High Capacity Image Steganography in the Spatial Domain Using Lehmer Code

Steganography is one of the modern techniques for covert communication through the internet. In addition to providing confidentiality, it also enables the communication of large amounts of data without raising suspicion. This paper presents a novel technique for image steganography using Lehmer code that provides high capacity and better performance. Lehmer code is a way of encoding each possible permutation of a sequence of n numbers. The pixel intensity values are perturbed such that the sorting order of the pixels within a neighbourhood encodes the message digit. If n is the number of pixels in the neighbourhood block then a message digit expressed in base ! n could be hidden. This allows high capacity embedding. In order to prevent high distortions of image, only blocks with variance below a set threshold is used for embedding. Experimental results show that the technique promises embedding capacities higher than 2 bits per pixel with minimal distortion. This technique also exhibits significant resistance against common steganalysis methods.