pdf password encryption

PDF Encryption & Security

Adobe Acrobat Encryption & PDF Password Security

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The origins of PDF encryption and PDF password security

Adobe Acrobat Encryption and Security History

The Adobe™ PDF document format has been in development since 1991, and from as early as 1994 included security features that were aimed at preventing users from being able to make changes to a published documents.  This involved the use of encryption as the only practical way of protecting information.  The basis of PDF encryption is to prevent users viewing the file if they are not authorized, and if they are authorized, to control what they can do with the file (i.e. whether printing is allowed, etc.).

Early PDF document security relied on weak 40 bit encryption and soon after it was released methods of breaking it were freely available on the Internet.  In 2001 128 bit encryption became available to prevent simple hacking of the native mode controls, and degraded printing, was also added.  In 2008 256 bit encryption was added to Adobe 9 but the implmentation was not as secure as Adobe 8’s 128 bit encryption (the password checking routine consists of just one call to the SHA256 hash function) enabling passwords to be cracked a lot quicker.

Password recovery software is able to break Adobe PDF encryption since common PDF security flaws still undermine Acrobat PDF security to this day.

PDF Password Cracks and Hacks

The early controls relied upon manual entry of either one or two passwords which allowed the user to override the controls initially placed on the document.  The commonest method of attacking an encrypted PDF document is to try and break the 40 bit key implementation (the default if security has been selected for compatibilty with version 6 PDF documents and below).  Advertisers such as Advanced PDF Password Recovery provide a solution that guarantees to break that level of protection in a few minutes, and can break higher levels of encryption (128 and 256) using various methods of attack.  PDF Restrictions can be removed instantly regardless of the encryption algorithm or strength used.  Other organizations such as Passware Kit Standard or PDF-Password-Recovery also use advanced techniques to remove PDF passwords, although they warn that the 128 bit algorithm itself cannot be practically attacked using brute force.

Fortunately (or unfortunately for some) most attacks are speeded up significantly by the choice of ‘poor’ passwords (8 characters or less that are common words).  Whilst the 128 bit or 256 bit PDF encryption algorithm may be good, the choice of a poor password, so that users can remember it, defeats all the good technical work.  If a weak (short and uncomplex) password is used  PDF password cracking software will quickly decrypt Adobe PDF files regardless of whether they have user or owner passwords set and regardless of whether they are protected by 128 bit encryption or higher.

But users don’t even need to crack the PDF encryption in order to share PDF files with others.  They can just forward the encrypted PDF along with the password.  This of course defeats the purpose of using PDF encryption if your main goal was to prevent unauthorized sharing.

Clearly the use of passwords for PDF encryption (or encryption of any other document) is not the way forwards!  In fact, we predict that password protected PDF documents will become obsolete in the near future as industry looks towards more secure solutions such as PDF DRM for secure document sharing.

PDF encryption security is in the process of moving towards using more secure methods such as public key technology for document protection.  A number of companies have moved into this space adding their own approaches to PDF encryption using certificates, but they over-complicate the approach and do not supply any key management, making their systems impossible to manage.  Some older products even had security flaws, such as plug-in systems where the key required to decrypt the PDF file is handed over to Adobe for processing – see PDF security flaws.  Famously, in 2001 a programmer from Elcomsoft was prosecuted in the USA for publishing a program for removing PDF copyright protection on FileOpen PDF DRM products by attacking this weakness in the system.

Regardless of whether passwords or public keys are used to encrypt PDF files, you need to use DRM controls to restrict document use – otherwise, once a user has decrypted the PDF document they can do what they like with it.  Adobe PDF restrictions can be removed regardless of whether a password or a certificate has been used to encrypt a PDF.

Locklizard: a secure alternative to PDF password encryption & plugins

Locklizard provides many advantages over Adobe PDF Password encryption

  • No Passwords

    No passwords or codes for users to enter – keys are transparently and securely transferred to authorized devices.

    We do not use passwords for PDF encryption since they can be easily compromised and shared with others.

