Watermarking methods

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Joe O’Ruanaidh Siemens Corporate

Research Princeton, NJ

Digital

Watermarking:

How it works!

SIGGRAPH’99 Panel

Friday 13 August 2:15pm - 4:00pm

Gabriella Csurka CUI, University of

Geneva

Switzerland

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Agend a

• Some Examples: almost but not quite!

– Glyphs

– Easter Eggs – Money Dots

• Spread Spectrum

• Image Watermarking

• Video Watermarking

• Security

• Conclusions

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Goals

• Context: distribution of documents over Internet

• Goal: copyright enforcement

• image

• video

• audio

• text

• Framework:

security architecture (e.g. DCT Switzerland, Fraunhof Institute);

public and private watermark.

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The Holy Grail

• No original image!

– watermark resistant to e.g.:photometric transformations, scanning; JPEG, MPEG compression; geometric transformations:

cropping, translation, rotation, scaling, aspect ratio change, flip, general linear or affine transformation; regular removal of rows/columns or videoframes, shearing

– video frame rate change (temporal scaling);

– cryptographic attacks.

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Spread Spectrum

• Looks like noise!

• Technically it’s a symmetric key cryptosystem

• Very very robust.

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Original Images

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Transformations of images

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Basic approach

• spread-spectrum sequence inserted in transform

domain;

• template: key- based grid to

recover geometric

transformations,

inserted and detected

in transform domain

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Template: key- based grid to recover aspect ratio and frame- rate changes,

•Inserted in

transform domain

• Detected in log-

log-log mapping of transform domain;

Video

watermarking:

frame by frame or

as 3D object

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Detecting a Watermark

-20dB SNR -40dB SNR

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Review

• We need a fully integrated and secure system. Complete

solution involves aspects of:

– Cryptography

– Communications

– Spatial Transformations

– Statistical Decision Theory