Mind the Gap? Not for SVP Hardness under ETH!
- URL: http://arxiv.org/abs/2504.02695v1
- Date: Thu, 03 Apr 2025 15:32:32 GMT
- Title: Mind the Gap? Not for SVP Hardness under ETH!
- Authors: Divesh Aggarwal, Rishav Gupta, Aditya Morolia,
- Abstract summary: We prove new hardness results for fundamental lattice problems under the Exponential Time Hypothesis (ETH)<n>First, we show that for any $p in [1, infty)$, there exists an explicit constant $gamma > 1$ such that $mathsfCVP_p,gamma$ (the $ell_p$-norm approximate Closest Vector Problem)<n>Next, we prove a randomized ETH-hardness result for $mathsfSVP_p,gamma$ (the $ell_p$-norm approximate
- Score: 2.682592098574199
- License: http://creativecommons.org/licenses/by/4.0/
- Abstract: We prove new hardness results for fundamental lattice problems under the Exponential Time Hypothesis (ETH). Building on a recent breakthrough by Bitansky et al. [BHIRW24], who gave a polynomial-time reduction from $\mathsf{3SAT}$ to the (gap) $\mathsf{MAXLIN}$ problem-a class of CSPs with linear equations over finite fields-we derive ETH-hardness for several lattice problems. First, we show that for any $p \in [1, \infty)$, there exists an explicit constant $\gamma > 1$ such that $\mathsf{CVP}_{p,\gamma}$ (the $\ell_p$-norm approximate Closest Vector Problem) does not admit a $2^{o(n)}$-time algorithm unless ETH is false. Our reduction is deterministic and proceeds via a direct reduction from (gap) $\mathsf{MAXLIN}$ to $\mathsf{CVP}_{p,\gamma}$. Next, we prove a randomized ETH-hardness result for $\mathsf{SVP}_{p,\gamma}$ (the $\ell_p$-norm approximate Shortest Vector Problem) for all $p > 2$. This result relies on a novel property of the integer lattice $\mathbb{Z}^n$ in the $\ell_p$ norm and a randomized reduction from $\mathsf{CVP}_{p,\gamma}$ to $\mathsf{SVP}_{p,\gamma'}$. Finally, we improve over prior reductions from $\mathsf{3SAT}$ to $\mathsf{BDD}_{p, \alpha}$ (the Bounded Distance Decoding problem), yielding better ETH-hardness results for $\mathsf{BDD}_{p, \alpha}$ for any $p \in [1, \infty)$ and $\alpha > \alpha_p^{\ddagger}$, where $\alpha_p^{\ddagger}$ is an explicit threshold depending on $p$. We additionally observe that prior work implies ETH hardness for the gap minimum distance problem ($\gamma$-$\mathsf{MDP}$) in codes.
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