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Topics: Users Discussion
Dec 27, 2015 at 9:46 AM
Edited Dec 27, 2015 at 9:49 AM
I am trying to use veracrypt for a decoy and hidden OS. From what I read it sounds like I first need to shrink my windows partition down to less than half of the drive? This is because it says the first partition behind the system partition must be at least 5% larger than the system partition. Does that mean 5% is used for the outer volume and 50% for the hidden volume?

Some other things not quite clear:
  • The size of the hidden volume is always the same as the size of the system partition. Does this mean I have to waste half my drive for the decoy OS? I wanted to make the decoy as small as possible since i'll almost never use it.
  • If I format the outer volume fat32 to avoid the 110% space with NTFS, can the hidden volume be NTFS? Its confusing because they are both created on 1 partition.
  • From the decoy OS, the outer volume would look like a D: drive, does that mean the hidden OS volume within it would just look like 1 large file?
The docs didn't say start by shrinking your drive.
Dec 30, 2015 at 9:40 AM
Anyone have an idea about this? I see the answer to question #1 from another post, but the rest I am still unaware.
Dec 30, 2015 at 6:17 PM

The documentation contains all the details. First, let's use the illustration from the documentation:

Indeed, when the outer volume is formatted using FAT32, its needs to be at least 5% larger than the system partition in order to be able to hold the hidden volume (the 5% are to be used by the outer volume data). In practice, you should give more space to the outer volume to avoid corrupting the hidden volume.

For your questions:
  • As you found, this has been answered here:
  • Yes, the hidden volume can be NTFS even if the outer volume is FAT32.
  • The hidden volume is a hidden volume inside the partition not a file! You can't mount the hidden volume and the outer volume at the same time. You can read the Hidden Volume section in the documentation to learn more about how this woks.
The documentation doesn't talk about shrinking or changing the partitioning of the disk. It is up to the user to configure his drive so that it's compatible with the hidden OS creation. Basically, we need the second partition to be large enough to hold a volume with the same size as the first partition. For example, if you have a 1TB drive, the first partition can have a size of 250 GB and the second partition can have 750 GB: this is a typical partitioning scheme that is compatible with the hidden OS constraints.