    Why you should not password protect PDF files.

  • No Plugins

    We do not use PDF plug-ins since they are a major source of security and operational problems.

    Decryption of the document occurs in our own secure Viewer application which also enforces DRM controls.  Decryption only ever occurs in memory and non-encrypted files are never stored to disk.

  • DRM Controls

    We provide many extra PDF restrictions beyond Adobe Acrobat password encryption such as expiry and revocation, dynamic watermarking, PDF tracking, and device and location locking to name just a few.

    • Stop screen grabbing
    • Stop printing (or limit the number of prints)
    • Expire PDF files after a number of days use, views, prints, or on a fixed date
    • Revoke PDF access instantly (regardless of where they are)
    • Track PDF use

    And unlike Adobe, our DRM controls cannot be easily removed.

  • Device & location locking

    • Automatically locks PDFs to devices to stop users sharing PDF files with others
    • Lock PDF files to locations to stop users viewing them on devices in unauthorized locations (i.e. allow only use in the office)
    • Control the number of devices your PDFs are viewed on
  • Dynamic Watermarks

    Dynamic watermarking – you only have to secure a PDF file once for all users rather than having to secure PDFs individually for each user in order to display unique user information (name, email, etc.).

    Unlike Adobe watermarks, our watermarks are permanent and cannot be removed with PDF editing software.

  • Secure Distribution

    • Secure PDF files on your local computer.  Unlike many other PDF security providers, you protect PDF files on your local computer – there is no uploading of unprotected files to a cloud server where they could be easily compromised.
    • Distribute secure PDFs just like any other file – upload them to a cloud server, your web site, send by email or distribute on CD, USB, etc.
  • Simple to use

    Our PDF encryption software is simple to use – secure PDFs by right clicking on them in Windows Explorer and select the DRM controls you want to enforce.

  • Simple Key Management

    Many organizations do not need or wish to purchase cryptographic keys from suppliers or have users generate key pairs that must then be managed.  They already have business relationships with their customers and do not need to prove who they are cryptographically or otherwise.  They are looking for a simple system to protect PDF files from any kind of password based attack and to ensure that users are not able to compromise the integrity of the system by sharing files, cryptographic keys, passwords or any other materials used to encrypt PDF files.

    Locklizard handles all key management transparently – ensuring keys are securely and transparently delivered to authorized devices.

  • Cost Savings

    No charges per PDF document – just a one off fee for unlimited users and PDF files.

Why Locklizard for PDF Encryption?

US Gov Strength PDF Encryption – secure PDF files without passwords

Locklizard takes your PDF protection seriously.

  1. See 10 things you really wished you had known about PDF DRM, but they didn’t tell you!
  2. Our DRM PDF Security products enable you to share PDF files securely without insecure passwords or plug-ins, and enforces access, location, expiry, and usage controls.  Revoke PDFs at any time regardless of where they are.
  3. Our DRM technology ensures your secure PDF files remain safe no matter where your documents reside.
  4. We use US Government strength encryption to protect PDF files – the AES encryption algorithm, licensing controls to authorize users, and DRM controls to prevent document misuse.

See our customer testimonials or read our case studies to see why thousands of organizations use Locklizard PDF security to securely share and sell their documents.

Simplified PDF Encryption & Protection

We have introduced a very simple method for allowing a copyright owner to specify controls that will be enforced on all recipients of a document.  It provides for a simple, but cryptographically secure method of customer registration that transfers the true encryption key into the registered product by secure key exchange, and holds the key in a secure form prior to use.  Locklizard enables you to encrypt PDF files without passwords – there are no passwords to manage or attack so the system cannot be compromised.

Customers, once registered, can receive files and use them seamlessly.  However, they cannot transfer their registration to another computer system, and do not have access to the underlying secrets by which their access is authorized, so they cannot give those to other users.  Your PDF files are locked to authorized users devices so they cannot be shared with others.

This creates a win-win for both supplier and customers and ensures your IPR and your revenue stream remains protected at all times.

Customer Testimonials