Conferences, workshops, seminars, etc... ↑
(aka where you may have seen me)
Ongoing:
Past:
 June/July 2017, Arithmetic Geometry and Computer Algebra, Oldenburg, Germany
 2013  2016, I was one of the editors of the
problem section
of the Nieuw Archief voor Wiskunde
 August 2016, Algorithmic Number Theory Symposium (ANTS) Kaiserslautern, Germany
 August 2016, with Léo Ducas, Hendrik Lenstra and Alice Silverberg, I organized Mathematical Structures for Cryptography at the Lorentz Center in Leiden
 September 2015, Modular Forms and Curves of Low Genus: Computational Aspects, ICERM Providence, RI, USA
 May 2015, Arithmetic, Geometry and Coding Theory, CIRM Marseille, France
 April 2015, I organized the 51st Netherlands Mathematical Congress, with
Ronald van Luijk, Evgeny Verbitskiy, Marcel de Jeu, Markus Heydenreich, Sander Hille, Charlene Kalle, Jacob van der Woude and Onno van Gaans
 March 2015, Constructive Methods in Number Theory 
with focus on modular forms and rational coverings,
bctp Bonn, Germany
 February/March 2015, Algant meeting, Regensburg, Germany
 August 2014, Algorithmic Number Theory Symposium (ANTSXI)
GyeongJu, South Korea
 August 2014, talk at KAIST, Daejeon, South Korea.
 June 2014,
Conference  Effective moduli spaces and applications to cryptography, Rennes, France (talk)
 May 2014, Discrete Logarithm Problem 2014,
Ascona, Switzerland (talk slides)
 November 2013,
DIAMANT Symposium, Lunteren
 September 2013, Elliptic Curve Cryptography (ECC) 2013, Leuven, Belgium (talk slides)
 July 2013,
Sage Days: Algorithms in Arithmetic Geometry, Leiden (talk slides)
 July 2013, Number Theory, Geometry and Cryptography, Warwick, UK (talk)
 May 2013,
Rational Points  Geometric, Analytic and Explicit Approaches,
Warwick, UK
 April 2013, Benelux Mathematical Olympiad (BxMO) 2013,
Dordrecht, Netherlands
 March 2013,
Explicit Methods for Modular Forms, Warwick, UK
 January 2013,
Trends in Arithmetic Geometry,
Leiden, The Netherlands
 November 2012, DIAMANT symposium,
Doorn, The Netherlands
 Fall 2012,
Informal seminar
on Arithmetic Intersection Theory in Amsterdam and Leiden
 July 2012, Algorithmic Number Theory Symposium
(ANTSX),
San Diego, USA
 2010, 2011, 2012, Warwick Mathematics Institute Number Theory Seminar (talks: 032012, 102010)
 Spring 2012, Series of talks on Moduli spaces of abelian varieties
Warwick, UK
 December 2011, SageFLINT Days, Warwick, UK
 September 2011, ECC 2011, Nancy, France (talk slides)
 September 2011, ECC Summer School 2011, Nancy, France
 July 2011, International Mathematical Olympiad 2011, Amsterdam, the Netherlands
 June 2011, GeoCrypt,
Conference on Geometry and Cryptography, Corsica, France
(talk slides)
 June 2011, Oxford Number Theory Seminar, Oxford, England (talk slides)
 May 2011, DIAMANT symposium, Heeze, The Netherlands (talk slides)
 May 2011, University of Nottingham, Number Theory Seminar (talk slides)
 May 2011, Conference
on the Birch and SwinnertonDyer conjecture, Cambridge, England
 April 2011, Cambridge Number Theory Seminar, Cambridge, England (talk slides)
 March 2011, Arizona Winter School on StarkHeegner Points,
Tucson, Arizona, USA
 Winter 2011, local tropical curves seminar at Warwick
 November 2010, University of Exeter, Pure Mathematics Seminar (talk slides)
 May 2010, Diamant/EIDMA Symposium, Nunspeet
 November 2009, DIAMANT/EIDMA Symposium, Lunteren, the Netherlands (talk slides)
 November 2009, LFANT Seminar, Bordeaux, France (talk notes)
 October 2009,
Miniworkshop series on computational number theory,
KU Leuven, Belgium (talk notes)
 Fall 2009, organized a local
seminar on complex multiplication in Leiden
 September 2009, Max PlanckInstitut für Mathematik, Bonn, Germany (talk notes)
 July 2009,
Explicit Methods in Number Theory, MFO Oberwolfach, Germany (talk slides)
 December 2008, University of Washington Number Theory and Computation Seminar, Seattle, USA (talk slides)
 Fall 2008, intern at Microsoft Research
 September 2008, Elliptic Curve Cryptography
 June 2008, C4, École Polytechnique, Palaiseau, France (talk slides)
 June 2008, GTEM Instructional Conference: Number Fields, Lattices and Curves, Cetraro, Italy (talk slides)
 May 2008, Diamant/EIDMA Symposium, Oegstgeest
 May 2008,
ANTSVIII, Banff, Canada
(talk slides)
 January 2008, Joint Mathematics Meetings, San Diego, USA (talk slides)
 January 2008,
UC Irvine Number Theory Seminar,
Irvine, USA (slides)
 November 2007, Diamant/EIDMA Symposium, Soesterberg
 Fall 2007, organized a local seminar on moduli spaces and modular forms in Leiden
 September 2007, Elliptic Curve Cryptography
 July 2007,
Journées Arithmétiques,
Edinburgh, Scotland (slides)
 June 2007,
Number Theory and Computability,
Edinburgh, Scotland (talk on EDS with CM)
 May 2007, DIAMANT/EIDMA Symposium,
Heeze, the Netherlands (talk slides)
 November 2006, Diamant/EIDMA Symposium, Vught
Notes (mostly old)
 notes of an introduction to complex
multiplication of abelian varieties.

notes of a talk about
abelian surfaces that admit an (l,l)endomorphism.

notes of the LAPPTop courses
for VWO (high school) students about number theory and RSA:
''De wiskunde van geheimschriften'' (in Dutch).

notes on division polynomials with complex multiplication.

notes of a talk about Néron models of elliptic curves in ps and pdf.

Master's thesis Elliptic Divisibility Sequences with Complex Multiplication (PDF).
June 2nd 2006, supervised by Gunther Cornelissen.
 notes of a talk about Kummer Theory.

notes on Hilbert's Tenth Problem over Q in ps and pdf.

kleine scriptie (in Dutch) about Eisenstein's proofs of the quadratic and quartic reciprocity laws using periodic functions.