{"id":56,"date":"2015-06-16T13:44:07","date_gmt":"2015-06-16T11:44:07","guid":{"rendered":"http:\/\/members.loria.fr\/thierrygartiser\/?page_id=56"},"modified":"2026-03-24T13:29:34","modified_gmt":"2026-03-24T12:29:34","slug":"accueil","status":"publish","type":"page","link":"https:\/\/members.loria.fr\/JKieffer\/","title":{"rendered":"Welcome !"},"content":{"rendered":"<p>I am a CNRS researcher (charg\u00e9 de recherche) in mathematics and computer science at <a href=\"https:\/\/www.loria.fr\/\">LORIA<\/a> (Nancy, France), in the <a href=\"https:\/\/caramba.loria.fr\/\">CARAMBA<\/a> team led by Emmanuel Thom\u00e9. My research centers on algorithms for abelian varieties and their moduli spaces and their applications in public-key cryptography.<\/p>\n<p>From 2021 to 2023, I was a postdoctoral fellow in mathematics at Harvard with Prof. Noam D. Elkies, and a member of the <a href=\"https:\/\/simonscollab.icerm.brown.edu\/\">Simons Collaboration on Arithmetic Geometry, Number Theory and Computation<\/a>. I defended my PhD in 2021 at the University of Bordeaux in the <a href=\"https:\/\/lfant.math.u-bordeaux.fr\/index.php?category=home\">LFANT<\/a> team under the supervision of Damien Robert and Aurel Page. Before that, I was a student at <a href=\"https:\/\/www.ens.psl.eu\/\"><span class=\"ILfuVd\" lang=\"fr\"><span class=\"hgKElc\">\u00c9<\/span><\/span>cole normale sup\u00e9rieure<\/a> (ENS) in Paris.<\/p>\n<p>This webpage was last updated on March 24, 2026. If you notice any link that doesn&#8217;t work, please let me know.<\/p>\n<h2>Internships<\/h2>\n<p>I welcome spontaneous internship or PhD applications in computational number theory\/algebraic geometry and isogeny-based cryptography. Prior to contacting me, please note the following:<\/p>\n<ul>\n<li>Please follow the guidelines given on the <a href=\"https:\/\/caramba.inria.fr\/en\/intern\/\">CARAMBA webpage<\/a>.<\/li>\n<li>I am usually away during the summer. Internships starting early in the spring are preferable.<\/li>\n<li>Internships are in-person at LORIA. There is a mandatory 3-month delay between the moment we send your file to the administrative staff and the start date of the internship. Corollary: contact me early.<\/li>\n<li>Internships are funded.<\/li>\n<li>In the case of a PhD, it will be necessary to jointly apply for funding. The application deadline is around April to start the PhD in October (usually). The PhD will be cosupervised with someone more senior.<\/li>\n<\/ul>\n<h2>Upcoming events<\/h2>\n<ul>\n<li><a href=\"https:\/\/eurocrypt.iacr.org\/2026\/\">EUROCRYPT<\/a>, Rome, May 10-14, 2026<\/li>\n<li><a href=\"https:\/\/www.antsxvii.org\/\">ANTS XVII<\/a>, Groningen, July 6-10, 2026<\/li>\n<li><a href=\"https:\/\/focm2026.univie.ac.at\/?page_id=1336\">FoCM workshop on Computational Number Theory<\/a>, Vienna, July 13-15, 2026<\/li>\n<li><a href=\"https:\/\/conferences.cirm-math.fr\/3613.html\">RT2N conference<\/a>, CIRM Luminy, September 7-11, 2026<\/li>\n<\/ul>\n<h2>Preprints<\/h2>\n<p>Search for all my publications and preprints\u00a0or <a href=\"https:\/\/arxiv.org\/search\/?query=0000-0002-9953-0137&amp;searchtype=orcid\">arXiv<\/a>. Most of them can also be found on the <a href=\"https:\/\/hal.science\/search\/index?q=orcid%3A0000-0002-9953-0137\">HAL<\/a> open archive. See also <a href=\"https:\/\/orcid.org\/0000-0002-9953-0137\">OrcID<\/a> for information on published articles.<\/p>\n<ul>\n<li>Joint with <a title=\"\" href=\"https:\/\/people.math.harvard.edu\/~elkies\/math.html\" data-url=\"https:\/\/people.math.harvard.edu\/~elkies\/math.html\" data-cke-saved-href=\"https:\/\/people.math.harvard.edu\/~elkies\/math.html\">Noam D. Elkies<\/a>: Fast evaluation of Riemann theta functions in any dimension. <a href=\"https:\/\/arxiv.org\/abs\/2505.22382\">arXiv<\/a>.