How to create a Mac encrypted disk image

Encrypting personal files
For high security, you can use Compress Files to encrypt part of your hard disk through the use of an encrypted disk image protected with a password. You can then also email this disk image to other people who know the password. The image will show up as a volume on your desktop. When your Keychain is locked, or when you send that disk image file to another person, the image is secure. When your Keychain is unlocked, you can copy, move and delete files as you would on any normal hard disk.

How to encrypt a file in Mac OS X
Compress Files allow you to create encrypted disk images in which you can store your personal files. To create an encrypted disk image, do as follows:

• Choose Encrypted Disk Image from the popup menu.
• Drag a folder or just some files you want to encrypt and protect with a password.
• You will be asked by the Finder to enter a password.
• Compress Files will create a .dmg compressed and encrypted file.

To mount the disk just double click on it and it will appear as a new drive. You can drag files to this drive and they will be added to the encrypted image. When you are finished, just eject the drive by clicking the eject icon next to the drive in the Finder. Once the drive is not mounted, anyone attempting to mount the image will be required to enter the password you specified.


Archive Creation Options

Omit Finder Desktop files from the archive
This option determines whether or not Finder specific information (such as the .DS_Store files) is preserved when adding files to Zip archives. Typically, if you are sending files to other users you do not need to include this information. If you are compressing files for your own use, we would recommend that you include those files to preserve your custom informations as icon size and position.

Omit Mac-specific content from the archive
This option determines whether or not Mac specific file attributes (such as a resource fork) is preserved when adding files to Zip archives. Typically, if you are sending files to a Windows user you do not need to preserve this information, as it will not be used on a Windows-based computer. If you are sending files to a Mac user or if you are compressing files for your own use, we would recommend that you preserve Mac file information.

Trash original files after the archive was created
This option determines whether or not the original files have to be moved into the Trash after the archive was created.


Troubleshoting

I am trying to compress a file and it doesn't get as small as I had hoped.
Some files compress better than others. Many multimedia files are already compressed. Such is the case for jpeg, gif, mpeg, mp3, pdf, mov, QuickTime and many others. These files often cannot be compressed further.


Frequently asked questions

So Compress Files can't de-compress files?
Yes, it's correct, the tool is designed for only compress, archive and encrypt files. We suggest to use "BOMArchiveHelper.app" which is the built-in archive unpacker program in Mac OS X or StuffIt Expander and The Unarchiver free tools which are designed to handle many more formats than BOMArchiveHelper. Anyway along with the version 3.0 of Compress Files we provide the application "UnXAR" (inside the Extras folder) which is designed to decompress XAR archives. To obtain the new "Extras" folder, please download the entire pakage from our download page instead of just to upgrade via the automatic update feature.


Compressing files

Limit to the size of a zip file
The zip format's theoretical limit is 4GB. We do not recommend exceeding 750 MB when creating a zip file since the potential for corruption rises greatly as the size increases past that point.

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