Cryptology ePrint Archive: Report 2019/197

Non-interactive Cryptographic Timestamping based on Verifiable Delay Functions

Esteban Landerreche and Marc Stevens and Christian Schaffner

Abstract: We present the first treatment of non-interactive publicly-verifiable timestamping schemes in the Universal Composability framework. Similar to a simple construction by Mahmoody et al., we use non-parallelizable computational work that relates to elapsed time to avoid previous impossibility results on non-interactive timestamping. We extend these ideas to the UC-framework and show how to model verifiable delay functions (VDF) related to a global clock, and non-interactive timestamping, in the UC-framework. Furthermore, we present new constructions that are substantial improvements over Mahmoody et al.ís construction, such that any forged timestamps by the adversary are now limited to within a certain time-window that depends only on its ratio to compute VDFs more quickly and the time-window of corruption. Finally, we discuss natural applications for our construction in decentralized protocols.

Category / Keywords: non-interactive cryptographic timestamping, universal composability, verifiable delay functions, time-lock cryptography

Date: received 21 Feb 2019, last revised 27 Feb 2019

Contact author: esteban at cwi nl

Available format(s): PDF | BibTeX Citation

Version: 20190227:092649 (All versions of this report)

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