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48th Annual IEEE Symposium on Foundations of Computer Science (FOCS'07)
Pseudorandom Bits for Polynomials
Providence, Rhode Island
October 21-October 23
ISBN: 0-7695-3010-9

We present a new approach to constructing pseudorandom generators that fool low-degree polynomials over finite fields, based on the Gowers norm. Using this approach, we obtain the following main constructions of explicitly computable generators G : \mathbb{F}^s \to \mathbb{F}^n that fool polynomials over a prime field \mathbb{F} : 1. a generator that fools degree-2 (i.e., quadratic) polynomials to within error 1/n, with seed length s = O(log n), 2. a generator that fools degree-3 (i.e., cubic) polynomials to within error \in, with seed length {\text{s = O(log}}\left| \mathbb{F} \right|n) + f( \in ,\mathbb{F}) where f depends only on \in and \mathbb{F} (not on n), 3. assuming the "Gowers inverse conjecture," for every d a generator that fools degree-d polynomials to within error \in, with seed length {\text{s = O(d\cdotlog}}\left| \mathbb{F} \right|n) + f{\text{(d,}} \in ,\mathbb{F}) where f depends only on {\text{d,}} \in , and \mathbb{F} (not on n). We stress that the results in (1) and (2) are unconditional, i.e. do not rely on any unproven assumption. Moreover, the results in (3) rely on a special case of the conjecture which may be easier to prove.

Our generator for degree-d polynomials is the component-wise sum of d generators for degree-1 polynomials (on independent seeds).

Prior to our work, generators with logarithmic seed length were only known for degree-1 (i.e., linear) polynomials (Naor and Naor; SIAM J. Comput., 1993). In fact, over small fields such as \mathbb{F}_2 = {0, 1}, our results constitute the first progress on these problems since the long-standing generator by Luby, Veli?ckovi?c andWigderson (ISTCS 1993), whose seed length is much bigger: s = exp (\Omega (\sqrt {\log n} )), even for the case of degree-2 polynomials over \mathbb{F}_2.

Citation:
Andrej Bogdanov, Emanuele Viola, "Pseudorandom Bits for Polynomials," focs, pp.41-51, 48th Annual IEEE Symposium on Foundations of Computer Science (FOCS'07), 2007
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