This book constitutes the refereed proceedings of the Third International Workshop on Fault Diagnosis and Tolerance in Cryptography, FDTC 2006, held in Yokohama, Japan in October 2006.The 12 revised papers of FDTC 2006 are presented together with 9 papers from FDTC 2004 and FDTC 2005 that passed a second round of reviewing. They all provide a comprehensive introduction to the issues faced by designers of robust cryptographic devices and to the currently available methodologies and techniques for protecting these devices against fault injection attacks. The papers are organized in topical sections on attacks on public key systems, protection of public key systems, attacks on and protection of symmetric key systems, models for fault attacks on cryptographic devices, fault-resistant arithmetic for cryptography, as well as fault attacks and other security threats.