Content protection can be categorized into two categories:
- Link protection
- File protection
Link protection as the name suggests, protecting the link. In other words, it prevents third-party application or entity that sniffs or hijacks the content transfer session. An example of link protection is SSL. The payload is encrypted before getting transferred through the link and decrypted as soon as it reaches the destination. Link protection is usually associated with the transfer session, and not the actual content or file. As link protection is only protecting the link, it does not have any control over how the media file is used once it reaches our client machine.
If we want to have a control over the media file itself, we would need a file protection mechanism. DRM is an good example of media file protection. For DRM content, the media data (usually samples) is already encrypted when the file was originally created. Web server or even streaming server can be agnostic about the media encryption. Because all they need to do is to deliver bits or samples. Whether the content is encrypted or not does not really matter. Decryption for DRM content happens when the user tries to view the content. Client machine needs to contact license server to get the license and decrypt the content.
WHAT IS DRM?
Digital rights management (DRM) is a class of technologies that is used by hardware manufacturers, publishers, copyright holders, and individuals with the intent to limit the use of digital content and devices after sale.
DRM is any technology that inhibits use of digital content that are not desired or intended by the content provider.
Digital Rights Management (DRM) technologies attempt to control what you can and can’t do with media and hardware you’ve purchased.
- Bought an ebook from Amazon but we can’t read it on our ebook reader of choice? That’s DRM.
- Bought a DVD but we can’t copy the video onto our portable media player? That’s DRM.
- Bought a video-game but we can’t play it today because the manufacturer’s “authentication servers” are off-line? That’s DRM.
HOW DRM WORKS???
DRM works by allowing the distributors of electronic information to control viewing access to the content. Some form of encryption is needed to control access to the content. Rights management solutions are based on a wrapper or container placed around a data file, which offers protection, sets the data life cycle and defines usage rules, payment and redistribution constraints.
A license must be acquired to unlock the wrapper and get access to the content. Individual “keys” for viewing or listening to the content are provided to the end user who has purchased the rights which generally include limitations on copying, printing and redistribution.
Keys are the main source to grant access and are commonly given to the computer instead of the end user. People are allowed to buy the product and download it to their computer. While that is happening, a small file is also downloaded which contains the key to open the product such as an ebook or a song. The key is tied to the identity of the computers hardware. The key takes a unique identifier from the computer and gives it back to the owner. The unique identifier can be something the users CPU, serial number and something that cannot be easily changed by the user. Whenever the file is opened the unique key is looked for and if found, the file will be opened up. If the end user tries to give it to someone then an error message is displayed.
The most common protection given by DRM is through encryption and digital watermarking.
Encryption is the process of scrambling information embedded within a digital object so that it cannot be used without a password or a unique key. This could include encoding the terms and conditions for which the material can be used. Use of the work is allowed only when the conditions of the key can be met.
Digital watermarking embeds the information into data. Watermarks can either be visible or invisible. It helps to reduce the likelihood that someone will bypass it or try to make illegal copies.
Pros of DRM
- Limit the unlicensed sharing of content beyond those who paid for it.
Cons of DRM
- It affects sales, people refuse to buy digital products that have DRM in place and/or objections to it on principle. Secured formats also cause ten times the number of customer service calls, when compared to unsecured formats. A customer who has a problem with a secured file is less likely to purchase DRM formats again.
- The inability to use a file they paid for across multiple operating systems they own personally. Secured formats are difficult or impossible to pass from device to device.
- The inability to back up and safeguard files.
- The added expense of DRM, which is passed along to the reader, in the form of higher prices.