Buyer-Seller Watermarking Protocols with Off-line Trusted Parties

In a buyer-seller watermarking protocol, buyers and sellers protect the ownerships or copyrights of their digital images or contents through the watermarks embedded in these images or contents. However, some attacks, such as the binding attack and the customer right problem, are threatening the security of the watermarking mechanisms. Moreover, the privacy of the buyers is not fully protected and the dispute between the buyers and the sellers cannot be fairly resolved. Although several buyer-seller watermarking protocols have been introduced in the literature, none can cope with all of the above problems. In this paper, we propose a novel buyer-seller watermarking protocol with an off-line trusted third party that can withstand these attacks and resolve the dispute between the buyers and the sellers fairly. Furthermore, our proposed protocol can guarantee the anonymity of the buyers as well.