Bidirectional Circular Shift-Based Reversible Steganography Algorithm with Dual Stego-Images

Reversible steganography with two stego-image deals with the embedding of secret data on another image that produce two stego-images in such a way that during extraction the initial cover image can be recovered. This research work proposes an algorithm capable of reversible hiding of data, which produce two stego-images based on bidirectional circular shifting i.e., shifting in clockwise and anti-clockwise direction. Initially, the approach involves categorizing the information into L bits and transforming it into a corresponding decimal representation. The two adjacent decimal number forms a pair such that the first decimal number is shifted in both clockwise and anticlockwise direction to produce clockwise value and anticlockwise value. From the clockwise value, anticlockwise value and secret decimal data a single minimum value is chosen with an index from which the minimum value is transformed on the basis of the minimum value’s histogram. The modified transformed values and indices are incorporated into pairs of cover image pixels to generate the stego-images. During the extraction process, adjusted transformed value and index are extracted from which the hidden data is reconstructed by finding the number of clockwise and anticlockwise shifts. Experimental evaluation shows higher Peak Signal-To-Noise Ratio (PSNR) than the conventional methods.