Abstract: An example operation may include one or more of generating a hashed timelock contract (HTLC) of an asset and storing the HTLC in a storage structure, where the HTLC requires proof of a condition by a receiver within a predetermined amount of time for the receiver to unlock the asset, executing, via a processing device, a sequential computation a predetermined number of steps and generating proof of a computational load based on an output of the serial computation, determining that the condition for the client to unlock the HTLC has expired, and transmitting a request for a refund of the asset which comprises the proof of the computational load as proof of elapsed time to the storage structure.