Analysis and Improving the Security of the Scalar Costa Scheme against Known Message Attack

The popular watermarking method with structured codebook is the scalar costascheme (scs) which is highly robust but poorly secure. known message attack (kma) isa type of the security attacks which its countermeasure is more difficult than others. thispaper proposes a novel scheme to increase security of scs in kma scenario. for thispurpose, the scs model is extended to a more general model. the security of generalizedscs (gscs) is analyzed using residual entropy as a security measure. then, fundamentaltrade-off between security and achievable rate of gscs is proved in kma scenario. basedon this trade-off and the practical security attack on scs, a new extension of scs isproposed, called surjective-scs (sscs). in comparison with scs, sscs clearly achievesmore security and achievable rate in low watermark to noise ratio (wnr) regime.