Book excerpt: This book constitutes the refereed proceedings of the 19th Annual Working Conference on Data and Applications Security held in Storrs, CT, USA, in August 2005. The 24 revised full papers presented together with an invited lecture were thoroughly reviewed and selected from 54 submissions. The papers present theory, technique, applications, and practical experience of data and application security with topics like cryptography, privacy, security planning and administration, secure information integration, secure semantic Web technologies and applications, access control, integrity maintenance, knowledge discovery and privacy, concurrency control, fault-tolerance and recovery methods.