Data Hiding In Images

Published Date: 02 Nov 2017

ABSTRACT

Internet is the Backbone of Modern Communication. Whenever we need to transfer information from one place to another we use Internet. It has been used by almost every organization whether it is corporate or government worldwide. Since internet has been accepted worldwide for communication, security of transfer of information over Internet is one of the major issues of Internet Communication. Because information travels through internet it can be detected and/or attacked by Hackers or anyone who doesn’t have the provision of getting access to it. A solution to this problem could be a technique that can help in maintaining the secrecy of message being transferred. A technique that can hide the information well in such a manner that it is not visible. A technique that could prevent it from malicious attack in addition helpful in maintaining the secrecy of information is Steganography. In the proposed paper we will explain in brief what steganography is, how it is helpful in information hiding, its importance, comparison of steganography with cryptography and techniques to implement steganography.

KEYWORDS

Steganography, Cryptography, LSB-Least Significant Bit.

INTRODUCTION

Internet has been one of the most revolutionary developments. The rise of internet has introduced a new era of communication and it opens many doors for efficient and fast communication where people across the globe can communicate and share information with each other. As an individual we all use internet as well as various organizations whether they are corporate or government, schools, research facilities and college and libraries in more than Hundred Countries uses internet. Since internet is now being used worldwide it opens new doors for communication and it changes the whole face of communication and now millions or I should say billions of people across the globe are using internet for various purposes. Whatever being the purpose the backbone of internet is transfer of information from one place to other. So the most important aspect of making information travel on internet is to transfer it in such a manner that it cannot be accessed and/or modified by anyone other than the person for whom the message is being initiated. A solution to this problem is steganography in which we uses a technique by the existence of message is unknown to attackers means other than the intended receiver does not even know about the existence of message. Since tey don’t know about the existence they won’t be able to attack it. This approach of data hiding is known as Steganography.

Steganography is the art and science or an technique by which we can hide the information in such a manner that other than the sender and receiver no one knows about the existence of the message of information being transferred. Steganography helps in maintain the integrity of message as well prevent the message from malicious attack or unauthorized access/modification. Hence ensures securely delivery of message over the internet.

Steganography includes methods that can be used to hide message so that it could prevent the messages from being maliciously attacked by intruders. The goal is to hide the existence of messages over the internet and it uses the concept of data hiding. This concept of information hiding is now being used in variety of areas such as audio files, videos files and image files this kind of files are now a day’s come with a digital signature kind of a thing which is hidden yet distinguishable which can contain or represent a copyright notice or a serial number etc.

OVERVIEW

The word steganography is derived from the Greek words "stegos" meaning "cover" and "grafia" meaning "writing" [1] defining it as "covered writing". Steganography is a technique that can help in maintaining the secrecy of message being transferred. It is a technique that can hide the information well in such a manner that it could prevent it from malicious attack in addition helpful in maintaining the secrecy of information. Steganography uses the approach where we are hiding the information in such a manner that the intruder will never know that this hidden information ever exists or not. Before Steganography comes into the existence there was a technique called Cryptography how is it different from Steganography we will discuss it further. The topic of Steganography becomes the topic of interest and its growth was started for two main reasons[2]:-

The publishing and broadcasting industries have become interested in techniques for hiding encrypted copyright marks and serial numbers in digital films, audio recordings, books and multimedia products.

Moves by various governments to restrict the availability of encryption services have motivated people to study methods by which private messages can be embedded in seemingly innocuous cover messages.

DIFFERNT TYPES OF STEGANOGRAPHY

Even though steganography can be implemented on almost every digital files format. The four main category in which steganography can be applied are:-

Steganography can be applied to four file format namely text, audio/video, images, protocol

