CSE 566- Wireless network Security

1. CSE 566- Wireless network Security A SECURITY AWARE ROUTING PROTOCOL FOR AD-HOC NETWORKSPRESENTED BYVishwasgramA nanjundaswamysandeepkumarpriyankarajansamarth

2. Wi-Fi LANs are organized and operate in either infrastructure(ESS) or ad-hoc(IBSS) mode. The significant difference in ad-hoc mode from infrastructure mode is there is no access point and any device can talk to any other directly. Any device can communicate with other device just by using MAC address of that device. In this case the device that creates the message is also the device that sends it. Similarly, the device that receives the message is also the one that processes it. So in ad-hoc frames, only two addresses are contained in the MAC header. AD-hoc networks

3. The lack of access point presents extra problems for security implementation as for example in ad-hoc network we can not have centralized authentication. The network is dynamic and keep changing. Nodes can join and leave any time. There is no process of association. Protocol packets at physical layer can be received by anyone and has no protection. Ad-hoc routing protocols are cooperative and rely on trust-your-neighbor policy. Malicious nodes can take advantage of this to insert erroneous routing information, replay attacks etc. Problems with ad-hoc networks

4. Use different security attributes to improve the quality of the security of an ad-hoc route Incorporate security levels of nodes into traditional routing metrics Goal : Quantify the notion of trust Trust relationship is defined by assigning trust values to each node. Integrate the trust value of a node and the security attributes of a route to provide an “integrated security metric” Security Aware routing (SAR) Protocol

5. Need of secure routing • Example Scenario – Battlefield communication Secure route Private Officer General Shortest route Transmission range

6. Basic protocol : On-demand protocol AODV Embed security metric into the RREQ packet itself and change the forwarding behavior of the protocol w.r.t. RREQs Source node : Specify desired level of security in the RREQ Broadcast the packet Intermediate node : Process/forward the packet only if it can provide the required security or has the required authorization or trust level ; Otherwise drop the RREQ If an end-to-end path with the required security found, the intermediate node or eventual destination sends a suitably modified RREP SAR- protocol overview

7. Route discovered by SAR may not be the shortest route in terms of hop-count SAR finds a route with a ‘quantifiable guarantee of security’ If one or more routes satisfying the required security attributes exists, SAR finds the shortest such route Optimal route: All nodes on the shortest path (in terms of hop-count) satisfy the security requirements Drawback: If no path with nodes that meet the RREQ’s security requirements exists, SAR fails to find a route even though the network may be connected SAR-protocol overview

8. Trust hierarchy Associate a number with each privilege level Numbers reflect security/importance/capabilities of mobile nodes and also of the paths QoP (Quality of Protection) bit vector Trust level or protection should be immutable Keys can be distributed a priori, or a key agreement can be reached by some form of authentication Encrypt the portion of the RREQ and RREP headers that contain the trust level. Trust hierarchy

9. Trust hierarchy is the main protection mechanism used. Nodes and users can be forced to respect trust hierarchy using cryptographic techniques, e.g., encryption, public key certificates, shared secrets Outsider attacks Threshold cryptography, key sharing, etc. can be used SAR uses simple shared secret to generate a symmetric encryption/decryption key per trust level. Insider Attacks Compromised users within a protection domain or trust level Secure transient associations, tamper proofing etc. can be used Protection in sar protocol

10. Threats to Information in Transit Interruption Interception and Subversion Modification Fabrication Replay Attacks: SAR uses sequence numbers and timestamps Passive Attacks: Examples: covert channels, traffic analysis, sniffing to compromise keys Using a suitable MAC layer encryption protocol for protection against sniffing/eavesdropping Protection in sar protocol

11. RREQ (Route REQuest) packet: RQ_SEC_REQUIREMENT : the security requirement Set by the sender; does not change during route discovery phase RQ_SEC_GUARANTEE : the security guarantee Indicates the maximum level of security afforded by all nodes on the discovered path Updated at every hop during the route discovery phase If the application requested integrity support, a new field to store the computed digital signatures added to the RREQ RREP (Route REPly) packet : RQ_SEC_GUARANTEE : the security guarantee Copied from RREQ and sent back to sender to indicate security level over whole path Implementation-SAODV ( Security-aware AODV):

12. Source node : Set the RQ_SEC_REQUIREMENT field in the RREQ packet Broadcast the packet just as in AODV When an intermediate node receives an RREQ First check if the node can satisfy the security requirement indicated in the packet If yes, update the RQ_SEC_GUARANTEE field; forward to its neighbors If no, drop the RREQ packet When RREQ arrives at the destination Indicates the presence of a path from the sender to the receiver that satisfies the security requirement specified by the sender Copy RQ_SEC_GUARANTEE from RREQ into RREP Send the RREP back to sender as in AODV SAODV Route Discovery

13. When an intermediate node receives an RREP The RREP packet arrives at an intermediate node in the reverse path Update its routing table Record the new RQ_SEC_GUARANTEE value This value indicates the maximum security available on the cached forward path. When a trusted intermediate node answers a RREQ query using cached information Compare RQ_SEC_GUARANTEE of the cached route to the security requirement in the RREQ packet Sent back RREP containing cached path information only if the forward path can guarantee enough security SAODV Route Discovery

14. SAR enables the discovery of secure routes in a mobile ad hoc environment. Though not optimal, routes discovered by SAR come with “quality of protection" guarantees. The processing overheads in SAR are offset by restricting the scope of the flooding for more relevant routes, providing comparable price/performance benefits. Its integrated security metrics allow applications to explicitly capture and enforce explicit cooperative trust relationships. SAR also provides customizable security (e.g., encryption for confidentiality etc.) to the flow of routing protocol messages themselves The techniques enabled by SAR can be easily incorporated into generic ad hoc routing protocols conclusion