<\/li>\n<li>Spanning isogeny classes of principally polarized abelian surfaces with RM. <a href=\"https:\/\/arxiv.org\/abs\/2405.19820\">arXiv<\/a>.<\/li>\n<li>Counting points on abelian surfaces over finite fields with Elkies&#8217;s method. <a title=\"\" href=\"https:\/\/arxiv.org\/abs\/2203.02009\" data-url=\"https:\/\/arxiv.org\/abs\/2203.02009\" data-cke-saved-href=\"https:\/\/arxiv.org\/abs\/2203.02009\">arXiv<\/a>.<\/li>\n<li>Evaluating modular equations for abelian surfaces. <a title=\"\" href=\"https:\/\/arxiv.org\/abs\/2010.10094\" data-url=\"https:\/\/arxiv.org\/abs\/2010.10094\" data-cke-saved-href=\"https:\/\/arxiv.org\/abs\/2010.10094\">arXiv<\/a>.<\/li>\n<\/ul>\n<h2>Publications<\/h2>\n<ul>\n<li>Joint with\u00a0<a href=\"https:\/\/www.uni.lu\/fstm-en\/people\/alexandre-benoist\/\">Alexandre Benoist<\/a>: The asymptotic distribution of Elkies primes for reductions of abelian varieties is Gaussian. <em>Res. Number Theory\u00a0<\/em><strong>11<\/strong> (2025). <a href=\"https:\/\/arxiv.org\/abs\/2411.18171\">arXiv<\/a>, <a href=\"https:\/\/link.springer.com\/article\/10.1007\/s40993-025-00645-7\">journal<\/a>.<\/li>\n<li>Joint with <a title=\"\" href=\"https:\/\/www.normalesup.org\/~page\/index-en.html\" data-url=\"https:\/\/www.normalesup.org\/~page\/index-en.html\" data-cke-saved-href=\"https:\/\/www.normalesup.org\/~page\/index-en.html\">Aurel Page<\/a> and <a title=\"\" href=\"https:\/\/www.normalesup.org\/~robert\/pro\/\" data-url=\"https:\/\/www.normalesup.org\/~robert\/pro\/\" data-cke-saved-href=\"https:\/\/www.normalesup.org\/~robert\/pro\/\">Damien Robert<\/a>: Computing isogenies from modular equations in genus two. <em>J. Algebra <\/em><strong>666<\/strong> (2025), 331-386. <a title=\"\" href=\"https:\/\/arxiv.org\/abs\/2001.04137\" data-url=\"https:\/\/arxiv.org\/abs\/2001.04137\" data-cke-saved-href=\"https:\/\/arxiv.org\/abs\/2001.04137\">arXiv<\/a>, <a href=\"https:\/\/www.sciencedirect.com\/science\/article\/pii\/S0021869324006537\">journal<\/a>.<\/li>\n<li>Joint with <a title=\"\" href=\"https:\/\/www.raymondvanbommel.nl\/\" data-url=\"https:\/\/www.raymondvanbommel.nl\/\" data-cke-saved-href=\"https:\/\/www.raymondvanbommel.nl\/\">Raymond van Bommel<\/a>, <a title=\"\" href=\"https:\/\/math.mit.edu\/~shivac\/\" data-url=\"https:\/\/math.mit.edu\/~shivac\/\" data-cke-saved-href=\"https:\/\/math.mit.edu\/~shivac\/\">Shiva Chidambaram<\/a> and <a title=\"\" href=\"https:\/\/math.mit.edu\/~edgarc\/\" data-url=\"https:\/\/math.mit.edu\/~edgarc\/\" data-cke-saved-href=\"https:\/\/math.mit.edu\/~edgarc\/\">Edgar Costa<\/a>: Computing isogeny classes of typical principally polarized abelian surfaces over the rationals. Proceedings of the conference &#8220;LMFDB, Computation and Number Theory&#8221; (<a title=\"\" href=\"https:\/\/icerm.brown.edu\/events\/sc-23-lucant\/\" data-url=\"https:\/\/icerm.brown.edu\/events\/sc-23-lucant\/\" data-cke-saved-href=\"https:\/\/icerm.brown.edu\/events\/sc-23-lucant\/\">LuCaNT<\/a>), Contemporary Mathematics, 2023. <a title=\"\" href=\"https:\/\/arxiv.org\/abs\/2301.10118\" data-url=\"https:\/\/arxiv.org\/abs\/2301.10118\" data-cke-saved-href=\"https:\/\/arxiv.org\/abs\/2301.10118\">arXiv<\/a>, <a href=\"https:\/\/www.ams.org\/books\/conm\/796\/16002\/conm796-16002.pdf\">book<\/a>.