I believe that Klaus is trying to tell you that if you create an index on an encrypted column, you are storing the encrypted data in plaintext within the index. An attacker can access the secure data via the index instead of the column.
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I am not sure about this. If I index the field without deciphering it and make the query by encrypting the search string. This permits not to expose the password or the encryption key in the definition of the index.
To do this, I need to use the encrypt () and decrypt () raw encryption functions which are immutable.With identical parameters, they always return the same value and can be used to index an encrypted column.
No need to encrypt/decrypt anything in that case. Just index the already ciphered content of the column and be done with it.
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I suppose you could partially mitigate this by putting the index in a separate table space and putting that table space on a virtual disk device that is encrypted.
But if that meets your needs why not just put the whole table on that encrypted table space and leave the column unencrypted inside Pg?
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Interesting recommendation, but it seems too complex for us.