Oblivious Keyword Search

In this paper, we introduce a notion of Oblivious Keyword Search (OKS). Let W be the set of possible keywords. In the commit phase, a database supplier T commits n data. In each transfer subphase, a user U can choose a keyword w ∈ W adaptively and find Search(w) without revealing w to T , where Search(w) is the set of all data which includes w as a keyword. We then show two efficient protocols such that the size of the commitments is only O(nB) regardless of the size of W , where B is the size of each data. It is formally proved that U learns nothing more than Search(w) and T gains no information on the keywords which U searched for. We further present a more efficient adaptive OTn k protocol than the previous one [19] as an application of our first OKS protocol.