The inapproximability of lattice and coding problems with preprocessing

  • Authors:
  • Uriel Feige;Daniele Micciancio

  • Affiliations:
  • Weizmann Institute of Science, Rehovot, Israel;Department of Computer Science and Engineering, University of California, San Diego, Mail Code: 0114, 9500 Gilman Drive, La Jolla, CA

  • Venue:
  • Journal of Computer and System Sciences - Special issue on computational complexity 2002
  • Year:
  • 2004

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Abstract

We prove that the closest vector problem with preprocessing (CVPP) is NP-hard to approximate within any factor less than √5/3. More specifically, we show that there exists a reduction from an NP-hard problem to the approximate closest vector problem such that the lattice depends only on the size of the original problem, and the specific instance is encoded solely in the target vector. It follows that there are lattices for which the closest vector problem cannot be approximated within factors γ lp, norm, for p ≥ 1, showing that CVPP in the lp norm is hard to approximate within any factor γ p√5/3. As an intermediate step, we establish analogous results for the nearest codeword problem with preprocessing (NCPP), proving that for any finite field GF(q), NCPP over GF(q) is NP-hard to approximate within any factor less than 5/3.