09-03-2011, 10:19 AM
[attachment=9830]
STEGANOGRAPHY:
Motivation
• Protection of digital media.
• Privacy of information transmitted across the world wide web.
Goal
• To make the transmitted information invisible by embedding the information in a cover media.
• We try to enhance the security and the robustness of the information against attacks and image processing techniques
• WHAT IS STEGANOGRAPHY?
STEGANOGRAPHY IS “DATA HIDING”
• Steganography is the practice of hiding private or sensitive information within something that appears to be nothing out of the usual.
• Steganography in the modern day sense of the word usually refers to information or a file that has been concealed inside a digital Picture Video or Audio file.
• Steganography terms
• A Original message or a file in which hidden information will be stored inside of it
• The medium in which the information is hidden
• Embedded or Payload– The information which is to be hidden or concealed.
• Steganalysis– The process of detecting hidden information inside a file
• Introduction:
• Advance security is not maintained by the password protection but it is gained by hiding the existence of the data which can only be done by Steganography
• Steganography is a subject which is rarely touched upon by most IT Security Enthusiasts
• Steganographic Systems can hide messages inside of Digital Objects such as a file that has been concealed inside a Digital Picture, Videoor Audio file.
• The main advantage of Steganography is it hides the information in such a way that there is no information hidden at all
• This is derived from the name of lizard “Stegosaurs”.
Steganography Basics
• The word steganography comes from the Greek steganos , meaning covered or secret, and graphy , meaning writing or drawing. Therefore, steganography literally means covered writing.
• Steganography simply takes one piece of information and hides it within another
– Computer files (images, sounds recordings, even disks) contain unused or insignificant areas of data
– Steganography takes advantage of these areas, replacing them with information (encrypted mail, for instance).
– The files can then be exchanged without anyone knowing what really lies inside of them
– An image of the space shuttle landing might contain a private letter to a friend.
– Rumor has it that terrorists used steganography to transmit messages to one another
Steganography Early Examples
In his history of the Persian Wars, Herodotus tells of a messenger who shaved his head and allowed a secret message to be tattooed on his scalp. He waited until his hair grew back. Then he journeyed to where the recipient awaited him and shaved his head again. The message was revealed. It was history’s first use of steganography.
Steganography Invisible Ink
Ancient Romans used to write between lines using invisible ink based on various natural substances such as fruit juices, urine, and milk. Their experience was not forgotten: even nowadays children play spies and write secret messages that appear only when heated.
Application of Steganography
• To hide a message intended for later retrieval
• Copyright marking-digital watermarking and fingerprinting
Types of Steganography carriers
• Image files as carriers
– using 24-bit images: too large to pass over the network
– using 8-bit images: prone to modification/ lossy compression
• Audio files as carriers
– Exploits imperfection of human auditory system called audio masking.
– In this case, weak signal is generally inaudible in loud signal.
• Video files as carriers
– A combination of sound and image techniques can be used
• Text files as carriers
– Uses open space in text files to encode the secret information. It works on the fact that to a casual reader an extra space anywhere does not prompt abnormality.
– Disadvantage is that it requires large amount of data to conceal little information
• DNA strands as carriers
Steganography using image files
• Common approaches to image steganography is:
– Least significant bit insertion
– Masking and filtering
– Algorithms and transformation
• LSB Technique
Based on three factors:
- large file size
- presence of ‘noise’
- the frailties of human perception
• Example of Steganography: Bit Plane Methods
Audio Steganography
-Human Auditory system operates over wide range of dynamic frequencies but is poor with regards to its differential range.
-loud sound masks the softer one.
Ways to hide data in audio
1.Low bit encoding replaces LSB of data in each sampling point with a coded binary string
2.Phase encoding substitutes the phase of an initial audio segment with a reference to the phase that represents the data.
-the phase of subsequent segments is adjusted in order to preserve the relative phase between segments
-more complicated than low-bit
3. Spread spectrum spreads the encoded data across as much of the frequency spectrum as possible.
- Data is encoded as a binary sequence which sounds like noise but which can be recognised by a receiver with the correct key.
- Spread spectrum techniques can be used for watermarking by matching the narrow bandwidth of theembedded data to the large bandwidth of the medium.