<\/li>\n<li>Joint with <a title=\"\" href=\"https:\/\/math.dartmouth.edu\/~eassaf\/\" data-url=\"https:\/\/math.dartmouth.edu\/~eassaf\/\" data-cke-saved-href=\"https:\/\/math.dartmouth.edu\/~eassaf\/\">Eran Assaf<\/a>, <a title=\"\" href=\"https:\/\/angelicababei.com\/research\/\" data-url=\"https:\/\/angelicababei.com\/research\/\" data-cke-saved-href=\"https:\/\/angelicababei.com\/research\/\">Angelica Babei<\/a>, <a title=\"\" href=\"https:\/\/sites.google.com\/view\/benjaminbreen\/home\" data-url=\"https:\/\/sites.google.com\/view\/benjaminbreen\/home\" data-cke-saved-href=\"https:\/\/sites.google.com\/view\/benjaminbreen\/home\">Ben Breen<\/a>, <a title=\"\" href=\"https:\/\/math.mit.edu\/~edgarc\/\" data-url=\"https:\/\/math.mit.edu\/~edgarc\/\" data-cke-saved-href=\"https:\/\/math.mit.edu\/~edgarc\/\">Edgar Costa<\/a>, <a title=\"\" href=\"https:\/\/math.dartmouth.edu\/~jduque\/\" data-url=\"https:\/\/math.dartmouth.edu\/~jduque\/\" data-cke-saved-href=\"https:\/\/math.dartmouth.edu\/~jduque\/\">Juanita Duque-Rosero<\/a>, <a title=\"\" href=\"https:\/\/people.maths.ox.ac.uk\/horawa\/\" data-url=\"https:\/\/people.maths.ox.ac.uk\/horawa\/\" data-cke-saved-href=\"https:\/\/people.maths.ox.ac.uk\/horawa\/\">Aleksander Horawa<\/a>, <a title=\"\" href=\"https:\/\/math.dartmouth.edu\/~akulkarn\/\" data-url=\"https:\/\/math.dartmouth.edu\/~akulkarn\/\" data-cke-saved-href=\"https:\/\/math.dartmouth.edu\/~akulkarn\/\">Avinash Kulkarni<\/a>, <a title=\"\" href=\"https:\/\/grantmolnar.com\/\" data-url=\"https:\/\/grantmolnar.com\/\" data-cke-saved-href=\"https:\/\/grantmolnar.com\/\">Grant Molnar<\/a>, <a title=\"\" href=\"https:\/\/math.mit.edu\/~sschiavo\/\" data-url=\"https:\/\/math.mit.edu\/~sschiavo\/\" data-cke-saved-href=\"https:\/\/math.mit.edu\/~sschiavo\/\">Sam Schiavone<\/a>, and <a title=\"\" href=\"https:\/\/math.dartmouth.edu\/~jvoight\/\" data-url=\"https:\/\/math.dartmouth.edu\/~jvoight\/\" data-cke-saved-href=\"https:\/\/math.dartmouth.edu\/~jvoight\/\">John Voight<\/a>: A database of basic numerical invariants of Hilbert modular surfaces. Proceedings of the conference &#8220;LMFDB, Computation and Number Theory&#8221; (<a title=\"\" href=\"https:\/\/icerm.brown.edu\/events\/sc-23-lucant\/\" data-url=\"https:\/\/icerm.brown.edu\/events\/sc-23-lucant\/\" data-cke-saved-href=\"https:\/\/icerm.brown.edu\/events\/sc-23-lucant\/\">LuCaNT<\/a>), Contemporary Mathematics, 2023. <a title=\"\" href=\"https:\/\/arxiv.org\/abs\/2301.10302\" data-url=\"https:\/\/arxiv.org\/abs\/2301.10302\" data-cke-saved-href=\"https:\/\/arxiv.org\/abs\/2301.10302\">arXiv<\/a>, <a href=\"https:\/\/www.ams.org\/books\/conm\/796\/16006\/conm796-16006.pdf\">book<\/a>.<\/li>\n<li>Certified Newton schemes for the evaluation of low-genus theta functions. <em>Numerical algorithms <\/em>(2022). <a title=\"\" href=\"https:\/\/arxiv.org\/abs\/2203.02000\" data-url=\"https:\/\/arxiv.org\/abs\/2203.02000\" data-cke-saved-href=\"https:\/\/arxiv.org\/abs\/2203.02000\">arXiv<\/a>, <a title=\"\" href=\"https:\/\/link.springer.com\/article\/10.1007\/s11075-022-01443-3\" data-url=\"https:\/\/link.springer.com\/article\/10.1007\/s11075-022-01443-3\" data-cke-saved-href=\"https:\/\/link.springer.com\/article\/10.1007\/s11075-022-01443-3\">journal<\/a>.<\/li>\n<li>Degree and height estimates for modular equations on PEL Shimura varieties. <em>Journal of the LMS<\/em>\u00a0 <strong>105<\/strong> (2022), 1314&#8211;1361. <a title=\"\" href=\"https:\/\/arxiv.org\/abs\/2001.04138\" data-url=\"https:\/\/arxiv.org\/abs\/2001.04138\" data-cke-saved-href=\"https:\/\/arxiv.org\/abs\/2001.04138\">arXiv<\/a>, <a title=\"\" href=\"https:\/\/londmathsoc.onlinelibrary.wiley.com\/doi\/abs\/10.1112\/jlms.12540\" data-url=\"https:\/\/londmathsoc.onlinelibrary.wiley.com\/doi\/abs\/10.1112\/jlms.12540\" data-cke-saved-href=\"https:\/\/londmathsoc.onlinelibrary.wiley.com\/doi\/abs\/10.1112\/jlms.12540\">journal<\/a>.<\/li>\n<li>Upper bounds on the heights of polynomials and rational fractions from their values. <em>Acta Arith.