This book constitutes the thoroughly refereed post-conference proceedings of the Joint Workshop on Automated Reasoning for Security Protocol Analysis and Issues in the Theory of Security, ARSPA-WITS 2009, held in York, UK, in March 2009, in association with ETAPS 2009.

The 12 revised full papers presented together with 2 invited talks were carefully reviewed and selected from 27 submissions. The papers feature topics including formal specification, analysis and design of security protocols and their applications, the formal definition of various aspects of security such as access control mechanisms, mobile code security and denial-of-service attacks, the modeling of information flow and its application to confidentiality policies, system composition and covert channel analysis