This book constitutes the refereed proceedings of four workshops held at the 25th International Conference on Financial Cryptography and Data Security, FC 2021, held virtually, in March 2021.The workshops are as follows: CoDecFin: The Second Workshop on Coordination of Decentralized Finance DeFi 2021 : First Workshop on Decentralized Finance VOTING 2021: Sixth Workshop on Advances in Secure Electronic Voting WTSC 2021: Fifth Workshop on Trusted Smart Contracts

This book constitutes the refereed proceedings of two workshops held at the 24th International Conference on Financial Cryptography and Data Security, FC 2020, in Kota Kinabalu, Malaysia, in February 2020. The 39 full papers and 3 short papers presented in this book were carefully reviewed and selected from 73 submissions. The papers feature four Workshops: The 1st Asian Workshop on Usable Security, AsiaUSEC 2020, the 1st Workshop on Coordination of Decentralized Finance, CoDeFi 2020, the 5th Workshop on Advances in Secure Electronic Voting, VOTING 2020, and the 4th Workshop on Trusted Smart Contracts, WTSC 2020. The AsiaUSEC Workshop contributes an increase of the scientific quality of research in human factors in security and privacy. In terms of improving efficacy of secure systems, the research included an extension of graphical password authentication. Further a comparative study of SpotBugs, SonarQube, Cryptoguard and CogniCrypt identified strengths in each and refined the need for improvements in security testing tools. The CoDeFi Workshop discuss multi-disciplinary issues regarding technologies and operations of decentralized finance based on permissionless blockchain. The workshop consists of two parts; presentations by all stakeholders, and unconference style discussions. The VOTING Workshop cover topics like new methods for risk-limited audits, new ethods to increase the efficiency of mixnets, verification of security of voting schemes election auditing, voting system efficiency, voting system usability, and new technical designs for cryptographic protocols for voting systems, and new way of preventing voteselling by de-incentivising this via smart contracts. The WTSC Workshop focuses on smart contracts, i.e., self-enforcing agreements in the form of executable programs, and other decentralized applications that are deployed to and run on top of specialized blockchains.