CryptDB has Onion layers of Encryption to provide wider functionality from weaker forms of encryption. How do we prove such things are indeed secure ? Intuitively It seems ok. Are there any parallels in theory that is related say, security of multiple encryption schemes etc? or Universal Composability etc?

Is this same as Cascade ciphers ? Product Ciphers ?

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    $\begingroup$ Haven't read it, but this might give some clues. $\endgroup$
    – mikeazo
    Commented Sep 6, 2014 at 12:47
  • $\begingroup$ That's a paper about Tor, not CryptDB. And OP: there aren't really security definitions that cover this "mixed-strength" setting, which comes up in all kinds of encrypted DB constructions. It's an open problem. $\endgroup$
    – pg1989
    Commented Apr 29, 2017 at 16:53

1 Answer 1


In CryptDB, it is not really cascaded. According to encryption schema the layers are decrypted. At the end, the lowest level is the your security.

The current layers are RND (Highest Security) , DET (For Joining queries), SWP (Search), HOM (Add), OPE (Sort) etc. OPE being least secure as it allows more inferences about the underlying data fields than others. A data field that is encrypted all these Onion layers offer security only as strong as the weakest (OPE or similar) !

The fact that there is no need for the removal of the layer implies there is no need to layers.


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