14.26

Some attributes of relations may contain sensitive data, and may be required to be stored in an encrypted fashion. How does data encryption affect index schemes? In particular, how might it affect schemes that attempt to store data in sorted order?

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Let \(r(A, B, C)\) be a relation. Suppose attribute \(B\) of relation \(r\) contains sensitive data and we want it encrypted. Suppose also we want to create an index on attribute \(B\).

But there are so many questions that we can ask from the above paragraph: 1. What kind of encryption algorithm are we going to use? 2. Are we going to create the index on attribute \(B\), before it is encrypted or after? That is, are we going to index on the plain text values of attribute \(B\) or the encrypted values of attribute \(B\)? 3. In what kinds of situation are we in? That is, what is the attack model? Who is Alice, Bob and Eve???