This book constitutes the refereed proceedings of three workshops heldat the 20th International Conference on Financial Cryptography and DataSecurity, FC 2016, in Christ Church, Barbados, in February 2016. The 22 full papers presented were carefully reviewed and selected from 49 submissions. They feature the outcome of the Second Workshop on Bitcoin and Blockchain Research, BITCOIN 2016, the First Workshop on Secure Voting Systems, VOTING 2016, and the 4th Workshop on Encrypted Computing and Applied Homomorphic Cryptography, WAHC 2016.

It is our pleasure to welcome you to the proceedings of the Second International Symposium on Engineering Secure Software and Systems. This unique event aimed at bringing together researchersfrom softwareen- neering and security engineering, which might help to unite and further develop the two communities in this and future editions. The parallel technical spons- ships from the ACM SIGSAC (the ACM interest group in security) and ACM SIGSOF (the ACM interest group in software engineering) is a clear sign of the importance of this inter-disciplinary research area and its potential. The di?culty of building secure software systems is no longer focused on mastering security technology such as cryptography or access control models. Other important factors include the complexity of modern networked software systems, the unpredictability of practical development life cycles, the intertw- ing of and trade-o? between functionality, security and other qualities, the d- culty of dealing with human factors, and so forth. Over the last years, an entire research domain has been building up around these problems. The conference program included two major keynotes from Any Gordon (Microsoft Research Cambridge) on the practical veri?cation of security pro- cols implementation and Angela Sasse (University College London) on security usability and an interesting blend of research, industry and idea papers.