Key-Policy Multi-Authority Attribute-Based Encryption
This work addresses the need for decentralized and flexible encryption systems in scenarios like cloud storage or access control, though it is incremental as it extends existing ABE frameworks to a new policy type.
The paper tackles the problem of constructing a multi-authority key-policy Attribute-Based Encryption (ABE) system, which had previously been limited to ciphertext-policy instances, and proposes a solution where authorities can be set up independently without coordination, proving security under the bilinear Diffie-Hellman assumption.
Bilinear groups are often used to create Attribute-Based Encryption (ABE) algorithms. In particular, they have been used to create an ABE system with multi authorities, but limited to the ciphertext-policy instance. Here, for the first time, we propose a multi-authority key-policy ABE system. In our proposal, the authorities may be set up in any moment and without any coordination. A party can simply act as an ABE authority by creating its own public parameters and issuing private keys to the users. A user can thus encrypt data choosing both a set of attributes and a set of trusted authorities, maintaining full control unless all his chosen authorities collude against him. We prove our system secure under the bilinear Diffie-Hellman assumption.