How to force a cloud storage service to synchronise an encrypted file?
How cloud synching works
OneDrive support replied & told me they don't support encrypted files (i.e. they use date & file name to detect changes, not file contents \ hash).
I've logged a request for them to use hashing: https://onedrive.uservoice.com/forums/262982-onedrive/suggestions/13292115-detect-changes-to-files-based-on-the-file-contents
I haven't found any information yet on how Dropbox \ Google Drive detects changes.
General solution that is tedious
The only general solution is to:
- move the file out of your sync folder
- rename it
- move it back again
OneDrive then detects it as a new file and uploads it (and deletes the old one in the cloud)
Best solution (if you use Veracrypt)
However here is the ideal solution if you're using Veracrypt (Truecrypt):
- Settings - Preferences - Disable 'Preserve modification timestamp'
Now the file date changes every time you change the contents and cloud backup services will always reupload it.
The solution to force a cloud storage service to synchronise an encrypted file
Herewith in English. I use the latest version 1.19 of Veracrypt
In Veracrypt setting, you have to put the "Preserve modification timestamp of file containers" option turned off. The timestamp on the Truecrypt volume file is then updated when you unmount it.
Google Drive synchronisation considers the modification of the date of the container to do the synchronisation of the crypted container.
Don't forget to put the new Preferences for all installed Veracrypt on your PCs. It is working very well with Google Drive.
I suppose that is ok for all other clouds but that must be verified