International Journal of Recent Advances in Engineering & Technology (IJRAET)
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A Method to Hide Secret Information: Steganography
1Beant Singh, 2Kul Bhusan Agnihotri
1Research Scholar SRKWGSS, Ferozepur, India,
2Shaheed Bhagat Singh State Technical Campus, Ferozepur, India
Abstract—In this internet era, the information hiding and sending this hidden information to desired target has received much more attention. Sending secret information through a common communication technique becomes unavoidable, so distinct methods have been applied to hide the information. Among these methods, steganography is one of the methods to hide secret information in a cover so that, except sender and receiver, no one other knows that there is some secret hidden message is there or not. This paper put some light on the concept of steganography and its different techniques.
Index Terms— Information hiding, communication technique, secret information, steganography.
I. INTRODUCTION
In now days, with the development of computer and internet in all areas of human activities, there is great need of security of sending the secret information via internet. Various methods which were used for secure communication are listed as:
Cryptography
Coding-decoding
Invisible inks
HTML codes
Pagers
Colored glasses that filter all but intended wavelengths to make hidden messages visible Most frequently, for secret information communication, cipher text is used, in which plain text is converted into a code (called encryption) then this coded data is sent to the recipient. This coded data is understood only by those peoples who know how to decode this data. The main drawback in this method is that the coded data by this method is not hidden. Although the data is coded even then some expert might put his/her hard work to decode the coded data. So with the encryption of data, data hiding remains an important part for secure communication.
So for safe and secure communication, a latest technique called Steganography, is developed which is also known as science of hidden communication.
Steganography is the advanced method for hiding secret information than any other methods used so far. The major advantage of steganography over other methods is that by this method, even the existence of hidden secret message will not be observed at all, where as in other methods, one may observe the hidden secret message[1].
The word Steganography comes from Greek words
―stegos‖ whose meaning is ―cover‖ and ―grafia‖ whose meaning is ―writing‖[2]. So in earlier stages steganography is defined as the technique of ―covered writing‖. Modern steganography is the practice of hiding secret messages. The main objective of steganography is to hide the information in a cover, so that no one (other than sender and receiver who knows about hidden message) can even notice the presence of hidden secret message.
In present paper, we will discuss the concept of steganography and its different techniques.
II. TECHNIQUES OF STEGANOGRAPHY
A. Old Techniques of Steganography B. Modern Techniques of Steganography A. Old Techniques of Steganography
Steganography has been commonly used from different past era to till dates. Some known examples from the history of data hiding techniques (steganography) are:
Roman General (485-525 BC) used to shave the head of his servant messenger and write a message on his scalp. When the servant messenger‘s hair grew back, the General sent the servant messenger to deliver the hidden message to its desired recipient [3].
Pliny and Elder (AD 23-79) explained, how the milk of thithymallus plant was dried to transparency when applied on a paper but it becomes darkened brown when it is heated, this was one of the earliest method of invisible ink.
Ancient Chinese used to write notes (secret message) on small pieces of silk, then compressed it into balls and coated it with wax to be swallowed by a messenger and then recipient extract small piece of silk (on which secret message is written) from the messenger‘s gastrointestinal.
Ancient Greeks had used covered tablets with wax and had written secret message on it. The tablets were composed of wooden slabs. A layer of melted wax was poured over the wooden slab and allowed to harden as it dried. Hidden messages could be carved into the wood before covering the slab. When the melted wax was poured over the slab, the now concealed message was later revealed by the recipient when they re-melted the wax and poured it from the tablet [4].
In AD 1518, Johannes Trithemius wrote the first printed book on cryptology. He invented a steganographic cipher (a secret way of writing) in which each letter was represented as a word taken from a succession of columns. The resulting series of words would be a legitimate prayer.
Giovanni Battista Porta described how to convey a message within a hardboiled egg by writing on the outer shell of egg with a special ink made with a very small amount of potash alum (nearly 30 grams) and of vinegar (nearly 500 ml). The solution penetrates the porous shell, leaving no visible trace on the shell but the message is stained on the surface of the hardened egg albumen (white part of egg), so it can be read when the outer shell of egg is removed.