- Makes it difficult for an adversary to reconstruct the pseudo random signal used to spread data across freq range
4. Echo data hiding embeds data into a host signal by introducing an echo. The data are hidden by varying 3 parameters of echo:
– initial amplitude
– Decay rate
– offset
- The echo blends as the echo between the original and the echo decreases. The echo is perceived as the original sound.’
Steganography Principles
• Computer Steganography is based on two principles.
– The first one is that the files containing digitized images or sound can be altered to a certain extend without loosing their functionality.
– The other principle deals with the human inability to distinguish minor changes in image color or sound quality, which is especially easy to make use of in objects that contain redundant information, be it 16-bit sound, 8-bit or even better 24-bit image. The value of the least significant bit of the pixel color won’t result in any perceivable change of that color.
Steganography Process
• The data to be concealed is compressed and hidden within another file.
• The first step is to find a file which will be used to hide the message (also called a carrier or a container.)
• The next step is to embed the message one wants to hide within the carrier using a steganographic technique.
• Two different techniques commonly used for embedding are:
– Replace the least significant bit of each byte in the [carrier] with a single bit for the hidden message.
– Select certain bytes in which to embed the message using a random number generator; resampling the bytes to pixel mapping to preserve color scheme, in the case of an image...; hiding information in the coefficients of the discrete cosine, fractal or wavelet transform of an image; and applying mimic functions that adapt bit pattern to a given statistical distribution.
Steganography Software
• EZStego (Stego Online, Stego Shareware, Romana Machado)
– Java based software program which supports only GIF and PICT formats;
• Gif-It-Up v1.0 (Lee Nelson)
– A stego program for Windows 95 that hides data in GIF files
• Hide and Seek (Colin Maroney)
– can hide any data into GIF images;
• JPEG-JSTEG (Derek Upham)
– can hide data inside a JPEG file
• MP3Stego (Fabien A.P. Petitcolas, Computer Laboratory, University of Cambridge)
– can hide data inside MP3 sound files;
• Steganos (Demcom, Frankfurt, Germany)
– encrypts files and then hides them within BMP, DIB, VOC, WAV, ASCII and HTML files
Steganography Software
S-Tools
• S-Tools is one of the most popular steganography tools.
– This program is Windows 95/98 compatible
– It has the ability to conceal files within BMP, GIF and WAV files.
– Allows you to simply point and click your way to hiding files.
– It also has the ability to hide multiple files in one container.
– It has been updated each year and can be easily downloaded by anyone.
Steganalysis Basics
• Steganalysis is the art of discovering and rendering useless such covert messages.
• Steganalysis involves analysis of the carrier file
– Simpler steganographic techniques produce some discernible change in the file size, statistics or both.
– These changes can manifest themselves in color variations, loss of resolution and other distortions that are visible to the human eye.
– This form of detection requires that you know what the original carrier image or file should look like.
Detection of Steganographic Content/Countermeasures
The detection of steganographically encoded packages is called Steganalysis.
– Visual Analysis tries to reveal the presence of secret communication through inspection, either with the naked eye or with the assistance of a computer.
– Statistical (Algorithmic) Analysis reveals tiny alterations in an image's statistical behavior caused by steganographic embedding.
• The nominally universal methods developed to detect embedded stego-data are generally less effective than the steganalytic methods aimed at specific types of embedding.
Advantages:
• It is used in the way of hiding not the Information but the password to reach that Information.
• Difficult to detect .Only receiver can detect.
• Can be applied differently in digital image, audio & video file.
• It can be done faster with the large no of software's.
Disadvantages:
• Huge number of data = huge file size, so some one can suspect about it.
• In sending and receiving information can be leaked.
• The confidentiality of information is maintained by the algorithms, and if the algorithms are known then its all over.
• If this technique is gone in the wrong hands like hackers, terrorist ,criminals then this can be very much dangerous for all.
Conclusion
As steganography becomes more widely used in computing there are issues that need to be resolved. Many currently used techniques are not robust enough to prevent detection and removal of embedded data.
For a system to be considered robust, it should have the following properties:
• The quality of the media should not noticeably degrade upon addition of a mark.
