Binary Document Images Authentication by Thinning Digital Patterns

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Binary Document Images Authentication by Thinning
Digital Patterns
Chu-Hsing Lin, Wen-Kui Chang, Yu-Ying Lin, and
Lun-Yuen Cheng Third International Conference on
International Information Hiding and Multimedia
Signal Processing (IIH-MSP 2007) Reporter ???
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Outline

• Introduction
• Yang and Kots method
• Patten extraction
• Embedding process
• Authentication process
• Experimental Results
• Conclusions

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Introduction

• Because binary documents are in pure binary
  format and thus there is no enough capacity for
  embedding information in the document.
• So it is always more difficult for the protection
  of binary documents than for colorful or gray
  images.
• In this paper, we focus on the binary document
  images authentication.

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Proposed Method

• The embedding and authentication process is based
  on Yang and Kots method
• Using Zhang-Suen thinning algorithm extracts the
  pattern.

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Yang and Kots method

• Embedding process

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Yang and Kots method (cont.)

• Authentication process

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Patten extraction

• At first, we define the two functions X(p) and
  B(p).
• X(p) is the number of value changes, from 0 to 1,
  in the order of p1, p2 , p3,, p8 .
• B(p) is the number of nonzero neighbors to p

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1
3
2
X(p) B(p)
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2
4
2
3
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Patten extraction (cont.)
A pixel p in the 3x3 block could be deleted using
the following two alternating iterations
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Example for patten extraction
original image
Pixels set to zero after the first iteration.
Pixels set to zero after the second iteration.
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Example for patten extraction (cont.)
Pixels set to zero after repeating the first
iteration.
Pixels set to zero after repeating the first
iteration.
The image skeleton
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Embedding process

• Odd/even feature
• If the number of black pixel is odd, then we
  embed 1.
• If the number of black pixel is even, then we
  embed 0.
• All-black or all-white blocks would not be used,
  because changing a pixel in such a block is
  visually detectable.

• It indicates an odd block and 1 is embedded.
• If we want to embed 0, we need to change the
  pixel P from white to black.

• if pixel A is changed from black to white, then
  the X(p)2 and the black patterns would be
  altered.

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Embedding process (cont.)
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Authentication process
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Experimental Results (1/6)
Host document
The watermark
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Experimental Results (2/6)
The stego document
The extracted watermark
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Experimental Results (3/6)
Adding noise point to the host document
The extracted watermark
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Experimental Results (4/6)
The word "1999" is changed to "1991"
The extracted watermark
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Experimental Results (5/6)
The "keyed/Unkeyed SHA" is cropped
The extracted watermark
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Experimental Results (6/6)
Host document
Host image Eyes are changed
The extracted watermark
The stego Image
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Conclusions

• Authors propose a method which can protect the
  integrity for binary documents.
• By extracting the black and the white patterns
  and using watermark technique, a document can be
  protected.