Paper 2026/440 Original: eprint.iacr.org/2026/440 ↗

Performance Analysis of a Thread Pool-Based Parallel Execution Model for Hybrid Post-Quantum TLS 1.3 Handshakes

Abstract

The transition to post-quantum cryptography (PQC) significantly increases the computational cost of TLS~1.3 handshakes. In particular, hybrid handshakes incur even greater overhead, as they require performing both classical and PQC algorithms for key exchange and authentication. This paper systematically analyzes the performance of hybrid PQC TLS~1.3 handshakes using a POSIX thread pool-based parallel execution model. We evaluate a total of 135 combinations comprising 3 classical KEMs, 3 ML-KEM variants, 3 classical DSAs, and 5 PQC DSAs. Sequential execution times range from 429.2 to 1,907.0~$\mu$s, while parallel execution times range from 356.7 to 1,380.8~$\mu$s, achieving speedups of 1.08$\times$ to 1.40$\times$ across all combinations. The highest speedup is observed in P-384-based configurations, where the overlap between classical and PQC operations is most pronounced. Furthermore, we recommend both throughput-oriented combinations based on FN-DSA and currently standardized ML-DSA combinations for each NIST security level. These results provide practical design guidance for mitigating performance degradation in hybrid PQC TLS deployments.