STEGANOGRAPHY VS CRYPTOGRAPHY

Before Steganography comes into the existence another concept known as Cryptography was used for data hiding. Even though both Steganography and Cryptography depends on the same principle of Data hiding both the terms Steganography and Cryptography has different meanings. Cryptography maintains the secrecy of message by adding public and private keys into it or by converting/encrypting the information into a format that can be only understood by the sender and the intended receiver. The intended receiver is the only person who can convert it back into readable form or we should say decrypt it by use of the secret keys. This approach may prevent unauthorized access into a message but since the message is still visible to the intruders the message/information is still exposed to attack and they can at least prevent this information to be reached to the destination. To solve this problem the concept of Steganography is introduced. Steganography is also based on the concept of Data Hiding but with a slight twist here we are hiding information in such a manner that the intruder will never know the hidden information ever existed or not. The difference between Steganography and Cryptography lies in that in Cryptography we are converting the information into a format which can be only understood by the intended receiver because he/she can decrypt it using the keys and can convert it back into readable format no other third party can read it however they may see the information they cannot understand it while in Steganography we are Hiding the information in such a manner that the third party intruder which is not allow to have access to the information will never come across to know that the information was ever existed or not. It’s like we are hiding the information in a kind of cover image so that no one would be able to see it [3].

TABLE 1 - Advantages and disadvantages comparison

Steganography

Cryptography

Unknown message

passing

Little known technology

Technology still being developed for certain formats

Once detected message is known

Many Carrier formats

Known message passing

Common technology

Most algorithms known to government departments

Strong algorithm are currently resistant to brute force attack

Large expensive computing power required for cracking

Technology increase reduces strength

IMAGE STEGANOGRAPHY

As per the research, images are the most popular means to implement steganography. They are used most commonly as cover objects.

There are many algorithms designed for image steganography.

Here, we will discuss LSB.

LEAST SIGNIFICANT BITS(LSB)

Least significant bit (LSB) insertion is a common, simple approach to embedding information in a cover image

[14]. The least significant bit (in other words, the 8th bit) of some or all of the bytes inside an image is changed

to a bit of the secret message. When using a 24-bit image, a bit of each of the red, green and blue colour components can be used, since they are each represented by a byte. In other words, one can store 3 bits in each pixel. An 800 × 600 pixel image, can thus store a total amount of 1,440,000 bits or 180,000 bytes of embedded data [19]. For example a grid for 3 pixels of a 24-bit image can be as follows:

(00101101 00011100 11011100)

(10100110 11000100 00001100)

(11010010 10101101 01100011)

When the number 200, which binary representation is 11001000, is embedded into the least significant bits of

this part of the image, the resulting grid is as follows:

(00101101 00011101 11011100)

(10100110 11000101 00001100)

(11010010 10101100 01100011)

Although the number was embedded into the first 8 bytes of the grid, only the 3 underlined bits needed to be

changed according to the embedded message. On average, only half of the bits in an image will need to be

modified to hide a secret message using the maximum cover size [19]. Since there are 256 possible intensities of

each primary colour, changing the LSB of a pixel results in small changes in the intensity of the colours. These

changes cannot be perceived by the human eye -thus the message is successfully hidden. With a well-chosen

image, one can even hide the message in the least as well as second to least significant bit and still not see the

difference [14].

In the above example, consecutive bytes of the image data – from the first byte to the end of the message – are

used to embed the information. This approach is very easy to detect [4]. A slightly more secure system is for

the sender and receiver to share a secret key that specifies only certain pixels to be changed. Should an

adversary suspect that LSB steganography has been used, he has no way of knowing which pixels to target

without the secret key [5].

In its simplest form, LSB makes use of BMP images, since they use lossless compression. Unfortunately to be

able to hide a secret message inside a BMP file, one would require a very large cover image. Nowadays, BMP

images of 800 × 600 pixels are not often used on the Internet and might arouse suspicion [19]. For this reason,

LSB steganography has also been developed for use with other image file formats

CONCLUSION

With this project I have learned a lot, especially about bit operations and bitmasking, something that I never understood before. This project was fun from the start and only got more interesting as I went on developing it. I became more interested in the subject the more I researched it.

I have learned that while implementing Image Steganography is important, thinking of how to detect and attack it and the methods to do so are far more complex than actually doing the Steganography itself. There is a lot of research that is beginning to discover new ways to detect Steganography, most of which involves some variation of statistical analysis. It is interesting to see what other methods will be developed and how accurate they will be at detecting Steganography.

FUTURE SCOPE

Although only major technique of image steganography is discussed in this paper. But, there exists large selection of approaches to data hiding techniques in images.all the major file formats have different techniques for data hiding. All, these techniques are large domain to work upon in future.