Watermarking

Matt Elliott

Brian Schuette

Overview

• Goals

• Methods

• Comparison

• Attacks

• References

Goals

Watermark Goals• Robust• Invisible• Recovery

Project Goals• Watermark Types

– Fragile

– Robust

• Techniques– Frequency Domain

– Spatial domain

Bit-Plane Slicing

• Spatial Domain• LSB contains

watermark• Simple detection

• Many options– Image blocks

– Encode Text

– Specific Areas

Cox Method

– Frequency Domain

– Transformation

– AC Coefficients• Sorted by size

• Largest 1000 selected

• Psuedo-random watermark embedded

– Reverse transformation

2D DCT sort v’=v (1+ w) IDCT & normalize

Original image

N largest coeff.

other coeff.

marked image

random vector generator

wmk

seed

Comparison

• Fragile Watermark– Very susceptible to attack– Used for tampering detection

• Robust Watermark– Resistant to tampering– Used with public images– Provides proof of ownership

Bit-Plane Slicing

Methods of Attack

• Scaling

• Cropping

• JPEG

• Print/Xerox

References

• ECE 738 Advanced Digital Image Processing• Professor Hu• Wikipedia• Digital Image Processing, Gonzalez and Woods• I. Cox, J. Kilian, T. Leighton, T. Shamoon:

“Secure Spread Spectrum Watermarking for Multimedia'', IEEE Transaction on Image Processing, vol.6, no.12, pp.1673-1687, 1997.

Questions?