From the historical examples given above, it is clear that if a steganographic system‘s key are discovered, then the security of the system is explored. Simply shaving the hair of the head of everyone passing through a checkpoint, or melting the wax off of any discovered tablets disclose the existence of a hidden message.
B. MODERN TECHNIQUES OF
STEGANOGRAPHY
In 1985, steganography entered into the new era along with the development of personal computers, which has been used to solve various classical steganography problems. Currently, the emphasis has been on different forms of digital steganography. Commonly there are a number of digital technologies used for secure steganography, namely:
Text files
Still images
Audio Signal
Video signal Text files
Hiding information in text files is the most important method of steganography. By shifting the words, lines, open spaces and word sequence [5 - 8], a secret message can be hidden. An obvious method was used to hide a secret message in every nth letter of every word of a text message. Text steganography is very commonly used, where the amount of secret data is very small, because this technique of steganography is very simple to understand and rapid communication [9] is possible. But text steganography technique using digital files is
difficult to use when we have to send a large amount of secret data in one step [10] since text files have a very small amount hidden data.
Still Images
Images, especially on the Internet, give large amount of unnecessary bits present in the digital representation of an image, so images are the most popular cover objects for steganography.
Audio Signal
To hide information in audio files, similar techniques are used as for image files. One different technique unique to audio steganography is masking, which exploits the properties of the human ear to hide information unnoticeably [11-12].
Video Signal
Video steganography uses video as cover media for embedding secret data [13] .Videos can be said as a collection of frames and audio, either in compressed domain or in uncompressed domain. The advantage of using video files in hiding information is primarily because video is more secure against hacker attacks due to the relative complexity of video compared to image files and audio files [14]. A video-based steganography technique generally takes such analysis into account that tries to maintain the statistics of the secret message before and after message hiding.
III. CLASSIFICATION OF MODERN STEGANOGRAPHY
Steganography is mainly classified into two ways [15]:
Pure steganography
Secret key steganography Pure steganography
When there is no stego key is imposed over the cover messege, it is called pure steganography. In this type of steganography there is assumption that except the receiver and the sender, no one other is aware about the secret communication. A possible formula of this process may be represented as follows:
Cover medium +Embedded message = Stego medium And to recover the message from stego medium the process is as follows:
Stego medium = Cover medium +Embedded message Secret key steganography
In secret key steganography, the secret key is exchanged between receiver and the sender before the start of secret communication. This way of steganography is more secure than pure steganography. As the secret is imposed to protect the embedded message. A possible formula of this process may be represented as follows[16]:
Cover medium +Embedded message + Stego key = Stego medium
To recover the message from stego medium the process is as follows:
Stego medium + Stego key = Cover medium +Embedded message
IV. CHARACTERSTICS OF
MODERN STEGANOGRAPHY
There are mainly three aspects in designing the modern steganography systems [17]:
• Security
• Robustness
• Hiding capacity Security
The security refers to the ability of the receiver to detect the hidden information easily. Security can be increased by increasing the distortion. Distortion means unnecessary text along with hiding message. One thing should be clear that the distortion must be restricted to cover text and integrity of the stego text should be as such as before steganography.
Robustness
Robustness refers to the ability of saving the hidden data from unusual surroundings mostly when transmitted through internet. For a system to be considered robust it should have the following properties:
a) The quality of the cover media should not noticeably degrade upon addition of a secret data.
b) Secret data should not be detectable without the knowledge of secret key.
c) If multiple data are present in cover media and secret message they should not be interfere with each other.
Hiding Capacity
Hiding capacity refers to the amount of secret information which can be hidden in the cover medium. It tells us the ability of a cover media (text, image, audio or video) to store secret information. Capacity ratio of a good stego messege should be high, capacity ratio is defined as :
Capacity Ratio = Size of hidden secret message Size of cover media
V. FEATURES OF STEGANOGRAPHY
A steganography feature should be [18]:
A. Accurate: It means detect stego images with high accuracy and low errors.
B. Consistent: The accuracy results should be consistent.
C. Monotonic: Steganograhic features should be monotonic in their relationship with respect to the secret message size
VI. STEGANALYIS
The purpose of steganography is to avoid drawing suspicion to the transmission of hidden information. A message is hidden information in the form of plain text, images or anything that can be encoded into a bit stream.
