Oblivious Group Storage

We propose Oblivious Group Storage (OGS), an extension of the oblivious storage (OS) model [1] to the setting of group data sharing. In addition to providing server-side data-secrecy and access-pattern obliviousness guarantees as in traditional OS protocols, an OGS protocol allows arbitrary subsets of clients to share read/write access to cloud-stored data while preserving data-secrecy and access-pattern obliviousness guarantees with respect to unauthorized clients. To show the feasibility of OGS, we describe a provably secure generic construction based on the notions of outsider-anonymous broadcast encryption [2] and multi-user oblivious RAM [3].