Strong PDF passwords are difficult to set up and use.
As a matter of history, passwords have been used to protect access to computers and access to files. At the time it was the only mechanism that could be implemented – smart cards and biometrics were just a gleam in manufacturer’s eyes (and some say still are).
Passwords have an increasingly bad press as a security mechanism, largely because of the appalling way in which programmers, with little understanding of either security or how human beings behave, have implemented poor systems that make impossible demands on the user.
The usual approach to password management is to insist on something that has 6 or 8 characters and/or numbers and changes regularly. The approach makes people pick easy passwords so they have a snowball in hell’s chance of remembering them.
The same goes when people pick passwords for protecting encrypted PDF documents (or zip files or anything similar). It is difficult to choose a password that you can easily pass on to the recipient and be sure they get it right unless you choose a short and simple one.
Managing PDF passwords & controlling use
Managing PDF passwords is in itself a nightmare:
You cannot stop users sharing the password(s) with other people and you have no way of being able to detect that.
And that creates the problem, because short passwords that are easy to remember and type in are just as easy for an attacker using a dictionary system. They can break it in minutes, if not seconds. Even using an exhaustive search for all numbers and letters for 8 character positions is stunningly quick with a P4 based computer. See Removing PDF Passwords.
But PDF passwords are still popular (as are zip passwords) even though they have such a weak effect and are so easily passed on to other people who have no authority to use the document(s).
So if you disclose what the password is to a document because you are using the password to enforce the PDF security or PDF digital rights management controls then any rights you gave to the recipient can be passed on to anyone else. But if you don’t disclose the password then how can the system be made to work?
And so we have to conclude that PDF password protection is not an effective way to implement PDF security because it is too difficult to manage and too easy to defeat.
10 Reasons NOT to password protect PDF files
Although PDF password protection seems to be a good idea because it’s easy, most implementations are not actually effective. Below are 10 reasons why you should not PDF password protect files.
So why do people password protect their PDF files?
The simple answer is laziness. They like to live under the delusion that incompetent or inadequate passwords provide some fig leaf of protection, whilst anybody with any ability to search the Internet can buy products that remove that irrelevant protection immediately. Search for pdf password, pdf password protect, pdf password protection, pdf password security, password protect pdf, password protect a pdf file, how to password protect a pdf, protect pdf with password, on the Internet and at least three of the first ten search queries are for pdf password crackers.
“Document-level password protection technically isn’t DRM (digital rights management). And because of the plug-in architecture of Acrobat and PDF readers, it makes PDF a less-secure platform for DRM.” – quote by ElcomSoft CEO Vladimir Katalov.
At a single click of a button pdf-Recover will remove the password regardless of whether it has been encrypted using the latest 256-bit AES encryption. The result is an exact replica of the original PDF without any security settings whatsoever – pdf-Recover removes all of the restrictions implemented.
So whilst you can use Adobe to password protect PDF files for free, the security you are getting may not be adequate.
If PDF password protection is not recommended, what should I use to protect my PDF documents?
The key to a secure system is to avoid the user having to know or be involved with passwords at all.
This is best achieved by ensuring that, in a cryptographic system, keys are exchanged securely and secretly, so that even the user is not aware of, and therefore cannot compromise, the security of the system. Only if you take these steps can you be confident that the protection method you have used is resistant to both deliberate and careless compromise.
It is an accepted fact by all security professionals that the people most able to compromise any security system are the authorized users themselves. That is not to say that users are deliberately dishonest or even malicious rather that in most cases they are over helpful or fail to understand the security functions that they are expected to perform.
It is not easy to design a system that does not rely upon the integrity of the user, but those that have been designed specifically to avoid the need for the user to become directly involved, through the use of passwords or direct use of cryptographic keys are to be preferred.
How to protect PDF files without passwords
Safeguard PDF Security and Enterprise PDF DRM do NOT use PDF password protection to protect your PDF documents. They ensure your PDF documents are encrypted and protected against unauthorized use and misuse without the use of passwords.
Using Safeguard Writer you can protect PDF files without passwords and apply DRM controls to prevent PDF copying, saving, modifying and printing.
Safeguard uses public key technology rather than passwords.