After our Windows encryption showdown, reader Jerod passed along this tip to make sure your encrypted volumes, especially external hard drives, in Windows play nicely with other platforms like OS X -- just format them as exFAT, and they will be mountable, readable and writable everywhere you go. The gist is pretty simple, as explained in Rowan Watson's post on the topic (now dead, but a cached link is below), using TrueCrypt as an example, but the process is very similar for VeraCrypt, a TrueCrypt fork that we love:
The first thing you want to do is format your drive as exfat. Windows will only format a drive as exfat if windows recognises it as a removable drive. Currently, you can't boot to an exfat formatted drive. If windows recognises your drive as removable, you should have a exfat format option like the picture shown. Once you've formatted your drive, we'll need to create a Truecrypt container to keep our encrypted files.
At this point you'll want to create an encrypted container and format it either NTFS or FAT. The post explains that it doesn't really matter which, since we're going to format it again as exFAT later, but he suggests that NTFS is a bit faster. Then:
Once you've created your container, mount it as a drive with Truecrypt. If you attempt to format the drive in the Windows GUI, you'll notice that your only options are NTFS and FAT (since Windows thinks Truecrypt volumes are internal drives). FAT will give us read/write support in both operating systems, but it won't be able to support files larger than 4GB. NTFS can support files larger than 4GB, but it has poor read/write support in OS X (even with NTFS-3G).
We can, however, format the volume from the command line. Using the following command:
format : /FS:exfat /Q
Format is a pretty basic command. Replace <drive letter> with the drive you want to format. The /FS:exfat tells format what format you want the drive to be (if this wasn't obvious) and the /Q tells format to do a quick format. I haven't found a compelling reason to not quick format the drive -- which takes significantly longer, especially for large drives.
He also notes you may need to run the command as an administrator to make it work, but aside from that, once the final format is complete, you're all set. You'll have an encrypted volume that you can work with and mount on a Mac or a Windows PC, and one that supports files larger than 4GB as well. Hit the link below to see the whole post via the Wayback Machine, and thanks to Jerod for sending in the tip!
Truecrypt Volume in Windows 7 and OS X with large file support [Rowan Watson via Wayback Machine]