<\/em>\u00a0 <strong>203<\/strong> (2022), 49&#8211;68. <a title=\"\" href=\"https:\/\/arxiv.org\/abs\/2105.07670\" data-url=\"https:\/\/arxiv.org\/abs\/2105.07670\" data-cke-saved-href=\"https:\/\/arxiv.org\/abs\/2105.07670\">arXiv<\/a>, <a title=\"\" href=\"https:\/\/www.impan.pl\/en\/publishing-house\/journals-and-series\/acta-arithmetica\/all\/203\/1\/114623\/upper-bounds-on-the-heights-of-polynomials-and-rational-fractions-from-their-values\" data-url=\"https:\/\/www.impan.pl\/en\/publishing-house\/journals-and-series\/acta-arithmetica\/all\/203\/1\/114623\/upper-bounds-on-the-heights-of-polynomials-and-rational-fractions-from-their-values\" data-cke-saved-href=\"https:\/\/www.impan.pl\/en\/publishing-house\/journals-and-series\/acta-arithmetica\/all\/203\/1\/114623\/upper-bounds-on-the-heights-of-polynomials-and-rational-fractions-from-their-values\">journal<\/a>.<\/li>\n<li>Sign choices in the AGM for genus two theta constants. <em>Pub. Math. Besan\u00e7on<\/em>,<em> Alg\u00e8bre &amp; Th. des nombres<\/em> (2022), 37&#8211;58. <a title=\"\" href=\"https:\/\/arxiv.org\/abs\/2010.07579\" data-url=\"https:\/\/arxiv.org\/abs\/2010.07579\" data-cke-saved-href=\"https:\/\/arxiv.org\/abs\/2010.07579\">arXiv<\/a>, <a title=\"\" href=\"https:\/\/pmb.centre-mersenne.org\/item\/PMB_2022____37_0\/\" data-url=\"https:\/\/pmb.centre-mersenne.org\/item\/PMB_2022____37_0\/\" data-cke-saved-href=\"https:\/\/pmb.centre-mersenne.org\/item\/PMB_2022____37_0\/\">journal<\/a>.<\/li>\n<li>Joint with <a title=\"\" href=\"https:\/\/defeo.lu\/\" data-url=\"https:\/\/defeo.lu\/\" data-cke-saved-href=\"https:\/\/defeo.lu\/\">Luca De Feo<\/a> and <a title=\"\" href=\"https:\/\/www.lix.polytechnique.fr\/~smith\/\" data-url=\"https:\/\/www.lix.polytechnique.fr\/~smith\/\" data-cke-saved-href=\"https:\/\/www.lix.polytechnique.fr\/~smith\/\">Benjamin Smith<\/a>: Towards practical key exchange from ordinary isogeny graphs. In T. Peyrin and S. Galbraith (editors), <em>Advances in Cryptology &#8211; AsiaCrypt 2018<\/em>, IACR, 365-394. <a title=\"\" href=\"https:\/\/arxiv.org\/abs\/1809.07543\" data-url=\"https:\/\/arxiv.org\/abs\/1809.07543\" data-cke-saved-href=\"https:\/\/arxiv.org\/abs\/1809.07543\">arXiv<\/a>, <a title=\"\" href=\"https:\/\/link.springer.com\/chapter\/10.1007\/978-3-030-03332-3_14\" data-url=\"https:\/\/link.springer.com\/chapter\/10.1007\/978-3-030-03332-3_14\" data-cke-saved-href=\"https:\/\/link.springer.com\/chapter\/10.1007\/978-3-030-03332-3_14\">journal<\/a>.<\/li>\n<\/ul>\n<h2>Software<\/h2>\n<p>My <a href=\"https:\/\/github.com\/j-kieffer\">GitHub account<\/a>.<\/p>\n<ul>\n<li><strong>acb_theta<\/strong>: a module for the <a title=\"\" href=\"https:\/\/flintlib.org\/\" data-url=\"https:\/\/flintlib.org\/\" data-cke-saved-href=\"https:\/\/flintlib.org\/\">FLINT<\/a> library featuring certified, quasi-linear time algorithms to evaluate Riemann theta functions in any dimension.<\/li>\n<li><strong>hdme:<\/strong> a C library for the evaluation of modular equations of Siegel and Hilbert type for abelian surfaces. <a title=\"\" href=\"https:\/\/github.com\/j-kieffer\/hdme\" data-url=\"https:\/\/github.com\/j-kieffer\/hdme\" data-cke-saved-href=\"https:\/\/github.com\/j-kieffer\/hdme\">GitHub<\/a>.<\/li>\n<\/ul>\n<h2>Students<\/h2>\n<ul>\n<li><a href=\"https:\/\/mokkapalat.cafe\/\">Hugo Nartz<\/a> (PhD student, from Nov. 2025, cosupervised with Emmanuel Thom\u00e9)<\/li>\n<li><a href=\"https:\/\/www.uni.lu\/fstm-en\/people\/alexandre-benoist\/\">Alexandre Benoist<\/a> (M2 internship, March-July 2024, and pre-PhD internship, Sept.-Nov. 2024)<\/li>\n<li>Ilan Ehrlich (M2 internship, Nov. 2025 &#8211; March 2026)<\/li>\n<\/ul>\n<h2>Teaching<\/h2>\n<ul>\n<li>Algorithms &amp; Complexity TA, Mines Nancy, Fall 2025.<\/li>\n<li>Isogeny graphs of abelian varieties over finite fields. 16-hour graduate mini-course, University of Luxembourg, November 2024. <a href=\"https:\/\/members.loria.fr\/JKieffer\/files\/isogenycourse.pdf\">Course notes<\/a>.<\/li>\n<li>Python programming TA, Mines Nancy, Spring 2024.