Construct time-lock puzzles from symmetric-key assumptions alone

Construct time-lock puzzles from symmetric-key assumptions alone, thereby obtaining a construction that does not rely on algebraic, lattice-based, obfuscation-based, or other non-symmetric-key assumptions.

Background

The paper surveys existing positive constructions of time-lock puzzles based on algebraic assumptions, post-quantum lattice assumptions, and generic assumptions such as succinct randomized encodings and worst-case non-parallelizing languages. These constructions do not establish time-lock puzzles from symmetric-key assumptions alone.

The authors explicitly identify the lack of such a construction as an unresolved limitation. This problem is distinct from the quantum random-oracle question addressed by the paper, because the paper’s main result constructs quantum time-lock puzzles in the QROM rather than deriving time-lock puzzles solely from symmetric-key assumptions.