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Re^2: Deterministic asymmetric encryption [Crypt::RSA]

by andreas1234567 (Vicar)
on Dec 16, 2010 at 06:03 UTC ( #877437=note: print w/replies, xml ) Need Help??

in reply to Re: Deterministic asymmetric encryption [Crypt::RSA]
in thread Deterministic asymmetric encryption [Crypt::RSA]

secure the channel.
I will protect data in transit. I also need to protect data at rest. Either is not sufficient.
The database files are encrypted using a key known only to the server:
Security regulations (e.g. like this) require protection against insider threats to make sure data does not escape, e.g. when backed up. To have a (symmetric) key and the data on the same server is out of question.
I would advocate avoiding use of deterministic encryption altogether, because I do not think it will ever provide the data-security and data-integrity that you need.
I would normally agree, but in this case I feel the disadvantage of a less secure encryption model is probably outweighted by the advantages of not having the (symmetric) key and the data on the same server.

There are apparently advances in cryptography research (e.g. here (RSA-DOAEP), here, and here) that suggests that deterministic asymmetric encryption is becoming increasingly secure. It takes of course a long time for new algorithms to find its way into actual, usable implmentations.

This is hardly an atypical or novel requirement.
I would compare it with to store data encrypted on your server that a root user does not have access to. I would be glad to use an of-the-shelf solution. Do such exist?

Thanks for your feedback.

No matter how great and destructive your problems may seem now, remember, you've probably only seen the tip of them. [1]
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Re^3: Deterministic asymmetric encryption [Crypt::RSA]
by jethro (Monsignor) on Dec 16, 2010 at 10:46 UTC

    Don't know how secure deterministic asymmetric encryption (lets call it DAE) is, but you want it to fill out exactly the role for which hashes aka trap-door functions were invented.

    I'm actually working in a facility for cryptographic research and I asked someone who should know the actual research in the field. He told me that there is not much research about the strength of DAE, I suspect because there are much better alternatives.

    Usually you would do the following: Store the data with symmetric encription and a random key that is encrypted with asymmetric encryption (this method is standard for any data bigger than a few hundred bytes, since asymmetric encryption is very slow). Beside this store the hash of the data. At the moment sha256 seems to be the hash everyone uses, with sha512 for the really paranoid.

    As you can see this fulfills all your requirements

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