But we know that properties of the media file (text, image, audio, video) are being affected after hiding secret information of it. As a result of this unusual characteristics are shown by the media file which can be observed by comparing with original media file, depending upon this a new technique is developed known as steganalysis. It is the technique to detect or estimate that some secret message is present in any given media (text, image, audio, video) file. Steganalysis is not only concerned with the presence of hidden message but also concerned with the functions of extraction of hidden message. Steganalysis can alter the hidden message,disable or destroy the hidden message [19,20].
The steganalysis technique depends upon the amount of information known about stego media file (text, image, audio, video). If more information is available to the attacker he can easily alter and destroy the secret message. In compact words we can say that staganalysis is the technique to detect steganography.
VII. APPLICATIONS OF MODERN STEGANOGRAPHY
Steganograhy is a technique which is used all over the world to hide information. It has various uses that can be classified in two types of categories [21]:
A. Legitimate Uses
1. Steganography techniques are widely used in protection of property secrets.
2. Steganography has vast uses in modern printers like as HP and Xerox brand color laser printers. These printers edit each page by adding dots which shows encoded printer‘s serial number, date and time.
3. Steganography becomes very mysterious along with watermarking. As watermarking technique‘s purpose is to extend the cover source with extra information (unnecessary data). By doing this people will not be able to detect the hidden or stego message.
4. Steganography is also used in forensic science.
Todays‘s forensic professionals should be aware of the proper use of steganography in any investigation. As along with the time, steganographic techniques are becoming more sophisticated and reliable. These techniques provides remarkable advantage to forensic professionals and becomes a valuable tool of the forensic tool kit.
5. Steganography offers a very important role in E-Commerce. In today‘s world, E-Commerce
transactions are readily used, in which each user is provided with a user Id and password and the user is protected by steganography techniques.
6. Steganographic techniques are used in National security systems for secure communication between military professionals and Governments.
B. Illegal Uses
Steganography is also being used in illegal way. There are many ways in which steganography technique is being used, especially related to computer/internet.
According to High Technology Crime Report illegal uses are classified into nine types:
1. Fraud
Steganography is used in cheating innocent people.
Steganographic techniques are used by devil minded people just for fun, money etc.
2. Hackers
Hacking is seconed bad illegal aspect in internet as well as in steganography technique. One can hack other‘s very secret information related to business, personal data etc.
Steganography plays a role of activator in hacking.
3. E-Payments
E-Payments meaning electronic payments are also very common in these days. But the hackers may attack the e-payment transactions.
4. Harassments
Steganography can be used to harass the people by stealing their personal information.
5. Criminal Communications
It is most dangerous and important misuse of steganography. If one destruction minded person uses steganographic technique along
with computer related techniques ,his potential will be doubled and it is very dangerous for the welfare of humanity.
6. Property Offences
One can dislclose the secret information related to property by using steganographic techniques.
Pedophilia
This is very illegal use of steganographic techniquesin which naked cover images of children are used to attract innocent people by exciting them in sexual way
7. Virsus
Sometimes, Steganography techniques along with computer related techniques can give birth to some sort of viruses. These system viruses can spoil the stored as well as current data of the system.
8. Gambling and Pornography
Some people enjoy to play gambling using new techniques like as steganography and internet.Pornography is the very shameful computer crime in which child‘s porn images and videos are used inside innocent images or sound files of stego medium.
Steganographyis very versatile technique .It should be used in positive sense and its negative use or illegai use should be controlled by cyber crime controllers so that one should not harassed by its negative use.
VIII. CONCLUSION AND FUTURE WORK
In this paper, various steganograhic techniques are discussed for embedding the secret data. Steganography is not only the method to hide the messege content but the messege itself. The purpose of steganography is to avoid drawing suspicion to the transmission of hidden information. A message is hidden information in the form of plain text, images or anything that can be encoded into a bit stream. This secret message is then embedded in a cover-carrier to create a stego-carrier. Unlike cryptography, steganography allows us to choose the cover object. In the end we can say that steganography and steganalysis are at earlier stage of research. Security and capacity of steganography needs serious intention for secret data communication.
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