Secure File Transmission System Using Steganographic Algorithm: Data Embodiment Using JPEG

Computer Science Project Material with Source Code Included

Abstract

Steganography is a technique that uses a combination of cryptography and steganography to hide data. In this paper, we propose a method of combining cryptography with STEGAG to solve the problem of unauthorized data access. We first encrypt a message using substitution cipher method and then embed the encrypted message inside a JPEG image using DCT in frequency domain. The combination of these two methods will enhance the security of the data embedded and will satisfy the requirements such as capacity, security and robustness for secure data transmission over an open channel. The proposed method will avoid illegal transmission of secret communication on the web and will provide a better secure system in case of Authentication.

Chapter One

Introduction

1.1 Background of the Study

In the field of Data Communication, security-issues have got the top priority. Internet users frequently need to store, send, or receive private information. The most common way to do this is to transform the data into a different form. The resulting data can be understood only by those who know how to return it to its original form. This can be done using Steganography or Cryptography. The word steganography is of Greek origin and it means “concealedwriting” from the Greek words steganos (στεγανός) meaning “covered or protected”, and graphia (γραυή) meaning “writing”. The first recorded use of the term was in 1499 by Johannes Trithemius in his Steganographia, a treatise on cryptography and steganography disguised as abook on magic (Choon, 2012; 2013).

Steganography is defined as the system of hiding secret or a confidential data in a cover media like image, text, video, and audio, in such a way that none other than the intended recipient knows the presence of data. In contrast to Cryptography, where the enemy is allowed to detect, intercept and modify messages without being able to violate certain security premises guaranteed by a cryptosystem, the goal of Steganography is to hide messages inside other harmless messages in a way that does not allow any enemy to even detect that there is a second message present”. In this digital world, both the concepts i.e. the cryptography and steganography hide the data from the unintended recipients or an intruder. Due to this fact, the authors prefer a multilayer security by using the benefits of steganography. The steganography concept can be implemented through various formats available worldwide. Various formats preferred are .jpeg, .gif, .png, .mp3, .mp4, .doc, .docx .bmp. Due to ease of availability of these formats on the internet, they are preferred to hide the secret message. Steganography research has been driven because of weakness in the cryptography systems that result in the security breach. Many tools and technologies created takes advantage of steganography techniques like coding in image, null ciphers, videos, audio, etc. (Cachin, 1998).

The goal of steganography is to avoid drawing suspicion to the existence of a hidden message. This approach of information hiding technique has recently become important in a number of application areas. Digital audio, video, and pictures are increasingly furnished with distinguishing but imperceptible marks, which may contain a hidden copyright notice or serial number or even help to prevent unauthorized copying directly (Chen and Wu, 2009).
Military communications system makes increasing use of traffic security technique which, rather than merely concealing the content of a message using encryption, seek to conceal its sender, its receiver or its very existence. Similar techniques are used in some mobile phone systems and schemes proposed for digital elections.
Some of the techniques used in steganography are domain tools or simple system such as least significant bit (LSB) insertion and noise manipulation and transform domain that involve manipulation algorithms and image transformation such as discrete cosine transformation and wavelet transformation. However, there are techniques that share the characteristic of both of the image and domain tools such as patchwork, pattern block encoding, spread spectrum methods and masking.

In contrast, steganography does not alter the structure of the secret message but hides it inside a cover-image so it cannot be seen. A message in cipher-text, for instance, might arouse suspicion on the part of the recipient while an “invisible” message created with steganographic methods will not. In other word, steganography prevents an unintended recipient from suspecting that the data exists. In addition, the security of classical steganography system relies on secrecy of the data encoding system. Once the encoding system is known, the steganography system is defeated. It is possible to combine the techniques by encrypting message using cryptography and then hiding the encrypted message using steganography. The resulting stego-image can be transmitted without revealing that secret information is being exchanged. Furthermore, even if an attacker were to defeat the steganographic technique and detect the message from the stego-object, he would still require the cryptographic decoding key to decipher the encrypted message.

1.2 Problem of Statement

In today’s society the most practical implementation of steganography is used in the world of computers. Data is the heart of computer communication and over the years a lot of methods have been created to accomplish the goal of using steganography to hide data. The trick is to embed the hidden object into a significantly larger object so the change is undetectable by the human ear.

As stated earlier, visible encrypted messages will draw suspicion from others. This will make them attempt to decrypt the cipher text. Indirectly it raises the chance of message being viewed by third party in the exception of sender and viewer. However, by hiding or embedding the text file into image, it is hard to raise the suspicion of others whether it contains any secret message or not as the processed image had not look different from the original image in naked eyes. This will make the message more secure. Indirectly, only the sender and receiver know the treat behind the image and hence ensure that the message can only be viewed by the sender and receiver.

1.3 Aim and Objectives

The primary aim of this project is to encode a message in an image in a way that avoids drawing suspicion to the transmission of the hidden message.

