基于可提取哈希证明系统的多策略加密方案

哈希证明系统由Cramer-Shoup在2002年首次提出，到目前为止仍是密码工作者的研究热点之一.进而，Wee在2010年提出可提取哈希证明系统的概念，其可用来构造基于查找性困难假设的公钥加密方案.本文在可提取哈希证明系统之上，通过重新定义系统参数的意义，扩大了可提取哈希证明系统的密码学应用范围.我们利用可提取哈希证明系统的框架构造了一个基本的基于Diffie-Hellman关系的All-But-One可提取哈希证明系统.在此基础上细粒度了辅助输入，引入权重计算，给出了一个基于标签和可变策略的CCA加密方案，并进行了详细的安全性证明.特别的，该方案比可提取具有更丰富的抽象表达，即是All-But-N的，也即在提取模式中由标签决定的分支数量可以有n个.同时，该方案是基于困难性可搜索问题，本质上是基于计算性的Diffie-Hellman问题.

A Multi-Policy Encryption Scheme Based on Extractable Hash Proof Systems

Hash proof systems,which was first introduced by Cramer and Shoup in 2002,is still one of the hottest research topics in cryptography.And then Wee proposed the concept of extractable hash proof system in 2010 and it is a concept extension on the hash proof system and as a paradigm of constructing PKE from search problems.On the basis of the extractable hash proof system,this paper expands the application scope of the extractable hash proof system by redefining the meaning of system parameters.We construct a basic All-But-One extractable hash proof system based on Diffie-Hellman relations by using the framework of extractable hash proof system.Based on this,fine-grained auxiliary input and weighting calculation are introduced.A new variable-policy CCA encryption scheme based on tag is proposed,and the security proof is also given in details.In particular,this scheme is a richer abstraction of extractable hash proof system that it is All-But-N,which means that the number of branches determined by the tag in the extraction mode could be n.At the same time,the scheme is based on the difficulty of the search problem and is essentially based on the computational Diffie-Hellman problem.