An Efficient Key-Policy Attribute-Based Encryption Scheme with Constant Ciphertext Length

There is an acceleration of adoption of cloud computing among enterprises. However, moving the infrastructure and sensitive data from trusted domain of the data owner to public cloud will pose severe security and privacy risks. Attribute-based encryption (ABE) is a new cryptographic primitive which provides a promising tool for addressing the problem of secure and fine-grained data sharing and decentralized access control. Key-policy attribute-based encryption (KP-ABE) is an important type of ABE, which enables senders to encrypt messages under a set of attributes and private keys are associated with access structures that specify which ciphertexts the key holder will be allowed to decrypt. In most existing KP-ABE scheme, the ciphertext size grows linearly with the number of attributes embedded in ciphertext. In this paper, we propose a new KP-ABE construction with constant ciphertext size. In our construction, the access policy can be expressed as any monotone access structure. Meanwhile, the ciphertext size is independent of the number of ciphertext attributes, and the number of bilinear pairing evaluations is reduced to a constant. We prove that our scheme is semantically secure in the selective-set model based on the general Diffie-Hellman exponent assumption.