Proofs of sequential work (PoSW) are proof systems where a prover, upon receiving a statement χ and a time parameter T computes a proof ϕ(χ,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 χ was received. PoSW were introduced by Mahmoody, Moran and Vadhan [MMV11], a simple and practical construction was only recently proposed by Cohen and Pietrzak [CP18]. In this work we construct a new simple PoSW in the random permutation model which is almost as simple and efficient as [CP18] but conceptually very different. Whereas the structure underlying [CP18] is a hash tree, our construction is based on skip lists and has the interesting property that computing the PoSW is a reversible computation. The fact that the construction is reversible can potentially be used for new applications like constructing proofs of replication. We also show how to “embed” the sloth function of Lenstra and Weselowski [LW17] into our PoSW to get a PoSW where one additionally can verify correctness of the output much more efficiently than recomputing it (though recent constructions of “verifiable delay functions” subsume most of the applications this construction was aiming at).
Advances in Cryptology – EUROCRYPT 2019
International Conference on the Theory and Applications of Cryptographic Techniques
2019-05-19 – 2019-05-23
Abusalah HM, Kamath Hosdurg C, Klein K, Pietrzak KZ, Walter M. Reversible proofs of sequential work. In: Advances in Cryptology – EUROCRYPT 2019. Vol 11477. Springer International Publishing; 2019:277-291. doi:10.1007/978-3-030-17656-3_10
Abusalah, H. M., Kamath Hosdurg, C., Klein, K., Pietrzak, K. Z., & Walter, M. (2019). Reversible proofs of sequential work. In Advances in Cryptology – EUROCRYPT 2019 (Vol. 11477, pp. 277–291). Darmstadt, Germany: Springer International Publishing. https://doi.org/10.1007/978-3-030-17656-3_10
Abusalah, Hamza M, Chethan Kamath Hosdurg, Karen Klein, Krzysztof Z Pietrzak, and Michael Walter. “Reversible Proofs of Sequential Work.” In Advances in Cryptology – EUROCRYPT 2019, 11477:277–91. Springer International Publishing, 2019. https://doi.org/10.1007/978-3-030-17656-3_10.
H. M. Abusalah, C. Kamath Hosdurg, K. Klein, K. Z. Pietrzak, and M. Walter, “Reversible proofs of sequential work,” in Advances in Cryptology – EUROCRYPT 2019, Darmstadt, Germany, 2019, vol. 11477, pp. 277–291.
Abusalah HM, Kamath Hosdurg C, Klein K, Pietrzak KZ, Walter M. 2019. Reversible proofs of sequential work. Advances in Cryptology – EUROCRYPT 2019. International Conference on the Theory and Applications of Cryptographic Techniques, LNCS, vol. 11477, 277–291.
Abusalah, Hamza M., et al. “Reversible Proofs of Sequential Work.” Advances in Cryptology – EUROCRYPT 2019, vol. 11477, Springer International Publishing, 2019, pp. 277–91, doi:10.1007/978-3-030-17656-3_10.