PQC and QKD — complementary, not rivals
The two quantum-safe approaches solve the same problem in different ways and are strongest combined.
Post-quantum cryptography (PQC) is new algorithms that run in software over any connection — covering authentication, digital signatures and end-to-end encryption. Its security rests on mathematical hardness assumptions.
Quantum key distribution (QKD) distributes keys using the laws of physics over fibre; any eavesdropping is detectable and the keys cannot be broken later by any computer.
It is ideal as an additional layer and scales to multi-node networks: China’s CN-QCN already secures over 10,000 km of fibre serving banks and critical infrastructure, while Europe’s EuroQCI is building the same capability across EU member states. As QKD security is not computational but physical, it has a completely different attack vector than PQC — combining both yields true defence in depth.
