This volume constitutes the refereed proceedings of the 4th IFIP WG 11.2 International Workshop on Information Security Theory and Practices: Security and Privacy of Pervasive Systems and Smart Devices, WISTP 2010, held in Passau, Germany, in April 2010. The 20 revised full papers and 10 short papers were carefully reviewed and selected from 69 submissions. They are organized in topical sections on embedded security, protocols, highly constrained embedded systems, security, smart card security, algorithms, hardware implementations, embedded systems and anonymity/database security.