We introduce a continuous analogue of the Learning with Errors (LWE) problem, which we name CLWE. We give a polynomial-time quantum reduction from worst-case lattice problems to CLWE, showing that CLWE enjoys similar hardness guarantees to those of LWE. Alternatively, our result can also be seen as opening new avenues of (quantum) attacks on lattice problems. Our work resolves an open problem regarding the computational complexity of learning mixtures of Gaussians without separability assumptions (Diakonikolas 2016, Moitra 2018). As an additional motivation, (a slight variant of) CLWE was considered in the context of robust machine learning (Diakonikolas et al.~FOCS 2017), where hardness in the statistical query (SQ) model was shown; our work addresses the open question regarding its computational hardness (Bubeck et al.~ICML 2019).
We introduce a continuous analogue of the Learning with Errors (LWE) problem, which we name CLWE. We give a polynomial-time quantum reduction from worst-case lattice problems to CLWE, showing that CLWE enjoys similar hardness guarantees to those of LWE. Alternatively, our result can also be seen as opening new avenues of (quantum) attacks on lattice problems. Our work resolves an open problem regarding the computational complexity of learning mixtures of Gaussians without separability assumptions (Diakonikolas 2016, Moitra 2018). As an additional motivation, (a slight variant of) CLWE was considered in the context of robust machine learning (Diakonikolas et al.~FOCS 2017), where hardness in the statistical query (SQ) model was shown; our work addresses the open question regarding its computational hardness (Bubeck et al.~ICML 2019).
We introduce a continuous analogue of the Learning with Errors (LWE) problem,
which we name CLWE. We give a polynomial-time quantum reduction from worst-case
lattice problems to CLWE, showing that CLWE enjoys similar hardness guarantees
to those of LWE. Alternatively, our result can also be seen as opening new
avenues of (quantum) attacks on lattice problems. Our work resolves an open
problem regarding the computational complexity of learning mixtures of
Gaussians without separability assumptions (Diakonikolas 2016, Moitra 2018). As
an additional motivation, (a slight variant of) CLWE was considered in the
context of robust machine learning (Diakonikolas et al.~FOCS 2017), where
hardness in the statistical query (SQ) model was shown; our work addresses the
open question regarding its computational hardness (Bubeck et al.~ICML 2019).
We introduce a continuous analogue of the Learning with Errors (LWE) problem, which we name CLWE. We give a polynomial-time quantum reduction from worst-case lattice problems to CLWE, showing that CLWE enjoys similar hardness guarantees to those of LWE. Alternatively, our result can also be seen as opening new avenues of (quantum) attacks on lattice problems. Our work resolves an open problem regarding the computational complexity of learning mixtures of Gaussians without separability assumptions (Diakonikolas 2016, Moitra 2018). As an additional motivation, (a slight variant of) CLWE was considered in the context of robust machine learning (Diakonikolas et al.~FOCS 2017), where hardness in the statistical query (SQ) model was shown; our work addresses the open question regarding its computational hardness (Bubeck et al.~ICML 2019).
We introduce Learning with Correlated Errors (LCE), a new lattice-based computationalhardness assumption in which observed samples carry noise generated by a low-rank linearcorrelation structure. Formally, given samples (A, b = As + Ce0 + e1 mod q), whereC ∈ Zm×rq is a publicly known correlation matrix and e0, e1 are short Gaussian vectors, thetask is to recover the secret s.Unlike LWE, the noise in LCE is globally correlated: up to r independent root noise sourcesdrive m observations simultaneously. Unlike the recent hybrid sparse-small assumptions ofGhosal et al. [GJL+25], LCE preserves a lattice structure that enables a reduction from theLearning with Errors (LWE) problem, thereby inheriting its worst-case hardness guarantees.We prove: (1) Worst-case hardness via reduction: We give a polynomial-timereduction from Decision-LWE to Decision-LCE, establishing that LCE is at least as hardas LWE and thereby inheriting its worst-case lattice hardness guarantees. (2) Search-to-Decision reduction: Search-LCE and Decision-LCE are polynomial-time equivalent (viaan explicit n-hybrid argument). (3) Cryptographic construction: an IND-CPA-securepublic-key encryption scheme from Decision-LCE. (4) Quantum resistance: by composingour reduction with Regev’s quantum reduction, we show that LCE resists known quantumattacks, with quantum lattice sieving requiring an estimated 20.265n quantum gates (matchingthe estimated cost for standard LWE).LCE provides a new, independently motivated hardness foundation for post-quantumcryptography and adds meaningful assumption diversity beyond LWE and LPN.
The swift advancement of quantum computing devices holds the potential to create robust machines that can tackle an extensive array of issues beyond the scope of conventional computers. Consequently, quantum computing machines create new risks at a velocity and scale never seen before, especially with regard to encryption. Lattice-based cryptography is regarded as post-quantum cryptography’s future and a competitor to a quantum computer attack. Thus, there are several advantages to lattice-based cryptographic protocols, including security, effectiveness, reduced energy usage and speed. In this work, we study the learning with errors (LWE) problem and the cryptosystems that are based on the LWE problem and, in addition, we present a new efficient variant of LWE cryptographic scheme.
The learning with errors (LWE) problem is one of the fundamental problems in cryptography and it has many applications in post-quantum cryptography. There are two variants of the problem, the decisional-LWE problem, and the search-LWE problem. LWE search-to-decision reduction shows that the hardness of the search-LWE problem can be reduced to the hardness of the decisional-LWE problem. The efficiency of the reduction can be regarded as the gap in difficulty between the problems. We initiate a study of quantum search-to-decision reduction for the LWE problem and propose a reduction that satisfies sample-preserving. In sample-preserving reduction, it preserves all parameters even the number of instances. Especially, our quantum reduction invokes the distinguisher only 2 times to solve the search-LWE problem, while classical reductions require a polynomial number of invocations. Furthermore, we give a way to amplify the success probability of the reduction algorithm. Our amplified reduction is incomparable to the classical reduction in terms of sample complexity and query complexity. Our reduction algorithm supports a wide class of error distributions and also provides a search-to-decision reduction for the learning parity with noise problem. In the process of constructing the search-to-decision reduction, we give a quantum Goldreich-Levin theorem over ℤq where q is a prime. In short, this theorem states that, if a hardcore predicate a・s (mod q) can be predicted with probability distinctly greater than (1/q) with respect to a uniformly random a ∈ ℤqn, then it is possible to determine s ∈ ℤqn.
Due to the advantages such as the worst-case hardness assumption, lattice-based cryptography is believed to the most promising research direction in post-quantum cryptography. As one of the two main hard problems commonly used in lattice-based cryptography, Learning With Errors (LWE) problem is widely used in constructing numerous cryptosystems. In order to improve the efficiency of lattice-based cryptosystems, Zhang et al. (2019) introduced the Asymmetric LWE (ALWE) problem. In this paper, the relation between the ALWE problem and the standard LWE problem is studied, and it shows that for certain error distributions the two problems are polynomially equivent, which paves the way for constructing secure lattice-based cryptosystems from the ALWE problem.