Dual Image-Based Dictionary Encoded Data Hiding in Spatial Domain

Dual Image-Based Dictionary Encoded Data Hiding in Spatial Domain

Giridhar Maji (Asansol Polytechnic, Asansol, India), Sharmistha Mandal (Kanyapur Polytechnic, Asansol, India) and Soumya Sen (University of Calcutta, Calcutta, India)
Copyright: © 2020 |Pages: 19
DOI: 10.4018/IJISP.2020040105

Abstract

In the modern digital era, the privacy of personal communication is a serious concern to all netizens. A better way to preserve privacy could be to hide the secret message inside some innocent looking digital object such as image, audio, video, etc., which is known as steganography. A new steganographic scheme using a reference image along with the cover image has been proposed in this article. It enhances the robustness and security by increasing the obscurity of the hidden message. It also employs an additional dictionary-based encoding module to increase the hiding capacity as well as security. Experiments show that bit changes in the reference image are very few and undetectable to human perception, it also evades common statistical tests. Evaluation of standard quality parameters such as MSE, PSNR, UIQI, SSIM along with chi-squared statistics based embedding probability testing has been performed. When dictionary-based encoding is applied it further improves the quality parameters.
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Introduction

Every day more and more people are getting connected to each other digitally and digital communication follows. The biggest issue in digital communication is that the channel is unsecured and anyone can watch the traffic. So even if cryptography is used to encrypt private communication, hackers are free to collect the encrypted message and brute force. All modern encryption techniques with large key length are very computation heavy when a large amount of information needs to be encrypted. In recent time conventional computing devices like PCs and laptops are outnumbered by mobile and handheld smart gadgets and people do most of the personal communication through smart devices. Smart devices like mobile phone or pad have limited computation capability due to memory and (battery) power constraints. It will not be a good idea to encrypt a large amount of information before sending from smart devices as it will drain the battery. So, some light-weight alternative is required to preserve privacy without high computation intensive encryption.

Let us consider a scenario where a person (spy on another country) needs to transmit some important strategic information but all his communications are being monitored. If authorities find the slightest hint of any covert communication, then they might block or manipulate all his communications. So, the goal is here two-fold. First, the information must be secure and second the existence of such information must be hidden. For the sake of completeness two other practical use cases of steganography are discussed next. Intellectual property rights and copyright protection of online digital content are achieved through digital watermarking using steganographic techniques (Bhaskar & Oruganti, 2019; Singh & Siddiqui, 2013; Singh & Shaw, 2018; Parameswaran & Anbumani, 2007). In such cases, the goal is to hide the copyright mark inside the digital object in such a way that no one knows about it and cannot remove/modify it. Owner or creator of the digital object embeds his copyright mark using his own secret embed key and share publicly. If someone selling other’s content illegally then the original owner can establish his claim by extracting the hidden copyright mark using his secret embed key which is not available with anyone else. Another practical use case is establishing the integrity or authenticity of digital object. Suppose some photograph is being shared in social media which is actually morphed and manipulated. In such a situation fragile watermarking is used. It is also a type of steganographic technique where the objective is to embed/hide some mark in the media in such a way that any image manipulation would corrupt the hidden mark. So, the digital object could be authenticated by matching the extracted hidden mark from the image with the original mark put inside the source object.

Steganography along with encrypted embed key fills the gap perfectly. The term “steganography” derives its origin from two Greek words namely “steganos” and “graphien.” In Greek “steganos” means hidden or covered and “graphien” implies art of writing (Morkel, Eloff & Olivier, 2005). Steganography techniques hide the secret into some cover media in such a way that even the existence of the secret communication is not known to any third party hence reducing the risk of trying some brute force attack by adversaries (Ali, 2017). Nearest sibling of steganography known as cryptography. It encrypts a secret text into gibberish that cannot be deciphered without the information of the encryption key used and the concerned encryption algorithm. When an encrypted message is communicated through a public channel, all others including some attacker or watchdog, know about the communication and have access to the ciphertext. They have the opportunity to brute force or try any other means to decipher the message. In the case of steganography, no third party knows about the communication, hence does not attract hackers (Cheddad, Condell, Curran & Mc Kevitt, 2010).

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