I have an encrypted file. I want to keep it in the cloud, but it contains my private data. I think it would be be more secure if i split it into four parts and upload each part to a different cloud service (Dropbox, etc.). Is this a good way to store private data in the cloud?
Edit: Which one is better? Encrypt file first then split into chunks or split file to chunks then encrypt each one?
Yes, splitting the file will make it more safer. But in addition, it will make the system more complicated/less usable (you'll have to join the encrypted bits, and then decrypt it to get the original contents).
But this also introduces one more weak point for availability. Let's say you're splitting the encrypted file in 4 parts, and keeping each part in different cloud. Even if one of the cloud gets compromised and the data on it gets deleted, you'd be unable to get your file(assuming you don't have backups). In contrast, if you have a single file encrypted with a standard algorithm stored on a single cloud, only that cloud provider should be compromised to render your file unavailable.
Ultimately, it boils down to usability vs security trade-off.
You could split the file into parts, and probably be a little bit safer. But the usability loss v. security gain trade off isn't very good.
With good crypto (such as AES) on the client there isn't really any need for that. Focus instead on keeping your key random and secret, and the system that does the encryption secure. Those are your weak points.
