Two Sequential Squaring Verifiable Delay Function
This reduces computational overhead for applications like randomness beacons and sustainable blockchains, though it is an incremental improvement over existing methods.
The paper tackles the problem of high verification cost in Verifiable Delay Functions (VDFs) by proposing a new VDF that requires only 2 modulo squarings for verification, making the sequential verification effort independent of the security parameter.
A Verifiable Delay Function (VDF) is a function that takes a specified sequential time to be evaluated, but can be efficiently verified. VDFs are useful in several applications ranging from randomness beacons to sustainable blockchains but are really rare in practice. Most of the VDFs are based on algebraic assumptions like time-lock puzzle in unknown group orders [6, 8] and isogenies over pairing groups [4]. The number of modulo squaring required for verification in the time-lock puzzle based VDFs are proportional to their security parameter. This paper proposes a verifiable delay function that requires only 2- modulo squaring for verification. So the sequential effort required for verification is independent of the security parameter.