支持通用电路的多线性映射外包属性加密方案

Outsourced attribute-based encryption for general circuit from multilinear maps

针对基于多线性映射的属性加密方案存在密文扩展率大、解密效率低、密钥托管的问题,将外包技术和用户秘密值法运用于方案中,设计了一个密钥策略的多线性映射属性加密方案。方案以通用多项式电路作为访问结构,支持任意扇出,其用户的私钥由密钥生成中心和用户共同产生。密文长度固定为|G|+|Z|,按照椭圆曲线标准设置合理参数后,与已知密文量最小的方案对比,存储代价减少25%。用户解密时仅对转换密文作运算,且外包正确性可验证,解密所需多线性运算次数仅为3次,大大降低了用户的计算代价。在标准模型下利用多线性判断DiffieHellman困难问题证明了方案的安全性。该方案也能适用于运算能力有限的小型移动设备。

Since the ciphertext length of attribute-based encryption scheme from multilinear maps is large, the decryption is inefficient and the scheme has key escrow problem, a key-policy attribute-based encryption scheme from multilinear maps was proposed by using outsourcing technology and user＇s secret value. The proposed scheme supported general polynomial-size circuit and arbitrary fanout, the private key was generated by key generation center and user. The length of the ciphertext is fixed to ｜G｜＋｜Z｜, compared with the known ciphertext scheme with the minimum ciphertext, the storage cost is decreased by 25% after setting reasonable parameters in accordance with the standards elliptic curves. Users only need to compute transformation ciphertext and the ciphertext is verifiable. The decryption multilinear operation count is only 3, which greatly reduces the computional cost. Selective security is proved in standard model under the multilinear decisional Diffie-Hellman problem. Additionally, it also can be applied in small mobile devices with limited computing capability.