An Efficient Image Steganography Method Using Block-Based Indexing and LSB Substitution

A secure and efficient image steganography algorithm is proposed in this paper that uses block-wise indexing and LSB embedding. First, the cover image is divided into blocks of size 4 × 4. Blocks are classified as embedding blocks (E-Blocks) and index blocks (I-Blocks). Here, the 3-bit LSB substitution scheme is applied. The secret bits are matched with the least significant bits of the row pixels of the image, and the index values of those pixels are saved separately. In case of a mismatch, the secret bits are embedded in default pixels. The effectiveness of the proposed scheme is increased because the approach involves fewer changes to the cover image and does not use any deterministic extraction technique using indexing. The experimental results carried out by implementing the proposed scheme on various images of sizes ranging from 64 × 64 pixels to 512 × 512 pixels revealed that it produces high-quality images and efficient extraction. In the case of gray-scale images, the average PSNR, SSIM, and UIQI measures were found to be 55.64583 dB, 0.99869, and 0.99800, respectively, whereas for color images, their values turned out to be 49.19303 dB, 0.99209, and 0.99671. Overall, the presented technique provides an effective compromise between embedding capacity, invisibility, and robustness, thus being a good choice for secure image transmission applications.