PublicationsCan Verifiable Delay Functions be Based on Random Oracles?Mohammad Mahmoody, Caleb Smith, and David J. Wu International Colloquium on Automata, Languages and Programming (ICALP), 2020 Resources
Abstract
Boneh, Bonneau, Bünz, and Fisch (CRYPTO 2018) recently introduced the notion of a verifiable delay function (VDF). VDFs are functions that take a long sequential time \( T \) to compute, but whose outputs \( y := \text{Eval}(x) \) can be efficiently verified (possibly given a proof \( \pi \)) in time \( t \ll T \) (e.g., \( t=\text{poly}(\lambda, \log T) \) where \( \lambda \) is the security parameter). The first security requirement on a VDF, called uniqueness, is that no polynomial-time algorithm can find a convincing proof \( \pi' \) that verifies for an input \( x \) and a different output \( y' \neq y \). The second security requirement, called sequentiality, is that no polynomial-time algorithm running in time \( \sigma\lt T \) for some parameter \( \sigma \) (e.g., \( \sigma=T^{1/10} \)) can compute \( y \), even with \( \text{poly}(T,\lambda) \) many parallel processors. Starting from the work of Boneh et al., there are now multiple constructions of VDFs from various algebraic assumptions. In this work, we study whether VDFs can be constructed from ideal hash functions in a black-box way, as modeled in the random oracle model (ROM). In the ROM, we measure the running time by the number of oracle queries and the sequentiality by the number of rounds of oracle queries. We rule out two classes of constructions of VDFs in the ROM:
BibTeX
@inproceedings{MSW20, author = {Mohammad Mahmoody and Caleb Smith and David J. Wu}, title = {Can Verifiable Delay Functions be Based on Random Oracles?}, booktitle = {{ICALP}}, year = {2020} } |