关键词: 移动云计算, 基于身份加密, 在线离线, 外包解密, 轻量级设备

Abstract: For the problems of data security and privacy of users in the mobile cloud computing, this paper modifies the encryption and decryption algorithms in Identity-Based Encryption（IBE） by introducing the offline/online and the outsourcing decryption, then proposes an Identity-Based Online/Offline Encryption scheme with Outsourcing Decryption（IBOOE-OD）, and proves its security. The IBOOE-OD is very suitable for lightweight devices to protect privacy data in mobile cloud computing environment. To reduce the costs of encryption and decryption in IBE for mobile devices, firstly, the encryption of IBE is decomposed into offline and online two phases by the online/offline technology, such that mobile devices can perform simple calculations to generate a ciphertext. Secondly, this paper uses the outsourcing technology to modify the key generation and decryption algorithms, and adds a ciphertext transformation algorithm, so that it can outsource the majority work of decryption to the cloud services and the mobile devices can perform one exponentiation to obtain plaintext. Compared with the performances of the existing IBE schemes, the scheme has the less amount of encryption and decryption costs and is very suitable for lightweight mobile devices.

Key words: mobile cloud computing, Identity-Based Encryption（IBE）, online-offline, outsourcing decryption, lightweight device