医疗大数据隐私保护多关键词范围搜索方案

随着医疗信息系统的急速发展，基于医疗云的信息系统将大量电子健康记录（EHRs）存储在医疗云系统中，利用医疗云强大的存储能力和计算能力对EHRs数据进行安全与统一的管理.尽管传统加密机制可以保证医疗数据在半诚实云服务器中的机密性，但对加密后的EHRs数据执行安全、快速、有效的范围搜索，仍是一个有待解决的关键问题.提出一种支持多关键词范围搜索的可搜索加密方案：利用向量积保持加密机制实现复杂查询结构的可搜索加密，可支持连接关键词查询、范围查询以及通配符的查询；通过随机化构建搜索索引和搜索陷门，实现搜索模式隐藏，达到搜索语句的隐私保护；采用矩阵哈达马积缩小所需密钥矩阵的维度.理论分析和实验结果表明：该方案在达到医疗数据隐私保证的同时，对用户的检索策略也进行了有效的隐私性保护，有效提高了检索效率，降低了创建索引及陷门所用时间，实现了多用户多文件下医疗数据的范围搜索能力.

Range-based Multi-keyword Searchable Scheme with Privacy Protection in e-Healthcare Cloud Systems

With the rapid development of medical information systems, the information system based on medical clouds stores massive electronic health records (EHRs) in medical cloud systems and employs the powerful storage and computing capacity of medical clouds to manage EHRs in a safe and unified manner. Although the traditional encryption mechanism can protect the privacy of medical data in semi-honest cloud servers, it is still an open problem to perform safe and efficient range-based search for the encrypted EHRs. To address this problem, in this work, a range-based multi-keyword searchable scheme is proposed. It can implement searchable encryption of complex query structures with scalar-product preserving encryption and support the query of connection keywords, ranges, and wildcard characters. Furthermore, the indexes and trapdoors are created in a random manner to hide the search mode and protect the privacy of search statements. The Hadamard product is adopted to reduce the dimension of the required key matrix. Theoretical analysis and experimental results show that the scheme can efficiently protect the privacy users'' search strategy while guaranteeing the privacy of medical data. This scheme improves the retrieval efficiency and reduces the time in index and trapdoor creation, achieving the range-based search of medical data in multi-user and multi-file medical environments.