Faster Verifiable Delay Function For Shorter Delay Parameter
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A Verifiable Delay Function (VDF) is a function that takes a specified sequential time T to be evaluated, but can be verified in O(log T)-time. For meaningful security, T can be at most subexponential in the security parameter λ but has no lower bound. VDFs are useful in several applications ranging from randomness beacons to sustainable blockchains but are really rare in practice. To the best of our knowledge, the sequential effort required for verification in all the VDFs [7,9,4] known to date, is in Ω(log T). This paper proposes a verifiable delay function that requires only two sequential squaring to verify when the delay parameter is polynomially-bounded i.e., T≤𝚙𝚘𝚕𝚢(λ). Thus in our VDF, the sequential effort required for verification is fixed and independent of the security parameter.
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