worked for SAP in various positions in Germany and the United States until 1998. The German software company produces business software. Bernhard Esslinger headed the development department for all security components of the SAP R/3 system, an information system at that time SAP's main product line, with which all business-relevant areas of a company could be viewed in context. He was also SAP's global Chief Information Security Officer (CISO) . From 1998 to 2013 he worked for Deutsche Bank as global head of information security (Head IT Security) in the Corporate Center and as head of the competence center for cryptography. Since 2008 he has been an honorary professor for IT security and cryptology and teaches at Faculty III for economics, business informatics and business law at the University of Siegen. CrypTool has been developed under his leadership since 1998. With CrypTool, many concepts of classic and modern cryptography can be grasped in a playful way, and corresponding methods of cryptanalysis can be understood. The software has been continuously expanded for more than twenty years and is freely available.