**6.2 Watermark detection**


**Figure 2.** *Watermark embedding for wavelet coefficients in the proposed scheme.*

**Figure 3.** *Watermark detection in the proposed scheme.*

The quantization process is done as shown in Eq. (7):

watermark embedding in a positive wavelet coefficient.

(excluding the LL3 and HH3 sub-bands).

*Watermark embedding for wavelet coefficients in the proposed scheme.*

**6.2 Watermark detection**

*Cyberspace*

**Figure 2.**

**Figure 3.**

**104**

*Watermark detection in the proposed scheme.*

If ¼ 1 and >0*,*then ¼ t2 � X1*,* If ¼ 0 and >0*,*then ¼ t1 þ X1*,* If ¼ 1 and<0*,*then ¼ �t2 þ X1*,*

where is the watermark bit corresponding to, and is the watermarked wavelet coefficient. The parameter x1 narrows the range between the two quantization levels t1 and t2 in order to perform a robust oblivious detection. **Figure 2** shows the

5. After all the selected coefficients are quantized, the inverse discrete wavelet transform (IDWT) is applied, and the watermarked image is obtained.

1. The possibly corrupted watermarked image is transformed into the wavelet domain using the same wavelet transform as in the embedding process.

2. The extraction is performed on the coefficients in the third wavelet level

less than or equal to t2 � X2 are chosen, which are named *<sup>w</sup>*0*<sup>s</sup>*

3. All the wavelet coefficients of magnitude higher than or equal to t1 + X2 and

value of X2 should be lower than the value of X1. This maintains that all the marked coefficients are recovered and dequantized after being attacked. The determination of parameters X1 and X2 to the watermarking technique gives a

If ¼ 0 and<0*,*then ¼ �t1 � X1*,* (7)

*ij*. Note that the

degree of tolerance to the system against attacks, i.e., the extraction of watermark bits from the selected wavelet coefficients is done using Eq. (8).

$$\text{If } < (\mathbf{t}1 + \mathbf{t}2)/2 \text{, the recovered watermark bit is 0.}$$

$$\text{If } \ge (\mathbf{t}1 + \mathbf{t}2)/2 \text{, the recovered watermark bit is 1} \tag{8}$$

The watermark detection process can be shown in **Figure 3**.

Then the correlation process is applied between the recovered watermark and the original watermark, obtained via the secret key, just only in the locations of the selected coefficients.
