• Head and deputy head of Department of Mathematics of University of Oldenburg, terms 2015-2017 and 2017-2019.
  

• Member of the steering committee of the Fachgruppe Computeralgebra of GI/DM/GAMM (since 2008, chair 2012-2015).
  
• Member of ISSAC steering committee, term 2015-2017.
  
• I have been involved in the number theoretic computer algebra system Kant and its shell KASH (see the Kant project) developed at TU Berlin and Magma at University of Sydney. Kant is also available through Magma.
• Projects on minimal regular models and complex multiplication in DFG priority program SPP1489 on computer algebra.
  

• Member on the steering committee of the Fachgruppe Kryptologie of GI, 2009-2017.
  
• Involved in PhD program OLCRYPT.
• Past BMBF project on algebraic curves and cryptography.
• Associate member of the past EU funded Network of Excellence ECRYPT 2.

I have been involved in a number of conferences from algorithmic number theory and cryptography, like

• Conference on Number Theory, Berlin, 2005 (co-organisation and programme co-chair)
• Algorithmic Number Theory Symposium (ANTS) VII, Berlin, 2006 (co-organisation and programme co-chair)
• Information Security and Cryptology : Second Sklois Conference, Inscrypt 2006 (programme committee)
• Western European Workshop on Research in Cryptology -- WEWoRC -- 2007 (programme committee)
• Sicherheit 2008, Tagung der Gesellschaft für Informatik (programme committee)
• Algorithmic Number Theory Symposium (ANTS) VIII, 2008 (programme committee)
• Pairing 2009 (programme committee)
• Sicherheit 2010 (programme committee)
• Workshop on Resolution of Singularities and Semistable Reduction, Hannover, 2010 (co-organiser) 
• North German Algebraic Geometry Seminar NoGAGS, Oldenburg, 2010 (co-organiser)
• Elliptic Curve Cryptography ECC 2011 (programme committee)
• Western European Workshop on Research in Cryptology -- WEWoRC -- 2011 (programme committee)
• 15. Kryptotag der Fachgruppe Kryptologie der GI 2011, Oldenburg (organiser)
• Western European Workshop on Research in Cryptology -- WEWoRC -- 2013 (programme committee)
• Algebraic Curves and Cryptography, Oldenburg, 2013 (organiser)
• ANTS 2016 Kaiserslautern (programme committee)
• Workshop on Arithmetic Geometry and Computer Algebra, Oldenburg, 2017 (co-organiser)
• Gauß Lecture, June 2018 Oldenburg (co-organiser)

• Marcus Wagner, Endomorphism rings of jacobian varieties via correspondences, 2008.
• Thorsten Lagemann, Asymptotics of Galois extensions: Wildly ramified abelian extensions of global function fields, 2010.
• Moritz Minzlaff, Zeta functions of curves over finite fields: Frobenius-stable lattices in the rigid cohomology of curves, 2013.
• Gerriet Möhlmann, Mordell-Weil groups and S-integral points of elliptic curves over function fields, 2014.
• Keno Eilers, Explicit formulae for higher genus hyperelliptic curves, 2018.
• Matthias Junge, Algorithms for Picard groups.
• Dietrich Kuhn, Recursive towers of function fields.

• Anita Krahmann, Computation of isogenies between elliptic curves over finite fields, 2007.
• Adolphe Elvis Lontchi, Application software protection against reverse engineering and illegal copy, 2007.
• Patrick Schweitzer, Pairing friendly elliptic and hyperelliptic curves, 2008.
• Anika Frischwasser, Efficient Pairings, 2008.
• Gerriet Möhlmann, Embedding algorithms for function fields, 2008.
• Markus Böttle, Zeta functions of g=3 curves over finite fields via the Cartier operator, 2008.
• Robert Klinzmann, Normalisation and blow ups of arithmetic surfaces, 2009
• Maike Massierer, Aspects of class field theory for global function fields, 2009.
• Jens Bauch, computation of divisor class groups via the Tate-Lichtenbaum pairing, 2009.
• Juliane Krämer, Algorithms for invertible ideals in rings of dimension two, 2010.
• Michael Mertke, Irregular primes for base extensions of curves, 2010.
• Stefan Hellbusch, Riemann-Roch Theory on Graphs and further topics, 2014.
• Maria Trei, Computational Aspects of L-series and Zeta functions of abelian extensions of global function fields, 2015.
• Matthias Junge, Asymptotically fast algorithms for Jacobians of algebraic curves, 2016.
• Dietrich Kuhn, Recursive towers of function fields, 2017.
• Linda Feeken, Fourier Analysis on Locally Compact Abelian Groups and Applications, 2017.
• Johanna Kenkel, Motzkin sets and euclidean number rings, 2017.