支持策略隐藏且密文长度恒定的可搜索加密方案

属性加密体制是实现云存储中数据灵活访问控制的关键技术之一，但已有的属性加密方案存在密文存储开销过大和用户隐私泄露等问题，并且不能同时支持云端数据的公开审计。为了解决这些问题，该文提出一个新的可搜索属性加密方案，其安全性可归约到q-BDHE问题和CDH问题的困难性。该方案在支持关键词搜索的基础上，实现了密文长度恒定；引入策略隐藏思想，防止攻击者获取敏感信息，确保了用户的隐私性；通过数据公开审计机制，实现了云存储中数据的完整性验证。与已有的同类方案相比较，该方案有效地降低了数据的加密开销、关键词的搜索开销、密文的存储成本与解密开销，在云存储环境中具有较好的应用前景。

Searchable Encryption Scheme Supporting Policy Hiding and Constant Ciphertext Length

The Attribute-Based Encryption (ABE) mechanism is one of the key technologies for implementing flexible access control of data in cloud storage. However, the existing ABE schemes have some problems, such as too much ciphertext storage overhead and user privacy leakage, and unsupported public auditing of cloud data. To solve these problems, a new searchable ABE scheme is proposed, and its security can be reduced to the difficulty of q-BDHE (q –decisional Bilinear Diffie-Hellman Exponent) problem and CDH (Computational Diffie-Hellman) problem. The proposed scheme achieves a constant ciphertext length on the basis of supporting keyword search. By introducing strategies to hide ideas, it prevents attackers from obtaining sensitive information and ensures the privacy of users. And the integrity of the data in cloud storage is verified through data public audit mechanism. Compared with the existing similar schemes, this scheme greatly reduces the data encryption overhead, keyword search overhead, ciphertext storage cost and decryption cost, which has a good application prospect to the cloud storage environment.