Toward Optimal Secure Distributed Storage Systems with Exact Repair

Ravi Tandon, Saidhiraj Amuru, Thomas Charles Clancy, Richard Michael Buehrer

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


Distributed storage systems (DSSs) in the presence of an external wiretapper are considered. A DSS is parameterized by (n, k, d), in which the data are stored across n nodes (each with storage capacity α), and must be recoverable by accessing the contents stored on any k out of n nodes. If a node fails, any d ≥ k out of (n-1) nodes help in the repair (regeneration) of the failed node (by sending dβ units of repair data, where β≤ α), so that the data can still be recovered from the DSS. For such a (n, k, d)-DSS, security from the two types of wiretappers is investigated: 1) Type-I (node data) wiretapper, which can read the data stored on any ℓ <k nodes and 2) Type-II (repair data) wiretapper, which can read the data that is used to repair a set of ℓ failed nodes. The focus of this paper is on the optimal tradeoff between the storage (α) and the repair bandwidth (dβ) in presence of a Type-I/Type-II wiretapper and the practically relevant constraint of exact repair in which a failed node must be replaced by its exact replica. In this paper, several new results and outer bounds for the storage-versus-exact-repair-bandwidth tradeoff(s) are obtained for the Type-I and Type-II security problems. Furthermore, new outer bounds are presented for the Type-II problem, which hold for general (n, k, d,ℓ) parameters. It is shown that these outer bounds strictly improve upon the existing cutset-based outer bounds. The key technical contribution of this paper is in developing novel information theoretic converse proofs for these problems. From our optimal characterization results, we show that in a Type-II setting, the only efficient point in the storage-versus-exact-repair-bandwidth tradeoff is the minimum bandwidth regenerating (MBR) point corresponding to α =dβ . This is in sharp contrast to the Type-I setting in which the optimal tradeoff allows a spectrum of operating points beyond the MBR point.

Original languageEnglish (US)
Article number7437480
Pages (from-to)3477-3492
Number of pages16
JournalIEEE Transactions on Information Theory
Issue number6
StatePublished - Jun 2016


  • Distributed Storage
  • Information Theory
  • Network Coding
  • Secure Storage

ASJC Scopus subject areas

  • Information Systems
  • Computer Science Applications
  • Library and Information Sciences


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