View source for PTLC

A '''Point Time Locked Contract''' ('''PTLC''') is a conditional payment that can be claimed by completing a Schnorr signature adaptor (equivalently, by revealing the discrete logarithm of a curve point), or refunded after a timeout. PTLCs are designed to replace hash time locked contracts (HTLCs) in [[Lightning Network]] routing and related atomic-swap style protocols so that hops do not share a single payment hash. As of 2026 they remain a design and implementation effort on top of Taproot-capable channels. They are not a completed BOLT that has replaced HTLCs on the public Lightning network.

An HTLC locks coins to the preimage of a hash. Every hop of a routed Lightning payment typically uses the same hash, which can let observers correlate those hops. A PTLC instead locks to a curve point and unlocks via an adaptor signature. Per-hop blinding can give each intermediary a different point, so adjacent hops need not share a common lock value. On-chain, cooperative settlement can stay off chain as with HTLCs. A force-close under Taproot need not reveal a shared payment hash the way a HASH160 HTLC script can.

Taproot and BIP340 made Schnorr adaptor constructions practical on Bitcoin. Lightning still routes with HTLCs because interoperable hops, invoices, and proof-of-payment flows are built around preimages. Mixed HTLC and PTLC paths would be needed during any transition.

== See also ==
* [[Lightning Network]]
* [[Taproot]]
* [[MuSig]]

== External links ==
* [https://bitcoinops.org/en/topics/ptlc/ Bitcoin Optech: PTLC]
* [https://github.com/bitcoin/bips/blob/master/bip-0340.mediawiki BIP340: Schnorr signatures for secp256k1]
* [https://download.wpsoftware.net/bitcoin/wizardry/mw-slides/2018-05-18-l2/slides.pdf Scriptless scripts slides (Poelstra)]

[[Category:Technical]]
[[Category:Privacy]]