HTLCs use hashlocks and timelocks to ensure payment security. HTLCs require that the receiver of a payment acknowledges receiving the payment prior to a deadline by generating cryptographic proof of payment or forfeits the ability to claim the payment, returning it to the payer. Because any receipt of funds triggers the creation of a new hash, this idea can be extended to allow a sequence of payments; with the right conditionality, payments can be securely routed through a series of users.