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Comment by MrMember | Hacker News Reader

I use an encrypted container in Dropbox. I retain complete control over my files but they are still backed up, and Dropbox is smart enough to only upload the diff if something in the container changes. It's a little inconvenient in that I can't for example access individual files on my phone without a lot of hassle but overall it's an adequate solution for my needs.

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A delta of changes in an encrypted container should be very close to the size of the full container, shouldn't?

It seems this will only be feasible when we have homorphic encryption ready.

If someone is interested on that kind of encryption, see "A FULLY HOMOMORPHIC ENCRYPTION SCHEME"[1] and "Fully Homomorphic Encryption without Bootstrapping "[2]

[1] https://crypto.stanford.edu/craig/craig-thesis.pdf

[2] https://eprint.iacr.org/2011/277.pdf

Well the whole hard drive is not overwritten every time a file changes when using disk encryption, so definitely not necessary.

Any encrypted disk image will work this way. It doesn’t require anything like homomorphic encryption, just a bit of metadata and key management.

No. AES encrypts blocks (I think 256kb?). So that's the only thing you have to sync.

If you use plain AES ECB, then little penguins will show up in your encrypted data. You would want to use a disk encryption scheme, like XTS, where the encryption is not just based on the data of the block, but also on the index of the block, to prevent identical blocks at different locations from looking identical. You also want it to be based on a nonce of some sort, to prevent attackers from reverting a block to an older copy.

Penguins? What are you talking about?

I don't care about low-level encryption details. That's why I use encryption software instead of coding my own.

ECB has issues:

https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation...

You should absolutely care about the difference between ECB and a stream cipher mode like CBC. ECB is way less safe.

That would depend on the cipher mode, no? Assuming the container is using something like CTR, the diff should only consist of changed bytes.

May I ask which container? Something like VeraCrypt or?

I have thought about doing this also. How about the sync'ing? Does it sync only parts of the container, when you change something or does it have to sync everything, when you make a small change?

I'm not the original commenter, but I just started using cryfs in Dropbox and it's working very well: https://github.com/cryfs/cryfs

KDE plasma has just started incorporating this into their desktop as a product called 'Vaults'.

I have been using Software called BoxCryptor for many years. Quite convenient.

Containers lime VeraCrypt would be quite inconvenient, but work if you don’t make changes on many computers at the same time.

Dropbox only syncs the difference of the encrypted files. Truecrypt uses by default AES which encrypts blocks of size 256kb. It's almost as efficient as syncing without encryption.

I am very happy with cryptomator.org

It's open source.

Oblig. Plug for cryfs.

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