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This paper investigates the impact of post-quantum cryptography (PQC) certificate chain sizes on Time to First Byte (TTFB) in TLS deployments, a critical metric for web performance. The authors measured TTFB under CDN-focused TLS conditions, comparing ECDSA and ML-DSA certificate schemes with varying sizes and extensions. They found that TTFB increases significantly when certificate chain sizes exceed transport layer data flight limits, and that Merkle Tree Certificates (MTC) offer a 2-3x improvement in supportable certificate chain size compared to CDN-based optimizations.
Quantum-safe certificates bloat TLS handshakes so much that they measurably degrade web performance, and current CDN optimizations aren't enough to fully compensate.
Post-Quantum Cryptography (PQC) is a rapidly growing deployment challenge as cryptographically relevant quantum computers (CRQC) continue to advance, leaving traditional cryptographic algorithms used in X.509 vulnerable to attack. However, PQC introduces significant deployment challenges in real-world networks, with handshake sizes increasing from 5x to over 20x compared to classical algorithms. In this work, we evaluate the time to first byte (TTFB) under CDN-focused TLS conditions to characterize the latency cost of transitioning existing internet infrastructure to quantum-safe certificate schemes. We observe discrete increases in TTFB as certificate chain sizes exceed transport layer data flight limits. To isolate the impact of certificate chains, we evaluate both ECDSA and ML-DSA-based certificate schemes, generating similarly sized certificate chains through controlled addition of certificate extensions. We additionally examine how CDN properties such as session resumption, certificate size optimizations, and geographical distribution reduce latency penalties. We utilize Zeek-monitored TLS traffic through a High-Performance Computing System (NCSA) with terabyte network connectivity across the nation to quantify real-world session resumption rates. We compare CDN-driven size optimization with Merkle Tree Certificates (MTC) to examine how size reductions allow certificate chains to remain under the flight limit threshold. We find that MTC allows for 2x-3x increase in supportable certificate chain size, whereas CDN-based optimizations yield more limited reductions, supporting up to approximately 1.6x certificate chain size increase.
