Burak Ustun

1. Burak Ustun Security Services in Group Communications over Wireless Infrastructure, Mobile Ad Hoc, and Wireless Sensor Networks

2. 1.Introduction Group Communications in wireless networks One sender - Multiple receiver Multiple sender - Multiple receiver Insecure Wireless Channels- various kind of attacks A survey of recent advances in Security requirements Services in group communications Wireless Networks: Wireless Infrastructure Networks Ad Hoc Networks Wireless Sensor Networks Security in Wireless Nets < Security in Wired Nets SGC(Secure Group Communication) establishment faces various challenges to meet security requirements

3. 2.Known Attacks in Wireless Networks There are various known attacks categorized as 2.1. Data Integrity and Confidentiality Related 2.2. Power Consumption Related 2.3. Service Availability and Bandwidth Consumption Related 2.4. Routing Related 2.5. Identity Related 2.6. Privacy Related Some figures related with them will be explained

4. 2.1 Data Integrity & Confidentiality Related This type of attack attempts to reveal or compromise the integrity and confidentiality of the data contained in the transmitted packets. Some attacks are 2.1.1. Denial of Service on Sensing (DoSS) attack-Attacker tampers with data before it is read by sensor nodes, therefore resulting in false reading. Targets physical reading. 2.1.2. Node Capture Attack-Attacker physically captures sensor nodes and compromises them such that sensor readings are inaccurate and manipulated. 2.1.3. Eavesdropping Attack-Attacker eavesdrop on ongoing communications between targeted nodes to collect information on connection & cryptography.

5. 2.2 Power Consumption Related This type of attack attempts to exhaust the device's power supply. Worst case would collapse a network communication. Some attacks are 2.2.1. Denial of Sleep attack-Attacker tries to drain a wireless device's limited power supply so that the node's lifetime is significantly shortened. Normally MAC reduces power consumption by regulating the node's radio communication.==> The attacker attacks the MAC layer protocol to Shorten the sleep period, or Disable the sleep period

6. 2.3 Service Availability & Bandwidth Consumption Related They also can be categorized as power consumption related attacks. They mainly aim to Overwhelm the forwarding capability of forwarding nodes, or Consume sparsely available bandwidth Some known attacks are 2.3.1 Flooding Attack 2.3.2 Jamming Attack 2.3.3 Replay Attack 2.3.4 Selective Forwarding Attack

7. 2.3 Service Availability & Bandwidth Consumption Related(Cont.)‏ 2.3.1 Flooding Attack Attacker typically sends a large number of packets to the access point or a victim to prevent from establishing or continuing communication 2.3.2 Jamming Attack Attacker can cut off wireless connection among nodes by transmitting continuous signals or jamming radio signals 2.3.3 Replay Attack Attacker copies a forwarded packet and later sends out the copies repeatedly and continuously to the victim in order to exhaust the victim's buffersor power supplies. 2.3.4 Selective Forwarding Attack A forwarding node selectively drops packets that have been originated or forwarded by central nodes.

8. 2.4 Routing Related These attacks attempt to change routing information, and to manipulate and benefit from such a change. Some known attacks are 2.4.1.Unauthorized routing update attack:-Attacker attempts to update routing info, to exploit the routing protocols, to fabricate the routing update message, to falsely update the routing table. It can lead to several incidents including: some nodes isolated from base station, network partition, messages are routed in a loop, messages forwarded to unauthorized attackers...

9. 2.4 Routing Related (Cont)‏ 2.4.2. Wormhole Attack:-An adversary intercepts communications originated by sender, copies a portion of or whole packet, and speeds up sending the copied packet through a specialized wormhole tunnel such that the packet arrives earlier than the original. 2.4.3. Sinkhole Attack:-Attacker attract all nodes to send all packets through one or several colluding nodes, called sinkhole nodes, so that the attacker has access to all traversing packets.

10. 2.5 Identity Related These attacks cooperate with eavesdropping attacks or other network-sniffing software to obtain vulnerable MAC and network addresses. Some known attacks are 2.5.1. Impersonate Attack:-Attacker impersonates another node's identity to establish a connection with or launch other attacks on a victim. 2.5.2. Sybil Attack:-A single node presents itself to another nodes with multiple spoofed identifications. Attacker can impersonate other node's identity or simply create multiple arbitrary identities in the MAC and/or network layer.

11. 2.6 Privacy Related This type uncovers the anonymity and privacy of the communications and in the worst case, can cause false accusations of an innocent victim. One of the known attack is 2.6.1. Traffic Analysis Attack-Attacker attempts to gain knowledge of network, traffic and nodes' behaviour. -Also he can correlate all incoming and outgoing packets at any router or member.-The attacker can also link any two members with any unrelated connection.

12. 2.7 Examples of Mixed Attack in a Wireless Net

13. 2.7 Examples of Mixed Attack in a Wireless Net

14. 3. Secure Group Communication System GCS cocnsists of 5 common operations: Initiate Join Leave Partition Merge The group is established by initial members, then one or several members join the group while some of them leave the group. This is called dynamic membership. A large number of membership changes require a special protocol without degrading the group performance. Groups partitioned into smaller or groups merge together in some scenarios. This dynamic membership ==> GCS to rekey the session keys –preserve key secrecy. WSN- dynamic membership not necessary, but for the others.

