Analyzing the implementation challenges of integrating large post-quantum keys and lattice math into existing IPsec protocols.
Classical elliptic curve Diffie-Hellman keys are compact (32 to 64 bytes), easily fitting into single UDP packets. In contrast, post-quantum lattice algorithms introduce significantly larger public keys and ciphertexts (ML-KEM-768 requires 1,184 bytes). This expansion causes IP fragmentation and packet drops across intermediate WAN firewalls. WanHSM implements IETF RFC 9370 multiple key exchange extensions with intelligent fragmentation handling.
Because post-quantum algorithms are relatively new compared to battle-tested elliptic curves, security best practices dictate hybrid key agreement: session keys are derived by hashing both a Curve25519 shared secret and an ML-KEM shared secret. An attacker must break both mathematical problems to compromise the session.
WanHSM completes the entire hybrid key derivation—including polynomial multiplication, SHAKE-256 expansion, and HKDF extraction—inside a physically shielded FIPS 140-3 Level 4 boundary, ensuring private lattice polynomials never touch server RAM.