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STEGANALYSIS

STEGANALYSIS

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  • 1. PERFORMANCE EVALUATION ON DIFFERENT STEGNOGRAPHIC ALGORITHMSJAYESH S, AP , Archana College Of Engineering – ALAPPUZHA AJAL.A.J , ASSISTANT PROFESSOR , FISAT – KOCHI VINOTHKUMAR.S , Scholar at PRIST University, Thanjavur HRIDYA K S - A P , K R G C E W – ALAPPUZHA
  • 2. http://edition.cnn.com/video/?/video/world/2012/04/30/pkg-robertson-al-qaeda-documen
  • 3. http://www.usatoday.com/tech/news/2001-02-05-binladen.htm
  • 4. ContentsSteganography and Steganalysis Steganographic schemes System Features Improvement / Comparison Conclusion and Future Work
  • 5. What is Steganography? Origin of the term: steganos: secret – graphy: writing
  • 6. Steganalysis♦ Passive steganalysis – detect the presence or absence of a message♦ Active Steganalysis – Estimate the message length and location – Estimate the Secret Key in embedding – Extract the message crypto + graphy ( secret + writing ) stegano + graphy ( cover + writing )
  • 7. Types of Steganalysis Targeted Steganalysis  Relys on knowing the method used to hide the data & using known distinguishing statistics to detect stego images  Sometimes steganalysts reverse engineer steganographic methods Blind Steganalysis  Most beneficial to forensics because it’s not based on knowing the algorithm  Most difficult because the type of images and method of hiding data are enormous and continuously changing.  The current trend is to develop a neural network using training images and multiple statistical features. A method beyond the scope of this talk.
  • 8. Other previous work in steganalysis Provos analyzed two million eBay images (jpeg) but although he identified thousands of “suspicious” images, nothing conclusive was recovered from any of them A statistical method based on pairs of values (POVs) was introduced by Pfitzmann and Westfeld, providing very reliable results if the message was placed in sequential pixel locations in the image Fridrich et al has a statistical method called RS steganalysis for detection of LSB embedding It uses dual statistics derived from spatial correlations in an image In a typical cover image the LSB plane can (to some degree) be predicted from the remaining 7 bit planes This intuitive idea is formulated mathematically resulting in the RS method The safe-bit rate for the LSB embedding algorithms is less than
  • 9. Modern Stego TechniquesOutguess Stego framework is created by embedding hidden data using redundancy of cover image. Outguess preserves statistics of the BDCT coefficients histogram Stego takes two measures before embedding data - Redundant BDCT coefficients, which has least effect on cover image. - Adjusts the untouched coefficients. 9
  • 10. Modern Stego Techniques (cont’d.)F5• Works on JPEG format only.• Two main security actions against steganalysis attacks: - Straddling: scatters message uniformly over the cover image - Matrix Embedding: Improves embedding efficiency (no. of bits/ change of BDCT coeff.) 10
  • 11. Modern Stego Techniques (cont’d.)MB (Model-based Steganography)• Correlates embedded data with cover image• Splits cover image into two parts - Models parameter of distribution of second given first part - Encodes second part using model and hidden message - Combine these two parts to form stego image• MB1 operates on JPEG images, uses Cauchy distribution to model JPEG histogram 11
  • 12. 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