There are times you need to share some sensitive data with associates or mates that you don't want to share to anyone else or leave any possibilities for others to open and read/copy. One possibility would be to use password protected packing like ZIP or RAR. But that wouldn't be flexible in terms of further editing which is why macheads use DMG.

As in the previous DMG-related articles Disk Utility comes in handy. You can find Disk Utility in Applications > Utilities.

Feb 02, 2014  So, on my external USB hard disk I had created two password-protected '.dmg' disc images. Both functioned normally for about 2 months. Then, suddenly, one of the two images now opens without asking for its password (the other file remains protected).

On the toolbar of Disk Utility, there's icon for the New Image, clicking on which produces the dialogue box:

As we go through the entries, the specs for the new password protected DMG disk image are following:

1. Save As sets the file name of the image file, e.g. My private data.dmg.
2. Where sets the location of the image file.
3. Volume name sets the name of the volume as it would appear in Finder later
4. Volume size sets the estimated size of the DMG file. If you are going to share stuff, you probably know what would the maximum size be. For the document files you'd be safe with 10 MB.
5. Volume Format is the disk format for the image that you may safely leave untouched.
6. Encryption refers to the file encryption strength as we set the password. 256-bit AES encryption would make a nice choice here.
7. Partitions would be fine with Single partition.
8. Image Format is best to remain at read/write in order to enable later changes, e.g. if you need to add files into the image in future.

With everything filled in, hitting the Create button will create the image file at your given location and prompt you for the password:

Make sure to uncheck the Remember password in my keychain checkbox if you are willing to be prompted for the password at all times, even on your own machine. Otherwise, if anyone opens the DMG file on the machine it was created on, they would not be prompted for the password because it would be pulled off the Keychain automatically.

As you have created the DMG file, you can open it and drag your sensitive files to it in Finder. Once you have completed, make sure to unmount the image from the eject button by the image name .

How To Open A Password Protected Dmg

Related:

In computing world, DMG or (Disk Image File) is a file extension that belongs to Mac OS X. DMG file can also be termed as Apple Disk Image. The icon used equivalent to this file is an Internal Hard-drive. Disk Images are generally used worldwide in-order to distribute applications and software across the Internet. DMG file provides some attractive features that allow securing password along with file compression.
These virtual or physical Apple disks can be cloned from one to another. This is one of the powerful features of Mac.

Tip: If you want to open and view DMG files of Apple Mac OS X so, you can try DMG Viewer tool.

Why DMG Files Are Created?

Earlier, Mac applications made use of Resource fork. These are the part of file system on Mac Operating System, which consists of both the structured data and non-structured data. Mac could not transfer these Resource forks over the mixed networks. Hence, the usage of Resource fork dwindled and this was the reason that Apple created disk image formats(DMG). The Resource forks are very important as they contain Meta data regarding the file.

Mounting and Dismounting on Mac OS

It is equivalent to plugging in a removable drive, where E drive is automatically created and while removing one chooses ‘Safely Remove Device’. Similarly, you have to eject the Mac drive for both the virtual and physical.
Two Disk Formats supported are:

• NDIF
  This was previously used as the default format of Mac, also known as New Disk Format. These files generally have an .img file extension.
• UDIF
  The native disk format of Apple Mac DMG file is UDIF (Universal Disk Image Format) with a file extension of .dmg.

MIME Type of DMG File:
application/x-apple-diskimage.

Supported File Systems

• Hierarchical File System (HFS) – This was developed by Apple Inc. for the systems supporting Mac OS. Earlier, these file systems were used in floppy disks and hard disks but later were used to read CD-ROM as well. It is known as Mac OS Standard.
• HFS Plus – It was developed after HFS, which is an extension of the same. It is known as Mac OS Extended.
• File Allocation Table (FAT) – It is a file system generally compatible with all file systems and helps in exchange of data between systems.
• ISO9960 – This is also a file system which was issued by ISO (International Organization for Standard) supporting various OS and helps in exchange of data.
• Universal Disk Format –This is a file system usually used to store broadcast media like DVD and optical disk formats.

How To Open A Password Protected Dmg Files

How to Open DMG Files?

In Mac:

How To Open Dmg Files Windows 10

• When you download a Disk image, all the applications in it must be copied to the Application files, because many of these files will be in read-only format. Running these files inside the drives may produce some erroneous results.
• Double clicking the DMG File will open the file and you can view the contents in it. It might be images, documents, programs, etc.
• The DMG File consists of an application file. You can simply drag and drop to install them. If there is a possibility of having an installer, you can run these files instead of installing.
• Right-click on the File >> “Eject” (click on virtual disk instead of, original file)
  Delete the old DMG Files after installing. The reason is old files may take more space when we install new programs.

Resize DMG Files

• Right click DMG File >> Click Get Info (View the original size).
• Open Disk Utility >>Select Images Tab>Click on Resize>>Select the DMG file to be resized.
• Click on Open >>Type the file size to be reduced>>Select Resize>>Done

In Windows:
Originally, DMG files are the default Disk Image file for Mac. Hence, they can be opened only on Mac OS.
Since there are no manual methods available to view the DMG Files in Windows, users can install external third-party software available online on Internet. DMG Viewer is one of the tools from such category.
The software provides you with the following features:

• Open DMG File in Windows OS based machine
• Read: Corrupt, Password Protected & Encrypted DMG
• Recover permanently deleted files from DMG
• Search a specific file type in large DMG Format Files

Open Dmg File Download

Conclusion

How To Open A Password Protected Dmg File

Considering the ongoing necessity to view DMG files, we have described a manual process to let the users understand how to open & view DMG files. Else, users can take the help of a reliable third-party tool named as DMG Viewer. It is the best application that helps to read .dmg files in Windows OS. Users can use any approach as per their choice.