A buyer-seller watermarking protocol

Digital watermarks have recently been proposed for the purposes of copy pro tection and copy deterrence for multimedia content, In copy deterrence, a c ontent owner (seller) inserts a unique watermark into a copy of the content before it is sold to a buyer. If the buyer sells unauthorized copies of th e watermarked content, then these copies can be traced to the unlawful rese ller (original buyer) using a watermark detection algorithm. One problem wi th such an approach is that the original buyer whose watermark has been fou nd on unauthorized copies can claim that the unauthorized copy was created or caused (for example, by a security breach) by the original seller. In th is paper, we propose an interactive buyer-seller protocol for invisible wat ermarking in which the seller does not get to know the exact watermarked co py that the buyer receives. Hence the seller cannot create copies of the or iginal content containing the buyer's watermark. In cases where the seller finds an unauthorized copy, the seller can identify the buyer from a waterm ark in the unauthorized copy, and furthermore the seller can prove this fac t to a third party using a dispute resolution protocol, This prevents the b uyer from claiming that an unauthorized copy may have originated from the s eller.