SasuriE ajal
description
Transcript of SasuriE ajal
PERFORMANCE EVALUATION ON DIFFERENT STEGNOGRAPHIC
ALGORITHMS
JAYESH S, AP , Archana College Of Engineering – ALAPPUZHAAJAL.A.J , ASSISTANT PROFESSOR , FISAT – KOCHI
VINOTHKUMAR.S , Scholar at PRIST University, ThanjavurHRIDYA K S - A P , K R G C E W – ALAPPUZHA
http://edition.cnn.com/video/?/video/world/2012/04/30/pkg-robertson-al-qaeda-documents-combined.cnn
http://www.usatoday.com/tech/news/2001-02-05-binladen.htm
Contents
Steganographic schemes
Steganography and Steganalysis
System Features
Improvement / Comparison
Conclusion and Future Work
What is Steganography?
Origin of the term: steganos: secret – graphy: writing
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 )
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.
Other previous work Other previous work in steganalysisin steganalysis
Provos analyzed two million eBay images (jpeg) but although he Provos analyzed two million eBay images (jpeg) but although he identified thousands of “suspicious” images, nothing conclusive was identified thousands of “suspicious” images, nothing conclusive was recovered from any of themrecovered from any of them
A statistical method based on pairs of values (POVs) was A statistical method based on pairs of values (POVs) was introduced by Pfitzmann and Westfeld, providing very reliable introduced by Pfitzmann and Westfeld, providing very reliable results if the message was placed in sequential pixel locations in the results if the message was placed in sequential pixel locations in the imageimage
Fridrich et al has a statistical method called Fridrich et al has a statistical method called RS steganalysisRS steganalysis for for detection of LSB embeddingdetection of LSB embedding
It uses dual statistics derived from spatial correlations in an imageIt uses dual statistics derived from spatial correlations in an image In a typical cover image the LSB plane can (to some degree) be In a typical cover image the LSB plane can (to some degree) be
predicted from the remaining 7 bit planespredicted from the remaining 7 bit planes This intuitive idea is formulated mathematically resulting in the RS This intuitive idea is formulated mathematically resulting in the RS
methodmethod The safe-bit rate for the LSB embedding algorithms is less than The safe-bit rate for the LSB embedding algorithms is less than
0.005 bpp0.005 bpp
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Modern Stego Techniques
Outguess 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.
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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.)
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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
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