We need some form of protection for our PDF documents that we want to secure from access by just about anybody. However, protecting documents in a comprehensive way is not just about preventing access to them but indeed ensuring that you can also control what users can do with them after they have gained access. For a long time we were accustomed to password protectedpdf files but which have since become vulnerable considering that password-based encryption keys can be shared and at the same time there are plenty of password-cracking tools available, many for free.
The most comprehensive way of
protecting documents can be realized via Digital Rights Management "" DRM controls, and which is used in combination with strong encryption algorithms such as the AES in its highest strength - 256 bit. DRM controls will regulate whether and how many times a protectedpdf file can be copied, shared, printed or edited. Since these functionalities are already available with the several password based PDF document viewing systems we need a special viewer that can enforce the regulations realized in the DRM controls which does not rely on passwords. Therefore, any person interested in reading or using your documents must have a secure document viewer installed in his/her computer that supports public key technology.
This secure viewer is also the interface that interacts with the
protected pdf document publisher"s server to confirm and register the user"s license thus authorizing use of the document. Using a secure viewer carries several advantages over the default PDF document viewing software (such as Adobe) in protecting documents. It addresses the weaknesses of the Adobe viewer by preventing the running of JavaScript (which is a hacker"s channel of choice for launching malicious attacks), preventing use of plug-ins, inhibiting use of third-party screen grabbers, and preventing printing by stopping loading of PDF drivers or print to file.
Protecting documents via DRM is very useful for publications which are made available on subscription basis. This is because you get to set up user accounts and you are empowered to decide when they expire, when your documents can no longer be viewed, and if your publications can be viewed offline or only online and whether in virtual or thin client environments. DRM controls can be integrated with your ecommerce system to facilitate the delivery of licenses. The best DRM systems provide a document watermarking capability whereby system and user information are dynamically displayed over the protectedpdf document whenever it is printed or viewed. This makes for a good printing and then sharing deterrent as the person who printed the documents can be identified via the watermarks.
