Attribute-Based Encryption with Publicly Verifiable Outsourced Decryption

Attribute-based encryption (ABE) is a useful cryptographic primitive for access control and fine-grained sharing on encrypted data. However, the main drawback of ABE is that the computational cost grows linearly with the complexity of the access policy. One of the promising solutions for the problem is to outsource computation securely. For example, the decryptor can outsource most of the decryption cost to others, while the underlying plaintext remains confidential. Nonetheless, the existing ABE with outsourced decryption cannot either outsource the decryption of existing ABE ciphertexts or support public verifiability. The first shortcoming demands that we need to design particular outsourced decryption for each ABE scheme. The second one hinders the use of ABE (with outsourced decryption) in the untrusted environment. To solve the above two problems, we propose a generic method to transform any ABE scheme (based on pairings) into an ABE scheme with publicly verifiable outsourced decryption. With the assumptions that the underlying ABE scheme is secure and that the one executing the outsourced decryption is rational, our proposal is secure.