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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Keywords Non-interactive cryptographic timestamping, Universal composability, Verifiable delay functions, Time-lock cryptography
Conference Financial Cryptography and Data Security
Note Cryptographic timestamping through Sequential Work (https://ir.cwi.nl/pub/28538) is a previous version of this work.
Landerreche, E, Stevens, M.M.J, & Schaffner, C. (2020). Non-interactive Cryptographic timestamping through based on Verifiable Delay Functions.