LAUSR

To extend the transmission distance and/or improve secret-key rate of QKD protocols, we propose to employ the joint QKD-post-quantum cryptosystems in which QKD is used for raw-key transmission while the post-quantum cryptography (PQC) subsystem to transmit parity bits for information reconciliation. We also describe a run-time configurable spatially coupled (SC)-LDPC code, derived from template quasi cyclic (QC)-LDPC, suitable for use in both information reconciliation and McEliece crypto-subsystem. For twin-field (TF)-QKD subsystem, the proposed joint cryptosystem, which takes the complexity of algorithm used to break the PQC subsystem into account, is able to achieve record distance of 1238 km over ultra-low-loss fiber.