可追责并解决密钥托管问题的属性基加密方案

Accountable Attribute-Based Encryption Scheme Without Key Escrow

属性基加密(attribute-based encryption,ABE)用于对存储在第三方的加密数据的细粒度共享.在ABE中:1)由于密钥不包含用户的身份信息,用户可以共享他她的密钥而不被发现;2)密钥生成中心(key generation center,KGC)可以生成带有任意属性集或访问结构的密钥;3)KGC可以用它的主密钥解密任意的密文.这3类问题的存在,使得使用ABE的系统中的数据面临极大的安全挑战.提出一个可追责并解决密钥托管问题的属性基加密方案(accountable key-policy attribute-based encryption scheme without key escrow,WoKE-AKP-ABE),包含2个机构:KGC和属性机构(attribute authority,AA),KGC生成用户密钥中与身份相关的部分,KGC和AA联合生成用户密钥中与属性相关的部分,在判定双线性Diffie-Hellman假设下达到了选择属性集模型下的选择明文安全,不仅可以抵抗恶意的用户或者机构的攻击,还可以抵抗用户与机构的合谋攻击,能够实现对于解密器的黑盒追踪.

To ensure the security of sensitive data on cloud storage,people need to store them in encrypted form.Attribute-based encryption（ABE）is widely applied to the fine-grained sharing of encrypted data stored in the third parties.However,there exist three types of data confidentiality issues in ABE schemes：1）As secret key does not contain identity-specified information,a user can share hisher secret key without being identified;2）Key generation center（KGC）can generate a user’s secret key with arbitrary access structure or attribute set;3）KGC can decrypt ciphertext directly using its master key.As the existence of these three issues,the security of data in the ABE system faces great challenges.In this paper,we proposed an accountable key-policy attribute-based encryption scheme without key escrow（WoKE-AKP-ABE）.In our construction,we have two authorities which are KGC and attribute authority（AA）.KGC generates identity-related part in user’s secret key,and KGC and AA generate attribute-related part through cooperation.Our scheme has chosen plaintext security in the selective-set model under the decisional bilinear Diffie-Hellman assumption and can resist the attack from not only dishonest user or authority but also the collusion between user and single authority.Our scheme can trace decoder box in black-box model.