A JPEG-tolerant Image Authentication Scheme Takeyuki Uehara, Rei - - PowerPoint PPT Presentation

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A JPEG-tolerant Image Authentication Scheme Takeyuki Uehara, Rei - - PowerPoint PPT Presentation

Dec 19, 2023 216 likes •338 views

A JPEG-tolerant Image Authentication Scheme Takeyuki Uehara, Rei Safavi-Naini, Philip Ogunbona Centre for Information Security, University of Wollongong Motorola Australian Research Centre AUSTRALIA To be published

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A JPEG-tolerant Image Authentication Scheme

  • Takeyuki Uehara,
  • Rei Safavi-Naini,
✁

Philip Ogunbona

  • Centre for Information Security, University of Wollongong
✁

Motorola Australian Research Centre AUSTRALIA To be published ACM Journal of Multimedia Communication

JPEG-tolerant Image Authentication – p.1/10

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Image authentication

Cryptographic authentication detects single bit change. Image authentication need not provide bit accuracy: redundancy and irrelevancy Image files are mainly in compressed form. Lossy compression systems : JPEG, JPEG2000, MPEG Changes that are caused by compression are acceptable: within a predefined compression rate High compression rate

  • large changes (data loss)

Low compression rate

  • small changes (small loss)

JPEG-tolerant Image Authentication – p.2/10

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A JPEG tolerant authentication system

JPEG compression : 1 Transform : divide the image into

  • ✁
  • pixel blocks

use two dimensional DCT transform to generate 64 coefficients ( 64 frequencies) 2 Quantization : Remove irrelevant information. 3 Entropy coding : Remove redundancy: run-length coding and Huffman/arithmetic coding.

JPEG-tolerant Image Authentication – p.3/10

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Calculating the authenticator

Authentication : Divide the image into

  • ✁
  • pixel blocks.

Transform each block using the DCT. Partition the blocks into

  • group,
✁✄✂ ☎✆ ✁ ✂ ✝ ✆ ✞ ✞ ✞

. Select a subset of frequencies. For each selected frequency

✟

, and for each group

✠

form a feature code

✡ ☛✌☞ ✍ ✎

. The authenticator is the sequence of feature codes, encoded in binary,

✡ ☛ ✏ ✍ ✏ ✡ ☛ ✑ ✍ ✏ ✡ ☛ ✒ ✍ ✏ ✞ ✞ ✡ ☛ ✏ ✍ ✑ ✡ ☛ ✑ ✍ ✑ ✞ ✞

JPEG-tolerant Image Authentication – p.4/10

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Calculating a feature code

A feature code is a linear sum of the coeffcients.

One−to−one mapping Transformed coefficients Linear sums Grouping

2

Y

1

Y Key Y 3

JPEG-tolerant Image Authentication – p.5/10

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Encoding a feature code

Use successive halving of the interval. The length depends on the required compression tolerance.

1

Y MAX Y MIN

1

Y

1 1 1 1

(u) j

JPEG-tolerant Image Authentication – p.6/10

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Verification

Compute

  • ✡
☛ ☞ ✍ ✎

from the reconstructed coefficients. Decode the feature codes. The two part must be almost equal.

1 1

YMIN YMAX

1 1 Accepted Rejected Rejected

Error Tolerance

1 1

JPEG-tolerant Image Authentication – p.7/10

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Performance

JPEG-tolerant Image Authentication – p.8/10

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JPEG-tolerant Image Authentication – p.10/10