The book "Trust, Privacy and Security in Digital Business" documents the proceedings of the 6th International Conference on Trust, Privacy and Security in Digital Business (TrustBus 2009), which took place on September 3rd and 4th, 2009, in Linz, Austria. This conference continues the tradition of previous events held in cities such as Zaragoza, Copenhagen, Krakow, Regensburg, and Turin. At a time when advances in information and communication technology create new opportunities for innovative applications and high-quality services across global networks, the book aims to improve the quality of life for all citizens, disseminate knowledge, and ensure the competitiveness of organizations and public institutions in the global electronic market. At the same time, it addresses the challenges posed by rapid technological development, particularly concerning trust in electronic processes and the assurance of information security and user data protection. The conference brought together academic researchers and industry developers to discuss the current state of the art in these fields.