digital "tag" for keeping track of images

hi i know this product exists, but can't remember what it is called. i am interested in imbedding a "tag" on my photographs so i can keep track of how they are being used, and who is using them. i know this cost $$, but i know it is worth it in the end, and this is the sort of thing that stock agencies do.

any idea what the company is called who does this, and what the URL is?

thanks in advance :)

- john

You are probably thinking about Digimarc (http://www.digimarc.com/).

Thanks Tuan -

That's it! :)

- john