A Verifiable and Secret Buyer-seller Watermarking Protocol

A trusted third party (TTP) is introduced to the buyer-seller protocol to guarantee the transaction fairness in protocol. However, the TTP practically increases the cost in the buyer-seller protocol. To address this issue, we propose a novel buyer–seller watermarking protocol to eliminate the need for a TTP. By dividing the buyer’s secret key into two primary mechanisms: the buyer’s watermark, embedded in digital content, and the transaction number produced by the seller; the seller can verify buyer’s watermark without decryption. After inserting a digital watermark from the seller, the buyer cannot remove the watermark from the digital content without a watermark extraction algorithm. The seller cannot fabricate piracy to frame an innocent buyer. When piracy is found, it can be traced clearly because of the privacy homomorphism property. In other words, the proposed protocol can trace piracy and protect the customer’s rights without a TTP. Therefore, the conspiracy problem can be solved. The proposed protocol also can protect the anonymity of the buyer and bind the buyer’s watermark to digital content. Moreover, the buyer is no longer required to participate in the dispute resolution in our scheme.