ABSTRACT

Steganography is the art of hiding information within other information in such a way that it is hard or even impossible to identify the existence of any hidden information. There are many different carriers for steganography. Of which, most popular ones are digital images. Due to recent developments in steganalysis, providing security to personal contents, messages, or digital images using steganography has become difficult. By using steganalysis, one can easily reveal existence of hidden information in carrier files. This project introduces a novel steganographic approach for covert communications between two private parties. The approach introduced in this project makes use of both steganographic as well as cryptographic techniques. The process involves converting a secret image into a text document, then encrypting the generated text into a cipher text using a key (password) based encryption algorithm, and finally embedding the cipher text on to a cover image. This embedding process is carried out using a threshold based scheme that inserts secret message bits into the cover image only in selected pixels. The security to maintain secrecy of message is achieved by making it infeasible for a third person to detect and retrieve the hidden message. The system is developed using Java programming language.

Keywords: Cipher, Cipher text, Steganalysis, Encryption, Decryption Least significant bits,

CHAPTER ONE

INTRODUCTION

1.1 Background of the Study

As the advancement of the internet increased, it has become an important factor in information technology and plays a vital role in communication. The security of information is becoming a bigger concern. Cryptography is the technique which secures the communication. There are various methods developed for encrypting and decrypting the information, which secures en-route messages. Due to the increase of the technology, sometimes cryptography is not enough for keeping the information as secret, it also important to retain the existence of the information while being secret. Steganography is the technique which is used to implement it. It is achieved by hiding the information inside other information, thus the existence of communicated message is hidden. This chapter provides the information about how steganography is different from cryptography and also how the steganography process is performed.

During the Second World War, Germans developed the Microdot technique. Using that technique, they have decreased the size of the information such as photographs to the typed period size. It is very difficult to detect, as the cover message is sent over a channel which contains the hidden message on one period of the paper. In today’s world steganography is most commonly used on computers with networks as the delivery channels and digital data as the carriers (Provos & Honeyman, 2003).

Steganography is different from the cryptography because cryptography focuses on keeping information secret whereas steganography focuses on making the existence of the information secret. Though both ways are used to protect the data/information from outsiders, the technology is not perfect and can compromised. Once it is suspected or revealed that the hidden information exists, the steganography purpose is defeated partly. Steganography can be strengthened by combining it with the cryptography. It is known that watermarking is a method used for hiding the trademark information in software, images and music. It is not considered as original form of steganography (Patel, & Tahilraman, 2016). In steganography the message is hidden in the image, but watermarking will add something on top of the image for example a word “Confidential”, which will become part of the picture. There is a misconception that steganography is related or similar to encryption, but in real they are different. Encryption is a technology which converts the message from a readable to an unreadable format for protecting the sensitive data. Whereas, in steganography the information is hidden from the plain view and it is not mandatory to be encrypted.

There are currently many steganographic techniques in place such as JSteg, JPHide and JPSeek, OutGuess, F3, F4 and F5. Analysis shows that they each have one drawback or the other. In this project, using a multilevel approach, we provide high level security to sensitive digital data against steganalysis techniques, while keeping the operational time low. This objective is achieved by encrypting and authenticating the image that has user’s sensitive data and then embedding the resultant document on to a carrier.

1.2 Statement of the Problem

Currently many cryptography and steganography techniques have come into existence. Encoding of plaintext is acheived using DES, AES, Triple DES, RSA and many other algorithms. Any individual can use his/her one’s own approach as encryption method. Many algorithms such as JSteg, JPHide and JPSeek, OutGuess, F3, F4 and F5 were invented for the purpose of embedding images. These algorithms follow a certain principle to embed and retrieve hidden contents. All the existing approaches have their own disadvantages as they can easily be compromised using steganalysis. It means that one way or another, an intruder can figure out the existence of hidden data which results in him/her compromise of sensitive data. Currently, no integrated cryptography and steganography approach in one application exists for image based information security. There are encryption and embedding approaches present that work with plaintext only.

All the available techniques used in early tools are old and follow some specified process with some improvements to previously proposed techniques. This makes the intruders work easy. The intruder may try a counter attack by making some changes to counter existing techniques. None of the existing techniques offers protection through multiple levels. That is one of the reasons why an intruder is able to view/obtain hidden data with just one or two attacks.

1.3 Aim and Objectives of the Study

The main aim of this study is to design a steganographic system using a secured encryption algorithm. To achieve the stated aim, the following specific objectives were laid out:

i. Use a multilevel approach for data hiding which involves encryption of data and embedment of the encrypted data in the image.

ii. The encrypted text is locked with a personal password which only the intended receiver has.

iii. The system should be efficient while providing a low operational time.

iv. The encrypted image must not be distorted either in appearance or size to avoid drawing suspicion to the existence of hidden information in it.

1.4 Justification of the Study

Initially, there were not many tools that could block the cryptanalysis or steganalysis attempts at various levels to secure/protect the hidden data in text or carrier media respectively. There were many situations this tool was needed. For, example attacks on military secrets and plans were occurred many times in many countries. Data hiding is a very important viewpoint of any user who transmits confidential information through networks. Sometimes trade secrets may have to be shared among different industries. In the same way, there can be many situations that require data hiding. Though there were many methods introduced for data hiding, still there has been a challenge. Many of them were designed in a way that follows the approach which shows a small change to previously introduced approaches. Each of them has their own disadvantages. Few of which are discussed in this document.

Digital images are being used as most common carriers to hide secret messages because the human visual system (HVS) has limitations. That is, the human visual system has no function like abstracting the illusion effects on what it looks. Steganography took advantage of using digital images so that small visual changes to an image cannot be suspected. Essentially any media such as plaintext, cipher text, can be hidden in a digital image that can be converted into a bit stream.

The new tool proposer here is a combination of both cryptography and steganography. This tool uses a digital image as a carrier to take advantage over HVS. This tool would try blocking an analyst through multiple levels up to maximum extent. The mechanism of this new tool is discussed below along with some screen shots of the tool while running it.

1.5 Methodology

This project uses waterfall model for the system development. Waterfall model was the first process model to be introduced and followed widely in software engineering to ensure success of a project. In the waterfall approach, the whole process of software development is divided into separate process phases. The phases in the waterfall model are: Requirement specification phase, Software design, Implementation and maintenance. All these phases are cascaded to each other so that second next is started as and when defined set of goals are achieved for previous phase. General overview of waterfall model is as follows.

1.6 Significance of the Study

The developed steganographic tool is a very useful to any user who shares confidential data through a network. The developed model has a customized access that gives more freedom to users. An interface has been developed that helps the user to interact with the tool. The interface is very user-friendly with different modules implemented to encode and decode the secret message. The developed tool was tested for various input conditions.

1.7 Scope and Limitation of the Study

The primary idea behind developing this project is to protect confidential data from an intruder’s counter-attacks and to block the intruder through various levels in his/her attacks. A new tool has been developed with a combination of cryptographic encryption and steganographic encryption for its implementation. The developed steganographic tool has a sender’s segment that can take a message, a password and a cover image as input and give a stego-image as output that has message embedded in it. On the other hand, it also has a receiver’s segment where the receiver inputs the stego-image and the same password is used 

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