Comments on a Buyer-Seller Watermarking Protocol for Large Scale Networks

Buyer-seller watermarking are protocols guaranteeing the buyer prevents false infringement accusations and the seller protects the watermark secrets from the buyer. Most recently, Chang et al. proposed an efficient and fair buyer-seller watermarking scheme for large scale networks quite recently. In this correspondence, we first shows its three weaknesses: the buyer can easily remove the watermark, the buyer can easily destroy the forensic information and the adversary can possibly learn about personal privacy of some honest customers. Thereafter, we suggest some countermeasures to defeat our described attacks while its merits are left unchanged.