Young Eun Kwon (Korea University), Ji Won Yoon (Korea University)
Low Earth Orbit (LEO) satellite networks operate under strict latency and reliability constraints, yet require Post-Quantum Cryptography (PQC) to secure them from future threats. The large signature sizes of most PQC algorithms, however, conflict with these network-level constraints. Through comprehensive ns-3 simulations (modeling fragmentation, packet loss, and handovers), this paper demonstrates that network performance, not raw CPU computation, is the dominant factor for PQC in LEO.
We find that PQC certificates exceeding the 1500-byte MTU, like Dilithium (2,588 B), incur IP fragmentation. While aggressive TCP congestion windows might mask the initial latency in ideal conditions, we demonstrate that this multi-packet nature induces a severe reliability penalty regardless of window size. Specifically, fragmentation doubles the exposure to packet loss, increasing the probability of a catastrophic TCP RTO (1,000 ms+) during ‘Rain Fade’ events to 51%, compared to just 30% for the single-packet Falcon (858 B). This results in a massive 100-500% latency penalty in lossy conditions, rendering Dilithium’s 18 μs CPU advantage negligible. Finally, we prove a Full-PQC data verification model is infeasible, creating a 345 ms CPU bottleneck and confirming the necessity of a Hybrid-PQC approach.
We conclude that the Falcon-based hybrid protocol is the only solution that simultaneously avoids both network-level (fragmentation, RTO) and CPU-level (bottleneck) penalties, establishing it as the most practical and robust quantum-resistant solution for future LEO satellite networks.
