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92523945 Image Steganography Project Report

Apr 12, 2015




Image Steganography

AcknowledgementI would like to express my deep gratitude towards my project guide Dr. Ashish Khare for his able guidance and supervision which helped me for starting this project. I am extremely grateful and remain indebted to him for being a source of inspiration and for his constant support in the idea and starting of the project. I am thankful to him for his constant constructive criticism and invaluable suggestions, which benefited me a lot while starting the project on Image Steganography I would also like to thank to Prof R.R.Tewari and Dr. T.J. Siddhiquie who were directly and indirectly instrument in enabling me to stay committed for the project. I am also very much thankful to my parents and other family members for being such a great source of inspiration of mine.

Ashesh Mishra M.Sc.IIIrd Sem(2011-12) Computer Science

Image Steganography

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ObjectiveSubject of steganography, mainly focused on embedding text data in digital images. The goal of steganography is covert communication. So, a fundamental requirement of this steganography system is that the hider message carried by stego-media should not be sensible to human beings. The other 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. This project has following objectives: To product security tool based on steganography techniques. To explore techniques of hiding data using encryption module of this project To extract techniques of getting secret data using decryption module. Steganography sometimes is used when encryption is not permitted. Or, more commonly, steganography is used to supplement encryption. An encrypted file may still hide information using steganography, so even if the encrypted file is deciphered, the hidden message is not seen.

Image Steganography

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IntroductionThe word steganography is derived from the Greek words stegos meaning cover and grafia meaning writing defining it as covered writing. Steganography refers to the science of invisible" communication. Steganographic techniques strive to hide the very presence of the message itself from an observer. The general idea of hiding some information in digital content has a wider class of applications that go beyond steganography. Steganography is the process of hiding a secret message within a larger one in such a way that someone cannot know the presence or contents of the hidden message. Although related, Steganography is not to be confused with Encryption, which is the process of making a message unintelligibleSteganography attempts to hide the existence of communication. Steganography is the practice of hiding private or sensitive information within something that appears to be nothing out to the usual.

Image Steganography

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History of Steganography440 B.C. Herodotus recounts the story of Histaiaeus, who wanted to encourage Aristagoras of Miletus to revolt against the Persian king. In order to securely convey his plan. Histiaeus shaved the head of his most trusted slave and tattooed it with a message which disappeared after the hair had regrown. To instigate a revolt against Persians. The messenger, apparently carrying nothing contentious, could travel freely. Arriving at his destination, he shaved his head and pointed it at the recipient.

1st and 2nd World Wars German spies used invisible ink to print very small dots on letters. Microdots Blocks of text or images scaled down to the size of a regular dot.

Early SreganographyPictographs: e.g., Sherlock Holmess Dancing Men.

Come Here At OnceAlthough steganography is an ancient subject, the modern formulation of it is often given in terms of the prisoners problem proposed by Simmons, where two inmates wish to communicate in secret to hatch an escape plan. All of their communication passes through a warden who will throw them in solitary confinement should she suspect any covert communication. The warden, who is free to examine all communication exchanged between the inmates, can either be passive or active. A passive warden simply examines the communication to try and determine if it potentially contains secret information.

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If she suspects a communication to contain hidden information, a passive warden takes note of the detected covert communication, reports this to some outside party and lets the message through without blocking it. An active warden, on the other hand, will try to alter the communication with the suspected hidden information deliberately, in order to remove the information.

ApplicationsImage Steganography has many applications, especially in todays modern, hightech world. Privacy and anonymity is a concern for most people on the internet. Image Steganography allows for two parties to communicate secretly and covertly. It allows for some morally-conscious people to safely whistle blow on internal actions.

It allows for copyright protection on digital files using the message as a digital watermark. One of the other main uses for Image Steganography is for the transportation of high-level or top-secret documents between international governments. Image Steganography has many legitimate uses; it can also be quite nefarious. It can be used by hackers to send viruses and Trojans to compromise machines, and also by terrorists and other organizations that rely on covert operations to communicate secretly and safely.

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Basic Structure of SteganographySteganography is the practice of hiding private or sensitive information within something that appears to be nothing out to the usual. The basic structure of Steganography is made up of three components:

1. Carrier 2. Message 3. Key

Carrier - The carrier can be a painting, a digital image, an mp3, even a TCP/IP packet among other things. It is the object that will carry the hidden message. Message - The message (hidden) is being carried by the object (carrier). Key - A key is used to decode/decipher/discover the hidden message. This can be anything from a password, a pattern, a black-light, or even lemon juice.

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Steganography versus CryptographySteganography is often confused with cryptology because the two are similar in the way that they both are used to protect important information. The difference between two is that steganography involves hiding information so it appears that no information is hidden at all. If a person or persons views the object that the information is hidden inside of he or she will have no idea that there is any hidden information, therefore the person will not attempt to decrypt the information. Steganography differs from cryptography in the sense that where cryptography focuses on keeping the contents of a message secret, steganography focuses on keeping the existence of a message secret . Steganography and cryptography are both ways to protect information from unwanted parties but neither technology alone is perfect and can be compromised. Once the presence of hidden information is revealed or even suspected, the purpose of steganography is partly defeated. The strength of steganography can thus be amplified by combining it with cryptography.

Steganography Hide, Without altering Obfuscates the fact of communication, not the data Preventative deter attacks

Crypyography Alter, without hiding Obfuscates the data, not fact of the communication Curative - defends attacks

Two other technologies that are closely related to steganography are watermarking and fingerprinting. These technologies are mainly concerned with the protection of intellectual property, thus the algorithms have different requirements than steganography.

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Different kinds of steganographyAlmost all digital file formats can be used for steganography, but the formats that are more suitable are those with a high degree of redundancy. Redundancy can be defined as the bits of an object that provide accuracy far greater than necessary for the objects use and display. The redundant bits of an object are those bits that can be altered without the alteration being detected easily . Image and audio files especially comply with this requirement, while research has also uncovered other file formats that can be used for information hiding.

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Image SteganographyImage definitionTo a computer, an image is a collection of numbers that constitute different light intensities in different areas of the image. This numeric representation forms a grid and the individual points are referred to as pixels. Most images on the Internet consists of a rectangular map of the images pixels (represented as bits) where each pixel is located and its colour. These pixels are displayed horizontally row by row. An image is a rectangular grid of pixels. It has a definite height definite width counted in pixels. and a

Each pixel has a color. The color is a 32-bit integer. The first eight bits determine the redness of the pixel, the next eight bits the greenness, the next eight bits the blueness, and the remaining eight bits the transparency of the pixel.

We can think of an image as a function f. f: R2 R f (x, y) gives the intensity at position (x, y) Realistically, we expect the image only to be defined over a rectangle, with a finite range: f: [a,b]x[c,d] [0,1] A color image is just three functions pasted together. We can write this as a vector-valued function:

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Images are the most popular cover objects used for steganography. In the domain of digital images many d