An Image Steganography Method Resistive to Fall Off Boundary Value Problem with Five Pixel Pair Differencing


Avinash K. Gulve - MCA Department, Government College of Engineering, Aurangabad, Maharashtra, India, Pin-431005 Madhuri S. Joshi - Computer Technology, Jawaharlal Nehru College of Engineering, Aurangabad, Maharashtra, India, Pin-431005


Although secret information can be securely hidden in the cover image using PVD approach, it suffers from fall off boundary problem especially when the pixel values are close to the boundaries. In the PVD approach, the pixel values of two pixels in a pair are so adjusted that the difference between these two pixel values represents the hidden information. But in this process, sometimes the pixel values exceed the boundaries and the cover image becomes unsuitable for hiding secret information. The proposed method is robust against the fall off boundary problem. Cover image is partitioned in the blocks of 2 × 3 pixels forming five pairs in each block. Difference value is calculated for each pair. If the difference value of at least one pair is greater than 127, the block is marked as edged block otherwise it is marked as smooth block. Fall off boundary problem is severe for edged blocks. Hence LSB substitution method is used for hiding secret data in the edged block and PVD approach is used for hiding secret data in smooth block. A separate selection process is used for selecting edged blocks for hiding secret data since hiding data using LSB substitution method can convert it into smooth block. This conversion of edged block into smooth block during embedding process results in the unsuccessful extraction of original secret data during extraction. The proposed method provides improved hiding capacity and PSNR values in comparison with existing image steganography methods based on PVD approach.