Jun 30, 2007

Why Photoshop doesn’t provide secure metadata

Source: John Nack on Adobe
Author: John Nack

Certain feature requests come up over and over, and customers wonder why Adobe doesn’t address them. In many cases it’s a matter of time, resources, and priorities (i.e. good idea, we just haven’t gotten there yet). In other cases, however, there are conceptual issues that make addressing the request impractical or impossible.

One of those cases concerns something that seems simple: letting Photoshop users apply copyright & other info, then lock it so that it can’t be removed. Photographers in particular request this capability year in and year out. Unfortunately there are good reasons why things don’t work as desired. If you’re interested in the details, read on for an explanation from Photoshop architect Russell Williams.

If I understand what you’re looking for — a way to distribute your image so that somebody can’t strip out the copyright, the only way to come close is to embed the copyright in the image with a watermark, either visible or invisible. Digimarc can do it with a mostly-invisible watermark. The less visible it is, the less robust it is to image manipulation.

It’s not just that the capability is lacking in Photoshop to attach a non-removable copyright. It is not logically possible to put a copyright notice in metadata (not embedded in the image data) in a way that it can’t be removed.

If the image data is accessible to someone, there’s no way to force them to keep the copyright notice with it. There are lots of programs that will open and re-save JPEGs, TIFFs, and even PSDs. It would be trivial to produce a version that doesn’t save the copyright with it. Not to mention metadata editing programs that can just remove or change arbitrary metadata. There’s no way to stop somebody from using one of those programs.

Even if they don’t happen to have a program that will re-save the image without the copyright or edit the metadata, they can always “print to PDF” out of any program that can open the image, or even show the image at 100%, do screenshots while scrolling around the image, and reassemble it. If they can see it, they can remove any attached copyright notice.

Everything else comes down to only sending the full resolution version to people you trust, because anybody who has the full resolution version can strip out any associated metadata.

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