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Brush up on Dropbox DBX decryption

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Few weeks ago I was contacted about how to decrypt Windows Dropbox DBX files and the same topic appeared on SANS DFIR mailing list too. So I decided to create an Open Source toolkit and this post to brush up on the DBX files create by the Dropbox client on a Windows machine.



The Windows Dropbox client keeps its own files - user info, configuration, 'my dropbox' files sync status and even more - inside the user profile: on the Windows 7 and Windows 10 machines I used for test they reside in '\Users\%USERNAME%\AppData\Local\Dropbox\' and sub folders. Among them there are files with .DBXextension, which are the target of this post. When you take a raw look at them, you see garbage, noise... encryption is in place.

Without too much suspence, this is well-known. Nicolas Ruff and Florian Ledoux had a talk at hack.lu2012 on the topic, “A critical analysis of Dropbox software security” (here). They discovered that the encryption key used for DBX files is kept in the registry …