CHAPTER ONE

INTRODUCTION

1. 1. Background of the Study

Since the rise of the Internet one of the most important factors of information technology and communication has been the security of information. Cryptography was created as a technique for securing the secrecy of communication and many different methods have been developed to encrypt and decrypt data in order to keep the message secret. Unfortunately, it is sometimes not enough to keep the contents of a message secret, it may also be necessary to keep the existence of the message secret. The technique used to implement this, is called steganography. Steganography is the art and science of invisible communication (Bin, 2011). This is accomplished through hiding information in other information, thus hiding the existence of the communicated information. The word steganography is derived from the Greek words “stegos” meaning “cover” and “grafia” meaning “writing” defining it as “covered writing”. In image steganography the information is hidden exclusively in images (Morkel et al., 2005).

The idea and practice of hiding information has a long history. In Histories, the Greek historian Herodotus writes of a nobleman, Histaeus, who needed to communicate with his son-in-law in Greece. He shaved the head of one of his most trusted slaves and tattooed the message onto the slave’s scalp. When the slave’s hair grew back the slave was dispatched with the hidden message (Silman, 2001). In the Second World War the Microdot technique was developed by the Germans. Information, especially photographs, was reduced in size until it was the size of a typed period. Extremely difficult to detect, a normal cover message was sent over an insecure channel with one of the periods on the paper containing hidden information (Morkel et al., 2005).

Steganalysis and steganography are the two different sides of the same coin. Steganography tries to hide messages in plain sight while steganalysis tries to detect their existence or even more to retrieve the embedded data. Both steganography and steganalysis received a great deal of attention, especially from law enforcement. While cryptography in many countries is being outlawed or limited, cyber criminals or even terrorists are extensively using steganography to avoid being arrested with encrypted incriminating material in their possession. Therefore, understanding the ways that messages can be embedded in a digital medium in most cases in digital images, and knowledge of state-of-the-art methods to detect hidden information, is essential in exposing criminal activity. Digital image steganography is growing in use and application. Many powerful and robust methods of steganography and steganalysis have been presented in many literatures over the last few years (Karampidis et al., 2018).

In Steganography, the most well-known techniques to data hiding in images are least significant bit (LSB) substitution, and masking and filtering techniques. LSB is a simple approach to embedding information in an image. But image manipulation can destroy the hidden information in this image. Applying LSB technique to each byte of a 24-bit image, three bits can be encoded into each pixel, as each pixel is represented by three bytes. Applying LSB technique to each byte of an 8-bit image, only one bit can be encoded into each pixel, as each pixel is represented by one byte. Least Significant Bit (LSB) embedding is a simple strategy to implement steganography. Like all steganography methods, it embeds the text data into the cover so that it cannot be detected by a casual observer. The technique works by replacing some of the information in a given pixel with information from the data in the image. While it is possible to embed data into an image on any bit-plane, LSB embedding is performed on the least significant bit(s) (Chitradevi et al., 2017).

1. 2. Statement of the Problem

According to government officials, terrorists use to hide secret textual information of their targets in images, which is quite evident that terrorist cells use the least significant bit method of steganography to conceal information and secretly communicate information among themselves. This is rumored to be a common technique used by Boko-Haram and other terrorist groups. This is been achieved by posting an encrypted image on a website or through an email for download by another terrorist cell and using the same steganography application program, the terrorist cell could then reveal the message with plans for a new attack, this in turn have been a major challenge for security agencies like the Nigerian Army and also the Nigerian army forward signal messages to its various units and formations in plain text format, which is susceptible to be read by anyone who happens to intercept the message signal and cause leakage of restricted intelligent information, as they have been losing a great chuck of restricted intelligent information to the public, thus the need for android based text encryption system.

1.3     Aim and Objectives of the Study

The aim of this project work is to design and implement an android based text encryption system using least significant bit steganalysis technique. To design and implement a software;

i. That allows the encryption and extraction of hidden textual message on an image using least significant bit technique.

ii. That will aid the Nigerian Army in concealing her signal text message data in images via steganalysis which is the hiding of one type of data(text) in another type of data format(images).

iii. That runs on any android mobile computing platform.

1.4     Significance of Study.

This research work will help in tackling the problems involve in other methods of steganalysis by using least significant bit method.

The Steganalysis using least significant bit is relevant in the following ways;

i.   The Steganalysis using least significant bit will aid in carrying out digital forensic investigation.

ii.  The designed software will be useful to law enforcement agencies in unveiling terrorist communication concealed in images via steganography.

iii. The proposed system will be also relevant in medical imaging and journalism to hide patients and news textual data in images.

1.5     Scope of the Study

This research is centered on encrypting and extracting hidden messages, embedded on images by using least significant bit steganalysis technique. The LSB based steganalysis will be based on encrypting textual data in image, taking a case study of the Nigerian Army.

1.6     Definition of Terms

1. Terrorist Cell: is a group of usually 3 to 5 members of a terrorist group to ensure operational security to the end that members of adjacent terrorist cells usually don't know each other or the identity of their leadership.
2. Communication: Communication is the act of conveying meanings from one entity or group to another through the use of mutually understood signs, symbols, and semiotic rules.
3. Cryptography: Cryptography or cryptology is the practice and study of techniques for secure communication in the presence of third parties called adversaries.
4. Data Extraction: is the act or process of retrieving data out of (usually unstructured or poorly structured) data sources for further data processing or data storage (data migration).
5. Decryption: Decryption is generally the reverse process of encryption. It is the process of decoding the data which has been encrypted into a secret format.
6. Encryption: Encryption is the process of encoding a message or information in such a way that only authorized parties can access it and those who are not authorized cannot.
7. Image: a representation of the external form of a person or thing in art.
8. Message: Message is a verbal, written, or recorded communication sent to or left for a recipient who cannot be contacted directly.
9. Parametric Model: a parametric model or parametric family or finite-dimensional model is a particular class of statistical models. Specifically, a parametric model is a family of probability distributions that has a finite number of parameters.
10. Steganalysis: is the study of detecting messages hidden using steganography; this is analogous to cryptanalysis applied to cryptography.
11. Steganography: Steganography is the practice of concealing a file, message, image, or video within another file, message, image, or video.
12. Technique: a way of carrying out a particular task, especially the execution or performance of an artistic work or a scientific procedure.
13. Text: text is any object that can be "read", whether this object is a work of literature, a street sign, an arrangement of buildings on a city block, or styles of clothing. It is a coherent set of signs that transmits some kind of informative message.