This book constitutes the proceedings of the 13th International Workshop on Security and Trust Management, STM 2017, held in Oslo, Norway, in September 2017, in conjunction with the 22nd European Symposium Research in Computer Security, ESORICS 2017. The 10 full papers and 6 short papers were carefully reviewed and selected from 33 submissions. The focus of the workshop was on the following topics: cryptosystems and applied cryptography; software security and risk management; authorization; security vulnerabilities and prools; and secure systems.