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