It seems the cache is just a normal sqlite database, that stores the filesystem blocks unencrypted. So you could restore the dynamically cached or pinned content even if not logged in.
The now defunct Wuala.com storage provider was very similar to CudaDrive, but with more focus on security. In Wuala the local cache was encrypted and only usable if you logged into the storage app.
I highly recommend to encrypt the cached data, especially since the "Pin" option exists.