security guarantees. Because of these high-security requirements, IIoT products are also increasingly equipped with additional hardware security elements — often Trusted Platform Modules (TPMs). In this work, we study how the current TPM 2.0 specification can supplement the migration towards PQC. Therefore, we integrate the post-quantum (PQ) key exchange CRYSTALS-Kyber, the post-quantum signature scheme SPHINCS, and TPM functionality into the open-source TLS library Mbed TLS. For our performance evaluations we propose three post-quantum TLS cipher suites alongside two different TPM utilization strategies. We report the standalone performance of the aforementioned post-quantum schemes under our proposed TPM utilizations and compare it to current elliptic curve cryptography (ECC). Finally, we report the handshake duration of post-quantum and mutually authenticated TLS (mTLS) connections for our proposed cipher suites with regards to the different TPM utilization scenarios. Our results show that the integration of PQC into mTLS is generally feasible, thus ensuring additional post-quantum client authentication. Regarding our TPM utilizations, we observe a significant decrease in performance when offloading computations of hash functions. However, offloading the generation of random numbers to TPMs in our integrated post-quantum schemes proves to be efficient, ultimately enhancing overall system security.