In July 2011 Marc became the first Heisenberg-Professor at Darmstadt University of Technology (TUD), Germany, and established the group “Cryptography and Complexity Theory” (Cryptoplexity) at the Department of Computer Science. The group has been initially funded by the German Research Foundation (DFG) as part of the Heisenberg Program, till June 2016.

Marc is also a PI of the "Center for Research in Security and Privacy" (CRISP), co-funded by the Federal Ministry of Education and Research and the State of Hesse from October 2015 on. CRISP unites the former “Center for Advanced Security Research Darmstadt” (CASED), funded by the State Hesse from September 2008 till June 2016, and the former "Competence Center for IT Security" (EC-Spride), funded by the Federal Ministry of Education and Research from October 2011 till September 2015. Since October 2019 Marc also acts as the speaker in the DFG-funded collaborative research center "Cryptography-based Security Solutions: Enabling trust in new and next generation computing environments" (CROSSING) which has started in October 2014.

From February 2006 till January 2011 Marc was the head of the Emmy Noether research group “Minimizing Cryptographic Assumptions” (MiniCrypt). This group was also located at the Darmstadt University of Technology and funded by the German Research Foundation as part of the Emmy Noether Program.

From September 2004 till August 2005, Marc was affiliated with the Information Security and Cryptography Group at the Computer Science Department of the Eidgenossische Technische Hochschule Zurich (ETH Zurich). This visit was mainly funded by the Emmy Noether fellowship of the German Research Foundation (DFG) and partly by ETH Zurich.

From September 2003 till August 2004, Marc visited the Cryptography Group at the Computer Science and Engineering Department (CSE), University of California, San Diego (UCSD). This visit was funded by the Emmy Noether Program.

Form June 2002 till August 2003, Marc worked at the Fraunhofer Gesellschaft, Institute for Secure Information Technology (SIT), formerly known as Institute for Secure Telecooperation, Department of Security and Smartcard Technology (SICA). There he was mainly involved in industry-related security projects.

From June 1997 till April 2002 (suspended due to community service in 1998) Marc worked as a research assistant and Ph.D. student at Prof. Schnorr's group at the University of Frankfurt. His research during that time mainly dealt with the design of efficient and provably secure cryptographic protocols. He completed his Ph.D. in December 2001 with grade “summa cum laude”. The title of his thesis was “Trapdoor Commitment Schemes and Their Applications”.

From 1992 till 1997 and 1998, respectively, Marc studied Mathematics and Computer Science at the Johann Wolfgang Goethe-University in Frankfurt, Germany, obtaining diplomas in both subjects. His theses, under supervision of Prof. Schnorr, both dealt with cryptography: one with incremental cryptography, the other one with fair exchange of digital signatures.