• Marks should be undetectable without secret knowledge, typically the key
• If multiple marks are present they should not interfere with each other
STEGANOGRAPHY:
Motivation
• Protection of digital media.
• Privacy of information transmitted across the world wide web.
Goal
• To make the transmitted information invisible by embedding the information in a cover media.
• We try to enhance the security and the robustness of the information against attacks and image processing techniques
• WHAT IS STEGANOGRAPHY?
STEGANOGRAPHY IS “DATA HIDING”
• Steganography is the practice of hiding private or sensitive information within something that appears to be nothing out of the usual.
• Steganography in the modern day sense of the word usually refers to information or a file that has been concealed inside a digital Picture Video or Audio file.
• Steganography terms
• A Original message or a file in which hidden information will be stored inside of it
• The medium in which the information is hidden
• Embedded or Payload– The information which is to be hidden or concealed.
• Steganalysis– The process of detecting hidden information inside a file
• Introduction:
• Advance security is not maintained by the password protection but it is gained by hiding the existence of the data which can only be done by Steganography
• Steganography is a subject which is rarely touched upon by most IT Security Enthusiasts
• Steganographic Systems can hide messages inside of Digital Objects such as a file that has been concealed inside a Digital Picture, Videoor Audio file.
• The main advantage of Steganography is it hides the information in such a way that there is no information hidden at all
• This is derived from the name of lizard “Stegosaurs”.
Steganography Basics
• The word steganography comes from the Greek steganos , meaning covered or secret, and graphy , meaning writing or drawing. Therefore, steganography literally means covered writing.
• Steganography simply takes one piece of information and hides it within another
– Computer files (images, sounds recordings, even disks) contain unused or insignificant areas of data
– Steganography takes advantage of these areas, replacing them with information (encrypted mail, for instance).
– The files can then be exchanged without anyone knowing what really lies inside of them
– An image of the space shuttle landing might contain a private letter to a friend.
– Rumor has it that terrorists used steganography to transmit messages to one another
Steganography Early Examples
In his history of the Persian Wars, Herodotus tells of a messenger who shaved his head and allowed a secret message to be tattooed on his scalp. He waited until his hair grew back. Then he journeyed to where the recipient awaited him and shaved his head again. The message was revealed. It was history’s first use of steganography.
Steganography Invisible Ink
Ancient Romans used to write between lines using invisible ink based on various natural substances such as fruit juices, urine, and milk. Their experience was not forgotten: even nowadays children play spies and write secret messages that appear only when heated.
Application of Steganography
• To hide a message intended for later retrieval
• Copyright marking-digital watermarking and fingerprinting
Types of Steganography carriers
• Image files as carriers
– using 24-bit images: too large to pass over the network
– using 8-bit images: prone to modification/ lossy compression
• Audio files as carriers
– Exploits imperfection of human auditory system called audio masking.
– In this case, weak signal is generally inaudible in loud signal.
• Video files as carriers
– A combination of sound and image techniques can be used
• Text files as carriers
– Uses open space in text files to encode the secret information. It works on the fact that to a casual reader an extra space anywhere does not prompt abnormality.
– Disadvantage is that it requires large amount of data to conceal little information
• DNA strands as carriers
Steganography using image files
• Common approaches to image steganography is:
– Least significant bit insertion
– Masking and filtering
– Algorithms and transformation
• LSB Technique
Based on three factors:
- large file size
- presence of ‘noise’
- the frailties of human perception
• Example of Steganography: Bit Plane Methods
Audio Steganography
-Human Auditory system operates over wide range of dynamic frequencies but is poor with regards to its differential range.
-loud sound masks the softer one.
Ways to hide data in audio
1.Low bit encoding replaces LSB of data in each sampling point with a coded binary string
2.Phase encoding substitutes the phase of an initial audio segment with a reference to the phase that represents the data.
-the phase of subsequent segments is adjusted in order to preserve the relative phase between segments
-more complicated than low-bit
3. Spread spectrum spreads the encoded data across as much of the frequency spectrum as possible.
- Data is encoded as a binary sequence which sounds like noise but which can be recognised by a receiver with the correct key.
- Spread spectrum techniques can be used for watermarking by matching the narrow bandwidth of theembedded data to the large bandwidth of the medium.
