Method to enable preview in DRM System
Original Publication Date: 2004-Apr-14
Included in the Prior Art Database: 2004-Apr-14
In general, a DRM (Digital Rights Management) system protects the copyrights of contents. It allows the distribution of digital contents in an encrypted form. The protected content can only be rendered by some special players/viewers. Since the content are encrypted, users cannot view the protected content before purchasing it. Promoters usually issue a separate preview rights object for customers to enjoy in limited time or counts (or make a separate preview version of the content). However, some contents may have lost their value after being viewed even only once. Moreover, additional rights object or content version will increase the cost of data management and delivery. Our invention provides a novel method to enable the preview feature in DRM systems, so that the customers could try a low-quality version of the multimedia content before purchasing it. In our invention, the protected content would not be encrypted; instead, we would embed a visible and reversible watermark to the content. Since the watermark is visible, it would reduce the quality of the content, so the user could only view a low-quality version before buying it. If the customer buys the content, a set of rights and a key would be sent to the customer. With the key, the visible watermark could be removed and the customer could then view the original high-quality content. Our invention can protect the content value during preview, and as well save the cost of additional preview rights object or preview version of the delivered content. Thus it facilitates the protected content to be forwarded from one user to another, which is usually encouraged by content/service providers. Furthermore, it can be well applied into the traditional encryption-based DRM system without explicitly infrastructure changing.
Method to enable preview in DRM System
In our invention, the protected content would not be encrypted; instead,
we would embed a visible and reversible watermark to the content. Since
the watermark is visible, it would reduce the quality of the content, so
the user could only view a low-quality version before buying it. If the
customer buys the content, a set of rights and a key would be sent to
the customer. With the key, the visible watermark could be removed and
the customer could then view the original high-quality content.
As we have described, traditional DRM systems would encrypt the contents
to protect the copyright. As an example, a typical DRM system is shown
in Figure 1. In this figure, content issuer is in charge of the delivery
of protected contents, and rights issuer manages the rights delivery. A
service process can follows such steps:
(1) User downloads encrypted content object from content issuer to
her device. She cannot view the content in this stage.
(2) User should acquire the corresponding preview rights from the
rights issuer before her device can decrypt and preview the content.
(3) User needs to purchase normal rights object from the rights
issuer to get a full usage of the content.
1. Acquire encrypted content
2. Acquire preview rights object
3. Purchase normal rights object
Encrypted Content (non-viewable)
Figure 1 A typical DRM system
In our invention, we do not encrypt the contents; instead, we embed a
visible and reversible watermark to the content. The so-called 'visible
and reversible watermark' means:
At least the watermark:
(1) Should be easily identified by human eyes;
(2) Could be removed provided a content key is given.
And furthermore, the watermark should better:
(1) Can reduce the quality of the content tremendously so that most
customers would not willing to enjoy the watermarked content;
(2) Cannot be removed without knowing the content key;
(3) After being removed, the content quality would be at least
almost the same as the original content.
Figure 2 and 3 below show some examples of the visible and reversible
watermark. Figure 2 is used for still image and Figure 3 is for video.
In these examples, we use the DataHiding- technology developed by IBM
Tokyo Research Lab., and other watermarking technology could also be
used in our invention provided it could fulfill the above requirements.
Content key from rights object
Figure 2 Example of Visible and Reversible Watermark for image
(C) International Business Machines Corporation 2002
Figure 3 Example of Visible and Reversible Watermark for video
After the content is watermarked, the content quality decreases