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HTLC (Hash Time-Locked Contract)

Quick Answer

An HTLC is a smart contract requiring payment acknowledgement within a set time window, enabling trustless cross-chain swaps and payment channels like Lightning Network.

Full Definition

A hash time-locked contract is a smart contract mechanism that requires the recipient to acknowledge receiving a payment within a set time window by providing a cryptographic proof (preimage of a hash). If the time expires, the funds are returned to the sender. HTLCs enable trustless cross-chain atomic swaps and are the foundation of payment channel networks like Bitcoin's Lightning Network.