Paper 2020/537

TARDIS: Time And Relative Delays In Simulation

Carsten Baum and Bernardo David and Rafael Dowsley and Jesper Buus Nielsen and Sabine Oechsner

Abstract

This work introduces an extension of the UC framework with an abstract notion of time that allows for modeling relative delays in communication and sequential computation without requiring parties to keep track of a clock. The potential uses of this extension are demonstrated by: (1) formalizing a functionality for (semi-)synchronous secure message transmission; (2) formalizing the notion of time-lock puzzles in the UC setting and showing how to realize it in the restricted programmable and observable global random oracle model; (3) showing that UC time-lock puzzles yield UC-secure fair coin flips; (4) showing that UC-secure two-party computation realizing a new notion of output-independent abort can be obtained leveraging composable time-lock puzzles. Finally, we show that a programmable random oracle is necessary to obtain UC-secure fair coin flip, secure two-party computation with output-independent abort or time-lock puzzles, which yields a new separation between programmable and non-programmable random oracles.