Re: Digital Watermark

[Adam Shostack <adam@lighthouse.homeport.org>]

	Creating watermarks that can't be removed without degrading
image quality is not especially difficult.  The two tricky bits are
durability and collusion protection.

	Durability involves ensuring enough of a watermark remains
after the image is converted to a JPEG.  Colusion protection is making
sure that users can't compare images and remove the watermark without
a large number of users being involved.

Adam


| Financial Times, 22 Feb 96

| Attempts to remove the watermark would be virtually
| impossible without degrading the image quality. Moreover,
| counterfeiting would be almost impossible, says NEC. the
| Japanese electronics company.

-- 
"It is seldom that liberty of any kind is lost all at once."
					               -Hume