Distributing documents securely and the role of encryption
Exchanges between computer-based applications generally use encryption in order to protect the transfer from being intercepted or misused. But managing the document content itself has proven rather more difficult. Trying to use encryption on its own is technically difficult because although it perfectly preserves the original content, it has no continuing control over how a file is used once it is decrypted and returned to its original form.

A simpler approach to exerting continuing content control has emerged with the increasing availability of Digital Rights Management technologies that can be applied to important documents in order to protect confidential content. This works because using DRM it is possible to control subsequent use of the document instead of relying upon ‘conventions’ or ‘understandings’ as to how the content is to be controlled once it has been disclosed.
Confidentiality through redaction
A commonly used alternative, although rather less successful in the world of digital documents, is the use of data redaction to control access to sensitive information.
Data redaction is used to render only specific data items inaccessible, and it does not seek to control the subsequent use of the sensitive documents’ content. It does so by blanking over the part of the document that is confidential, but leaving the surrounding information untouched. In many systems, this is achieved by putting a mask over the visible content without removing the underlying content. This is problematic because the underlying data remains accessible to anyone able to edit the file or view its code. Thus, an unauthorized user can read and process the unredacted text.

A redacted document in Safeguard PDF viewer
Adding confidential watermarks
While many applications (Adobe, MS Office, Google Docs, etc.) can be used to easily add a confidential watermark to a PDF, they all suffer from the same problem – namely it is trivial to remove them. Users can instantly remove restrictions and then edit the document to remove all watermarks in a single action.

DRM is used to prevent users editing PDF content and stop screenshots being readily taken, so that watermarks cannot be easily removed.
Content available for a limited time
According to James Bond, “Diamonds are forever,” but the same certainly isn’t true for document content. Frequently, controlled content has limited accessibility. This may be due to information being superseded and so is no longer valid, or that it is only given a certain lifetime to begin with. Controls are needed to prevent this content from being available before it is officially released or after it has reached the end of its lifecycle.

Overall, document distribution software needs to take into account a number of dates:
- the date before which the content may not be used
- the length of time the content can be used for (some legislatures mandate 6 years maximum from collection to use personal information); the date on which the content ceases to be available, or on which it becomes publicly available
- the length of time content can be used after first being used
- the number of times that the content may be used by a specific user.
Document expiry should happen automatically whether the user is online or offline, with the ability to also revoke access manually when the need occurs.
Content kept confidential by location
Further content controls may be applied at the IP address level. At one level, this kind of content control is used to prevent data leakage outside of specific networks or groups of networks. Either all documents are restricted to one or more individual or groups of network addresses, or specific users are restricted to the range of acceptable addresses they can use content that is protected.

Using IP level controls may also be extended to determining the geographic locations that are permitted. This may prove to be an essential technique when some documents may be embargoed in some countries, or where content is country specific. For instance French content may be restricted to France and Canada and not available in Belgium, where English content may be provided. Also, some countries may forbid or censor content and prosecute publishers who fail to prevent content use when it is not approved.
Auditing use of confidential content
Underpinning content control is providing audit information about the use of content. It is all well and good having applied content controls, but how do you know they are working? Where content is being used, logs need to be maintained that list which users have opened the documents, at what time, and from what IP. This may also enable content controllers to identify if sensitive data is being accessed in locations that are inconsistent (appearing in a country they are not expected to be in, for instance, or being in several places at the same time) and might require investigation.

Summary: Secure document distribution and content management
In summary, secure document distribution and content management for confidential documents may be achieved by using DRM security features. These enable you to bind controls to the content that are abiding. Confidential content in a lifecycle management sense has many dimensions beyond file access controls: Controls are needed by dates, numbers of accesses, numbers of printed copies made, and location in order to allow the content owner to be effective in managing confidentiality. Further, there must be provisions for the content owner to change their minds about controls such as start and expiry dates and prints.