An Improved Anonymous Buyer-Reseller Watermarking Protocol

Although digital watermarking protocols have been studied extensively for achieving copyright protection over the Internet for many years, the new issue of secondhand watermarking protocols has been largely ignored. Cheung and Curreem first proposed a buyer-reseller watermarking protocol for digital content redistribution in the second-hand markets. Later, Chen et al. showed that Cheung and Curreem’s scheme is vulnerable to malicious attacks and further proposed a simple improvement. However, in this paper, we show that the aforementioned schemes are still insecure, specifically by seller cheating problems, and propose an improved one. Moreover, the proposed scheme accounts for requirements of anonymity, unlinkability, coalition-resistance, and traitor traceability.