A Hypothesis Testing Approach to Semifragile Watermark-Based -Authentication –java

This paper studies the problem of achieving watermark semi-fragility in multimedia authentication through a composite hypothesis testing approach. The embedding of a semi-fragile watermark serves to distinguish legitimate distortions caused by signal processing manipulations from illegitimate ones caused by malicious tampering. This leads us to consider authentication verification as a composite hypothesis testing problem with the watermark as a priori information. Based on the hypothesis testing model, we investigate the best embedding strategy which assists the watermark verifier to make correct decisions. Our results show that the quantization; based watermarking method is more appropriate than the spread spectrum method to achieve the best tradeoff between two error probabilities. This observation is confirmed by a case study of additive Gaussian white noise channel with Gaussian source using two figures of merit: relative entropy of the two hypothesis distributions and the receiver operating characteristic. Finally, we focus on certain common signal processing distortions such as JPEG compression and image filtering, and investigate the best test statistic and optimal decision regions to distinguish legitimate and illegitimate distortions. The results of the paper show that our approach provides insights for authentication watermarking and allows better control of semi-fragility in specific applications