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Beginners Guides: Decrypting Document & File Passwords
Beginners Guides: Decrypting Document & File Passwords - PCSTATS
As PCSTATS illustrates in this article, a lot of the methods of protection used by common software packages are far from invulnerable.
Filed under: Beginners Guides Published:  Author: 
External Mfg. Website: PCSTATS Feb 19 2007   M. Dowler  
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Beginners Guides: Decrypting Document & Zipped File Passwords

Quick and simple way to unlock those Microsoft Word, Zip, or PDF files that you've forgotten the password to. - Version 1.2.0

Security is a cause for concern in all areas of computer use. As we have shown in previous beginner's guide articles, nothing is quite as easy a target as an unprotected, un-passworded, un-updated computer floating on the tides of the Internet like a fat, juicy duck. You should always keep your system updated and password protected, lest someone take a bite out of your data.

Security does not begin and end with the operating system however. Many businesses routinely keep all computer communications encrypted and confidential, and even secure individual documents created with their office software.

While many operating systems allow users with administrative privileges to set permissions on documents, this method is not always easy or straightforward, and thus not particularly desirable to the average user. If you want to make sure that only you and your compatriots can access certain documents, encrypting and password protecting said documents is the obvious way to go. To this end, many popular software packages provide a method of safeguarding files, generally based on a password.

This is fine, but what if you forget the password? You might as well have deleted your work, right? Only this time the 'previous saved document' function will not save you...

But not so fast. As we will endeavor to show in this article, a lot of the methods of protection used by common software packages far from invulnerable. With time, the right software and the right instruction, you can crack the protection on your files and reclaim your documents. You can also recover incorrectly deleted documents, even if they have already passed beyond the recycle bin into that digital bit of heaven somewhere between the plug and wall socket.

Common methods of password protection and recovery

The most common method of protecting files is to use a numerical value generated from the password as a key, and use that key to encrypt the document. Microsoft office (pre-Office XP) uses this method on WORD documents, using 40-bit encryption which is fairly strong.

40-bit encryption is considered the minimum to safely protect data, but with the increased speed of modern computers, it is now feasible for an average home computer to break this level of encryption over the course of a few days. This is done by a key-search in which every possible 40-bit numerical key (the value generated from the password and used to encrypt or decrypt data) is tried until the correct one is found.

Any software that uses passwords is vulnerable to dictionary attack using a program to try words against the password until the correct one is found.

The other method is the good old brute-force attack in which all combinations of letters and/or characters and numbers up to a certain length are fed into the program until the correct password is found. They call this the '1000 monkeys with typewriters' method.

The only sure protection against dictionary and brute force attacks is to either make very complex passwords, which will ensure that brute-force attacks take far too long to be effective, or to have some sort of mechanism to limit the amount of times that a user can attempt to enter a password.

While the latter method of protection is common in operating system security, where password safety is considered extremely important, it is unknown in regular software applications like Office. This means that the dictionary and brute-force attack methods are the most common and effective means of recovering passwords for just about any application.

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Contents of Article: PCSTATS
 Pg 1.  — Beginners Guides: Decrypting Document & File Passwords
 Pg 2.  Recovering Passwords to Word, Excel and Office files
 Pg 3.  Guaword and Cracking ZIP File Passwords
 Pg 4.  Recovering Passwords to Adobe PDF files
 Pg 5.  Protecting documents with 3rdparty encryption
 Pg 6.  Using ABI-Coder to Encrypt
 Pg 7.  Restoration Deleted File Recovery

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