This book is a thorough process of refereeing of the 11th International Conference on Financial Cryptography and Data Security, FC 2007, and a co-located International Workshop on Usable Security, USEC, 2007, both held in Scarborough, Trinidad / Tobago, in February 2007. This book includes 17 revised full papers, 1 paper presentation system and transcription of the 5 panel sessions from FC 2007. The papers, which are reviewed and selected from 85 submissions, arranged in topical sections on Payment Systems, Anonymity, Authentication, Anonymity and Privacy, Cryptography and Commercial Transactions, Financial Transactions and Web Services, and Cryptography.