My question is quite related to the concept of homomorphic encryption, which is not practical at all nowadays.

In short, I would like to know how to query encrypted databases. Simple queries which test the equivalence of the entries can be easily implemented. Fine.

How about queries like: "select all employees with salary greater than 10000"?

The naive approach would be to select all employee id's along with their corresponding salary, decrypt everything and then check which ones match the aforementioned condition. Obviously this is far from being efficient.

Is there a more efficient way to handle such queries into encrypted data? Maybe some partially homomorphic algorithm?

My background: I have been in the academia for a while, so I know quite a lot about the concepts, but have no idea how these concepts have been employed by the industry so far.

  • $\begingroup$ Please try to stick to one question per question. I see two questions: (a) how does the industry deal with encrypted databases? (b) is there anything that simulates somewhat homomorphic encryption? Question (a) is too broad. Question (b) is not well-defined (what do you mean by "at least simulate somewhat") so probably not suitable for this site in its current form. What research have you done? Have you looked at CryptDB (which has seen some deployment in industry)? $\endgroup$ – D.W. Sep 28 '14 at 3:31
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    $\begingroup$ @mczraf I tried to address some of D.W.'s concerns with an edit. Feel free to roll back or edit further if you think I butchered it. $\endgroup$ – otus Sep 28 '14 at 7:54
  • $\begingroup$ @D.W. thanks for the tips. For the next question, I'll be more careful. Regarding the CryptDB, I am aware about what these MIT guys have done. However, since it's a very recent result, I don't think it is being used in any production system. My question is how this problem is being addressed by the industry right now. $\endgroup$ – mczraf Sep 28 '14 at 14:20
  • $\begingroup$ @otus thank you very much for improving my text, it captures what I meant in a much more clear and concise way! Thanks! ;-) $\endgroup$ – mczraf Sep 28 '14 at 14:21
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    $\begingroup$ @mczraf, in fact, my understanding is that there has already been some industry adoption of CryptDB / the ideas in CryptDB. See e.g. css.csail.mit.edu/cryptdb/#Impact $\endgroup$ – D.W. Sep 28 '14 at 16:42

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