Abstract: A novel buyer-seller watermarking protocol was designed for piracy tracing. In the proposed protocol, a memoryless Watermark Certification Authority (WCA) was introduced, that can produce many watermarks for a buyer at a time and is not required to participate in each transaction of digital content between the buyer and seller. In order to guarantee the anonymity of the buyer, the WCA also can encrypt the digital certificate of buyer and hand over the encrypted message to seller via the buyer. In addition, the proposed protocol also can resolve other problems, such as the customer right problem, the binding attack problem, the digital conspiracy problem, the dispute problem. The analysis indicate that the proposed protocol is secure and practical.

Key words: Digital watermarking, Piracy tracing, Securer protocol