Nested Two-Layer RGB Based Reversible Image Steganography Method

Abstract

In this study, a new reversible image steganography method based on Red-Green-Blue (RGB) which hides the
colored image into the colored images in two layers nested is proposed. The proposed method hides the 24-bit
image to be hidden by hiding two layers of data firstly in the resized version of the cover image with the LSB
method, and then hides the resized cover image to the original cover image with the 4-bit method. The proposed
method offers a secure communication environment as it hides the hidden image in two layers. When third
parties extract data by using the LSB method, they only access the resized version of the cover image. The 4-bit
method divides the image to be hidden into 8-bit segments. While the first 4 bits, which are the most important
bits of 8-bit data, are hidden directly, 4 bits that can be neglected with less significance are completed by rounding
at approximate value through the method function. In this way, since the 8-bit data is reduced to 4-bits, the
method performs lossy hiding, but doubles the hiding capacity. Peak signal to noise ratio (PSNR), structural
similarity quality criterion (SSIM) and chi-square steganalysis method, which are frequently used in the literature,
are used to measure the immunity level of the proposed method. When it is concealed at the same rate
with the LSB method and the proposed method, a higher measurement value is obtained in the PSNR image
criterion, which is 1.2 dB, SSIM 0.0025, BER 0.0129 and NCC image criterion 0.00027. In additional, it was
shown that the proposed method achieved more successful results in chi-square steganalysis and histogram
tests compared to the traditional LSB method.