Large Universe CP-ABE With Whitebox Traceability

Abstract

In a ciphertext-policy attribute-based encryption (CP-ABE) system, decryption keys are defined over attributes shared by multiple users. Traceability is the ability of ABE to trace the malicious users or traitors who intentionally leak the partial or modified decryption keys for profits. Nevertheless, due to the nature of CP-ABE, it is difficult to identify the original key owner from an exposed key since the decryption privilege is shared by multiple users who have the same attributes. In this paper, we propose a new CPABE system that supportstraceability of malicious users who leaked their decryption privileges.Thistraceable CP-ABE does not weaken the expressivenessor efficiency when compared with the most efficient conventional(non-traceable) CP-ABE systems. In our newsystems attributes need not be fixed at system setup,the attributes’ size is not polynomially bounded and thepublic parameters’ size does not grow linearly with thenumber of attributes.