Secure Routing Protocol for Ad Hoc Networks

1. Secure Routing Protocolfor Ad Hoc Networks Li Xiaoqi

2. Outline • Introduction to Ad Hoc Networks • Overview of Ad hoc On-demand Distance Vector (AODV) Routing Protocol • Attacks to AODV Ad Hoc Networks • Securing AODV Routing Protocol • Flaws of SAODV • Future Works

3. Ad Hoc Networks • “Infrastructureless” Networks without fixed infrastructure such as base stations or access points • Multi-hop routing when nodes are not in each other’s radio range • Nodes are mobile • Underlying communication medium is wireless • Each node acts as a router • Useful in: personal area networking, meeting rooms, disaster relief, battlefield operations, etc.

4. Motivation • Applications such as military exercises, disaster relief, and mine site operation need more secure and reliable communication • Prior routing protocols generally assume a trusted environment with non-adversarial settings • Securing routing protocols for ad hoc networks are needed

5. AODV Routing Protocol (Ad Hoc On-Demand Distance Vector) • Establish or maintain routes only when nodes need to communicate • Each node maintains a monotonically increasing sequence number to ensure loop free routing • Only one mutable field “Hop Count” in routing messages which implies the distance from the originator. Hop Count is increased by one at each hop. • Four types of routing messages: • RREQ: Route Request • RREP: Route Reply • RERR: Route Error • RREP-ACK: Route Reply Acknowledgement

6. Routing Discovery in ADOV RREQ BroadCast S D RREP RREP

7. Attacks on Mobile Networks • Eavesdropping  Confidentiality • Disclosure  Confidentiality • Masquerading  Authenticity • Modification  Integrity • Man-In-Middle Attack • Drop / Replay / Delay  Integrity • Flooding  Availability • Denial of Service Attack

8. RREQ D S M RREP D S M Actual Attacks on AODV(one malicious node) • Forge a RREQ with its address as the originator address. • Forge a RREP with its address as the destination address • Does not increase the hop count, even reduce it when forwarding a RREQ • Increase destination sequence number “fresher” enough in order to update the intermediate nodes’ route table • Does not forward certain RREQ, RREP and certain data messages

9. Actual Attacks on AODV(more malicious nodes) • Tunneling Attacks • Two malicious nodes simulate that they have a link between them • By tunneling messages between them • Achieve having certain traffic through them • Do any type of attacks one malicious node can do • Hard to detect and prevent so far, even in SAODV mentioned below

10. SAODV Routing Protocol(WiSe’02 by SigMobile) • Focus on • Protecting only Routing messages • Mainly Concerning Authentication & Integrity • Situation of One malicious node • More routing protocol than key management • Two Main Ideas • Hash chains to secure the Hop Count information, the only mutable information in the messages  Integrity • Digital signatures to authenticate the non-mutable fields of the messages  Authenticity

11. SAODV Hash Chains • Attackers often decrease Hop Count of a RREQ to increase the life of this message, thus gain more time to analyze the communication • Hash chains are used to protect this Hop Count field • A hash chain is formed by applying a one-way hash function (h) repeatedly to a seed. • When a node originates a RREQ or a RREP message, it performs the following operations:

12. SAODV Hash Chains Algorithm • Generates a random number (seed) • Sets field Max_Hop_Count = TTL • Sets field Hash = seed • Sets field Hash_Function = h, - h is the hash function which is going be used • Calculates field Top_Hash by hashing seedMax_Hop_Count times. Top_Hash = h Max_Hop_Count (seed) - hi(x)is the result of applying the function h to xi times. • When a node receives a RREQ or a RREP message, it will verify if Top_Hash == h Max_Hop_Count – Hop_Count (Hash) - Hop_Count is the number of hops this message has passed. • Before rebroadcasting a RREQ of forwarding a RREP, a node do Hash = h(Hash)

13. SAODV Digital Signatures • Digital Signatures are used to protect the integrity of the non-mutable data in RREQ and RREP messages • Sign every field of the message except the Hop Count and hash chain fields • Extend original AODV routing protocol’s headers • Secure AODV protocol has six types of messages • RREQ (Single) Signature Message • RREQ Double Signature Message • RREP (Single) Signature Message • RREP Double Signature Message • RERR Signature Message • RREP-ACK Signature Message

14. SAODV Digital Signatures RREQDouble Signature Message RREQ Double Signature Message RREP Single Signature Message • An originator sends a RREQ double signature message including the RREP flags every time • An intermediate node, if it hasn’t the destination’s route entry, rebroadcasts RREQ with double signatures, one of which is needed for RREP • An intermediate node, if it has the destination’s route entry, sends a RREP with double signatures, one of which is get from the RREP flags it reserved • A destination node sends a RREP single signature message when replying a RREQ D S B A RREP Double Signature Message

15. Key Management of Securing Ad Hoc Routing protocol • Symmetric VS Asymmetric Cryptography • Symmetric: everybody that wants to participate in this network has to know the secret key. Maybe not suitable • Asymmetric: everybody can participate freely. The originator of the route messages signs the messages when using an asymmetric cryptosystem. Maybe feasible. • SAODV assumes that each ad hoc node has a signature key pair from a suitable asymmetric cryptosystem.

16. Flaws of SAODV • Does not consider how to protect data messages • Can not solve attacks performed by more coordinated malicious nodes • More emphasis on secure routing protocol and has not its own key management mechanism

17. Future Work On This Topic • To realize security in Ad Hoc Networks • Intrusion Prevention • Design a secure routing protocol • Design a efficient and effective key management mechanism • Intrusion Detection • Study more attacks to AODV and SAODV routing protocol

18. Q & A