<\/li>\n<\/ul>\n<h2>Manuscripts<\/h2>\n<ul>\n<li>Higher-dimensional modular equations, applications to isogeny computations and point counting. Ph.D. thesis, University of Bordeaux, 2021. Official <a title=\"\" href=\"https:\/\/tel.archives-ouvertes.fr\/tel-03346032\" data-url=\"https:\/\/tel.archives-ouvertes.fr\/tel-03346032\" data-cke-saved-href=\"https:\/\/tel.archives-ouvertes.fr\/tel-03346032\">TEL open archive<\/a>.<\/li>\n<li>Internship report on the implementation of the SEA algorithm for crypto-sized elliptic curves (in French): <a href=\"https:\/\/members.loria.fr\/JKieffer\/files\/sea.pdf\" data-fid=\"730614\" data-cke-saved-href=\"https:\/\/scholar.harvard.edu\/files\/kieffer\/files\/sea.pdf\">pdf<\/a>.<\/li>\n<\/ul>\n<h2>Talks<\/h2>\n<ul>\n<li><a href=\"https:\/\/canari.inria.fr\/seminar\/2024.html\">CANARI seminar<\/a> (ex LFANT), Bordeaux, March 2025: Fast evaluation of Riemann theta function in any dimension.<\/li>\n<li><a href=\"https:\/\/flintlib.github.io\/workshop2025.html\">FLINT workshop<\/a>, Inria Saclay, January 2025: Theta functions in FLINT. <a href=\"https:\/\/members.loria.fr\/JKieffer\/files\/theta-flint.pdf\">Slides<\/a>.<\/li>\n<li><a href=\"https:\/\/mathexp.eu\/seminar\/\">MATHEXP seminar<\/a>, Inria Saclay, November 2024: Fast evaluation of Riemann theta function in any dimension.<\/li>\n<li><a href=\"https:\/\/www.esat.kuleuven.be\/cosic\/projects\/isocrypt\/lid5\/\">Leuven Isogeny Days 5<\/a>, KU Leuven, September 2024: Fast evaluation of genus 2 modular polynomials via theta functions. <a href=\"https:\/\/members.loria.fr\/JKieffer\/files\/leuvenisogenydays.pdf\">Slides<\/a>.<\/li>\n<li><a href=\"https:\/\/nuscap.gitlabpages.inria.fr\/Paris2024.html\">NuSCAP meeting<\/a>, Paris, May 2024: Evaluating theta functions in uniform quasi-linear time in any dimension. <a href=\"https:\/\/members.loria.fr\/JKieffer\/files\/nuscap.pdf\">Slides<\/a>.<\/li>\n<li><a href=\"https:\/\/www.esat.kuleuven.be\/cosic\/projects\/isocrypt\/seminars\/\">KULB mathematical cryptography seminar<\/a>, Leuven, May 2024: Modular polynomials for abelian surfaces and related algorithms. <a href=\"https:\/\/members.loria.fr\/JKieffer\/files\/leuven.pdf\">Slides<\/a>.<\/li>\n<li><a href=\"https:\/\/caramba.loria.fr\/seminars\/\">CARAMBA seminar<\/a>, Nancy, Jan. 2024: Evaluating theta functions in uniform quasi-linear time in any dimension.<\/li>\n<li><a title=\"\" href=\"https:\/\/iecl.univ-lorraine.fr\/ad2023\/\" data-url=\"https:\/\/iecl.univ-lorraine.fr\/ad2023\/\" data-cke-saved-href=\"https:\/\/iecl.univ-lorraine.fr\/ad2023\/\">Journ\u00e9es Arithm\u00e9tiques<\/a>, Nancy, July 2023: Isogeny classes of abelian surfaces over the rationals.<\/li>\n<li><a title=\"\" href=\"https:\/\/conferences.cirm-math.fr\/2675.html\" data-url=\"https:\/\/conferences.cirm-math.fr\/2675.html\" data-cke-saved-href=\"https:\/\/conferences.cirm-math.fr\/2675.html\">Arithmetic statistics<\/a>, Luminy, May 2023: Isogeny classes of abelian surfaces over the rationals.<\/li>\n<li><a title=\"\" href=\"https:\/\/conferences.cirm-math.fr\/2805.html\" data-url=\"https:\/\/conferences.cirm-math.fr\/2805.html\" data-cke-saved-href=\"https:\/\/conferences.cirm-math.fr\/2805.html\">COUNT<\/a> (Computations and their uses in number theory), Luminy, Feb. 2023: Isogeny classes of abelian surfaces over the rationals (in replacement of Edgar Costa). <a href=\"https:\/\/members.loria.fr\/JKieffer\/files\/count.pdf\" data-fid=\"764666\" data-cke-saved-href=\"https:\/\/scholar.harvard.edu\/sites\/scholar.harvard.edu\/files\/kieffer\/files\/count.pdf\">Slides<\/a>.