Ch 6. Security in WMNs Myungchul Kim [email protected]

Ch 6. Security in WMNs

Myungchul Kim

[email protected]

– Generic security servies

Security technology overview

– IEEE 802.11i (Wi-Fi Protected Access: WPA, WPA2)

• A shared key or AAA server

• AAA server– Extensible authentication protocol (EAP)

– EAP: EAPOL between MS and AP and RADIUS between AP and AAA server

– Master session key (MSK)


– IEEE 802.11i (Wi-Fi Protected Access: WPA, WPA2)


– IPsec and virtual private networks

– Transport layer security protocol (TLS)

– Secure socket layer (SSL)

– S/MIME or PGP


– Mesh node (MN), user node (UN), mesh user node (MUN)

– Ad hoc mesh networks: managed or open networks

Mesh usage scenarios

– Factors distringuishing the usage scenarios


• Single administrative domain– Keep the outsiders out

– Shared key or node certificate

• Network infrastructure extension– The mesh network is used by end users to access the infrastructure

network

– Security of infrasturcture network access by end users and security within the mesh extension itself

• Mesh federation– The MNs forming a mesh netowrk belong to different adminstrative

domains (operators)

• Community mesh– Not knowing or even trusting each other


– Ad hoc networks vs WMNs

• Security challenges– Multihop wireless communications

– Nodes are not physically protected

– Use of wireless links

– Dynamic: topology and membership

– The same security solution may not work for both mesh routers and mesh clients

• Overview of potential attacks to WMNs– External attacks vs internal attacks

– Passive and active attacks

– Protocol layers

Mesh security issues

– Attack types for MANET• Impersonation• Sinkhole attack

– Behaving “logical” next hop for forwarding packets and droping them

• Wormhole attack– Use a malicious paths through legitimate means

• Selfish and greedy behavior attack– Increase own share of the common transmission resource

• Sybil attack– A malicious node pretends the identity of several nodes– Geographic routing protocols?

• Sleep deprivation– Request services from a certain node over and over again

• DoS and flooding


• Authentication– Hard in WMN because of the open nature of wireless comm.

– Approaches

• PSK authentication

• Certificate authentication– How to enable the authentication across different domains?

• Authentication to roaming UNs?

• Authentication of MNs ?

– Examples

• Wireless Dual Authentication Protocol (WDAP)

• Secure Unicast Messaging Protocol (SUMP)


• Secure MAC layer– IEEE 802.11: nodes that are heavily loaded tend to capture the

channel by continually transmitting data thereby causing lightly loaded neighbors to back off again and again. -> unfairness

– Attacks

• Flooding attack

• Jamming attack by jamming the RTS signal

• Sleep deprivation attack

• Packet dropping attack

– Countermeasures to selfish mishbehavior

• Catch: makes the cooperative neighbors of a selfish node to disconnect it from the rest of the network.


– Countermeasures to greedy mishbehavior

• The receiver can detect any misbehavior of the sender and penalize it by increasing the back-off value.

• DOMINO

– Countermeasures to MAC-layer DoS attacks• Single adversary attack and two colluding adversaries

• Ways– Fair MAC protocol

– Protecting traffic flow

– Distance adjustment


• Secure routing– Threats for ad hoc mesh routing functionality

• Eavesdropping

• Sinkhole, wormhole

• Routing table overflow: attempts to create routes to nonexistent nodes

• Rushing attack: An attacker forwards RREQs more quickly than legitinate nodes can do so. Thus, …

• Sleep deprivation

• Location disclosure


• Secure routing– A secure ad hoc mesh routing protocol should fulfill:

• Certain discovery

• Isolation: immune to malicious nodes

• Lighweight computation

• Location privacy

• Self-stabilization

• Byzantine robustness: a stricter version of the self-stabilization property


– Cryptography-based solutions

• Authenticated ruting for ad hoc networks (ARAN) utilizes cryptographic certificates to achieve authentication and nonrepudiation

• Secure routing protocol (SRP): a shared key

• Secure efficient ad hoc distance vector (SEAD): DSDV, hash chains to authenticate hop counts and sequence numbers

• Secure ad hoc on-demand distance vector routing (SAODV): AODV, digital signatures and hash chains


– Reputation-based solutions

• The pathrater assesses the results of the watchdog and selects the most reliable path for packet delivery.

– Add-ons to existing protocols• Security-aware ad hoc routing utilizes a security metric for

the route discovery and maintenance functions.

– Countermeasures to specific attacks• In best-effort fault tolerant routing, path redundany is used

to tolerate misbehavior by using disjoint routes.


• Key management and communications security– Key management: supports the establishment and maintenance

of keying relationships between authorized parties.

– How to distribute initial keys?

– A suitable infrastructure can be used

• A single stakeholder

• A public-key infra

• Security master


• Key management and communications security– For routing traffic, options are

• No security at all• Protect integrity of routing messages through a MAC• Protect integrity of routing messages through a digital signature

in a hop-by-hop mode• Protect integrity of routing messages through a digital signature

in an end-to-end mode • Condifentializty of routing messages

– For the protection of user data, options are• No security at all• Secure comm within a group that shares a secret group key• Secure end-to-end communication using public-key crptography


• Intrusion detection– Use “training” data to determine characteristics of normal

routing table updates and normal MAC layer.


• System proposals– Tropos

• 802.1x/EAP-based authentication against a AAA-server (RADIUS)

• A secure IPsec-based VPN

Concrete proposals

• Authentication protocols– WDAP for IEEE 802.11 WMNs

– SUMP for sensor networks

– The overhead at the server side

– Wireless dual authentication protocol (WDAP)

• Mitigation of the overhead of 802.11i– The authentication is already completed when the UN

arrives within the range of the next AP

– A key caching options to allow the UN and the AP to remember the last used PMK

– Since both WS and AP are assumed not to trust each other until the AS authenticates both of them.

Concrete proposals

• Authentication protocols– Wireless dual authentication protocol (WDAP)

Concrete proposals


Concrete proposals


Concrete proposals

Documents

Ch 6. Security in WMNs Myungchul Kim [email protected]