Improvement of LSB Image Steganography Using Feistel Cipher
Rupesh Kumar Mohapatra, Spandan Udgata, Susmita Panda · 2024
In this paper, we have proposed an improved LSB image steganography method where unlike the existing LSB message text is encrypted using Feistel Cipher technique. In existing LSB, plain text is stored as binary bits in each of the pixels of the image, but in this proposed paper we have tried to encrypt the plain text further using Feistel Cipher technique. We have used JAVA as a tool to implement the entire steganography. Considering this LSB steganography, each pixel is selected randomly and the last bit of each colour component of a pixel is replaced by the binary bit of the string message. This process is more secured using another layer of security in form of Feistel Cipher. In the Feistel Cipher technique that we have used here, the plain text message is converted to 8bit binary format and then it is divided into two blocks ‘Left part’ and ‘Right part’ as per the concept of block cipher. We have used 16 rounds for our encryption, each round generating a random key. A function “f” is used which is a bitwise AND operation. In each round the bitwise AND is performed on the ‘Right part’ with the ‘key’ for that round and the corresponding result is XORed with the ‘Left Part’, then the final result is used as ‘Right part’ of next round. The ‘Left Part’ of next round is the ‘Right part’ of previous round. This process goes on for 16 rounds. Then the generated cipher text after all rounds is stored bit wise in the last bit of each of the colour components of the pixel in the cover image. The final image produced can be sent securely as the chances of suspecting and retrieving the message decreases significantly. Each pixel of the cover image with text differs by only “1”, from the original image thus making it imperceptible to human eyes. Similarly, the same reverse process is used to decrypt the encrypted image. The previously studied research papers have worked on calculating the efficiency or just the simple LSB steganography process where the plain message is encrypted as it is. But in our proposed paper, instead of selecting continuous rows of pixel we have chosen pixels from random positions thus making it hard for steganalysis to decrypt. Further unlike encrypting the message directly as suggested by previously proposed 90 research papers we have encrypted the message using Feistel cipher and the same is then encrypted onto the cover image. Payload, efficiency and degree of protection are used to measure the effectiveness of the proposed steganography procedure. The projected approach is appraised by the computation of Mean Squared Error (MSE), Peak Signal-to-Noise Ratio (PSNR) and structural similarity index (SSIM). The investigation shows that proposed LSB method has more improved PSNR and MSE, than the existing LSB, indicating strong and robust cover image quality. This paper LSB image steganography serves the purpose for securely delivering the message from sender to receiver getting it hidden in a cover image without being noticed by any third person.