An Expressive Decentralizing KP-ABE Scheme with Constant-Size Ciphertext

Decentralizing attribute based encryption is a variant of multi-authority attribute based encryption which doesn’t require a trusted central authority to conduct the system setup. In this paper, we propose an expressive decentralizing KP-ABE scheme with constant ciphertext size. In our construction, the access policy can be expressed as any non-monotone access structure. Meanwhile, the ciphertext size is independent on the number of attributes used in the scheme. We prove that our scheme is semantic secure in so-called Selective-Set model based on the n-DBDHE assumption. To the best of our knowledge, this is the first multi-authority attribute based encryption scheme realizing such expressive access policy and constant ciphertext size.