With another release of information from Wikileaks, we’re reminded of the importance of information security policy and practice. This 2-part posting discusses PDF content security strengths and weaknesses and the importance of vigilance, and will guide you in developing a comprehensive PDF content security policy.
I’m pleased that Dean Sappey , President of Docs Corp – is the contributing editor for Part I and II of this blog posting on PDF content security.
PART I – What is PDF Content Security
PDF content is generally considered to be a more secure way to publish and share documents because the PDF standard allows several levels of security and several ways to apply security. However, as hard as we try to make content secure, there is no format which is truly secure against any and all risks and this includes PDF documents.
PASSWORDS
There are two types of passwords for PDF documents. The first is called a “Master” password which controls access to security settings for editing, copying, and printing (as examples). A second password is an “Open” password which is created by the PDF owner and must be supplied by a PDF user to open a PDF file.
Perhaps since the first password was created people have endevored to unlock them. Quite simply, there are tools available which can crack passwords. This is not a revolutionary notion but should be taken into account when securing PDF content. As long as parties need or want to circumvent security measures – there will be parties providing software or services to facilitate that circumnavigation. Since PDF security relies heavily on password protections it is not uncommon to hear of software designed for PDF password cracking or unlocking.
SECURITY – Tier 1
PDFs created by solutions like pdfDocs Desktop (Docs Corp) and Adobe provide the ability to add security to a PDF document which affects the “functionality” of the PDF document. This security relies on a “Master” document password and allows the creator of the document to:
- prevent the PDF from being edited,
- prevent information from being copied from the PDF to the clipboard,
- prevent commenting,
- prevent combining of PDF documents with others,
- prevent printing,
SECURITY – Tier 2
Additional security can be added with digital certificates and an open password .
A digital certificate can provide assurances about (a) who created the PDF document and (b) whether the document has been changed or tampered with in any way. A digital certificate” creates a numeric value when applied. The numeric value takes into account all of the bits and settings within the PDF file. The digital certificate will become invalid if the numeric value changes at any time after it is applied. It’s the equivalent of a wax seal on a PDF.
Another important security measure is the “Open” password which prevents a reader from even opening a PDF for viewing without a password. This type of password tends to be much harder to ‘crack’ and – importantly – prevents viewing and reading (or screenshots etc..) without knowing the password.
ADDING SECURITY – Tier 3
Another level of security is found with 3rd party encryption options including PGP Security but these options are beyond the scope of this posting.
SUBTRACTING SECURITY – Where there is a Will there is a Way
While it is important as the creator of a PDF that you can rely on the fact that your PDF cannot be easily edited by the person receiving your document, it is also important to understand that in reality there is no way to completely ensure your document is never tampered with or recreated.
Many tech-savvy computer users have discovered a range of software products which allow you to remove the security applied to a protected PDF. These software products allow you to view and edit a PDF even if the PDF is secured because they can unlock the Master password.
Whilst these software products may break copyright and terms of use rules for PDF content, in my own personal view, they avoid being classified as illegal and prevented from selling their software primarily because their End User License Agreements stipulate that use is limited to unlocking documents that you own. In other words, they stipulate that you should only unlock documents that you created and possibly just forgot the password of - and not use it to unlock any documents that you do not legally own.
So be aware even when you create a PDF and secure it, the document can still be unlocked and modified by anyone willing to buy a commercial software application.
Speaking personally as President of Docscorp, it is my view that software should not allow this and for this reason pdfDocs does not allow you to unlock a secured PDF (as is the case with Adobe Professional). Of course, even if there were no commercial software available to unlock PDFs, there would always be the hacker willing to provide products for this purpose. .
SUBTRACTING SECURITY - OCR Conversion and Print Attribute
In reality, as long as a PDF can be viewed without a password, security is very hard to enforce because the properties of the PDF can be modified using commonly available programming languages.
Even without resorting to programming, if you can print the PDF to paper – you can scan it and use OCR software to convert the scanned file to PDF or MS Word. Software products like pdfDocs allow the user to take any scanned document and convert it quickly and easily to a full text-searchable PDF or to an editing format like MS Word - in a format that is almost identical to the original document.
This means that even when a PDF is secured from editing, if the PDF can be printed then an almost exact replica of that document can be created using scanners and OCR software. This further emphasizes the limited ability of security on PDFs to prevent changes.
In the next blog posting, we’ll discuss some steps you can take to enforce the security of your PDF content.
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