1. CPS 182s 1.1 Digital Watermark l What is a watermark? A digital watermark?  Message about a work is embedded in the work l What is steganography?  The existence of the watermark is hidden ( Digital Watermarking by Cox, Miller, Bloom)

2. CPS 182s 1.2 www.hermitagemuseum.org l The contents of this site, including all images and text, are for personal, educational, non-commercial use only. The contents of this site may not be reproduced, in whole or in part, in any form without the written permission of the State Hermitage Museum. Images on this web site have been invisibly watermarked; any attempt to remove the watermarks from these images is expressly forbidden.

3. CPS 182s 1.3 More examples l If information embedded is not about the object in which the embedding occurs, then this isn't watermarking  Salt II treaty: sensor to verify if missile silo occupied What if sensor sends more information hidden in an otherwise "legal" transmission?  Early radio broadcasts embedded a time-signal at a specified frequency (800 Hz) every 15 minutes l Rumored 1981 British Cabinet leaks: distribute identical memoranda with different word-spacing used in each to identify the leaker  Is this watermarking? Steganographic?

4. CPS 182s 1.4 Watermarking Terminology l Embedding terminology  Effectiveness: just after embedding what is probability that detection works?  Fidelity: Perceptual similarity between original and watermarked version (either before/after transmission)  Data payload: how many bits are embedded in image, audio, video, … How many messages possible with N-bit watermark?

5. CPS 182s 1.5 More terminology l Detection terminology  Blind or Informed: is the original unwatermarked work available during detection? (aka public/private)  False Positive Rate: detection when not present. Accepted standard for DVD: 1 in 10 12 frames (1,000 years running)  Robustness: detection after common signal processing: filters, compression, printing, scanning, rotation, etc. Sometimes we want fragile watermarking: any dsp operation will lose the watermark, e.g., for ownership rights  Security: resistance to attack: removal, embedding, detection

6. CPS 182s 1.6 Multiple watermarks l Describe a scenario for watermarking video to permit time- shifting fair-use  One copy is allowed, more than one copy not allowed (no copy from copy)  Two options: one changeable watermark or two watermarks. How does this work? l What about distribution: from record company to website to consumer  Identify all the "players" along the way