An Architecture for Secure Wide-Area Service Discovery

1. An Architecture for Secure Wide-Area Service Discovery Todd D. Hodes, Steven E. Czerwinski, Ben Y. Zhao, Anthony D. Joseph, and Randy H. Katz Imrich Wireless Networks 8, 213-230 (2002) 2005. 10. 17. MMLAB, Seongil Han sihan@mmlab.snu.ac.kr

2. Contents • Introduction • Features and components • Design concepts • Operations • SDS servers and services • Secure communications • Wide-area support • Multi-criteria search • Query filtering

3. Introduction • Service discovery system • Features • Security • Flexible and multi-criteria search • Wide-area deployed • Fault tolerence • Scalability

4. Components • Clients • Discover the services, using query • Services • Announce their own descriptions • SDS server • Solicit information from the services and manage queries from clients

5. Design concepts • Announcement-based • ‘Soft State’ • Periodic multicast announcements and caching • Fast react to faults • XML service descriptions • Flexibility and semantic-rich content • Privacy and authentication • Hybrid of asymmetric and symmetric-key cryptography • Authentication : certificate • Capabilities • Hierarchical organization

6. SDS servers • Basic operations • Send authenticated messages periodically • List of the domain • Multicast address for service announcements • Desired service announcement rate • Contact information for CA and CM • Well-known SDS multicast channel • Cluster operation and fault tolerance • Load balancing, mirrors • Accepting services and clients • Register the services’ description • Process the clients’ queries

7. Services • Find the correct SDS server • Listen for SDS server announcements • Not a one-time task • Send the descriptions to SDS server • Proper channel, proper frequency • Contact Capability Manager • Defining the capabilities for individual users

8. ID Ciphered Secret Payload Secure SDS communications • Authenticated server announcements • Sign but not encrypt announcements • Timestamp • Secure one-way service description announcements • Hybrid public / symmetric key system • Authenticated RMI • Two-way authenticated and encrypted • Use certificates for authentication {…, Expire, SK, …}EK {…datas…}SK

9. Multi-criteria search • Very difficult function • Complex queries and wide-area distribution • Mechanism category • Centralization • Single point of failure • Name-specified mapping • Hashing, only single criteria • Flooding • Scalability

10. Wide-area support • Objective • Full rechability • Multi-criteria selection • Filtered query flooding (query filtering) • Dynamic construction and adaptation of the neighbor relationship • Set of hierarchical interconnections • Multiple tree with various metrics • Application-level filtering infrastructure • Aggregation and query routing • Bloom-filtered crossed terminals (BCT)

11. Filtering • Terminal set • Nth-degree crossed terminal set • Lexigraphic concatenation • Reduction of N ⇔ increase of ‘false positive’ • Bloom filter • Routing • Parent based filtering (PBF) • Full indexing • Adaptation of service change • Table rebuilt, per-bit count v1 v2 v1 HIT S1 S2 query MISS False Positive query

12. Other issues • Range query, wildcards • BCT supports neither naturally • Known false positives (KFPs) caching • Soft-state messaging • Updates • Differences + fragment of table • Queries • Stateless, always with query • Query replies • Stateless, except for KFPs

13. Summary • SDS • Complex query • Automatic handle of failures • Security-minded • XML • Service-specific tag • Powerful query • Soft-state and announcement-based