Gandharba Swain ¹

Affiliations
1 Department of Information Technology, GMR Institute of Technology, Rajam-532127, Srikakulam, Andhra Pradesh, IN

Abstract

To provide higher embedding capacity without sacrificing the imperceptibility, a novel steganographic technique based on nine-pixel differencing with modified Least Significant Bit (LSB) substitution is proposed. The image is divided into 3×3 non-overlapping blocks. In each block the average difference value is calculated. Based on this value the block is classified to fall into one of the four levels such as, lower, lower-middle, higher-middle, and higher. If a block belongs to lower level then 2-bit LSB substitution is used in it. Similarly, for lower-middle, higher-middle, and higher level blocks 3, 4, and 5 bit LSB substitution is used. After LSB substitution the pixel values are readjusted to minimize distortion such that these modified values do not disturb the embedded bits. The experimental results reveal that the stego-images are imperceptible and hiding capacity is higher.

Keywords

Modified LSB Substitution, Nine-pixel Differencing, Pixel Value Differencing, Steganography

Full Text

   

Anita Pradhan ¹, K. Raja Sekhar ¹, Gandharba Swain ¹

Affiliations
1 Department of CSE, K L University, Vaddeswaram - 522502, Andhra Pradesh, IN

Abstract

Background/Objectives: This paper presents a steganographic method by calculating the pixel value differences along seven directions using nine-pixel blocks. Methods/Statistical Analysis: The centrally located pixel in nine-pixel block is used to form seven pairs with its seven neighboring pixels. The eighth neighbor pixel is used as the indicator to identify whether a block suffers with Fall Off Boundary Problem (FOBP) or not. Findings: Seven pixel value differences are calculated and based on these differences embedding is done. After embedding, the central pixel value is normalized to have a single value for all the seven pairs by suitable adjustments. After adjustments if any pixel value in the block falls off boundary, then the entire block is exempted from embedding. This is noted at the eighth neighbor pixel, so that it can also be exempted during extraction. Furthermore, to increase the capacity and peak signal-to-noise ratio, the nine-pixel blocks which suffer with FOBP are embedded using Wu and Tsai’s PVD method. The extraction process is very simple and the secret message can be extracted from the stego-image without using the original cover image. Application/ Improvements: Without compromising the security and imperceptibility the hiding capacity is almost 50% increased as compared to Wu and Tsai’s Pixel Value Differencing (PVD) method.

Keywords

Data Hiding, Fall Off Boundary Problem, Seven-Way Pixel Value Differencing, Steganography.

Full Text