<\/li>\n<li><a title=\"\" href=\"https:\/\/lmbp.uca.fr\/seminaires\/gt_tna.php\" data-url=\"https:\/\/lmbp.uca.fr\/seminaires\/gt_tna.php\" data-cke-saved-href=\"https:\/\/lmbp.uca.fr\/seminaires\/gt_tna.php\">Clermont<\/a>, <a title=\"\" href=\"https:\/\/www.lmno.cnrs.fr\/sem\/TN\/archive?field_date2_value%5Bvalue%5D%5Byear%5D=2023\" data-url=\"https:\/\/www.lmno.cnrs.fr\/sem\/TN\/archive?field_date2_value%5Bvalue%5D%5Byear%5D=2023\" data-cke-saved-href=\"https:\/\/www.lmno.cnrs.fr\/sem\/TN\/archive?field_date2_value%5Bvalue%5D%5Byear%5D=2023\">Caen<\/a> and <a title=\"\" href=\"https:\/\/lmb.univ-fcomte.fr\/Seminaire-d-Algebre-et-de-Theorie?lang=fr\" data-url=\"https:\/\/lmb.univ-fcomte.fr\/Seminaire-d-Algebre-et-de-Theorie?lang=fr\" data-cke-saved-href=\"https:\/\/lmb.univ-fcomte.fr\/Seminaire-d-Algebre-et-de-Theorie?lang=fr\">Besan\u00e7on<\/a> number theory seminars, Feb\/Feb\/June 2023: Isogeny classes of abelian surfaces over the rationals.<\/li>\n<li><a title=\"\" href=\"https:\/\/www.jointmathematicsmeetings.org\/meetings\/national\/jmm2023\/2270_program_ss71.html#title\" data-url=\"https:\/\/www.jointmathematicsmeetings.org\/meetings\/national\/jmm2023\/2270_program_ss71.html#title\" data-cke-saved-href=\"https:\/\/www.jointmathematicsmeetings.org\/meetings\/national\/jmm2023\/2270_program_ss71.html#title\">Joint Math Meetings<\/a> (JMM), Boston, Jan. 2023: Certified quasi-linear algorithms for the evaluation of theta functions in low genus.<\/li>\n<li><a title=\"\" href=\"https:\/\/irmar.univ-rennes1.fr\/seminars-old?f%5B0%5D=seminar_old_type%3A234\" data-url=\"https:\/\/irmar.univ-rennes1.fr\/seminars-old?f%5B0%5D=seminar_old_type%3A234\" data-cke-saved-href=\"https:\/\/irmar.univ-rennes1.fr\/seminars-old?f%5B0%5D=seminar_old_type%3A234\">Geometry and Effective algebra seminar<\/a>, Rennes, Nov. 2022: Isogeny classes of abelian surfaces over the rationals.<\/li>\n<li><a title=\"\" href=\"https:\/\/webmath.univ-rennes1.fr\/crypto\/\" data-url=\"https:\/\/webmath.univ-rennes1.fr\/crypto\/\" data-cke-saved-href=\"https:\/\/webmath.univ-rennes1.fr\/crypto\/\">Cryptography seminar<\/a>, Rennes, Nov. 2022: Analytic techniques for isogeny graphs of abelian surfaces.<\/li>\n<li><a title=\"\" href=\"https:\/\/caramba.loria.fr\/seminars\" data-url=\"https:\/\/caramba.loria.fr\/seminars.en.html\" data-cke-saved-href=\"https:\/\/caramba.loria.fr\/seminars.en.html\">CARAMBA seminar<\/a>, Nancy, Nov. 2022: Theta functions and isogenies between abelian surfaces.<\/li>\n<li><a title=\"\" href=\"https:\/\/researchseminars.org\/seminar\/ExplicitModularity\" data-url=\"https:\/\/researchseminars.org\/seminar\/ExplicitModularity\" data-cke-saved-href=\"https:\/\/researchseminars.org\/seminar\/ExplicitModularity\">Explicit methods for modularity<\/a>, Apr. 2022: Asymptotically faster point counting on abelian surfaces. This event replaces the AMS special session that was originally scheduled as part of the JMM in Seattle, Jan. 7-8, 2022. <a href=\"https:\/\/members.loria.fr\/JKieffer\/files\/explicitmethodsmodularity.pdf\" data-fid=\"738933\" data-cke-saved-href=\"https:\/\/scholar.harvard.edu\/files\/kieffer\/files\/explicitmethodsmodularity.pdf\">Slides<\/a>.<\/li>\n<li><a title=\"\" href=\"https:\/\/ed-mi.u-bordeaux.fr\/L-Ecole-doctorale\/Les-temps-forts\/Journee-de-l-EDMI\" data-url=\"https:\/\/ed-mi.u-bordeaux.fr\/L-Ecole-doctorale\/Les-temps-forts\/Journee-de-l-EDMI\" data-cke-saved-href=\"https:\/\/ed-mi.u-bordeaux.fr\/L-Ecole-doctorale\/Les-temps-forts\/Journee-de-l-EDMI\">Bordeaux Math &amp; CS Ph.D. day<\/a>, Apr. 2022: Isogenies and point counting for curves over finite fields.<\/li>\n<li><a title=\"\" href=\"https:\/\/lfant.math.u-bordeaux.fr\/index.php?category=seminar\" data-url=\"https:\/\/lfant.math.u-bordeaux.fr\/index.php?category=seminar\" data-cke-saved-href=\"https:\/\/lfant.math.u-bordeaux.fr\/index.php?category=seminar\">LFANT seminar<\/a>, Mar. 2022: Certified Newton schemes for the evaluation of low-genus theta functions. <a href=\"https:\/\/members.loria.fr\/JKieffer\/files\/bordeaux.pdf\" data-fid=\"738936\" data-cke-saved-href=\"https:\/\/scholar.harvard.edu\/files\/kieffer\/files\/bordeaux.pdf\">Slides<\/a>.