This book constitutes the thoroughly refereed post-conference proceedings of the 12th International Conference on Financial Cryptography and Data Security, FC 2008, held in Cozumel, Mexico, in January 2008. The 16 revised full papers and 9 revised short papers presented together with 5 poster papers, 2 panel reports, and 1 invited lecture were carefully reviewed and selected from 86 submissions. The papers are organized in topical sections on attacks and counter measures, protocols, theory, hardware, chips and tags, signatures and encryption, as well as anonymity and e-cash.