Communications in Cryptology IACR CiC

Proximity Testing with Logarithmic Randomness


Benjamin E. Diamond, Jim Posen
Benjamin E. Diamond
Ulvetanna, United States
bdiamond at ulvetanna dot io
Jim Posen
Ulvetanna, United States
jposen at ulvetanna dot io


A fundamental result dating to Ligero (Des. Codes Cryptogr. '23) establishes that each fixed linear block code exhibits proximity gaps with respect to the collection of affine subspaces, in the sense that each given subspace either resides entirely close to the code, or else contains only a small portion which resides close to the code. In particular, any given subspace's failure to reside entirely close to the code is necessarily witnessed, with high probability, by a uniformly randomly sampled element of that subspace. We investigate a variant of this phenomenon in which the witness is not sampled uniformly from the subspace, but rather from a much smaller subset of it. We show that a logarithmic number of random field elements (in the dimension of the subspace) suffice to effect an analogous proximity test, with moreover only a logarithmic (multiplicative) loss in the possible prevalence of false witnesses. We discuss applications to recent noninteractive proofs based on linear codes, including Brakedown (CRYPTO '23).


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Submitted: 2023-12-11
Accepted: 2024-03-05
Published: 2024-04-09
How to cite

Benjamin E. Diamond and Jim Posen, "Proximity Testing with Logarithmic Randomness," IACR Communications in Cryptology, vol. 1, no. 1, Apr 09, 2024, doi: 10.62056/aksdkp10.


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