Steganography (1)

Steganography (1)

• 1.
  Digital Steganography Pelin Gul Sankar Das
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  Outline  What isSteganography?  Uses of Steganography  Its Relation to Cryptography  Digital Watermarking  Network Security and Steganography  Types of Steganography  Detecting Steganography: Steganalysis  Future of Steganography
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  What is Steganography? Origin of the term: steganos: secret – graphy: writing
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  History of Steganography Steganography in Ancient Greece  Ancient Rome - 1499, Steganographia, the first book about steganography  World War II Germany - microdots  Modern Steganography - 1985, with the development of personal computers  Digital Steganography – with internet (e.g.digital watermarking)
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  Uses of Steganography Governments  Businesses: Digital Watermarking  Individuals
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  Steganography & Cryptography Steganography and Cryptography are closely related  The difference is in their goals... – Cryptography: although encypted and unreadable, the existence of data is not hidden – Steganography: no knowledge of the existence of the data  Steganography and Cryptography can be used together to produce better protection
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  Digital Watermarking Image “painted”with the watermark: “Invisible Man” © 1997, Neil F. Johnson
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  Digital Watermarking  Usedprimarily for identification  Embedding a unique piece of information within a medium (typically an image) without noticeably altering the medium  Almost impossible to remove without seriously degrading an image
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  Digital Steganogaphy &Watermarking  Digital watermarking hides data in a file, and the act of hiding data makes it a form or steganography  The key difference is their goals... – Steganography: hiding information – Watermarking: extending the file with extra information  Steganographic information must never be apparent to a viewer unaware of its presence.
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  Network Security andSteganography  Confidentiality: any unauthorized person does not know that sensitive data exists  Survivability: verifying that the data does not get destroyed in the transmission  No detection: cannot be easily found out that the data is hidden in a given file  Visibility: people cannot see any visible changes to the file in which the data is hidden
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  Types of DigitalSteganography  Hiding a Message inside Text  Hiding a Message inside Images – Most popular technique  Hiding a Message inside Audio and Video Files
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  Hiding a Messageinside Text  Partially effective randoM capitalosis is a rarE disEase ofTen contrAcTed by careless inTernet users. tHis sad illnEss causes the aFfected peRsON To randomly capitalize letters in a bOdy oF texT. please do not confuse this disease witH a blatant attEmpt aT steganogRAPhy. Reveals: MEET AT THE FRONT OF THE TRAP
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  Hiding a Messageinside Text  First-letter algorithm  Every n-th character  Altering the amount of whitespace  Using a publicly available cover source
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  Hiding a Messageinside Images  The most popular medium!  Least-significant bit (LSB) modifications – 24-bit vs. 8-bit images – Tools to implement LSB: EzStego and S-Tools  Masking and Filtering  Algorithms and Transformations
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  Hiding an Imagewithin an Image  Removing all but the two least significant bits of each color component produces an almost completely black image. Making that image 85 times brighter produces the image below  source: wikipedia.org
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  Hiding a Messageinside Audio or Videos Files  Advantages – Human limitations – 20.000 Hz. – Large amount of data that can be hidden inside – Hard to recognize because of because of the continuous flow of information (moving stream of images and sound)
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  Steganalysis  Detecting anddecoding the hidden data within a given medium  Even if secret content is not revealed, modifying the cover medium changes the medium’s statistical properties  Distributed Dictionary Attack
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  Future of Steganography The most important use of steganographic techniques will probably lie in the field of digital watermarking  Might become limited under laws - governments claimed that criminals use steganography to communicate ...the End