computational complexity

, Volume 15, Issue 1, pp 82–91

A tight lower bound for restricted pir protocols

Original Paper

DOI: 10.1007/s00037-006-0208-3

Cite this article as:
Beigel, R., Fortnow, L. & Gasarch, W. comput. complex. (2006) 15: 82. doi:10.1007/s00037-006-0208-3


We show that any 1-round 2-server Private Information Retrieval Protocol where the answers are one bit long must ask questions that are at least n−2 bits long, which is nearly equal to the known n−1 upper bound. This improves upon the approximately 0.25n lower bound of Kerenidis and deWolf while avoiding their use of quantum techniques.


Private information retrievallower boundsprivacy

Subject classification.


Copyright information

© Birkhäuser Verlag, Basel 2006

Authors and Affiliations

  • Richard Beigel
    • 1
  • Lance Fortnow
    • 2
  • William Gasarch
    • 3
  1. 1.Department of Computer and Information SciencesTemple UniversityPhiladelphiaU.S.A.
  2. 2.Department of Computer ScienceUniversity of ChicagoChicagoU.S.A.
  3. 3.Department of Computer Science and Institute for Advanced Computer StudiesUniversity of MarylandCollege ParkU.S.A.