<\/li>\n<li>Simons Collaboration meeting, Mar. 2022: Certified Newton schemes for the evaluation of low-genus theta functions.<\/li>\n<li>Simons Collaboration meeting, Oct. 2O21: Software presentation on theta constants and modular equations in genus 2. <a href=\"https:\/\/members.loria.fr\/JKieffer\/files\/octobermeeting.pdf\" data-fid=\"737404\" data-cke-saved-href=\"https:\/\/scholar.harvard.edu\/files\/kieffer\/files\/octobermeeting.pdf\">Slides<\/a>.<\/li>\n<li><a title=\"\" href=\"https:\/\/fabiangundlach.org\/harvard-nt-seminar\/\" data-url=\"https:\/\/fabiangundlach.org\/harvard-nt-seminar\/\" data-cke-saved-href=\"https:\/\/fabiangundlach.org\/harvard-nt-seminar\/\">Harvard number theory seminar<\/a>, Oct. 2021: Higher-dimensional modular equations and point counting on abelian surfaces.<\/li>\n<li><a title=\"\" href=\"https:\/\/math.mit.edu\/nt\/\" data-url=\"https:\/\/math.mit.edu\/nt\/\" data-cke-saved-href=\"https:\/\/math.mit.edu\/nt\/\">MIT number theory seminar<\/a>, Oct. 2021: Higher-dimensional modular equations and point counting on abelian surfaces.<\/li>\n<li>Thesis defense, Bordeaux, July 2021: <a href=\"https:\/\/members.loria.fr\/JKieffer\/files\/soutenance.pdf\" data-fid=\"730608\" data-cke-saved-href=\"https:\/\/scholar.harvard.edu\/files\/kieffer\/files\/soutenance.pdf\">Slides<\/a> (in French).<\/li>\n<li><a title=\"\" href=\"https:\/\/conferences.cirm-math.fr\/2579.html\" data-url=\"https:\/\/conferences.cirm-math.fr\/2579.html\" data-cke-saved-href=\"https:\/\/conferences.cirm-math.fr\/2579.html\">AGCT<\/a>, May 2021 (online): On the complexity of modular equations in genus 2. <a href=\"https:\/\/members.loria.fr\/JKieffer\/files\/slides-agct21.pdf\" data-fid=\"730613\" data-cke-saved-href=\"https:\/\/scholar.harvard.edu\/files\/kieffer\/files\/slides-agct21.pdf\">Slides<\/a>.<\/li>\n<li><a href=\"https:\/\/www.math.u-bordeaux.fr\/imb\/seminaire-geometrie\" target=\"_blank\" rel=\"noopener\" data-cke-saved-href=\"https:\/\/www.math.u-bordeaux.fr\/imb\/seminaire-geometrie\">Geometry seminar<\/a>, Bordeaux, Nov. 2020 (online): Algorithmic aspects of the moduli space of principally polarized abelian surfaces.<\/li>\n<li><a href=\"https:\/\/jc2-2020.inria.fr\/en\/\" target=\"_blank\" rel=\"noopener\" data-cke-saved-href=\"https:\/\/jc2-2020.inria.fr\/en\/\">C2 days<\/a>, Nov. 2020 (online): Genus 2 point counting using isogenies. <a href=\"https:\/\/members.loria.fr\/JKieffer\/files\/jc2-2020.pdf\" data-fid=\"730610\" data-cke-saved-href=\"https:\/\/scholar.harvard.edu\/files\/kieffer\/files\/jc2-2020.pdf\">Slides<\/a>.<\/li>\n<li><a href=\"https:\/\/conferences.cirm-math.fr\/2326.html\" target=\"_blank\" rel=\"noopener\" data-cke-saved-href=\"https:\/\/conferences.cirm-math.fr\/2326.html\">Computer algebra days<\/a> (JNCF), Luminy, March 2020: Heights and interpolation of rational fractions. <a href=\"https:\/\/members.loria.fr\/JKieffer\/files\/slides-jncf20.pdf\" data-fid=\"730609\" data-cke-saved-href=\"https:\/\/scholar.harvard.edu\/files\/kieffer\/files\/slides-jncf20.pdf\">Slides<\/a>.<\/li>\n<li><a href=\"https:\/\/caramba.loria.fr\/seminars\" target=\"_blank\" rel=\"noopener\" data-cke-saved-href=\"https:\/\/caramba.loria.fr\/seminars.en.html\">CARAMBA seminar<\/a>, Nancy, Feb. 2020: Computing isogenies from modular equations in genus 2.<\/li>\n<li><a href=\"https:\/\/webmath.univ-rennes1.fr\/crypto\/presentation_en.html\" target=\"_blank\" rel=\"noopener\" data-cke-saved-href=\"https:\/\/webmath.univ-rennes1.fr\/crypto\/presentation_en.html\">Cryptography seminar<\/a>, Rennes, Jan. 2020: Computing isogenies from modular equations in genus 2.