Abstract
The combination of pixel value differencing (PVD) and least significant bit (LSB) substitution gives higher capacity and lesser distortion. However, there are three issues to be taken into account: (i) fall off boundary problem (FOBP), (ii) pixel difference histogram (PDH) analysis, and (iii) RS analysis. This paper proposes a steganography technique in two variants using combination of modified LSB substitution and PVD by taking care of these three issues. The first variant operates on 2 × 3 pixel blocks and the second technique operates on 3 × 3 pixel blocks. In one of the pixels of a block, embedding is performed using modified LSB substitution. Based on the new value of this pixel, difference values with other neighboring pixels are calculated. Using these differences, PVD approach is applied. The edges in multiple directions are exploited, so PDH analysis cannot detect this steganography. The LSB substitution is performed in only one pixel of the block, so RS analysis also cannot detect this steganography. To address the FOBP, suitable equations are used during embedding procedure. The experimental results such as bit rate and distortion measure are satisfactory.
Highlights
Least significant bit (LSB) substitution is a very old image steganography approach, wherein the LSB bits of the pixels are substituted by secret data bits
This paper proposes a combination of modified LSB substitution (M-LSB) and pixel value differencing (PVD)
If the condition R−m − S−m > Rm − Sm is true, the RS analysis succeeds in detecting the steganography technique. From these figures it is evident that Khodaei and Faez’s technique and the proposed technique both escape from RS analysis. Steganography techniques, those using the principles of LSB substitution and PVD, need to address three issues: Percentage of the regular and singular pixel groups
Summary
Least significant bit (LSB) substitution is a very old image steganography approach, wherein the LSB bits (one, two, three, or four) of the pixels are substituted by secret data bits This simplest technique is detected by RS analysis. Wu and Tsai [1] exposed the fact that the edge regions in an image can conceal more amounts of data as compared to the smooth regions Based on this principle they proposed pixel value differencing (PVD) steganography. The PVD technique with block size 2 × 2 has been proposed to enhance the embedding capacity [2, 3]. Balasubramanian et al [18] proposed a PVD scheme with 3 × 3 size pixel blocks, to achieve higher hiding capacity. There are two main contributions in this paper: (i) discovering the FOBP that exists in Khodaei and Faez’s [11] technique (ii) and addressing it by proposing an improved technique with larger block size
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