You may have a WinZip or Zip archive that contains sensitive files, and have the archive protected with a password.  What happens if you lose the password?  Your options depend on the version that you used to create the archive.

Read on to find out more about WinZip and Zip passwords.

The first thing to know is that WinZip versions after version 8.0 use strong AES encryption, while the earlier versions used the generic zip encryption.  This distinction makes a lot of difference in how likely it is that you can recover the password, or otherwise unlock the archive.

When an archive is protected, you can usually see the titles of the files, but not extract them unless you have the password.

The old PKZip / GZip standard used quite a weak encryption algorithm, vulnerable to attack due to problems with the cryptographic standard used.  If you have five or more files in an archive, you can always open the archive without the password.  You need software that will run what is called a collision attack.  

If you have a single file from the archive in decrypted form, you can also recover the archive without the password.  Again, you will need software to do this.

The last resort is to try a dictionary attack (trying dictionary words), and if this fails, do a brute force attack (this means trying out all possible character combinations.  The old zip standard has a simple and fast encryption approach, so you can run through the combinations very quickly.

With AES encryption, as found in WinZip 8.1 and later, there are no short cuts that you can use.  AES is an encryption standard, and is secure.  There is no known way of bypassing it.

You will have no choice but use the dictionary attack and brute force attacks.  Again, you will need software to do this.  Since the AES encryption algorithm is more complex, it is also far slower.  It is helpful if you remember the structure of the password, because you can use this in the password software to reduce the number of combinations that need to be searched.  If you have used a very long password that is not a dictionary word, it may be impractical to recover the archive.

Since there is no single approach that recovers all WinZip / Zip passwords, commercial recovery services are not as readily available as for Word / Excel passwords.  Generally it is best to buy your own software.

Check out our software pages for criteria to choose commercial software for WinZip and Zip password recovery.

Tags: winzip password, winzip password recovery, zip password

This entry was posted on Saturday, December 13th, 2008 at 6:29 pm and is filed under WinZip Passwords. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.