High Capacity Data Hiding by Detecting Weak Edges Through Declivity Operator

Region based steganography hides secret information in a particular region of the image. Here the regions are selected based on image attributes or the characteristics of human perceptions. The challenges of this kind of steganography approach are enhancement in capacity and the proper extraction of target data at the receiver side. Edge based steganography is special kind of region based approach where the data is embedded in edge pixel. In this paper, a new steganography method is proposed which uses the declivity edge detection technique to detect the edges. The use of declivity operator gives better edge detection in low contrast images and increases the no. of edge pixels. This increment of edge pixels helps in the enhancement of the capacity of stego media. The first five bits of each pixel of the cover image are involved in edge detection where the data is embedded in the last three bits of edge pixels. The non-involvement of LSBs ensures proper extraction of target data at the receiver side where embedding of three bits in each pixel helps in the improvement in capacity. Embedding not in all pixel of cover image also enhances stego quality.

I. Introduction

Steganography is the science of hiding digital information in such a way so that no one can suspect its existence. Although hiding data by using other techniques may arouse suspicions, steganography is a stealthy method which enables sending and receiving of data in total secrecy [1]. Steganography has been exploited throughout history by individuals, military, secret intelligence, and governments to stealthily communicate and transmit information without drawing any attraction. The objective of any steganographic technique is to meet three challenges - high capacity, robustness and imperceptibility, while embedding messages within the cover media [2].