Design of image steganographic systems for covert communication

Abstract

The Steganography is a technique of embedding secret information in newlinethe cover object to generate stego object, which is almost same as newlinecover object. The Steganography does not attract intruders as in the case of cryptography technique. The steganography techniques, advantages, limitations, applications and definitions are discussed in detail in chapter one. The detailed literature survey of existing related works on spatial, transform and hybrid domain steganographic techniques are discussed in chapter two. The Wavelet based Non LSB steganographic technique is proposed in chapter three. The DWT/IWT is applied on cover image. The payload MSB bit pairs are converted into 2*2 matrix using identity matrix. The 2*2 HH subband of cover image is multiplied with 2*2 payload matrix to obtain modified HH band. The inverse wavelet transform is used on modified HH band to derive stego image. The PSNR value of projected algorithm is high as compared to existing algorithms. The secure steganography with scramble payload using LWT is discussed in chapter four. The secret image is decomposed into four equal parts and integer LWT is used on two parts. The transform domain coefficient values and pixel intensity values are converted into binary and index reversal is applied. The cube root is applied on each decimal value of index reversal bits to convert 8 - bits into 3 - bits length. The scramble 3 - bits of payload are implanted into XD subband of cover medium to obtain stego object. The Decision Factor ix Based Manipulation (DFBM) is applied on stego object for further scrambling of stego XD band. The inverse lifting wavelet transform is used on stego object to generate stego image. The payload is more secure, since index reversal, cube root and DFBM are used. The value of PSNR is high as compared to existing algorithms. In chapter five adaptive steganography using LWT is presented. The secret image is decomposed into two equal parts and LWT is used on one part.