{"title":"Endomorphism Rings of Supersingular Elliptic Curves and Quadratic Forms","authors":"Guanju Xiao, Zijian Zhou, Longjiang Qu","doi":"arxiv-2409.11025","DOIUrl":null,"url":null,"abstract":"Given a supersingular elliptic curve, the supersingular endomorphism ring\nproblem is to compute all of its endomorphisms. We use the correspondence\nbetween maximal orders in quaternion algebra $B_{p,\\infty}$ and positive\nternary quadratic forms with discriminant $p$ to solve the supersingular\nendomorphism ring problem. Let $c<3p/16$ be a prime or $c=1$. Let $E$ be a\n$\\mathbb{Z}[\\sqrt{-cp}]$-oriented supersingular elliptic curve defined over\n$\\mathbb{F}_{p^2}$. There exists a subgroup $G$ of order $c$, and\n$\\text{End}(E,G)$ is isomorphic to an Eichler order in $B_{p,\\infty}$ of level\n$c$. If the endomorphism ring $\\text{End}(E,G)$ is known, then we can compute\n$\\text{End}(E)$ by solving two square roots in $\\mathbb{F}_c$. In particular,\nlet $D<p$ be a prime. If an imaginary quadratic order with discriminant $-D$ or\n$-4D$ can be embedded into $\\text{End}(E)$, then we can compute $\\text{End}(E)$\nby solving one square root in $\\mathbb{F}_D$ and two square roots in\n$\\mathbb{F}_c$. As we know, isogenies between supersingular elliptic curves can be translated\nto kernel ideals of endomorphism rings. We study the action of these kernel\nideals and express right orders of them by ternary quadratic forms.","PeriodicalId":501064,"journal":{"name":"arXiv - MATH - Number Theory","volume":"9 1","pages":""},"PeriodicalIF":0.0000,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"arXiv - MATH - Number Theory","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/arxiv-2409.11025","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0
Abstract
Given a supersingular elliptic curve, the supersingular endomorphism ring
problem is to compute all of its endomorphisms. We use the correspondence
between maximal orders in quaternion algebra $B_{p,\infty}$ and positive
ternary quadratic forms with discriminant $p$ to solve the supersingular
endomorphism ring problem. Let $c<3p/16$ be a prime or $c=1$. Let $E$ be a
$\mathbb{Z}[\sqrt{-cp}]$-oriented supersingular elliptic curve defined over
$\mathbb{F}_{p^2}$. There exists a subgroup $G$ of order $c$, and
$\text{End}(E,G)$ is isomorphic to an Eichler order in $B_{p,\infty}$ of level
$c$. If the endomorphism ring $\text{End}(E,G)$ is known, then we can compute
$\text{End}(E)$ by solving two square roots in $\mathbb{F}_c$. In particular,
let $D