An efficient and fair buyer–seller fingerprinting scheme for large scale networks

In digital watermarking, most existing schemes focus on the owners' copyright protection rather than protection of the customers' rights. Therefore, these schemes are unfair to legitimate customers who have no certificate to prove their right to use the watermarked digital content that they have purchased. In addition, these schemes are also unable to identify those who leak pirated copies of the watermarked digital content. To protect customers' rights and to identify the users of unauthorized copies, the fingerprinting technique is a feasible method for embedding a watermark so that content owners can identify users who have purchased the right to use the content and users who have not purchased this right. Although some fingerprinting schemes have been proposed in recent years, most of them are inefficient due to their homomorphic architecture that is based on public key cryptography. Therefore, in this paper, we propose a fair, traceable, and efficient watermarking scheme with a novel architecture. Due to the high computational complexity of the asymmetric cryptography, such as modular multiplications and exponentiations which lead much heavier burden than operations in symmetric cryptography, the proposed protocol transfers the demanding computational requirements from the buyer to a powerful server in protocol design. The proposed method can achieve these benefits: 1) the rights of legitimate buyers can be protected; 2) the proposed scheme is traceable; 3) the proposed scheme is more efficient than the previous schemes because public key cryptography is not frequently used; and 4) the buyer's anonymity can be well-protected until there is an infringement accusation.