This book constitutes the refereed proceedings of three workshops held at the 19th International Conference on Financial Cryptography and Data Security, FC 2015, in San Juan, Puerto Rico, in January 2015. The 22 full papers presented were carefully reviewed and selected from 39 submissions. They feature the outcome of the Second Workshop on Bitcoin Research, BITCOIN 2015, the Third Workshop on Encrypted Computing and Applied Homomorphic Cryptography, WAHC 2015, and the First Workshop on Wearable Security and Privacy, Wearable 2015.

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.

This book constitutes the refereed proceedings of 5 workshops held at the 21st International Conference on Financial Cryptography and Data Security, FC 2017, in Sliema, Malta, in April 2017.The 39 full papers presented were carefully reviewed and selected from 96 submissions. They feature the outcome of the 5th Workshop on Encrypted Computing and Applied Homomorphic Cryptography, WAHC 2017, the 4th Workshop on Bitcoin and Blockchain Research, BITCOIN 2017, the Second Workshop on Secure Voting Systems, VOTING 2017, the First Workshop on Trusted Smart Contracts, WTSC 2017, and the First Workshop on Targeted Attacks, TA 2017.The papers are grouped in topical sections named: encrypted computing and applied homomorphic cryptography; bitcoin and blockchain research; advances in secure electronic voting schemes; trusted smart contracts; targeted attacks.