Extracting Randomness Using Few Independent Sources

  • Authors:
  • Boaz Barak;Russell Impagliazzo;Avi Wigderson

  • Affiliations:
  • -;-;-

  • Venue:
  • SIAM Journal on Computing
  • Year:
  • 2006

Quantified Score

Hi-index 0.00

Visualization

Abstract

In this work we give the first deterministic extractors from a constant number of weak sources whose entropy rate is less than 1/2. Specifically, for every $\delta 0$ we give an explicit construction for extracting randomness from a constant (depending polynomially on $1/\delta$) number of distributions over $\bits^n$, each having min-entropy $\delta n$. These extractors output $n$ bits that are $2^{-n}$ close to uniform. This construction uses several results from additive number theory, and in particular a recent result of Bourgain et al. We also consider the related problem of constructing randomness dispersers. For any constant output length $m$, our dispersers use a constant number of identical distributions, each with requires min-entropy $\Omega(\log n)$, and outputs every possible $m$-bit string with positive probability. The main tool we use is a variant of the “stepping-up lemma” of Erdo˝s and Hajnal used in establishing a lower bound on the Ramsey number for hypergraphs.