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 ?
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.
