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.’s 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.

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Lecture Notes in Computer Science/Lecture Notes in Artificial Intelligence
Financial Cryptography and Data Security

Landerreche, E., Stevens, M., & Schaffner, C. (2020). Non-interactive cryptographic timestamping through based on Verifiable Delay Functions. In International Conference on Financial Cryptography and Data Security, FC 2020 (pp. 541–558). doi:10.1007/978-3-030-51280-4_29