Single-database private information retrieval with constant communication rate

  • Authors:
  • Craig Gentry;Zulfikar Ramzan

  • Affiliations:
  • DoCoMo Communications Laboratories USA, Inc;DoCoMo Communications Laboratories USA, Inc

  • Venue:
  • ICALP'05 Proceedings of the 32nd international conference on Automata, Languages and Programming
  • Year:
  • 2005

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Abstract

We present a single-database private information retrieval (PIR) scheme with communication complexity ${\mathcal O}(k+d)$, where k ≥ log n is a security parameter that depends on the database size n and d is the bit-length of the retrieved database block. This communication complexity is better asymptotically than previous single-database PIR schemes. The scheme also gives improved performance for practical parameter settings whether the user is retrieving a single bit or very large blocks. For large blocks, our scheme achieves a constant “rate” (e.g., 0.2), even when the user-side communication is very low (e.g., two 1024-bit numbers). Our scheme and security analysis is presented using general groups with hidden smooth subgroups; the scheme can be instantiated using composite moduli, in which case the security of our scheme is based on a simple variant of the “Φ-hiding” assumption by Cachin, Micali and Stadler [2].