摘要：

由于云服务器能够提供强大的存储和计算能力, 因此个人和企业更趋向于将加密数据存储于云端。为了解决密文数据检索困难的问题, 利用同态加密的密文检索方式成为研究热点。然而, 现有的方案主要集中在单关键词检索上, 由于检索限制条件较少、搜索精度较低, 从而导致通信和计算开销较大。另外, 将数据托管到第三方提供的不可信云主机上, 可能出现删除、修改、返回不真实和不全面的搜索信息等恶意情况。为此, 基于全同态加密和不经意伪随机函数提出一种新型的密文检索方案。通过构造加密的关键词索引和哈希表, 使得方案能够支持多关键词的连接查询。利用文件的标识和大小生成验证标签, 使得数据接收者能够对检索结果的正确性和完整性进行验证。理论分析和实验结果表明, 相比于基于全同态加密的单关键词检索方案, 在检索2~3个多关键词时, 所提方案的密文搜索效率提升36.2%~45.9%, 并且在检索更多关键词时拥有更好的综合性能。

关键词: 云存储, 全同态加密, 密文检索, 安全共享, 可验证

Abstract:

Individuals and businesses are more inclined to store encrypted data in the cloud because cloud servers offer powerful storage and computing capabilities. Ciphertext retrieval using homomorphic encryption has become a research hotspot to address the issue of difficult ciphertext data retrieval. However, existing schemes mainly focus on single-keyword retrieval, which results in high communication and computation overheads owing to fewer retrieval constraints and lower search accuracy. In addition, owing to the hosting of data on untrustworthy cloud hosts provided by third parties, malicious situations such as the deletion, modification, or return of untrue and incomplete search information may occur. Therefore, a novel ciphertext retrieval scheme is proposed based on full homomorphic encryption and an inadvertent pseudo-random function. By constructing an encrypted keyword index and hash table, the scheme can support multi-keyword conjunctive retrieval. The identification and size of the file are used to generate authentication tags that enable the data receiver to verify the correctness and integrity of the retrieval results. Theoretical analysis and experimental results show that, compared to the single-keyword retrieval scheme based on full homomorphic encryption, the efficiency of searching ciphertexts is improved by 36.2%-45.9% when retrieving 2-3 multiple keywords, and the proposed scheme exhibits better overall performance when retrieving more keywords.

Key words: cloud storage, fully homomorphic encryption, ciphertext retrieval, secure sharing, verifiable