Recently I bought a DVD print of the movie, The Blind Side. While I was watching the movie, I saw DRM (Digit Rights Management aka copyright) messages popping up. I have been seeing these types of messages for a couple of months. But this one was altogether new. In this case, it is hard to find the information in the meta data (in plain text format) and even even after multiple format conversions and encodings it was hard to find the actual ‘point of encryption’.

Well, Digital Watermarking is a method adopted by copyright holders to enforce and manage digital rights. If you are new this, you should not confuse yourself this technique  with the classic watermarking process (in which we will merely add a layer on top of the media and add the copyright text). In Digital Watermarking we embed specific information (relative to each copyright holder) into any digital media (images, audio or video). We perform this by altering the media data without meddle with the actual ‘information’ which the data is carrying. In trivial methods, this will be shown in the meta data information. Hence if you want to look for pirated copy you can use a meta data reader for reading this information. But it is easy to mask meta data information (ofcourse, by using advanced tools). This made researchers to encode the data in such a way that it is hard to remove or hide the watermark. This method is adopted in the case which we were discussing before.

As per the theory, it is not possible to remove or change the watermark without a passphrase (key) which was used when the actual watermark information was added to the media. Thus one can confirm the authenticity (and even security) of the data can be confirmed. A good watermarking technique is so hard to break so that even if you transcode the media to other formats, it will still carry the watermark information.

It is also interesting to note that by adding the digital watermark we are in no way changing the quality of the digital medium (unlike in the classical way where we will be printing text over the media). A typical example is shown below:

Hence you will be able to use the medium in the same way as it was not watermarked. You may also note that there are various DRM techniques in which conversion to other formats can be prohibited.

Privacy Issues

There is no privacy issues when it comes to the first generation digital watermarking tools. It is a non-restrictive technique. And there is no special reporting mechanisms available. Yet, it is still detectable and traceable. This is not the case when it comes to the next generation DRM tools that employ spyware type bots (agents) that can report if the digital media is uploaded  to networks like P2P (Peer to Peer). This invites lot much of privacy issues.

This was actually proposed in a white paper (Future of Watermarking) published last. In this paper, the authors clearly elucidates that it will also keep a track of the ‘file history’. To quote:

"Watermarking can potentially tell you this content is ‘Stairway to Heaven,’ distributed through Starbucks, last transferred through the Hear Music kiosk in downtown San Francisco on Dec. 8th, to a registered Hear Music user who has this profile and uses a Microsoft Zune."

When Apple released their DRM-Free Music they added iTunes’s id in the meta information. They can easily adopt this method to ‘track’ the file they sold. You may think that the new bot may not be able to communicate with the outside world (Internet) since your firewall will block the access. But this is note the case. It can do this by using reporting services provided by media players. Thus it will be you media player which will be accessing the internet. And you may have already granted internet access for it for viewing / playing online streaming files.

So be very careful if you are using a player provided by any staunch supports of DRM (say, MS media player). Some of the copyright holders even prohibit coping of media (sometimes, even parts of the media) to your computer. And if you copy the disk to your PC,  FBI may greet you at your doorstep.