Ensuring security, privacy and trust

Trust is a conditio sine qua non for all transactions and inter-human communication. In a society that is increasingly interconnected, the trustworthiness of socio-technical systems depends on a myriad of components linked in ways that are frequently obscure and implicit. Moreover, these systems (whether they be enterprises, governments, or even society as a whole) are highly dynamic and adapt constantly to new circumstances.
Trust is forged by security, control of privacy sensitive data, access to information we can rely on, and, in general, systems that work. Trust is threatened by the endless list of failures that we have seen in recent years, in a world where trains stop running because of software bugs, where attackers compromise nuclear reactors and Certificate Authorities, where companies and governments keep losing sensitive data, and where the failure of many major ICT projects (passports, electronic medical dossiers, and public transport cards) undermine the public faith in these systems.
As we clearly cannot afford the trust in our digital world to be eroded by such incidents, the question is, how can we prevent it?