Reversible Proofs of Sequential Work.

Proofs of sequential work (PoSW) are proof systems where a prover, upon receiving a statement \(\chi \) and a time parameter T computes a proof \(\phi (\chi ,T)\) which is efficiently and publicly verifiable. The proof can be computed in T sequential steps, but not much less, even by a malicious party having large parallelism. A PoSW thus serves as a proof that T units of time have passed since \(\chi \) was received.