【摘要】 可验证延迟函数(verifiable delay function, VDF)是由Boneh等人于2018年提出的一种密码学原语,无论并行与否,该函数的计算时间都是固定的,但要求验证其结果是快速的.在诸如随机信标和区块链协议设计等去中心化应用中, VDF能使用例如重复平方的计算任务来提供可靠的消逝时间证明(proof of elapsed time, PoET),以实现区块链的共识.本文重点介绍了五种VDF候选方案及其构造,比较它们之间的优劣,说明其可能存在的问题和特性,阐述VDF在随机信标、资源高效的区块链、复制证明、计算时间戳和延迟加密上的应用,尤其对于2021年刚引入的延迟加密(delay encryption, DE)做了详细的调查和分析,对现有的两种延迟加密方案及构造进行了重点分析.在现有VDF研究基础上,本文总结了VDF的现状,提出所需要关注的研究动态,进而指出Loe等人的P-VDF是目前五种VDF候选中最为实用的,优势明显.它具有空证明和高效验证的优点,且验证算法的运行时间为O(1).最后,本文对VDF的未来发展趋势作了有益的分析和展望.更多还原

【Abstract】 Verifiable delay function(VDF) is a novel cryptographic primitive proposed by Boneh et al. in 2018. Whether it is performed in parallel or not, it calculates and outputs the function result at a fixed time of computation, and the verification is fast. In de-centralized applications such as random beacon and blockchain protocols, it can be used to some computational tasks such as repeated squares to provide reliable proof of elapsed time(PoET). This paper focuses on five VDF candidate schemes and their constructions, compares their advantages and disadvantages. It also illustrates their possible problems and characteristics, and describes the applications of VDF in random beacons,resource-efficient blockchains, proof of replication, computation of timestamp, delayed encryption, etc.In particular, the delayed encryption introduced in 2021 is analyzed in detail, and two existing delayed encryption schemes are also analyzed. On the basis of existing VDF studies, this paper summarizes the current state-of-the-art of VDFs and puts forward their views. It shows that Loe et al. P-VDF is the most practical protocol among the five VDF candidates, and it has the advantage of empty proof and efficient validation, and its validation algorithm runs with time complexity O(1). Finally,the development trends and discussion of VDFs are presented.更多还原