The CP-ABE with Full Verifiability Outsourced Decryption and White-Box Traceability

In the CP-ABE scheme, the private key is defined on attributes shared by multiple users. For any private key that can not be traced back to the owner of the original key, the malicious users may sell their decryption privileges to third parties for economic benefit and will not be discoverable. In addition, most of the existing ABE schemes have a linear increase in decryption cost and ciphertext size with the complexity of access structure. These problems severely limit the application of CP-ABE. By defining the traceable table to trace the user who intentionally disclosed the key, the cost of the decryption operation is reduced through the outsourcing operation, in this paper, a CP-ABE scheme was proposed that is traceable and fully verifiability for outsourced decryption. The scheme can simultaneously check the correctness for transformed ciphertext of the authorized user and unauthorized user. And this scheme supports any monotonous access structure, increasing traceability in the existing CP-ABE scheme will not have any impact on its security. This paper is proved to be selective CPA-secure in the standard model.