In Depth

Digital Rights and Restrictions

Sony, Apple and especially Microsoft illustrate differing approaches to Digital Rights Management

By Simson Garfinkel, Simson Garfinkel

March 01, 2006 — CSO —

Here is a typical problem: I have a document file that I want to share with my coworker James. I want James to be able to read the file and send me his thoughts and corrections, but I don't want him to be able to print it or share it with anybody else in his office.

You might wonder why I am sending this document to James at all, since I obviously don't trust him to behave in a responsible manner. But perhaps I don't have a choice. Perhaps the document is a price list that James needs to get his job done: I'm worried that James might be thinking about taking a job with a competitor, but the data may help him close a deal for our company today. Perhaps what I've been calling a "document" is really a movie file and James is a critic for the Los Angeles Times. I want him to write a review, but I don't want him to share copies of the DVD with 10,000 of his closest friends. Perhaps my real fear isn't James at all, but his 16-year-old son who recently installed file-sharing software on his home computer. With all the Trojan horses that are loose in the world, the document might get out without James even realizing his complicity in the act.

What's needed here is a strong dose of digital restrictions management, better known as DRM. Many people in the computer industry think that DRM stands for digital rights management. Don't believe it. DRM is all about imposing restrictions and limitations on computer users and their systems so that certain activities are difficult or virtually impossible. DRM is about restrictions, not about rights.

Microsoft's Word on DRM

There are many different kinds of DRM systems. Some are based on strong cryptography, others lock up content so that it can be accessed only with special readers or viewers that implement particular restriction policies, but all are fundamentally based on the honor system. Each of these approaches is built into the current version of Microsoft Word, which makes Word an excellent tool for exploring DRM.

Next time you edit a document in Microsoft Word, click on the Options menu and then on the Security tab. You'll have an option to give your document a password to open or a password to modify. Although these passwords sound similar, they have very different implementations. Word turns your password to open into an encryption key that's used to scramble the contents of your document when it is saved. Anybody who doesn't know the password can't open the document. This restriction is implemented by the mathematics of cryptography, not by the Word application, so you can't get around it by trying to open the document with another application—for example, using the TextEdit application that's built into the Macintosh operating system.