Source Title: Advanced Digital Image Steganography Using LSB, PVD, and EMD: Emerging Research and Opportunities

Copyright: © 2019
|Pages: 28
DOI: 10.4018/978-1-5225-7516-0.ch005

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TopThis technique was proposed by Khodaei & Faez (2012). The embedding procedure is mentioned in the following steps.

**Step 1:**The image is raster scanned and divided into 1×3 size non-overlapping blocks, Figure 1. The pixels are designated as , , and .

**Step 2:**In k-bit LSB substitution is applied, where k is chosen from the list {5, 6, 7, 8}. The new value of is . Let L be the decimal value of the k LSBs of and S be the decimal value of k-data bits hidden in . The value can be further optimized using Eq. (1), where d=L-S.*(1)*

,**Step 3:**Using .the following two differences are calculated as in Eq. (2).*(2)***Step 4:**The Table 1 is range table for variant-1 and Table 2 is range table for variant 2.

Range table of variant 1

Range table of variant 2

**Step 5:**The value falls into a range whose embedding length is and lower bound is . Similarly, the value falls into a range whose embedding length is and lower bound is .**Step 6:**From the secret binary data stream bits of data is taken and converted to a decimal value . Similarly, from the secret binary data stream bits of data is taken and converted to a decimal value . Two new difference values and are computed as in Eq. (3). + , +*(3)***Step 7:**Using and two new values for namely, and .are calculated. Similarly, using and two new values for namely, and are calculated using Eq. (4). = - , = + , = - , = +*(4)***Step 8:**Now the stego value of , say is calculated using and . Similarly, the stego value of, say is calculated using and . This is done using Eq. (5) and Eq. (6).*(5)**(6)*

Hence the stego block is represented in Figure 2.

The extraction of secret embedded data can be done in the following manner. Suppose the stego-block is as shown in Figure 2 from which we have to extract the hidden data. The following steps are used.

**Step 1:**From the center pixel , k-LSBs are extracted. The value k is one of the values in the list {5, 6, 7, 8} which was chosen during embedding.

,**Step 2:**Using and , the difference value is computed. Similarly, using and , the difference value is computed as in Eq. (7).*(7)***Step 3:**The difference belongs to a range whose lower bound is and embedding length is . Similarly, the difference belongs to a range whose lower bound is and embedding length is . Refer the range table.**Step 4:**As in Eq. (8), using and , calculate the decimal value and convert to binary bits. Similarly using and , calculate the decimal value and convert to binary bits. = , =*(8)*

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