PQLN Prototype Raises Concerns Over Lightning Network's Post-Quantum Extensions

A recent research prototype has proposed a post-quantum extension for five off-chain functions of the Lightning Network, but its default design raises concerns about increased bandwidth usage. The PQLN (Post-Quantum Lightning Network) test aims to provide quantum-safe protection across these five functions.

The researchers built a feature-gated rust-lightning fork and a modified ldk-sample node to test the compatibility of post-quantum and vanilla binaries. They found that the default ML-DSA and ML-KEM settings increased gossip downloads by 10.2 times compared to vanilla Lightning in static synchronization tests.

However, PQLN still leaves Bitcoin-rooted risks untouched. It does not secure on-chain keys protecting funding, commitment, and HTLC outputs or penalty transactions, so safeguarding channel funds requires Bitcoin-layer post-quantum changes.