- Makes it difficult for an adversary to reconstruct the pseudo random signal used to spread data across freq range
4. Echo data hiding embeds data into a host signal by introducing an echo. The data are hidden by varying 3 parameters of echo:
– initial amplitude
– Decay rate
– offset
- The echo blends as the echo between the original and the echo decreases. The echo is perceived as the original sound.’
Steganography Principles
• Computer Steganography is based on two principles.
– The first one is that the files containing digitized images or sound can be altered to a certain extend without loosing their functionality.
– The other principle deals with the human inability to distinguish minor changes in image color or sound quality, which is especially easy to make use of in objects that contain redundant information, be it 16-bit sound, 8-bit or even better 24-bit image. The value of the least significant bit of the pixel color won’t result in any perceivable change of that color.
Steganography Process
• The data to be concealed is compressed and hidden within another file.
• The first step is to find a file which will be used to hide the message (also called a carrier or a container.)
• The next step is to embed the message one wants to hide within the carrier using a steganographic technique.
• Two different techniques commonly used for embedding are:
– Replace the least significant bit of each byte in the [carrier] with a single bit for the hidden message.
– Select certain bytes in which to embed the message using a random number generator; resampling the bytes to pixel mapping to preserve color scheme, in the case of an image...; hiding information in the coefficients of the discrete cosine, fractal or wavelet transform of an image; and applying mimic functions that adapt bit pattern to a given statistical distribution.
Steganography Software
• EZStego (Stego Online, Stego Shareware, Romana Machado)
– Java based software program which supports only GIF and PICT formats;
• Gif-It-Up v1.0 (Lee Nelson)
– A stego program for Windows 95 that hides data in GIF files
• Hide and Seek (Colin Maroney)
– can hide any data into GIF images;
• JPEG-JSTEG (Derek Upham)
– can hide data inside a JPEG file
• MP3Stego (Fabien A.P. Petitcolas, Computer Laboratory, University of Cambridge)
– can hide data inside MP3 sound files;
• Steganos (Demcom, Frankfurt, Germany)
– encrypts files and then hides them within BMP, DIB, VOC, WAV, ASCII and HTML files
Steganography Software
S-Tools
• S-Tools is one of the most popular steganography tools.
– This program is Windows 95/98 compatible
– It has the ability to conceal files within BMP, GIF and WAV files.
– Allows you to simply point and click your way to hiding files.
– It also has the ability to hide multiple files in one container.
– It has been updated each year and can be easily downloaded by anyone.
Steganalysis Basics
• Steganalysis is the art of discovering and rendering useless such covert messages.
• Steganalysis involves analysis of the carrier file
– Simpler steganographic techniques produce some discernible change in the file size, statistics or both.
– These changes can manifest themselves in color variations, loss of resolution and other distortions that are visible to the human eye.
– This form of detection requires that you know what the original carrier image or file should look like.
Detection of Steganographic Content/Countermeasures
The detection of steganographically encoded packages is called Steganalysis.
– Visual Analysis tries to reveal the presence of secret communication through inspection, either with the naked eye or with the assistance of a computer.
– Statistical (Algorithmic) Analysis reveals tiny alterations in an image's statistical behavior caused by steganographic embedding.
• The nominally universal methods developed to detect embedded stego-data are generally less effective than the steganalytic methods aimed at specific types of embedding.
Advantages:
• It is used in the way of hiding not the Information but the password to reach that Information.
• Difficult to detect .Only receiver can detect.
• Can be applied differently in digital image, audio & video file.
• It can be done faster with the large no of software's.
Disadvantages:
• Huge number of data = huge file size, so some one can suspect about it.
• In sending and receiving information can be leaked.
• The confidentiality of information is maintained by the algorithms, and if the algorithms are known then its all over.
• If this technique is gone in the wrong hands like hackers, terrorist ,criminals then this can be very much dangerous for all.
Conclusion
As steganography becomes more widely used in computing there are issues that need to be resolved. Many currently used techniques are not robust enough to prevent detection and removal of embedded data.
For a system to be considered robust, it should have the following properties:
• The quality of the media should not noticeably degrade upon addition of a mark.
• Marks should be undetectable without secret knowledge, typically the key
• If multiple marks are present they should not interfere with each other
