Mobile cloud computing has become an important technology for mobile services. It overcomes physical limitations of mobile devices towards flexible and scalable mobile services. When using mobile clouds, people usually upload and store their data in cloud servers, and access the data through mobile devices from anywhere. As the privacy of the sensitive data is the major concern of users, the data is often encrypted before storing in cloud servers. However, the flexibility using the data is thereby affected, such as a Boolean search over the encrypted data, or ranking search results. To address these problems, in this paper we first propose a novel multi-user Boolean keyword search scheme (MBKSS) to achieve a rapid Boolean query outcome, while eliminating query interactions between users and the data owner. To rank search results and protect the privacy of relevance scores between files and keywords, we design a new homomorphic cryptosystem with partial decryption, which could be used as a basis for constructing a fast ranking search protocol (FRSP). A comprehensive security analysis shows that the proposed MBKSS and FRSP can achieve secure Boolean search and ranking. The experimental results demonstrate that the proposed MBKSS and FRSP are efficient and suitable for mobile devices.

移动云计算已成为移动服务的重要技术。它克服了移动设备对灵活和可扩展的移动服务的物理限制。使用移动云时，人们通常将其数据上载和存储在云服务器中，并从任何地方通过移动设备访问数据。由于敏感数据的私密性是用户的主要关注点，因此通常在将数据存储在云服务器之前对其进行加密。但是，使用数据的灵活性因此受到影响，例如对加密数据进行布尔搜索或对搜索结果进行排名。为了解决这些问题，本文首先提出了一种新颖的多用户布尔关键字搜索方案（MBKSS），以实现快速的布尔查询结果，同时消除了用户与数据所有者之间的查询交互。为了对搜索结果进行排名并保护文件和关键字之间的相关性分数的私密性，我们设计了一种具有部分解密的新同态密码系统，该系统可以用作构建快速排名搜索协议（FRSP）的基础。全面的安全性分析表明，提出的MBKSS和FRSP可以实现安全的布尔搜索和排名。实验结果表明，所提出的MBKSS和FRSP是有效的，适用于移动设备。