适应性安全的多主密钥KP-ABE方案

摘要

功能加密能很好地满足多对多的网络环境下的机密性需求,功能性函数提供了比传统公钥更灵活的密文存取能力.已有的功能加密系统均只支持单主密钥功能性函数,本文提出了功能加密子类KP-ABE(key-policy attribute-based encryption)上的多主密钥适应性安全模型,该模型具有更强的表达能力及更广义的特性.利用线性多秘密共享方案,设计了该安全模型下的一个加密方案,并采用对偶法在标准模型下证明方案是IND-CPA(indistinguishability against chosen-ciphertext attacks)安全的.该方案加密数据的存取策略更为灵活,用户可根据权限存取多种类型的密文；提出的构造方法可应用于功能加密的其他子类,且计算量与单主密钥方案相比不存在线性扩张,具有较高的效率.%Functional encryption provides a good way for sharing encrypted data in the network environment, which is sufficient for new emerging applications. Several recent works only focused on the systems that supported single-authority-key functionality. In order to solve the open problem of the construction of multiple authority keys functional encryption, an adaptive security model of multiple-authority-key key-policy attribute-based encryption (M-KP-ABE) was presented, which allows for functionalities that take in multiple authority keys. In this system, an encryptor can specify a policy and a capability describing what the decryptor can learn from the ciphertext. A new M-KP-ABE scheme was proposed for any attribute access structure that could be expressed by a linear multi-secret sharing scheme (LMSSS). This scheme is proven to be adaptively secure in the standard model by using the dual system encryption methodology recently introduced. The key generation centre (KGC) with multiple authority keys can combine user's capabilities in a specified manner and users can decrypt many kinds of ciphertexts. It is easy to apply this methodology to other subclasses of functional encryption with equal security and efficiency, which makes it more appropriate for applications.