Digital Rights Management(DRM)

Digital Rights Management (DRM) is a technology that affects all users of computers, media players, mobile phones and other devices.DRM is being used to restrict individuals' use of their own copies of published works.This is to control use of digital media by preventing access, copying or conversion by end users to other formats.Digital watermarks involve data steganographically embedded within the audio or video data.

Rights owners are typically copyright-holding companies like music, film, book or software publishers. They use DRM to control how documents, entire software programs, or even e-mails are used.It is used in a number of media, but is most commonly found in video and music files.

How does DRM work?

DRM is a two-part scheme. It relies on encryption to protect the content itself and authentication systems to ensure that only authorised users can unlock the files. When applied, DRM scrambles the data in a file rendering it unreadable to anyone without the appropriate unlocking key.

Authentication systems stand between users and the decryption keys, ensuring that only people with the proper permissions can obtain a decryption key. Without a username and password or if a file has been decrypted too many times, the system will not provide the key. This means music files with DRM, for example, can be swapped over the internet and remain unusable to those who have not paid for them.

It also means only authorised programs and portable players can use the tracks.

Music without DRM, like the popular MP3 music format, retain the ability to be played regardless of the number of times or to whom they have been copied

Watermarks can be used for different purposes that may include:

• for recording the copyright owner
• for recording the distributor
• for recording the distribution chain
• for identifying the purchaser of the music

Read more in Wikipedia .How it works in HowStuffWorks

How to copy protect a CD or DVD .Another tutorial here

HASP from Aladdin is one of the DRM softwares .Security issues, fair use issues, and issues of creative expression are all at the forefront of the DRM battle.