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I use a cloud service for my off-site backup, and all my files are encrypted. But I am wondering whether to enable filename encryption or not. Are there any security advantages to be gained by encrypting the filenames as well?

The downside to encrypted filenames is that it leaves the cloud web browser utterly useless.

  • Is the encryption performed on the client side (ie. by you) or on the server side (ie. by them)? What kind of files are they and what kind of names do they have? – thexacre Dec 28 '14 at 0:26
  • Encryption is done on the client side, before uploading. File types are documents, programming projects, pictures etc. The naming is not exactly consistent, everything from "New textfile1.txt" to "Complete cigar inventory.xml". But nothing that I would consider sensitive. Might give someone an idea of what file to try and open, such as "My account numbers.txt". – Thomas Jensen Dec 28 '14 at 0:32
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If filenames are sensitive then encrypt them, if not then don't. Eg. are you happy for staff at your backup service or possibly others (in the case of breach) to see Secret Government Contract bid.docx listed?

That's all it comes down to. A cost/benefit analysis for your particular usage. You should also find out if the client software can restore the original folder structure and filenames upon recovery from backup. Consider if this original information stored encrypted in the cloud and where the decryption key is kept.

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The security advantage would be that encrypting the filenames would somewhat obscure the contents. Unfortunately, there are still other tells (like file size and directory structure) that would give clues as to which files are and aren't valuable to a potential attacker. Overall, it's security by obscurity, which isn't worth very much.

If anyone needs to use the web interface, I'd say you shouldn't encrypt the filenames.

If no one needs to use the web interface, then your choice doesn't really make a difference either way.

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  • When the filenames are encrypted they seem to be all placed in a flat folder structure, so quite obscured. Which is also a bit worrying as I am left clueless if my cloud ever becomes corrupt or anything goes missing. Thanks for your answer :) – Thomas Jensen Dec 28 '14 at 0:50

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