Pseudorandom Bits From Points on Elliptic Curves

TL;DR

This paper provides bounds on character sums over elliptic curve points, confirming conjectures related to extracting pseudorandom bits from sequences of elliptic curve points over finite fields.

Contribution

It introduces new average bounds on character sums involving elliptic curve points, supporting conjectures on pseudorandom bit extraction methods.

Findings

Bounds confirm several recent conjectures

Supports pseudorandom bit extraction from elliptic curve points

Advances understanding of elliptic curve-based randomness

Abstract

Let $\E$ be an elliptic curve over a finite field $\F_{q}$ of $q$ elements, with $\gcd(q,6)=1$, given by an affine Weierstra\ss\ equation. We also use $x(P)$ to denote the $x$-component of a point $P = (x(P),y(P))\in \E$. We estimate character sums of the form $$ \sum_{n=1}^N \chi\(x(nP)x(nQ)\) \quad \text{and}\quad \sum_{n_1, \ldots, n_k=1}^N \psi\(\sum_{j=1}^k c_j x\(\(\prod_{i =1}^j n_i\) R\)\) $$ on average over all $\F_q$ rational points $P$, $Q$ and $R$ on $\E$, where $\chi$ is a quadratic character, $\psi$ is a nontrivial additive character in $\F_q$ and $(c_1, \ldots, c_k)\in \F_q^k$ is a non-zero vector. These bounds confirm several recent conjectures of D. Jao, D. Jetchev and R. Venkatesan, related to extracting random bits from various sequences of points on elliptic curves.