1 Intrusion Tolerance for NEST Bruno Dutertre, Steven Cheung SRI International NEST 2 Kickoff Meeting November 4, 2002

2 Administrative Project Title: Intrusion Tolerance for Networked Embedded Sys. PM: Vijay Raghavan PI: Bruno Dutertre and Steven Cheung PI phone # : (650) , (650) PI Institution: SRI International Contract #: F C-0212 Award start date: 9/20/2002 Award end date: 12/20/2004 Agent name & organization: Raymond Liuzzi, AFRL/Rome

3 Subcontractors and Collaborators Collaborators: –Hassen Saïdi –Ulf Lindqvist –Joshua D. Levy

4 Problem Description, Project Overview Objective: –Low-cost, intrusion-tolerant authentication and key management for NEST (resource-limited wireless devices) Impact: –Fundamental building blocks on which higher-level security services can be implemented –Enable the secure deployment of sensor networks, or other NEST applications. Success criteria: –Demonstrate deployment on a representative network of small wireless sensors (Motes) –Relevant metrics: network size, fraction of compromised sensors, overhead

Problem and Challenge Impact New Ideas Schedule  Build low-cost key-management services for sensor networks:  Localized authentication protocols for bootstrapping  Chains of trusted intermediaries for  Secret sharing + disjoint paths for tolerating compromised nodes  Intrusion detection for motes:  Detect denial-of-service attacks  Detect misbehaving nodes Intrusion Tolerance for NEST Intrusion-tolerant key-distribution services for large networks of microsensors 2QFY03: Design Bootstrapping Protocols 3QFY03: Baseline Intrusion Detection 4QFY03: Design Inturion-tolerant Key-Distribution Protocols 1QFY04: Experimental Validation and Demo 1QFY05: Integration and Final Demo FY03 FY04 FY05  Enable deployment of sensor networks in hostile environments  Support other security services for wireless sensor networks:  Confidentiality and integrity of communication  Robust NEST services Self organizing protocols Low cost cryptography Detect/respond to DoS attacks

6 Outline Existing approaches to authentication and key management –PKI, Diffie-Hellman, trusted servers Proposed approach: –Local authentication and initial key establishment –Leveraging local trust –Intrusion detection and response Plan

7 Objective Low-cost key management for large-scale networks of small wireless devices Constraints: –Limited memory, processing power, and bandwidth –Networks too large and not accessible for manual administration/configuration

8 Traditional Key Management Decentralized approaches: –Public-key infrastructure, certificates –Diffie-Hellman style key establishment Approaches based on symmetric-key cryptography –Trusted authentication and key distribution server (e.g., Kerberos) Too expensive Limited scalability High administrative overhead to set up long-term keys Vulnerable to server failure Server may be a bottleneck

9 Proposed Approach Goals: –Intrusion-tolerant architecture for key management in NEST –Use only inexpensive cryptographic algorithm –Decentralized (no server) and self organizing Approach: –Build initial secure local links –For nonlocal communication, rely on chains of intermediaries –Use secret sharing when intermediaries are not fully trusted –Develop complementary intrusion detection methods to locate nontrustworthy nodes

10 Bootstrapping Establish secure local links between neighbor devices quickly after deployment –Weak authentication is enough (need only to recognize that your neighbor was deployed at the same time as you) –Exploit initial trust (it takes time for an adversary to capture/compromise devices) –Focusing on local links improves efficiency

11 Basic Bootstrapping Scheme For a set S of devices to be deployed –Construct a symmetric key K –Distribute it to all devices in the set K enables two neighbor devices A and B –To recognize that they both belong to S (weak authentication) –To generate and exchange a key for future communication Possible drawback: –Every device from S in communication range of A and B can discover. More robust variants are possible.

12 Leveraging Local Trust To establish keys between distant nodes: –use chains of trusted intermediaries To tolerate compromised nodes: –disjoint chains and secret sharing A B C D E

13 Tradeoffs Security increases with –the number of disjoint paths –the number of shares but these also increase cost Challenges: –Implement cheap secret sharing techniques –Quantify the security achieved –Find the right tradeoff for an assumed fraction of compromised nodes

14 Intrusion Detection Goals: –Detect compromised nodes (to remove them from chains) –Detect other intrusions: denial-of-service attacks, attempt to drain power –Cryptography is ineffective against these

15 Intrusion Detection Approach Develop models of attacks and relevant signatures: –What must be monitored? –How to collect and distribute the data? Develop diagnosis methods: –Identify the source of the attack if possible Possible responses: –Avoid nodes that are considered compromised –Hibernation to counter DoS or power-draining attacks

16 Experimental Evaluation Platform: –“motes” with TinyOS – nodes with upto 20% compromised nodes –Objective: show feasibility, measure overhead Experiment scenario remains to be defined

17 Project Status Participating in the security minitask Identifying security threats for a NEST environment Getting familiar with the TinyOS platform and the NEST Challenge In the process of setting up a sensor network testbed; motes ordered

18 Schedule