On the PIR capacity of MSR codes

Abstract: We consider the problem of private information retrieval (PIR) from multiple storage nodes when the underlying database is encoded using regenerating codes, i.e., the database has the ability to recover from individual node failures. We seek optimality in terms of download rates when a user wants to retrieve a message privately (in an information-theoretic sense) from the database. We focus mostly on the more extensively explored Minimum Storage Regenerating (MSR) codes and formally state and prove the PIR capacity of such codes. We also give a simple scheme to achieve this capacity which is based on the similarly motivated construction for MDS codes. Furthermore, we give a PIR scheme for a specific class of Minimum Bandwidth Regenerating (MBR) codes that achieves the same rate as its minimum storage counterpart.