Distributed Storage Systems with Secure and Exact Repair - New Results

Distributed storage systems (DSS) in the presence of a passive eavesdropper are considered in this paper. A typical DSS is characterized by 3 parameters (n, k, d) where, a file is stored in a distributed manner across n nodes such that it can be recovered entirely from any k out of n nodes. Whenever a node fails, d ∈ [k, n) nodes participate in the repair process. In this paper, we study the exact repair capabilities of a DSS, where a failed node is replaced with its exact replica. Securing this DSS from a passive eavesdropper capable of wiretapping the repair process of any l < k nodes, is the main focus of this paper. Specifically, we characterize the optimal secure storagevs- exact-repair-bandwidth tradeoff region for the (4, 2, 3) DSS when l = 1 and the (n, n − 1, n − 1) DSS when l = n − 2.