新型功能加密体制中的关键问题研究

In the recent years, functional encryption has emerged as a new general framework, which is shown to capture as special cases a number of well-known notions of public key cryptosystem, and can be readily generalized to broader applications. One of its main strength relies on its ability to provide both data confidentiality and access control, two major components of modern cryptography. Still at an early stage, functional encryption has only been studied on special instances that are independent of each other, and there is to date few records of general approaches from an overall viewpoint. Meawhile,new techniques are springing one after another in public key cryptography, which provide tools for deeper research on functional encryption..The goal of this project is to systematically study functional encryption and its provable security using new cryptographic techniques. (1) The first step consists in incorporating distributed encryption within functional encryption and extending its ability through this new framework. (2) Then new tools emerging from case studies on functional encryption can be used to design more efficient and expressive functional cryptosystem featuring provable security in fully secure models. (3) Eventually the varieties of functionalities can be analyzed such that efficient general constructions in strong model will be revealed. An upper bound of the expressiveness in stronger model will be provided. Hence the successful implementation of this project will show both theoretical and practical significance in a wide range of domain, including the rapidly expanding areas of secure remote data storage and data sharing.

功能加密是公钥密码学领域新近研究热点之一。其定义涵盖了多种新型公钥加密体制，并可灵活拓展至更广阔的应用。功能加密体制在保障数据安全的同时，实现了对数据的访问控制，一步解决了现代密码学研究中的两个重要问题。目前，对功能加密的研究处于相对初级阶段，对具有特定表达能力的功能加密的研究彼此独立，对功能加密的整体思考尚欠深入。.本项目将利用公钥密码新技术对功能加密及其可证安全性进行系统研究：(1)将分布式加密纳入功能加密，扩大功能加密涵盖范围；(2)利用对具有特殊表达能力的功能加密的研究中所涌现的新技术，设计高效且具有更强表达能力的功能加密体制，并在完备安全模型下进行形式化证明；(3)研究具有不同层次表达能力的功能加密间的内部联系并给出高效的通用构造，并在更强安全模型下构造更有效的通用功能加密。本项目的成功实施，对实现基于公钥技术的远程安全数据存储与安全数据共享，具有重要的理论意义和广泛的应用价值。

本项目研究工作依照研究计划展开，在分布式环境下对功能加密进行了定义并根据实际应用抽象出了所对应的新型密码学原语，将功能加密的内涵进行了扩大；针对多种类型的新型功能加密体制进行了深入研究，丰富了对应的攻击模型，并在新的模型下设计了新方案并证明了新方案的安全性；针对多个具体的功能加密体制进行了设计和实现。在本项目支持下，共发表论文37篇，培养博士研究生3名，培养硕士研究生5名。举办2次国内学术讨论会和1次国际学术学习班。