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I'd like to request if people can suggest or share ways to encrypt files backed up online (Goolge Drive, Dropbox, etc).

I know some of these services do encryption of some sort, but it was recommended to do your own encryption. So I would like to explore how.

The easiest option I had considered was to use Winzip to create a password protected zip and save that on the cloud. I think this should work okay for infrequently updated data. But couple of issues for frequently accessed data:

  • You'd need to keep two copies. An unencrypted version on an offline/unsynced folder. And a zipped version on the Google drive or Dropbox folder. Each time you edit the data, you would need to remember to create a new zip.
  • Or if you just kept one copy, the encrypted one, then you would need to unzip each time you wanted to access the data (and zip again afterwards).
  • Both these ways sound cumbersome.

Another solution I came across is called Cryptomator (and I think encfs works similarly). You point it to your online/synced folder and it saves the encrypted version there (and takes care of encryption/decryption in the background). But one security/privacy feature of these programs is: [b]scrambling [/b]the filenames. There is no way to disable this for people who don't want it. I think this feature conflicts with the online store function when it comes to recovering a single file. Let's say you backup 20 files online, the filenames will be scrambled. Now if you want to recover just one of them, you'll need to download all 20, and open them in the unencrypted container to see the actual filenames.

Similarly I don't think you'd be able to use the file versioning feature of some cloud providers.

I think similar issues would occur with Veracrypt or Truecrypt.

Have you thought about these things and found something that works well? Please share.

Thank you.

  • A friend and I once wrote a tool that used GPG and GDrive to encrypted files, with meaningless file names but with an (encrypted) index file as well, so you only needed to decrypt the index file to know which file was your actual desired one. It was designed as a backup tool; it would detect changes to the file system and automatically encrypt and upload them. Is this the sort of thing you wanted? Also, GPG (or similar) is way more secure than Zip encryption. – CBHacking Jul 12 at 1:36
  • @CBHacking - Zip supports AES 128 & 256, so it's capable of the same security as GPG (or similar). – user10216038 Jul 12 at 16:10
  • @user10216038 Well, if for some reason you used GPG in symmetric mode, sure, but why would you do that? The overall security of a cryptographic scheme is dependent on the weakest link, and in situations like this, the strength of the cipher is probably less important that the security of the key. Password-based encryption is all-but-guaranteed to be less secure than public-key-based encryption (with the private key potentially being password-protected for defense-in-depth, but more importantly being totally out of the attacker's reach). – CBHacking Jul 12 at 16:59
  • @user10216038 Yes, but it still comes down to the key (how it's derived/protected). With a password-derived key, the attacker has everything needed except the password, which is highly unlikely to have enough entropy to resist brute-forcing for very long, especially if it wasn't derived with a very slow key derivation algorithm. Asymmetrically-encrypted symmetric keys - like GPG uses - don't have this problem; they are generated by a secure (pseudo-)random number generator and impossible to brute force, and without the private key file the attacker can't even begin attacking its password. – CBHacking Jul 12 at 22:00
  • To put it another way, password-based encryption is roughly as secure as using GPG with asymmetric encryptiong and then including the private key, protected only by its passphrase, with the ciphertext. This is obviously a terrible idea. Yes, if the password is really good, and if the Zip encryption utility used a good scheme, you're OK. Legacy Zip encryption was garbage, easily broken; I haven't looked at the new "strong" encryption scheme but just because it uses AES doesn't mean it's any good; a strong cipher is a necessary but insufficient component of a secure crypto scheme. – CBHacking Jul 12 at 22:07

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