Secure Routing for Mobile Ad hoc Networks Panagiotis Papadimitratos - PowerPoint PPT Presentation

Secure Routing for Mobile Ad hoc Networks Panagiotis Papadimitratos & Zygmunt J. Haas Presented by Leland Smith CS 6204, Spring 2005 1

Overview ♦ What are MANETs? ♦ Motivation ♦ Secure Routing Protocol ♦ Protocol Description ♦ Discussion CS 6204, Spring 2005 2

Mobile Ad hoc NETworking ( MANET ) [1] ♦ Self-organized wireless interconnection of communication devices that would: – Extend or operate in concert with the wired networking infrastructure – Possibly evolve to autonomous networks ♦ Unique characteristics and challenges CS 6204, Spring 2005 3

Mobile Ad hoc NETworking ( MANET ) [2] ♦ Characteristics – Absence of fixed infrastructure – Decentralized operation ♦ Challenges – Physical limitations – Difficult to determine which nodes to trust – Difficult to have a clear picture of membership • Cannot make trust assumptions in large networks – No guarantee paths are free of malicious nodes CS 6204, Spring 2005 4

Motivation ♦ Current MANET routing protocol cannot cope with disruptions due to malicious behavior. – Denial of service attacks on end nodes ♦ Propose the Secure Routing Protocol (SRP) – Applied as an extension to existing routing protocols. – Guarantees acquisition of correct topological information in a timely manner. CS 6204, Spring 2005 5

Secure Routing Protocol (SRP) ♦ Features – Guarantees that a node initiating a route discovery will be able to identify and discard replies providing false topological information. • Or avoid receiving them all together. – Places computational overhead on end-nodes • Efficient and scalable • Doesn’t rely on state stored on intermediate nodes. – Only requires a security association between the pair of end nodes. • Security association? ♦ Assumptions – Adversary nodes are not capable of colluding within one step of protocol execution – Each broadcast is received by all neighbors within range. Nodes operate in promiscuous mode. CS 6204, Spring 2005 6

Basic Concept ♦ Request: – A source node initiates a route discovery and broadcasts the request packet along with a secure Message Authentication Code and secret key shared between the source and destination. – IP addresses are accumulated along the path. ♦ Propagation: – Intermediate nodes relay route requests such that one or more request packets arrive at the destination. – Discard previously seen route requests. – Provide feedback in the event of path breakage. ♦ Reply: – Calculates new MAC covering route reply contents. – Returns packet to source along the reverse of the accumulated path. – Responds to one or more requests from the same query to provide the source with a diverse topology picture. – Querying node validates replies and updates its topology view. CS 6204, Spring 2005 7

Packet Format Builds on underlying basis protocol 6 words = 192 byte header CS 6204, Spring 2005 8

SRP Packet Components ♦ Query Sequence number ( Q seq ): – Increases with each route request by a node – Allows destination to detect outdated routes – Initialized at establishment of security association ♦ Query Identifier ( Q id ): – Used by intermediate nodes to identify request – Output of secure pseudorandom number generator ♦ Message Authentication Code ( MAC ): – Generated by a keyed hash function – Input: entire IP header, basis protocol route request packet, shared key K S,T – Excludes: accumulated addresses of intermediate nodes, mutable IP header fields. CS 6204, Spring 2005 9

10 Process Example CS 6204, Spring 2005

Query Propagation ♦ Determine whether SRP header is present – If not, route according to basis protocol – If so: • Route according to SRP • Extract Q id , source and destination addresses and store in query table. • If incoming packet Q id , source and destination addresses match one already in the query table, discard the packet. • Query frequency heuristics CS 6204, Spring 2005 11

Route Reply ♦ Verifies request packet – Security association? – In sequence? ♦ Calculate hash of request fields and compare to the request header MAC – Verification complete ♦ Formulate reply using the same Q id and Q seq as the request and recompute the MAC for the new packet. ♦ Destination generates numerous replies to a single valid request. – Disallow malicious neighbor to control multiple replies. CS 6204, Spring 2005 12

Reply Validation ♦ Source discards reply if it does not correspond to a currently pending query ♦ Compare reply IP source-route with the reverse of the route carried in the reply payload. Discard if they differ ♦ Calculate MAC using data in reply payload and the shared key. ♦ Upon verification, source is assured that the request reached destination T, and that the reply was not tampered with on its way from T to S. CS 6204, Spring 2005 13

Route Maintenance ♦ Topology changes must be detected ♦ Route error packets source-routed along the prefix of the route reported as broken. ♦ The path source compares the route traversed by the error packet to the prefix of the corresponding route. ♦ Verifies error feedback refers to the actual route, and was generated by a node on the route. ♦ Correctness of feedback cannot be verified – A malicious node on route S->T can at most invalidate that route, mislead S by corrupting error packets from another node, or mask a dropped packet as a link failure CS 6204, Spring 2005 14

Summary & Conclusion ♦ Proofs in paper ♦ Implementations? ♦ How to establish security associations? CS 6204, Spring 2005 15