Bitcoin may go quantum-safe while Lightning privacy stays exposed

According to CryptoSlate, a research preprint outlines how five parts of the Bitcoin Lightning Network's off-chain payment system would require separate upgrades even if Bitcoin adopts post-quantum protections for on-chain outputs. The paper proposes PQLN, a hybrid post-quantum extension implemented as a rust-lightning research prototype, which targets gossip, encrypted peer connections, signed invoices, reusable payment offers, and onion packets.

CryptoSlate reported that PQLN retains classical mechanisms while incorporating ML-DSA signatures and hybrid ML-KEM key exchanges. In tests, default ML-DSA and ML-KEM settings increased full network graph gossip downloads 10.2-fold and stored graph data 8.8 times compared to vanilla Lightning. Furthermore, private payment routing incurred bandwidth penalties from a fixed post-quantum ciphertext list, adding latency per hop depending on link speeds. The preprint notes that PQLN does not secure on-chain keys protecting funding, commitment, and HTLC outputs or penalty transactions, meaning safeguarding channel funds still requires Bitcoin-layer post-quantum changes. The software remains a research artifact and does not establish network-wide readiness against a future cryptographically relevant quantum adversary.