This book constitutes the refereed proceedings of the 31st IFIP TC 11 International Conference on ICT Systems Security and Privacy Protection, SEC 2016, held in Ghent, Belgium, in May/June 2016. The 27 revised full papers presented were carefully reviewed and selected from 139 submissions. The papers are organized in topical sections on cryptographic protocols, human aspects of security, cyber infrastructure, social networks, software vulnerabilities, TPM and internet of things, sidechannel analysis, software security, and privacy.