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Mar 14, 2023 at 10:07 vote accept Mike Anast
Jul 13, 2018 at 12:54 comment added Hilder Vitor Lima Pereira Hi, Mike. I see your point. But even in that particular case, I think you have to give Babai's algorithm the basis instead of ${\bf A}$. For instance, consider the following diagonal matrix ${\bf A}$ with diagonal $(5, 2)$, $q = 5$, ${\bf v} = (5, 5) \in \mathcal{L}({\bf A})_q$, and ${\bf e} = (1, 0)$. Then, Babai's algorithm should output ${\bf v}$, but if you pass ${\bf A}$ instead of the basis, it will probably output either $(5, 4)$ or $(0, 1)$ depending on how you represent ${\bf t}$ (as $(6, 5)$ or as $(1, 0)$, which is reduced mod 5).
Jul 12, 2018 at 9:16 comment added Mike Anast Thank you for your answer. I specifically want to solve LWE by reducing it to BDD problem. Lindner and Peikert in [web.eecs.umich.edu/~cpeikert/pubs/lwe-analysis.pdf] (page 11) assume, that we can view an LWE instance $({\bf A},{\bf t}={\bf A}^{T}{\bf s}+{\bf e})$ as a BDD problem in the lattice $\mathcal{L}_{q}({\bf A}^T)$. We can use the Babai algorithm with input a basis ${\bf B}$ of a lattice $\mathcal{L}_{q}({\bf A}^T)$ and a target vector ${\bf t}={\bf A}^{T}{\bf s}+{\bf e}$. Then Babai is able to find a lattice vector ${\bf v}$ such that ${\bf t}={\bf v}+{\bf e}$.
Jul 11, 2018 at 15:06 history edited Hilder Vitor Lima Pereira CC BY-SA 4.0
Improved explanation.
Jul 11, 2018 at 15:02 history undeleted Hilder Vitor Lima Pereira
Jul 11, 2018 at 15:00 history deleted Hilder Vitor Lima Pereira via Vote
Jul 11, 2018 at 15:00 history answered Hilder Vitor Lima Pereira CC BY-SA 4.0