What is DRM (Digital Rights Management)?

The internet gives everybody the opportunity to publish or download contents of all kinds easily and cheaply. On the internet you find nearly everything you would normally have to pay for for free. The media files (especially videos, music files…) can be copied and shared via many ways and a to control who gets the files is nearly impossible. DRM - Digital Rights Management - tries to change that.

What is DRM?

First of all, DRM is only an umbrella term for all the technologies that prevent unlimited contribution of data and instead enable owners to limit access to the file to certain ways of distribution and usage. There are three technologies that differ enormously.

Marking of data

The aim of marking of data is to prevent an uncontrollable spreading of data. Based on the marking a background system can decide whether a file can be passed on or prevent the sharing. Three different methods are used today:

Watermarking - Here an inconspicuous mark is embedded. This could be a change in a picture that is not noticed by the viewer but that the same time contains information like the copyright holder. It is mainly applied in digital TV - the mark for example contains the information whether a TV show can be recorded by a person or not.

Perceptual Hashing - Algorithms are used that generate a hash based on significant changes made in a film. This enables the recognition of copies even if they have been converted into a different file type or the compression has been changed. It is usually used in file exchange systems to have a certain amount of control over the exchanged files.

Copy protection for data carriers

This is a very simple method which is applied to data carriers like CD-ROMs, Audio-CDs or floppy discs. This DRM mechanism is not usually considered when people talk about DRM though as a proper DRM mechanism usually can be used more widely.

Fingerprinting

Technically fingerprinting is the same as watermarking. The most important difference is the assignment of e.g. a customer to e.g. a music file he has bought legally. The customer can be identified if he - illegally - passes the file on to friends, colleagues, other internet users….

Most often you will come across DRM in connection with medial context. Apart from copy protection all three mechanisms are applied here in all possible combinations. You might download a piece of music and are only able to copy it a certain amount of times - or even only listen to it a certain amount of times. Also you might only be able to listen to it on certain devices.