DMG files for Mac are similar to ISO files on Windows since they can both create sector-by-sector copies of folders or optical storage media. But, unlike ISO files, files with a .dmg extension can be password-protected and encrypted. Additionally, they might have a different file extension such as .img and .smi, when they use an NDIF (New Disk Image Format). Modern DMG files use UDIF (Universal Disk Image Format), which can be compressed, better encrypted, and have a file extension .sparsebundle. Now that you know that, here’s how to recover .dmg password.
1. Recover .dmg password manually
Look through your notebooks, TextEdit documents, password management software, or browser extensions, or try passwords that come to mind. You can also open the .dmg file while signed in to Apple ID. There’s a strong chance that you clicked on Remember password after opening the disk image file for the first time. If so, the Apple Keychain feature might have saved it to iCloud, like with method 4 of recovering Mac password. Also, since about 2017, Apple Keychain automatically saves the password for .dmg files.
2. Bypass .dmg password via decryption
Sometimes even a correct password without a decryption key isn’t sufficient to open .dmg files. Whether that’s the case for you, or you haven’t discovered the password yet, don’t lose hope. We aren’t affiliated with any, but you can try this software:
- VileFault. A tool that reverse-engineered Apple .dmg file implementation and decrypted it first. Find it on GitHub (github.com/fswrangler/VileFault).
- DMG Extractor. Same thing, but with a modern interface. The tool might still require passwords on newer .dmg files. Find it on the official website (reincubate.com/dmg-extractor).
3. Recovering .dmg password by brute force
Did you create the .dmg file on a newer version of Mac? Apple upgraded to AES-128-bit or AES-256-bit military-grade encryption, which means decryption is nearly impossible. Luckily, guessing the password still works. And for your sake, we hope you’ve used a simple one. Obviously, doing this manually would be labor and time-intensive. Again, we can’t vouch for these password-cracking tools you can use on .dmg files:
- General. The most up-to-date password cracker with the largest database seems to be John the Ripper (https://www.openwall.com/john).
- Dedicated. Some companies have produced exclusive password cracking tools. One example is DMG Password Recovery (thegrideon.com/dmg-password-recovery.html).