Advances in Cryptology — EUROCRYPT ’99

Volume 1592 of the series Lecture Notes in Computer Science pp 402-414


Computationally Private Information Retrieval with Polylogarithmic Communication

  • Christian CachinAffiliated withIBM Zurich Research Laboratory
  • , Silvio MicaliAffiliated withLaboratory for Computer Science, MIT
  • , Markus StadlerAffiliated withCrypto AG


We present a single-database computationally private information retrieval scheme with polylogarithmic communication complexity. Our construction is based on a new, but reasonable intractability assumption, which we call the Φ-Hiding Assumption (ΦHA): essentially the difficulty of deciding whether a small prime divides Φ(m), where m is a composite integer of unknown factorization.


Integer factorization Euler’s function Φ-hiding assumption Private information retrieval