适用于移动用户高效访问外包数据的非对称代理重加密方案

为使移动设备更加方便快捷地解密存储于云端的外包数据，根据基于身份的广播加密（IBBE）系统和基于身份的加密（IBE）系统，使用Green等提出的解密外包的技术（GREEN M，HOHENBERGER S，WATERS B.Outsourcing the decryption of ABE ciphertexts.Proceedings of the 20th USENIX Conference on Security.Berkeley：USENIX Association，2011：34），提出一种改进的非对称跨加密系统的代理重加密（MACPRE）方案。该方案更适合计算能力有限的移动设备安全共享云端数据。移动用户在解密重加密后的数据时，运行一次指数运算和一次配对运算便可以将明文恢复，大大提高了移动用户解密的效率，降低了移动用户的能耗。该方案的安全性可以归约到底层的IBE方案和IBBE方案的安全性。理论分析和实验结果表明，该方案使得移动设备花费较少的时间便可以将存储在云端的数据解密，缓解了移动设备计算能力的不足，实用性较强。

Asymmetric proxy re-encryption scheme of efficient access to outsourcing data for mobile users

In order to make the mobile device more convenient and faster decrypt the outsourcing data stored in the cloud, on the basis of Identity-Based Broadcast Encryption (IBBE) system and Identity-Based Encryption (IBE) system, using the technique of outsourcing the decryption proposed by Green et al. (GREEN M, HOHENBERGER S, WATERS B. Outsourcing the decryption of ABE ciphertexts. Proceedings of the 20th USENIX Conference on Security. Berkeley:USENIX Association, 2011:34), a Modified Asymmetric Cross-cryptosystem Proxy Re-Encryption (MACPRE) scheme across the encryption system was proposed. The proposed scheme is more suitable for mobile devices with limited computing power to securely share the data stored in the cloud. When the mobile user decrypts the re-encrypted data, the plaintext can be restored by performing one exponent operation and one bilinear pairing operation, which greatly improves the decryption efficiency of the mobile user and saves the power consumption of the mobile user. The security of this proposed scheme can be reduced to the security of the IBE and IBBE scheme. The theoretical analysis and experimental results show that, the proposed scheme can allow the mobile devices to decrypt data stored in the cloud by spending less time, and ease the problem of limited computing power of the mobile devices. The proposed scheme is more practical.