基于区块链的公钥可搜索加密研究

Searchable encryption is a cryptographic primitive that allows search of specific keyword on ciphertext, and a core technique to achieve encrypted data retrieval. Public key encryption with keyword search (PEKS) gains growing interests due to no complicated key management problem and supporting data sharing. The server in PEKS is usually regarded to be honest and reliably execute the searching operation. However, a malicious server may return ineffective result once it has some interest demands while the user receives no compensation. This breaks the search reliability. Reliable search against the malicious server is a desirable issue for PEKS. By borrowing the blockchain technique, this project plans to research blockchain-based PEKS. This project consists of the following three aspects. First, this project will build the general system model and the general security model for blockchain-based PEKS, to reach a balance between storage and search, sharing and reliability. Second, this project will refine different privacy definitions and design entity privacy-aware blockchain-based PEKS schemes, to enhance the privacy concern. Third, this project will explore the algorithm optimization including lightweight search fee transaction and multi-entity search, to improve the search performance. All the results of this project will help to supplement the existing theory of searchable encryption, drive the application mode of blockchain, and promote the innovation and development of Cryptography.

可搜索加密是一种通过关键字对密文进行检索的密码学原语，是实现加密数据有效查询的核心技术。公钥可搜索加密因无需复杂的密钥管理、支持数据共享等优势受到广泛关注。搜索服务器通常被默认为诚实地执行搜索操作并返回正确的结果，但实际中的利益诉求和软件入侵都会引起服务器的恶意转变，破坏搜索的可靠性。在恶意服务器下执行可靠的搜索是公钥可搜索加密必须解决的问题。本项目拟利用区块链公平可靠等特点，研究基于区块链的公钥可搜索加密，包括以下三个方面：建立区块链公钥可搜索加密通用的系统模型和安全模型，实现存储与搜索、共享与可靠之间的平衡；细化隐私定义，设计支持实体隐私的区块链公钥可搜索加密方案，加强隐私保护技术；探索区块链公钥可搜索加密的算法优化，构造轻量级的费用交易算法和多实体搜索算法，提升搜索性能。本项目的研究成果将补充现有的可搜索加密理论，丰富区块链的应用模式，促进密码体系的创新发展。

公钥可搜索加密因无需复杂的密钥管理、支持数据共享等优势受到广泛关注，是实现加密数据有效查询的核心技术。实际中的利益诉求和软件入侵都会引起服务器的恶意转变，破坏搜索的可靠性，在恶意服务器下执行可靠的搜索是公钥可搜索加密必须解决的问题。本项目拟利用区块链公平可靠等特点，研究基于区块链的公钥可搜索加密，提出了基于区块链的公钥可搜索加密框架SearchBC；利用层级化思想，设计了基于区块链的密文检索系统；利用智能合约结合密码学技术提出了多种强化隐私机制；利用在线/离线可穿剌搜索算法提出了一种快速搜索机制，将搜索和计算复杂度优化为次线性；提出了可否认和可问责的可搜索消息审核系统；提出了区块链可控的条件隐私保护加密学习；提出了基于在线/离线功能加密的去中心化和部分隐私数据访问；提出了具有隐私性和抗泄露性的基于区块链的动态访问控制系统；提出了针对恶意数据发布者的安全云存储的可净化访问控制系统。本项目的研究成果将补充现有的可搜索加密理论，丰富区块链的应用模式，促进密码体系的创新发展。