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  2. 2. What is Steganography ? Is the art and science of writing messages in such a way that the existence of the communication is hidden Steganography is often confused with cryptography Both are used to protect confidential information Cryptography: although encrypted and unreadable, the existence of data is not hidden Steganography: no knowledge of the existence of the data
  3. 3. HISTORY OF STEGANOGRAPHY In 480 BC Greek history Histaiacus & the king of Persia. Ancient Rome - 1499, Steganographia, the first book about steganography Mary Queen of Scots Invisible inks and Microdots in World War II 5 x 5 Tap code used by Armed Forces prisoners in Viet Nam (Morse Code)
  4. 4. MODERN DAY APPLICATION OF STEGANOGRAPHY Applied in digital watermarking Watermarking is about establishing identity of information to prevent unauthorized Use of microdots to mark equipment Use of subliminal suggestion anything that sends you a message without your Knowledge of It, usually picked up on by your subconscious mind, often violent thoughts, that can be left un harmed to slowly work its way into your brain. people rarely catch them, even when they are right in front of their eyes--more obvious than anything. Suspected as Communication tool used by Al-Qaeda
  5. 5. TYPES OF STEGANOGRAPHIC TECHNIQUES There are basically three steganographic techniques : 1. Pure steganography 2. Secret key steganography 3. Public key steganography
  6. 6. CHARACTERISTICS OF STEGANOGRAPHY CAPACITY The notion of capacity in data hiding indicates the total number of bits hidden and successfully recovered by the stegosystem. ROBUSTNESS Ability of the embedded data to remain intact if the stego-system undergoes transformation, such as linear and non-linear filtering; addition of random noise; and scaling, rotation, and loose compression. UNDECTETABLE The embedded algorithm is undetectable if the image with the embedded message is consistent with a model of the source from which images are drawn.. INVISIBILITY (PERCEPTUAL TRANSPARENCY) This concept is based on the properties of the human visual system (HVS) or the human audio system (HAS). SECURITY The embedded algorithm is secure if the embedded information is not subject to removal after being discovered by the attacker and it depends on the total information about the embedded algorithm and secret key.
  7. 7. CLASSIFICATION OF STEGANOGRAPHICAL TECHNIQUES Steganographic techniques categorized according to: The type of covers used for secret communication or According to the cover modifications applied in the embedding process. From the second approach, the steganographic methods are grouped in six categories, although in some cases an exact classification is not possible.
  9. 9. SUBSTITUTIONAL SYSTEMS Basic substitution systems try to encode secret information by substituting insignificant parts of the cover by secret message bits. The receiver can extract the information if he has knowledge of the positions where secret information has been embedded. Since only minor modifications are made in the embedding process, the sender assumes that they will not be noticed by an attacker.
  10. 10. SUBSTITUTIONAL SYSTEMS CONTINUE.. Least Significant Bit Substitution (LSB). Pseudorandom Permutation Image Downgrading and Cover Channels Cover Regions and Parity Bits Palette-Based Image
  11. 11. TRANSFORM DOMAIN Transformation domain methods hide message in a significant area of the cover image which makes them more robust to attack, such as adding noise, compression, cropping some image processing. Many transform domain variations exist. Common used are: Discrete Cosine Transformation (DCT) Wavelet transforms. Transforms embedding embeds a message by modification (selected) transform (e.g., frequency) coefficient of the cover message
  12. 12. SPREAD SPECTRUM TECHNIQUE Spread spectrum techniques are now widely used in military radio communications, due to their very high robustness to detection and extraction The carrier's frequency is continually shifted using a pseudorandom noise generator fed with a secret key. In this way the spectral energy of the signal is spread over a wide band, thus decreasing its density, usually under the noise level. To extract the embedded message, the receiver must use the same key and noise generator to tune on the right frequencies and demodulate the original signal. A casual observer won't be able even to detect the hidden communication, since it is under the noise level
  13. 13. OTHER STEGANOGRAPHICAL TECHNIQUES Statistical method Distortions techniques Cover generating methods
  14. 14. STEGANOGRAPHY IN APPLICATION Greece slaves were used to play this role, in present times, various types of data files have the potential for this function. Therefore file formats can be assigned to the following domains: text, image, audio, video, and program files.
  15. 15. STEGANOGRAPHY IN APPLICATION CONTINUE CHOOSING MEDIA TYPE Based on the weakness of the human visual systems (HVS) and the human audio systems (HAS), most steganographical tools take advantages of this weakness and embeds secrete messages within media files. ENCRYPTION Encrypting a stega-media in most cases is an option but it helps to improve the authenticity and security of the steganographical scheme.
