Bitcoin may go quantum-safe while Lightning privacy stays exposed
A research preprint introduces PQLN, a prototype adding post-quantum protections to five Lightning Network functions while retaining classical cryptography. Tests found compatible post-quantum and standard nodes could coexist, though some mixed routes fell back to classical protection or failed closed. The upgrade substantially increased network costs: the default design multiplied gossip downloads by 10.2 and graph storage by 8.8, while larger onion packets added routing delays, especially on slow links. Cryptographic signing itself was fast in the researchers’ hardware tests. PQLN remains a research artifact, has not been tested with other Lightning implementations, and does not protect Bitcoin on-chain keys. The work identifies migration costs, not a present-day quantum attack or evidence that Lightning is ready to upgrade.