<\/li>\n<li><a href=\"https:\/\/lambda.apps.math.cnrs.fr\/seminaires\/\" target=\"_blank\" rel=\"noopener\" data-cke-saved-href=\"https:\/\/lambda.apps.math.cnrs.fr\/seminaires\/\">Lambda PhD seminar<\/a>, Bordeaux, Oct. 2019: Counting points on elliptic curves over finite fields.<\/li>\n<li><a href=\"https:\/\/conferences.cirm-math.fr\/1921.html\" target=\"_blank\" rel=\"noopener\" data-cke-saved-href=\"https:\/\/conferences.cirm-math.fr\/1921.html\">AGCT<\/a>, Luminy, June 2019: Computing isogenies from modular equations in genus 2. <a href=\"https:\/\/members.loria.fr\/JKieffer\/files\/slides-agct19.pdf\" data-fid=\"730612\" data-cke-saved-href=\"https:\/\/scholar.harvard.edu\/files\/kieffer\/files\/slides-agct19.pdf\">Slides<\/a>.<\/li>\n<li><a href=\"https:\/\/asiacrypt.iacr.org\/2018\/\" target=\"_blank\" rel=\"noopener\" data-cke-saved-href=\"https:\/\/asiacrypt.iacr.org\/2018\/\">AsiaCrypt<\/a>, Brisbane, Dec. 2018: Towards practical key exchange from ordinary isogeny graphs. <a href=\"https:\/\/members.loria.fr\/JKieffer\/files\/slides-asiacrypt18.pdf\" data-fid=\"730611\" data-cke-saved-href=\"https:\/\/scholar.harvard.edu\/files\/kieffer\/files\/slides-asiacrypt18.pdf\">Slides<\/a>.<\/li>\n<li><a href=\"https:\/\/lfant.math.u-bordeaux.fr\/index.php?category=seminar\" target=\"_blank\" rel=\"noopener\" data-cke-saved-href=\"https:\/\/lfant.math.u-bordeaux.fr\/index.php?category=seminar\">LFANT seminar<\/a>, Bordeaux, May 2018: Implementing the SEA algorithm.<\/li>\n<\/ul>\n<h2>Events I participated in organizing<\/h2>\n<ul>\n<li><a href=\"https:\/\/caramba.loria.fr\/seminars\/\">CARAMBA seminars<\/a>, Nov. 2024 &#8211; June 2025.<\/li>\n<li><a href=\"https:\/\/caipi_symposium.pages.math.cnrs.fr\/page-web\/index-en.html\">CAIPI Symposium<\/a> on endomorphism and invariants of abelian varieties over finite fields, Nancy, April 7-8, 2025<\/li>\n<li><a href=\"https:\/\/icerm.brown.edu\/events\/sc-23-smf\/\">Siegel modular forms in LMFDB<\/a> workshop at ICERM, Providence, Nov. 16-19, 2023<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>I am a CNRS researcher (charg\u00e9 de recherche) in mathematics and computer science at <a href=\"https:\/\/www.loria.fr\/\">LORIA<\/a> (Nancy, France), in the <a href=\"https:\/\/caramba.loria.fr\/\">CARAMBA<\/a> team led by Emmanuel Thom\u00e9. My research centers on algorithms for abelian varieties and their moduli spaces and their applications in public-key cryptography.<\/p>\n<p>From 2021 to 2023, I was a postdoctoral fellow in mathematics at Harvard with Prof. Noam D. Elkies, and a member of the <a href=\"https:\/\/simonscollab.icerm.brown.edu\/\">Simons Collaboration on Arithmetic Geometry, Number Theory and Computation<\/a>. I defended my PhD in 2021 at the University of Bordeaux in the <a href=\"https:\/\/lfant.math.u-bordeaux.fr\/index.php?category=home\">LFANT<\/a> team under the supervision of Damien Robert and Aurel Page.<\/p>\n","protected":false},"author":5,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-56","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/members.loria.fr\/JKieffer\/wp-json\/wp\/v2\/pages\/56","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/members.loria.fr\/JKieffer\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/members.loria.fr\/JKieffer\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/members.loria.fr\/JKieffer\/wp-json\/wp\/v2\/users\/5"}],"replies":[{"embeddable":true,"href":"https:\/\/members.loria.fr\/JKieffer\/wp-json\/wp\/v2\/comments?post=56"}],"version-history":[{"count":69,"href":"https:\/\/members.loria.fr\/JKieffer\/wp-json\/wp\/v2\/pages\/56\/revisions"}],"predecessor-version":[{"id":407,"href":"https:\/\/members.loria.fr\/JKieffer\/wp-json\/wp\/v2\/pages\/56\/revisions\/407"}],"wp:attachment":[{"href":"https:\/\/members.loria.fr\/JKieffer\/wp-json\/wp\/v2\/media?parent=56"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}