encryption – Best option for secure cloud file sync

Please let me know if this is not the appropriate forum for this question, and I will move it.

I would like to sync my files, as dropbox does for example. However, I want my files to be very secure. The main things I want are for it to be secure, ‘just work’ without hassle, and reasonably fast.

Options I am considering:

  • Local encryption such as Veracrypt/Truecrypt with Dropbox sync or equivalent.
  • Rclone encrypted sync to unencrypted cloud such as Dropbox.
  • mega.io, icedrive.net, tresorit.com

My constraints are:

  1. Content is “large” in that I cannot resync the whole content every change.
  2. I am using Linux.
  3. It must be a cloud service available over the public internet (I don’t want to host my own service / hardware).
  4. The files will be synced to multiple computers I own.
  5. The files should be continually automatically synced to minimize conflicts (ie. not manually triggered).
  6. I don’t trust the cloud storage provider.

Bonus nice to have constraints:

  1. Ideally I would like good OS integration. ie. Sync starts on system start, standard packages with provided updates, so I don’t have to write my own scripts which may get out of date and break.
  2. Occasionally I edit files in offline locations leading to conflicts. The system should be able to handle this. Software I have used in the past renames one of the files to indicate the conflict and that is a good solution.
  3. Some files are “large” in that I would prefer not to resync the whole file if a small change is made.

From what I have read, there is no perfect answer today. To make this question more answerable, just saying which of the options I have listed is best (or worst) for my requirements would be a great answer. For example, if the answer is none are truly secure, but mega.io security is at least as good as any other option, plus it has change conflict handling, then I would use mega.io.

I think local encrypted volume, unencrypted cloud is not so good for handling change conflicts?

I don’t mind paying for the service. The things I am storing are things like business information. I won’t die if they get stolen.

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