$\mathbf{V}\mathbf{D}\mathbf{F}⊊\mathbf{P}\mathbf{S}\mathbf{P}\mathbf{A}\mathbf{C}\mathbf{E}$

Verifiable delay functions (VDF) are functions that take a specified number of sequential steps to be evaluated but can be verified efficiently. In this paper, we show that every VDF is provable in PSPACE but every language in PSPACE does not admit to a VDF.