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.