[Resource Topic] 2020/461: A Polynomial-Time Algorithm for Solving the Hidden Subset Sum Problem

Welcome to the resource topic for 2020/461

Title:
A Polynomial-Time Algorithm for Solving the Hidden Subset Sum Problem

Authors: Jean-Sébastien Coron, Agnese Gini

Abstract:

At Crypto ’99, Nguyen and Stern described a lattice based algorithm for solving the hidden subset sum problem, a variant of the classical subset sum problem where the n weights are also hidden. While the Nguyen-Stern algorithm works quite well in practice for moderate values of n, we argue that its complexity is actually exponential in n; namely in the final step one must recover a very short basis of a n-dimensional lattice, which takes exponential-time in n, as one must apply BKZ reduction with increasingly large block-sizes. In this paper, we describe a variant of the Nguyen-Stern algorithm that works in polynomial-time. The first step is the same orthogonal lattice attack with LLL as in the original algorithm. In the second step, instead of applying BKZ, we use a multivariate technique that recovers the short lattice vectors and finally the hidden secrets in polynomial time. Our algorithm works quite well in practice, as we can reach n=250 in a few hours on a single PC.

ePrint: https://eprint.iacr.org/2020/461

Talk: https://www.youtube.com/watch?v=LXWtgl54Eos

Slides: https://iacr.org/submit/files/slides/2020/crypto/crypto2020/41/slides.pdf

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