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.

翻译：验证延迟函数（VDF）是一种需要指定顺序时间才能求值，但可高效验证的函数。VDF在随机信标、可持续区块链等多种应用中具有重要价值，但在实践中极为罕见。现有VDF大多基于代数假设，如未知群阶时间锁谜题[6,8]和配对群同源映射[4]。基于时间锁谜题的VDF中，验证所需的模平方运算次数与安全参数成正比。本文提出一种验证延迟函数，其验证过程仅需两次模平方运算，因此验证所需顺序计算代价与安全参数无关。