Aljosha Judmayer received a master's degree in Software Engineering and Internet Computing at the TU Wien. He has five plus years experience in penetration testing as an IT security consultant. At the moment, he is working as an IT security researcher at SBA Research, where he is also working toward his Ph.D. degree on applications of cryptographic currencies and resilience aspects of distributed systems. His research interests include cryptographic currency technologies as well as network and systems security.Nicholas Stifter received a master's degree in Computer Science Management and a bachelor's degree in Software Engineering from Vienna University of Technology. He is currently working toward a Ph.D. on security and maintainability aspects of blockchain technologies and smart contracts, and his research interests include Nakamoto consensus, distributed agreement protocols, and computing education for distributed systems topics.Katharina Krombholz is a post-doctoral security researcher at SBA Research in Vienna, Austria, and a university lecturer for digital forensics at the Vienna University of Technology and the FH Campus Vienna University of Applied Sciences. She completed her Ph.D. in 2016 with distinction. Her research focuses on usable security, privacy, and digital forensics.Edgar Weippl is Research Director of SBA Research and associate professor at TU Wien. After graduating with a Ph.D. from the TU Wien, Edgar worked in a research startup for two years. He then spent one year teaching as an Assistant Professor at Beloit College, WI. From 2002 to 2004, while with the software vendor ISIS Papyrus, he worked as a consultant in New York, NY, and Albany, NY, and in Frankfurt, Germany. In 2004 he joined the TU Wien and founded the research center SBA Research together with A Min Tjoa and Markus Klemen. Edgar is a member of the editorial board of Computers & Security (COSE), organizes the ARES conference, and is General Chair of SACMAT 2015, PC Chair of Esorics 2015, and General Chair of ACM CCS 2016.

• Acknowledgments.- Introduction.- Background.- History of Cryptographic Currencies.- Bitcoin.- Coin Management Tools.- Nakamoto Consensus.- Conclusion and Open Challenges.- Bibliography.- Authors' Biographies.

Aljosha Judmayer received a master's degree in Software Engineering and Internet Computing at the TU Wien. He has five plus years experience in penetration testing as an IT security consultant. At the moment, he is working as an IT security researcher at SBA Research, where he is also working toward his Ph.D. degree on applications of cryptographic currencies and resilience aspects of distributed systems. His research interests include cryptographic currency technologies as well as network and systems security.Nicholas Stifter received a master's degree in Computer Science Management and a bachelor's degree in Software Engineering from Vienna University of Technology. He is currently working toward a Ph.D. on security and maintainability aspects of blockchain technologies and smart contracts, and his research interests include Nakamoto consensus, distributed agreement protocols, and computing education for distributed systems topics.Katharina Krombholz is a post-doctoral security researcher at SBA Research in Vienna, Austria, and a university lecturer for digital forensics at the Vienna University of Technology and the FH Campus Vienna University of Applied Sciences. She completed her Ph.D. in 2016 with distinction. Her research focuses on usable security, privacy, and digital forensics.Edgar Weippl is Research Director of SBA Research and associate professor at TU Wien. After graduating with a Ph.D. from the TU Wien, Edgar worked in a research startup for two years. He then spent one year teaching as an Assistant Professor at Beloit College, WI. From 2002 to 2004, while with the software vendor ISIS Papyrus, he worked as a consultant in New York, NY, and Albany, NY, and in Frankfurt, Germany. In 2004 he joined the TU Wien and founded the research center SBA Research together with A Min Tjoa and Markus Klemen. Edgar is a member of the editorial board of Computers & Security (COSE), organizes the ARES conference, and is General Chair of SACMAT 2015, PC Chair of Esorics 2015, and General Chair of ACM CCS 2016.

• Acknowledgments.- Introduction.- Background.- History of Cryptographic Currencies.- Bitcoin.- Coin Management Tools.- Nakamoto Consensus.- Conclusion and Open Challenges.- Bibliography.- Authors' Biographies.

Aljosha Judmayer received a master's degree in Software Engineering and Internet Computing at the TU Wien. He has five plus years experience in penetration testing as an IT security consultant. At the moment, he is working as an IT security researcher at SBA Research, where he is also working toward his Ph.D. degree on applications of cryptographic currencies and resilience aspects of distributed systems. His research interests include cryptographic currency technologies as well as network and systems security.Nicholas Stifter received a master's degree in Computer Science Management and a bachelor's degree in Software Engineering from Vienna University of Technology. He is currently working toward a Ph.D. on security and maintainability aspects of blockchain technologies and smart contracts, and his research interests include Nakamoto consensus, distributed agreement protocols, and computing education for distributed systems topics.Katharina Krombholz is a post-doctoral security researcher at SBA Research in Vienna, Austria, and a university lecturer for digital forensics at the Vienna University of Technology and the FH Campus Vienna University of Applied Sciences. She completed her Ph.D. in 2016 with distinction. Her research focuses on usable security, privacy, and digital forensics.Edgar Weippl is Research Director of SBA Research and associate professor at TU Wien. After graduating with a Ph.D. from the TU Wien, Edgar worked in a research startup for two years. He then spent one year teaching as an Assistant Professor at Beloit College, WI. From 2002 to 2004, while with the software vendor ISIS Papyrus, he worked as a consultant in New York, NY, and Albany, NY, and in Frankfurt, Germany. In 2004 he joined the TU Wien and founded the research center SBA Research together with A Min Tjoa and Markus Klemen. Edgar is a member of the editorial board of Computers & Security (COSE), organizes the ARES conference, and is General Chair of SACMAT 2015, PC Chair of Esorics 2015, and General Chair of ACM CCS 2016.

• Acknowledgments.- Introduction.- Background.- History of Cryptographic Currencies.- Bitcoin.- Coin Management Tools.- Nakamoto Consensus.- Conclusion and Open Challenges.- Bibliography.- Authors' Biographies.