Home How Tos How to easily encrypt and Lock ZIP files

How to easily encrypt and Lock ZIP files


The question can be elucidated in two ways. Do you want to hack someone else’s documents? Or do you want to avoid a form of encryption that won’t give you much protection? I believe most of our readers are good people who won’t need to hack someone else’s document.

For years now, the zip format always have an encryption which is intended primarily for compression. But the type of encryption it gives you depends on the program you use to create and open the ZIP file.

The .zip format supports two forms of encryption and password protection. This first one which is also known as ZipCrypto is very easy to crack. Saying it is very easy doesn’t mean everyone could do it, but the Info-ZIP organization calls ZipCrypto ”quite weak”—a view shared by other organzations as well.

You will be more secure using the other option, AES-256. Unlike ZipCrypto, AES was not made for ZIP files. It’s a well known and strong encryption technique used in many programs. Assuming you use a strong password, it’s for all practical purposes unbreakable.

But when you use it for ZIP archives, AES-256 generates another problem: Windows’ own, built-in compression tool doesn’t support AES. Email someone an AES-encrypted file, text them the password (safer than emailing it), and if they try to open it in Windows Explorer or File Explorer, they won’t be able to open any of the files within the archive.

Fortunately, most third-party zip tools, including the free 7-zip, support AES-256. To encrypt an archive in 7-zip, once you’re at the Add to Archive dialog box, enter a password and select the Encryption method AES-256. You’ll find these options near the lower-right corner of the dialog box.


One more hitch with encrypted ZIP files: No matter which form of encryption you use, anyone with access to the files can see the name of the files within the archive. If the file names provide sensitive information, a thief could take advantage of that. Of course, they would not be able to open any of the files without the password.

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