Reversible image steganography using cyclic codes and dynamic cover pixel selection

Abstract

One of the methods of steganography is LSB substitution using cyclic code. Whereas this method increases the PSNR of the cover image, it compromises on the embedding capacity, which is always less than 1 bit/pixel for a (n, k) single error correcting code. Also, this method is not reversible. This paper proposes a method of LSB steganography wherein any cyclic code can be used. The LSBs of the cover image pixels are selected dynamically depending on the secret message content. For a (n,k) code, a variable block of n pixels is selected each time, as against the traditional way in which fixed blocks of n pixels are taken. Every secret message bit is thus randomly placed in the cover image, increasing the robustness against steganalysis. There is an improvement in the embedding capacity as well, which can approach a value of k bits/pixel at best depending on the size and content of the secret message. Simulation results using Hamming code (7, 4) show an increase of approximately three fold in the embedding capacity as compared to the traditional method, while still maintaining a PSNR of around 60 dB which is equivalent to the PSNR of the conventional method.