## 3 The Proposed Method
\begin{table}
\begin{tabular}{c l} \hline \hline
**Input** & \multicolumn{2}{l}{Stego image (S) and stego key (\(K\))} \\
**Output** & Secret message (\(m\)) \\ \hline
**Step 1** & Extraction process \\ \hline \multirow{4}{*}{**(a)**} & If [\(B_{\text{L,1}}\); \(B_{\text{R,1}}\) = [1; 0] \\  & i. & Save \(C_{\text{L,1}}\) as \(M_{1}\). \\  & ii. & Save \([B_{\text{L,2}}\); \(B_{\text{R,2}}\)] as \(M_{2}\). \\  & iii. & Repeat Step 1 with pixel number 3 of S. Continue with \(M_{3}\) and \(M_{4}\). \\ \hline \multirow{4}{*}{**(a)**} & If [\(B_{\text{L,1}}\); \(B_{\text{R,1}}\)] = [0; 1] \\  & i. & Save \([B_{\text{L,2}}\); \(B_{\text{R,2}}\)] as \(M_{1}\). \\  & ii. & Save \(C_{\text{R,1}}\) as \(M_{2}\). \\  & iii. & Repeat Step 1 with pixel number 3 of S. Continue with \(M_{3}\) and \(M_{4}\). \\ \hline \multirow{4}{*}{**(a)**} & If [\(B_{\text{L,1}}\); \(B_{\text{R,1}}\)] = [0; 0] \\  & i. & Repeat Step 1 with pixel number 2 of S. Continue with \(M_{1}\) and \(M_{2}\). \\ \hline \multirow{4}{*}{**(a)**} & If [\(B_{\text{L,1}}\); \(B_{\text{R,1}}\)] = [1; 1] \\  & i. & Save \(C_{\text{L,1}}\) as \(M_{1}\). \\  & ii. & Save \(C_{\text{R,1}}\) as \(M_{2}\). \\  & iii. & Repeat Step 1 with pixel number 3 of S. Continue with \(M_{3}\) and \(M_{4}\). \\ \hline \multirow{4}{*}{**Step 2**} & Continue step 1 until all \(M_{\text{pair}}\) have been extracted. \\ \cline{2-2}  & **Step 3** & Combine all extracted \(M_{\text{pair}}\) as \(M\). \\ \hline \multirow{4}{*}{**(a)**} & For \(K\) into \(Sum\) value. \\ \cline{2-2}  & & Find values of \(K\) components \(P_{1}\), \(P_{2}\), \(P_{3}\),..., \(P_{\text{k}}\) where \(k\) is the length of \(K\) using ASCII table. \\  & (e.g., \(K\) = AllZs) \\ \cline{2-2}  & i. & Refer ASCII table to search values of \(K\) components. \\  & & \(P_{1}\) = A = 65, \(P_{2}\) = 1 = 108, \(P_{3}\) = i = 105, \(P_{4}\) = f = 102, \(P_{5}\) = 2 = 50, \(P_{6}\) = s = 115 \\ \hline \multirow{4}{*}{**(b)**} & Compute \(Sum\) value using the following formula \\  & i. & \(Sum=\sum_{i=1}^{k}(P_{i}\times i)\bmod 256\) \\  & & \(=[(65\times 1)+(108\times 2)+(105\times 3)+(102\times 4)+(50\times 5)+(115 \times 6)]\bmod 256\) \\ \hline \multirow{2}{*}{**Step 5**} & Compute \(m\). \\ \cline{2-2}  & **(a)** & Set the bits in \(M\) as \(M_{\text{bit}}=M_{\text{b1}}\), \(M_{\text{b2}}\), \(M_{\text{b3}}\),..., \(M_{\text{bin}}\) where \(n\) is the length of \(M\). \\ \hline \multirow{2}{*}{**(b)**} & Set the permutated bits in \(M\) as \(f_{\text{bit}}=f_{1}\), \(f_{2}\), \(f_{3}\),..., \(f_{n}\) \\ \hline \multirow{2}{*}{**(c)**} & Set the bits in \(m\) as \(m_{\text{bit}}=m_{1}\), \(m_{2}\), \(m_{3}\),..., \(m_{n}\) \\ \hline \multirow{4}{*}{**(d)**} & Set the permutated bit position of \(M_{\text{bit}}\) as \(pos_{\text{bit}}=pos_{1}\), \(pos_{2}\), \(pos_{3}\),..., \(pos_{n}\). \\ \cline{2-2}  & & Find \(m\) by permuting \(M_{\text{bit}}\) using following formula. \\ \cline{2-2}  & i. & For \(1\leq i\leq n\), compute \(pos_{i}=(i-Sum)\bmod(n+1)\) \\ \cline{2-2}  & ii. & For \(1\leq i\leq n\), \(f_{i}=M_{\text{b}posi}\) \\ \cline{2-2}  & iii. & For \(1\leq i\leq n\), set \(m_{i}=f_{1}\) \\ \cline{2-2}  & iv. & Combine all \(m_{\text{bit}}\) as \(m\). \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The proposed extraction steps.