Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR...

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Digital Camera Identification Neil Jenkins

Transcript of Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR...

Page 1: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

Digital Camera Identification

Neil Jenkins

Page 2: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

The Problem

?

Page 3: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

The Digital Image Pathway

Light

Magic

Page 4: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

Noise

• Shot noise

• Pattern noise

- Fixed pattern noise

- Photo-response non-uniformity noise (PRNU)

Page 5: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

Modelling theSensor Output

yij = fij(xij + ηij) + cij + εij

Page 6: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

The Algorithm

1. Calculate the camera reference patterns

2. Look for correlation between the image and the different patterns

Page 7: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

Calculating the Reference Pattern

Page 8: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

Calculating the Reference Pattern

Page 9: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

Looking for Correlation

?

Page 10: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

Looking for Correlation

Page 11: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

Looking for Correlation

Page 12: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

Looking for Correlation

Original Image Filtered Image

Page 13: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

Looking for correlation

Original Image Filtered Image

Page 14: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

Looking for Correlation

Original Image Filtered Image

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Page 15: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

Looking for Correlation

Noise Residual

Page 16: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

Looking for Correlation

corr(n, r) =(n− n) · (r− r)�n− n��r− r�

Page 17: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

Experiment

Page 18: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

Experiment

100x

Page 19: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

Experiment

Page 20: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

Experiment

Page 21: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

Results

-0.02 0 0.02 0.04 0.05 0.07

Webcam Images Other Images

Page 22: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

Paper results

• Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11

• Gamma correction of images barely affects reliability

• JPEG also irrelevant unless high compression

• Stable over time

Page 23: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

Algorithm Mark II

• More detailed mathematical model of how light is captured by sensor

I = gγ · [(1 + K)Y + Λ + Θs + Θr]γ + Θq

Page 24: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

Algorithm Mark II

• Determine PRNU using a maximum likelihood estimator

• Detection is binary hypothesis testing

• Correlation Predictor

Page 25: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

Large scale test

• Apply algorithm to 1,000,000+ images

• Extensive test of reliability

• False rejection rate < 0.024 when threshold such that false acceptance < 2.4

Page 26: Digital Camera Identification · 2018. 11. 30. · Paper results • Setting FAR to 10-3 gives FRR of 4.68x10-3 in worst case and down to 1.14x10-11 • Gamma correction of images

Questions