Lightning Privacy Remains Exposed Despite Bitcoin's Potential Quantum Upgrade
A recent research preprint suggests that even if Bitcoin adopts post-quantum protections for on-chain outputs, certain parts of its Lightning Network's off-chain payment system would still require separate upgrades.
The study proposes a hybrid post-quantum extension called PQLN, which targets five areas of the Lightning Network: gossip, encrypted peer connections, signed invoices and reusable payment offers, onion packets that conceal payment-routing details, and BOLT 12 privacy paths.
PQLN keeps classical mechanisms while adding ML-DSA signatures to gossip, invoices, and offers. It also adds hybrid ML-KEM key exchange to transport, payment onions, and BOLT 12 privacy paths.
The authors built a feature-gated rust-lightning fork and a modified ldk-sample node. Their results showed that post-quantum and vanilla binaries could coexist in certain setups, but this compatibility does not establish network-wide readiness.