IACR News item: 28 November 2012
Zhen Liu, Zhenfu Cao, Duncan S. Wong
ePrint ReportIn this paper we propose the first \\emph{Expressive Black-box Traceable CP-ABE} system which has two main merits: (1) it supports fully collusion-resistant black-box traceability, that is, an adversary is allowed to access an arbitrary number of keys of its own choice when building the decryption-device, and (2) it is highly expressive, that is, the system supports policies expressed in any monotonic access structures. In addition, the traceability of this new system is public, that no secret input is required and no authority needs to be called in, instead, anyone can run the tracing algorithm. We show that the system is secure against adaptive adversaries in the standard model, and is efficient, that when compared with the expressive (non-traceable) CP-ABE due to Lewko et al. in Eurocrypt 2010, our new system \\emph{adds} fully collusion-resistant black-box traceability with the price of adding only $O(\\sqrt{\\cal K})$ elements into the ciphertext and public key, rather than increasing the sizes linearly with ${\\cal K}$, which is the number of users in the system.
Additional news items may be found on the IACR news page.