A NEW IMPERCEPTIBLE STEGANOGRAPHY METHOD FOR GRAYSCALE IMAGES

Abstract

A standard Least Significant Bit (LSB) algorithm changes average 50% of the least significant bits of an image. This causes approximately a 0.2% distortion on a grayscale image. Therefore, the application of LSB on non-sharp grayscale images causes too much noise that can be easily detected by the human visual system. In addition; when the image is scanned pixel by pixel, hidden message can be easily read by unauthorized persons. A robust and imperceptible block-based LSB steganography method is developed in this study. First, cover image is divided into blocks, then median geometric mean and arithmetic mean of each block is calculated to select blocks those contain less detail of the image. Method has an advantage of calculating data load capacity of image before embedding process. Proposed method also makes it difficult for unauthorized people to detect hidden messages. Performance of the method is measured by mathematical methods such as MSE, PSNR and SSIM. The method achieved structured similarity score over 0.9999% on four test images, indicating a 20-fold better result than the standard LSB algorithm.