Like a lot of people, I use TrueCrypt on my USB drive. Even though it's not strictly portable it works for me. For backing up my USB drive I use SyncBack which uses file dates to determine which files have changed. I assumed that every time I used the TC encrypted drive that the timestamp of the container file would change and, therefore, be backed up.
Yesterday I needed to restore my container file from the backup. It turns out that TC by default does not update the timestamp when the volume is unmounted. It's part of plausible deniability. Therefore, my backup process had not backed up the container file since I first created it.
There are 2 solutions:
- turn off the TC option (GUI and/or command line) to preserve timestamps
- force your backup program to always backup the container file