Lightning Payments Proven in Zero-Knowledge
Zerosats is an early-stage experiment in making Bitcoin transactions private while keeping the base chain maximally transparent. A useful analogy is that Zerosats aims to be for Bitcoin what a VPN is for HTTP - a "Bitcoin VPN" for its users. The prevalence of Lightning payment providers shaped the protocol's core requirement: it must connect to the Lightning Network to allow fast and final settlement. Establishing that connection in a trust-minimized, non-custodial way required implementing timelocks, a key component of Hash Time Locked Contracts (HTLCs) and a fundamental primitive for both cross-chain atomic swaps and Lightning payment routing. HTLCs normally depend on a timelock supplied by the underlying blockchain. In private, zero-knowledge settings no such timelock is available inside the circuit, which forces reliance on trusted sequencers or external oracles. To make the Lightning connection viable, we introduce a method for constructing verifiable timelocks inside zero-knowledge circuits by reusing Bitcoin's accumulated proof-of-work as a computational reference clock. We describe the protocol, discuss its security margins, and report preliminary benchmarks for the proving cost of the resulting circuits.
