Security Flaws in Kuribayashi-Tanaka Fingerprinting Protocol

The buyer-seller watermarking protocol enables a seller to successfully identify at least one traitor from a pirated copy, while prevent the seller from framing an innocent buyer. Kuribayashi and Tanaka proposed a fingerprinting protocol whose objectives are : (1) a buyer can obtain a watermarked copy anonymously, (2) a seller can trace the illegal distributor effectively. However, this paper points out that Kuribayashi-Tanaka fingerprinting scheme has flaws in achieving the above objectives. Furthermore, we improve Kuribayashi-Tanaka fingerprinting scheme so as to patch the security flaws.