  16. 16. STEGANOGRAPHY IN APPLICATION CONTINUE EMBEDDING Steganography encompasses methods of transmitting secret messages in such a manner that the existence of the embedded message is undetectable. Among these, most methods are employed depending upon characteristics specific to a carrier type or format while other methods may work without relying on a specific file format. Most commonly employed message embedding techniques: Embedding data into text Embedding data into images, audio and video Embedding data into program files Embedding data into archive files Embedding data into network protocols
  17. 17. EMBEDDING DATA INTO TEXT In this technique the message is hidden within a plain text file using different schemes like: use of selected characters. extra white spaces of the cover text. There are some online tools for doing textual steganography, the most famous is
  18. 18. EMBEDDING DATA INTO IMAGES, AUDIO AND VIDEO Numerous methods exist for hiding information in audio, images, and video. Some common embedding techniques range from least significant bit (LSB) manipulation over masking and filtering to applying more sophisticated image or audio processing algorithms and transformations LSB methods insert the embedding data in the carrier byte stream, substituting insignificant information in a carrier file with secret data. Some tools utilize two least significant bits or even more to hide a message
  19. 19. EMBEDDING DATA INTO IMAGES, AUDIO AND VIDEO CONTINUE.. In general there are two types of LSB embedding which apply to images: 1. Simple LSB embedding in raw images Change LSB in one up to all three colour channels of the pixel Increment/decrement the pixel value instead of flipping the LSB Matrix encoding 2. LSB embedding in palette images Change color index to similar palette entry (e.G. Ezstego) Change palette entry
  20. 20. EMBEDDING DATA INTO IMAGES, AUDIO AND VIDEO CONTINUE.. The LSB manipulation concept can also be applied to audio. The least significant bit of information at each audio sampling point is replaced with a bit from the hidden message. This method introduces significant noise into the audio file.
  21. 21. EMBEDDING DATA INTO IMAGES, AUDIO AND VIDEO CONTINUE.. LSB manipulation is a quick and easy way to hide information but is vulnerable to small changes resulting from file processing or lossy compression. Another technique for hiding data into image or multimedia files is called appending which means that the secret data is added after the very last byte of the carrier file
  22. 22. EMBEDDING DATA INTO PROGRAM FILES The common technique for hiding data in program files is appending the data at the end of the carrier file as practiced with image, audio, and video files. Another possibility is stashing a secret message by transforming program instructions. This technique substitutes an instruction by an equivalent which represents the bit(s) of the secret data. A simple example: add %eax,+50 can be substituted by sub %eax, -50.
  23. 23. EMBEDDING DATA INTO ARCHIVE FILES The secret data is embedded during the compression process through overwriting the least significant bits.
  24. 24. EMBEDDING DATA INTO NETWORK PROTOCOLS The embedding process in network protocols takes place by manipulation of unused spaces and other features of the packet header. The most common tools for embedding data into network protocols are found in this website
  25. 25. STEGANALYSIS TECHNIQUES Steganalysis is the process of identifying steganography by inspecting various parameter of a stego media. Steganalysis process determines whether that media contains hidden message or not and then try to recover the message from it. Most techniques are based on Network Steganography and Visual detection steganalysis
  26. 26. STEGANALYSIS TECHNIQUES CONTINUE.. In the case of network steganography unusual patterns are introduced in the TCP/IP packet header. If the packet analysis technique of intrusion detection system of a network is based on white list pattern (unusual pattern), then the method of embedding data into network protocol can be defeated.
  27. 27. STEGANALYSIS TECHNIQUES CONTINUE.. In the case of Visual detection steganalysis technique a set of stego images are compared with original cover images and not the visible difference. Signature of the hidden message can be derived by comparing numerous images. Cropping or padding of image also is a visual clue of hidden message because some stego tool is cropping or padding blank spaces to fit the stego image into fixed size. Difference in file size between cover image and stego images Increase or decrease of unique colors in stego images.
  28. 28. Steganography Attacks Steganographic attacks consist of detecting, extracting and destroying hidden object of the stego media. Steganography attack is followed by steganalysis. There are several types of attacks based on the information available for analysis. known carrier attack: the original cover media and stego media both are available for analysis steganography only attack: In this type of attacks, only stego media is available for analysis. Known message attack: the hidden message is known in this case. Known steganography attack: The cover media, stego media as well as the steganography tool or algorithm are known.
  29. 29. ADVANTAGE OF STEGANOGRAPHY The advantage of steganography, over cryptography alone, is that messages do not attract attention to themselves. Plainly visible encrypted messages-no matter how unbreakable-will arouse suspicion, and may in themselves be incriminating in countries where encryption is illegal. Therefore, whereas cryptography protects the contents of a message, steganography can be said to protect both messages and communicating parties.
  30. 30. CHALLENGE BROUGHT BY STEGANOGRAPHY Steganography pose a serious problems because it's difficult to detect. Network surveillance and monitoring systems will not flag messages or files that contain steganographic data. Therefore, if someone attempted to steal confidential data, they could conceal it within another file and send it in an innocent looking email.
  31. 31. CONCLUSION Steganography transmits secrets through apparently innocuous covers in an effort to conceal the existence of a secret. Digital image steganography and its derivatives are growing in use and application. In areas where cryptography and strong encryption are being outlawed, citizens are looking at steganography to circumvent such policies and pass messages covertly. As with the other great innovations of the digital age: the battle between cryptographers and cryptanalysis, security experts and hackers, record companies and pirates, steganography and Steganalysis will continually develop new techniques to counter each other.

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