I use an S3-comptaible hoster with the rclone client which supports encryption/decryption on the fly. That is, I don't even need to trust my S3 provider.
For syncing between devices, I guess `rclone sync` should do the trick.
For syncing between devices, I guess `rclone sync` should do the trick.
For example if you saved a folder of mp3 files using the rclone crypt functionality that you downloaded from a known BitTorrent, it would be easy for an adversary to match that set of known sized objects with high confidence at the storage provider end, or from observing encrypted network traffic (which in the S3 case leaks object size through traffic patterns) and deducing object sizes from there.