PDF In-Depth

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Encryption and authorization

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The PDF file is then strongly encrypted with a very large randomly generated key and saved on your disk with the same name plus an additional file extension ".drmx" indicating that it a fully secure and locked file. The document details, settings and secure key information are separately encrypted and automatically transferred to the central Drumlin digital rights management (DRM) service -- the document itself never leaves your site. You can now safely place the .drmx version of the PDF on a web site, CD or email it to a user, without concern that it might be intercepted, read, decrypted and/or copied.

The last step in the process is Authorization. This is carried out by the recipient or customer of the document using the File menu, Authorize option. Only documents with the .drmx extension require authorization before they can be used. The end user selects your .drmx file and is prompted for an authorization (or 'authentication') code -- this is a long string of alphanumerics you provide to them, and is input when prompted:

The document name field shows the name the file will be saved as once it has been decrypted -- it is the same filename as before but with the .drm extension rather than .drmx extension. As soon as a code has been entered it is checked against the records on the central DRM service and if all is OK the file is decrypted, saved and the user can view it and print it (if allowed) according to the settings you have made.

Authorization codes can be obtained in one of two ways: the first is by logging in to the online web service, selecting the document(s) you require codes for and the number of codes needed, and then ordering these via the secure system provided; alternatively you can contact sales@drumlinsecurity.co.uk and they will provide the codes you require. Any number of codes can be provided, with unit prices being very low. Codes are single-use by default, but multiple-use codes can be provided (e.g. to allow a user to install a copy of the document on their laptop and their desktop).

In addition, an entirely free secured document facility is provided. This is available if the Generate DRM file box is ticked on the "Publish" form. It creates a file with restricted usage (typically a maximum of 5 views and no printing, although these can be relaxed) but which is readable using Drumlin on any PC, i.e. is not restricted to a single user. These locally generated DRM files are great for sending out sample documents or providing entire documents with basic restrictions on usage.

Finally, there are many options to tailor the software and service to meet specific customer requirements, including corporate branding. For example, a major international engineering company wanted to create a CD containing all its technical and marketing information (several 1000 files) to send out to their distributors throughout the world. They used the bulk creation facility to generate the necessary files, with start and end dates for 2008, and unlimited viewing but no requirement for individual document authorization, keeping everything simple, secure and easy for their customers.

More information can also be found on the the Drumlin Security web site.

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For people who don't spend their time looking at PDF files in text editors*, PDF security is a sometimes misunderstood beast.

For example, those document restrictions that PDF files sometimes have -- no Printing, Content Copying, Page Extraction, etc -- are essentially useless unless the PDF also has a User Password.

January 09, 2014
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