An anonymous buyer-seller watermarking protocol with anonymity control

Anonymity is one of important requirements for electronic marketplaces to offer similar privacy as current marketplace. Unfortunately, most watermarking protocols in the literature have been developed without considering a buyer's anonymity. It would be unsatisfactory for the buyer to reveal his/her identity to purchase multimedia contents. In this paper we propose an anonymous buyer-seller watermarking protocol, where a buyer can purchase contents anonymously, but anonymity control is provided, i.e., a seller can trace the identity of a copyright violator. The proposed scheme also provides unlinkability of contents purchased by a buyer. Another distinct feature of our scheme is that the identification of an illegal buyer is accomplished in a way such that the seller can directly convince a judge that the buyer has redistributed contents. This feature removes any possibility of dispute. Furthermore, when the innocent buyer is falsely accused by a malicious seller, it is possible to prove his/her innocence without attending a court and revealing any privacy.