On Hiding Secret Information in Medium Frequency DCT Components Using Least Significant Bits Steganography

This work presents a new method of data hiding in digital images, in discrete cosine transform domain. The proposed method uses the least significant bits of the medium frequency components of the cover image for hiding the secret information, while the low and high frequency coefficients are kept unaltered. The unaltered low frequency DCT co-efficients preserves the quality of the smooth region of the cover image, while no changes in the high DCT coefficient preserve the quality of the edges. As the medium frequency components have less contribution towards energy and image details, so the modification of these coefficients for data hiding results in high quality stego images. The distortion due to the changes in the medium frequency coefficients is insignificant to be detected by the human visual system. The proposed methods demonstrated a hiding capacity of 43.11% with the stego image quality of a peak signal to the noise ration of 36.3 dB, which is significantly higher than the threshold of 30 dB for a stego image quality. The proposed technique is immune to steganalysis and has proved to be highly secured against both spatial and DCT domain steganalysis techniques.