ElcomSoft’s Advanced PDF Password Recovery software makes it easy to remove both password encryption and usage restrictions from Adobe Acrobat PDF files. It provides super-fast guaranteed recovery of PDF files with 40-bit encryption.
Types of PDF Passwords & how to crack them
You can protect Adobe PDF files with two different passwords:
Free PDF password cracking tools will normally only remove the permissions password although some will also remove the PDF document open password if the PDF has been encrypted with 40 bit encryption. However, when it comes to removing PDF restrictions you don’t even need to use a PDF password cracker program – there are other simpler methods – see Removing PDF Restrictions.
To remove the Permissions password you must know the Document Open password. If you don’t then you need to purchase a PDF password cracking program to remove it (free PDF password crackers only remove the permissions password. Some will remove the Document Open password if the document was protected with 40 bit encryption but this is rare unless it was protected with a very old version of Adobe Acrobat). One of the first and best programs for cracking PDFs is Elcomsoft’s Advanced PDF Password Recovery. The professional edition removes PDF document open and permissions passwords using both brute force and dictionary attacks.
How do PDF Password cracker tools work?
PDF Password cracking tools (usually marketed as PDF Password Recovery tools for legal reasons) use several techniques to remove a PDF Document Open password:
How long does it take to crack PDF Passwords?
Any PDF password cracking software can easily remove the Permissions password (and thus the document restrictions) in seconds.
Time to crack the Document Open password will depend on:
Brute force and dictionary attacks can therefore take several days or more to crack a PDF password depending on the above factors. If the PDF password is particularly long you might be waiting a while!
Cracking of PDF files encrypted with 40-bit keys usually takes a few minutes if you use Elcomsoft’s Enterprise edition of Advanced PDF Password Recovery. This is because it attacks the encryption key instead of attempting to guess the password. Other PDF password crackers will take 1-2 days to crack 40 bit encrypted PDFs.
Adobe 9 passwords using AES 256 bit are 100 times quicker to crack because of a security implementation flaw – a password checking routine consist of just one call to SHA256 hash function. It is not the AES 256 bit algorithm at fault but the password checking routine implemented by Adobe which checks if you have entered the correct password or not.