This project also comprehends the following objectives:

To store a text file (.txt) in image.
To protect the text file (.txt) from being viewed by third party using encryption.
To restore the stored text file in image.

1.4 Scope of the Study

In this paper we propose a technique of combining cryptography and steganography to solve the problem of unauthorized data access. Steganography also can be implemented to cryptographic data so that it increases the security of this data. In this method we first encrypt a message using substitution cipher method and then embed the encrypted message inside a JPEG image using DCT in frequency domain. A substitution cipher is one in which each character in the plaintext is substituted for another character in the ciphertext. Thus the content of the message appears meaningless to the third party. Thus it is very difficult to detect hidden message in frequency domain and for this reason we use transformation like DCT in our proposed technique. The combination of these two methods will enhance the security of the data embedded and will satisfy the requirements such as capacity, security and robustness for secure data transmission over an open channel. Furthermore, if an attacker were to defeat the steganographic technique to detect the message from the stego-object, he would still require the cryptographic method to decipher the encrypted message. The intended receiver should be able to recover the embedded data successfully, without any errors.

1.5 Significance of the Study

Secure data transfer by using steganography provides an efficient technique for data hiding by using covert channel. Covert channel is a subject which can be seen in many areas. Hiding the medium itself has a strong impact on the network communication providing high level of security and a more secure system respectively. The TCP/IP suite along with the covert medium further enhances the security of the system since attackers are more concerned over the “http”. The proposed technique will avoid illegal transmission of secret communication on the web and will provide a better secure system in case of Authentication.

This study will be of utmost importance to security agencies which transfer data electronically as the data transferred cannot be tampered with or information in it gotten except from authorized user with the key.
This thesis will serve as a reference point to scholars who are researching the field of online security as it will provide a basis for research

1.6 Definition of Terms

Steganography:

Steganography is defined as the system of hiding secret or a confidential data in a cover media like image, text, video, audio, in such a way that none other than the intended recipient knows the presence of data.

“Steganography” is the art and science of communicating in a way which hides the existence of the communication.
Cryptography: Cryptography is used to provide security to the plain text. It is used to encrypt the message with key so that no intruder can read the message and decrypt to get the message back.

Stego-object:

Refers to the object which is carrying a hidden message. So, given a cover object, and a message the goal of the steganographer is to produce a stego object which would carry the message.

Stego-image:

Refers to the object used as the carrier to embed messages into. Many different objects have been employed to embed messages into for example images, audio, and video as well as file structures, and html pages to name a few.

LSB:

Least Significant Bit.

Cipher-text:

The text representing the original text on encryption.

Cryptosystem:

This is a system for encryption and decryption of information.

RGB:

It is an acronym for colour images which means Red, Green and Blue.

Chapter Five

Summary, Conclusion and Recommendation

5.1 Summary

Steganography is a branch of cryptography. While most cryptography applications are used to encrypt information so that only the sender and recipient can understand it, steganography hides information that only the sender and recipient knows it exist. The secret message is hidden in plain sight. The public may see the data, unaware that a hidden message is present.

Steganography is used not only to digital images but also to other media such as voice, text and binary files, and communication channels.

Steganography can be used for a variety of reasons. Legitimate purposes include watermarking images for copyright protection. Digital watermarks are similar to steganography in that they appear to be part of the original object and is not easily detectable by the casual eye. Steganography can also be used to tag notes to online images and is used to maintain the confidentiality of valuable information.

Steganography can also be used for illegitimate purposes. For example, if someone was trying to steal data, they could conceal it in files and send it out in an innocent looking email or file transfer.

5.2 Conclusion

The security of the image steganography process mainly resides in the fact that the attacker does not know they are looking at a stego-image. If the message is hidden well enough in the cover image, then the attacker will not know to check the image. If, however, the attacker does try to decode the image, then they will potentially have to go through the entire key space to check for the key that decodes the image.

Image Steganography is very applicable to this day and age as the internet and social media are main communication avenues. A well-crafted stego-image could easily pass thousands of eyes without a second thought before it reached its destination and delivered a message.

5.3 Recommendation

For anyone wishing to develop this project further, I would suggest bringing the software more up-to-date. This could be achieved by reviewing the more recent stego-systems and considering how they can be attacked. It should hide all file formats as this allows for a much broader spectrum of uses: one would be able to encode .exe, .doc, .pdf, .mp3, .mp4, etc. The program would be more versatile because often hiding text just isn’t enough.

Alternatively, additional steganalytical functions could be added such that the system is better equipped to operate on a wider range of images. This could be done by implementing some more blind attacks such as through methods such as Machine Learning.

A more vigorous test strategy could also be developed such that the functions are scrutinized as much as possible, and any improvements could be made to the existing files. I feel this is important because if any of the processes are incorrect, then they cannot provide a good enough service for educating people in the field, and not can they be used on a more professional basis in the real world.

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