Ciphertext-policy attribute-based encryption with user and authority accountability

Abstract

To ensure the security of sensitive data, people need to encrypt them before uploading them to the public storage. Attribute-based encryption (ABE) is a promising cryptographic primitive for fine-grained sharing of encrypted data. However, ABE lacks user and authority accountability. The user can share his/her secret key without being identified, while key generation center (KGC) can generate any user’s secret key. In this paper, we propose a practical large universe ciphertext-policy ABE (CP-ABE) with user and authority accountability in the white-box model. As embedding the user’s identity information into this user’s secret key directly, the trace stage has only O(1) time overhead. The property of accountability is proved against the dishonest user and KGC in the standard model. We implement our scheme in Charm. Experiments show that CP-ABE of Rouselakis and Waters in CCS 2013 is enhanced in user and authority accountability by our method with small computational cost.