Towards Optimal Secure Distributed Storage Systems with Exact Repair
Ravi Tandon, SaiDhiraj Amuru, Thomas Clancy, R. Michael Buehrer · 2016
Distributed storage systems in the presence of a wiretapper are considered. A distributed storage system (DSS) is parameterized by three parameters (n, k, d), in which a file stored across n distributed nodes, can be recovered from any k out of n nodes. This is called as the reconstruction property of a DSS. If a node fails, any d out of (n − 1) nodes help in the repair of the failed node so that the regeneration property of the DSS is preserved. For such a (n, k, d)-DSS, two types of wiretapping scenarios are investigated: (a) Type-I (node) adversary which can wiretap the data stored on any l 4, we present extensions of these results to a (n, n − 1, n − 1)-DSS, in presence of a Type-II adversary that can observe the repair data of any l = (n − 2) nodes. The key technical contribution of this work is in developing novel information theoretic converse proofs for the Type-II adversarial scenario. From our results, we show that in the presence of Type-II attacks, the only efficient point in the storage-vs-exact-repair-bandwidth tradeoff is the MBR (minimum bandwidth regenerating) point. This is in sharp contrast to the case of a Type-I attack in which the storage-vs-exact-repair-bandwidth tradeoff allows a spectrum of operating points beyond the MBR point.