Adaptive Watermarking Scheme Using Biased Shift of Quantization Index

Algorithm 3

Watermark extraction procedure

Procedure {Watermark_Extraction }

begin {

 initialize LFSR with a key (key_embed);

 for   𝑖=0  to  2^𝑚+𝑛−1{

  if   (LFSR_𝑝(𝑖)=^1”)  then    {

   if (⌊(𝑎^𝑏(𝑢,𝑣)+Δ_𝑏(𝑢,𝑣)/2)/Δ_𝑏(𝑢,𝑣)⌋=even)  then

      𝑤^𝑖=^0”  by (6);

   else    𝑤^𝑖=^1”  by (6); }}

 initialize LFSR with key (key_LFSR);

 for  𝐼=1  to  2^𝑚+𝑛−1{

  𝑥_𝑖=𝑧_{𝑚+𝑛−1}2^𝑚−1+𝑧_{𝑚+𝑛−2}2^𝑚−2+⋯+𝑧_𝑛+12¹+𝑧_𝑛2⁰;

  𝑦_𝑖=𝑧_𝑛−12^𝑛−1+𝑧_𝑛−22^𝑛−2+⋯+𝑧₁2¹+𝑧₀2⁰;

  𝑤^(𝑥_𝑖,𝑦_𝑖)=𝑤^(𝑖);}}

  apply one clock to LFSR; }

end {Watermark_Extraction }