By Martin Stut, 2013-10-09

By now it is common sense that personal data should only go to external services if it's encrypted.

A good and common means to achieve encryption is to store the personal files inside a Truecrypt container and then to store that Truecrypt container in the cloud.

But there are

Caveats with this Approach

In late July 2013, I decided to spend a day to try, with Truecrypt containers in mind, various synchronization and backup

Services Tested

Cloud services on the Internet, in the order they came into my mind for testing:

I've skipped, because their free offer has a file size limit of 250 MB, which is too small for many Truecrypt use cases.

Running on the LAN, there are less products, but a larger variety of concepts, all offering unlimited disk space - whatever hard drive you've bought for your server or peer:

For each service, I ran a small

Test Parcours

  1. Download and install the software. With most products, this includes signing up for the service. For some products I had already done that months or years ago, so in those cases I've skipped this step.
  2. Copy a freshly created Truecrypt container into the local synchronized directory. Measure the time it takes to perform the initial upload. For services storing to the Internet, I've used a container of 50 MB, which should take about 17 minutes to upload on my home DSL line. For services storing on another computer in the LAN, I've used a container of 4700 MB, which would take a little over an hour to upload on my 2005 WLAN.
  3. Mount the container and create a small text file with just a few characters in the root directory. This should be about the smallest change one can do to a container.
  4. Dismount the container. This modifies the timestamp and triggers the synchronization software to upload the change. Measure the time it takes to finish synchronization.

Test Results

Efficiency for Small Changes to a Large File

For Truecrypt users, this is the first and main criterion. Slightly surprising, only these four services showed to transfer less than the full size of the container, after a small change had been made to it (beginning with the best):

All others did a full re-upload of the full container, even when only a few kB had changed.

Ease of Use

A backup not done regularly is useless, so it should be easy to use.

Most services are on the same level: modify the contents of the synchronized directory, and it will automatically be mirrored to the cloud/backup site, as long as there is reasonably good Internet connectivity. But for some services there are things to keep in mind:

Ease of Setup

Setup is an important part of use, because if you can't get it running in the first place, it's useless.

Most services require the user to sign up, download the software, install it, enter username and password (many apps can do the signup within the app, not requiring a web visit) and specify the folder to be shared.

The locally running products of course differ from this baseline:

Sharing with others tends to be a lot harder to set up. Products vary widely here. A few examples:


You are considering Truecrypt, because you care for privacy. This is not a luxury, but a requirement of German data privacy (protection) law. Penetration testing etc. is far beyond my capability, but I did evaluate, what the manufacturer and others say about the security of their product.

The baseline is not overwhelming:

So your options are:


It's the usual "it depends".