Preimage

A preimage is the original data or secret input that, when processed through a specific cryptographic hash function, produces a unique hash value. In the context of financial protocols, the preimage serves as the digital key required to unlock funds secured by a hash lock.

By revealing the preimage, a participant proves they possess the secret, thereby satisfying the condition to claim the assets. Because hash functions are one-way, it is computationally impossible to derive the preimage from the hash itself, ensuring the security of the locked funds.

This cryptographic proof is fundamental to the operation of atomic swaps and various payment channel mechanisms. The integrity of these protocols relies entirely on the secrecy and correct management of the preimage until the moment of settlement.