Restricted adaptive oblivious transfer
In this work we consider the following primitive, that we call restricted adaptive oblivious transfer. On the one hand, the owner of a database wants to restrict the access of users to this data according to some policy, in such a way that a user can only obtain information satisfying the restrictions imposed by the owner. On the other hand, a legitimate user wants to privately retrieve allowed parts of the data, in a sequential and adaptive way, without letting the owner know which part of the data is being obtained. After having formally described the components and required properties of a protocol for restricted adaptive oblivious transfer, we propose two generic ways to realize this primitive. The first one uses a cryptographic tool which has received a lot of attention from the literature in recent years: cryptosystems which are both multiplicatively and additively homomorphic. Our second generic construction is based on secret sharing schemes. (C) 2011 Elsevier B.V. All rights reserved.
oblivious transfer secret sharing homomorphic encryption