15. 3.1. Security Requirements and Security Services in SGC 3.1.1. Group Key Management (GKM): The fundamental security service= the group key Shared group key is used to encript a group message, sign the message, authenticate members and messages, and authorize access to traffic and group resources. GKM scheme deployed in any secure group communications should satisfy the following: Key generation is secure Imitation of the group key should be infeasible or computationally difficult The group key is securely distributed and only the legitimate users can receive a valid group key. Revocation of the group key upon every membership change should be immediate Every membership change must result in rekeying of associated keys Rekeying of the key is secure

16. 3.1.2. Group Authentication- A member of the group can be transmitter, receiver or both. Both users and messages should be authenticated to safeguard identity related attacks. 3.1.3. Group Authorization and Access Control-A member who holds a decrypting key can access full contents in a flow. This is referred as single access privilege. Group members can be assigned with multiple access privileges.=> The stream should be accessed with different access privileges such that only members who have an appropriate privilege can access the related content. 3.1.4. Group Accounting and Nonrepudiation-Any group operation should be available for tracking in order to detect any abusive usage of resources or operations.-A nonrepudiation service can ensure that the identity of a member can be fully or precisely determined by the designated entity. 3.1. Security Requirements and Security Services in SGC

17. 3.1.5. Group Privacy and Anonymity:-Any information related to a group message can be protected and hidden to preserve privacy and anonymity of members. An anonymous message is the message which carries no info about sender and receiver. 3.1.6 Group Message Integrity and Confidentiality-Message integrity should be preserved by several means, including hashing and signing the message along with strong encryption keys. Confidentialty ensures that only authorized members can retrieve meaningful data from the message. 3.1.7 Group Survivability and Availability:-Attacker can attack routing hosts to isolate some or all group members, or partition the group. ==> All routing hosts must be protected to ensure group survivability. 3.1. Security Requirements and Security Services in SGC

18. 4. SGC Over Wireless Infrastructure Networks DeCleene et alpresented a hierarch based key management protocol that divides the operation field into administratively independent areas. The area key is used to encrypt the message containing the data key. When user moves to another area, the area key is rekeyed ==> decrease in performance. Thus, several rekeying algorithms have been proposed to reduce the need of rekeying.-EKOL(Extra key owner list) is used to store the area keys belonging to the leaving member and that members ID. =Pros: low overhead, highly dynamic membership is supported=Cons: the area keys may be compromised easily

19. 4. SGC Over Wireless Infrastructure Networks(Cont)‏ Sun et almatched tree-based key management with the physical cellular network topology in order to build a TMKM(topology matching key management) tree. When the users move among cells, an efficient handoff mechanism handles the relocation of that user in TMKM tree. Each cell has a corresponding Wait-to-be-removed (WTB) list that tracks previous and current cell members.=Pros: low communication overheads=Cons: the scheme does not consider the overheads incurred by the KDC that could result in poor performance in the actual development.

20. 4. SGC Over Wireless Infrastructure Networks(Cont)‏ Gupta and Cherukuripresented three schemes: SSK(single session key), DSK(different session key), and a combination (HYBRID). SSK: Base station assigns the same session keyDSK: Base station assigns different session key HYBRID: Base station assigns the same session key to who have been stable for some duration of time and different session key to who have been unstable.=Pros: communication overhead of HYBRID < other communication overheads=Cons: strict time synchronization is required to determine whether a member is classified as stable or nonstable.

21. 4. SGC Over Wireless Infrastructure Networks(Cont)‏ Westerhoff et alpresented a decentralized architecture called mobility support- a multicast based approach (MOMBASA) to achieve low latency for handoffs with minimum packet loss as well as secure protocol operation=Pros: MOMBASA is secure from many threads, performance degradation is negligible, less packet loss=Cons: The scheme only considers handoffs when the Mobility enabling proxy is no longer functioning, but not the case when the membership is highly dynamic.

22. 5. SGC Over Mobile Ad Hoc Networks Kaya et alproposed a dynamic multicast group management protocol that attempts to equally distribute the workload of securing communications to all members.=Pros: Communication overheads and latency of joining/leaving/key revocation processes do not substantially degrade the group performance.=Cons: how the group manager is selected is not discussed.

23. 5. SGC Over Mobile Ad Hoc Networks (Cont)‏ Lazos and Poovendran presented the routing-aware key distribution(RAwKey) and proposed an optimal solution that minimize energy expenditure caused by the rekeying process.=Pros: the performance of the optimal energy efficient solution for rekeying does not substantially change=Cons: how the group manager is selected is not discussed.

24. 5. SGC Over WSN Zhu et alproposed a key management protocol, called localized encryption and authentication protocol (LEAP) for large scale distrubuted sensors. =Pros: Low communication overhead=Cons: scheme did not discuss the power consumption of the nodes

25. 6. SGC Over WSN(Cont)‏ Wadaa et alproposed an energy efficient protocol to provision anonymity in WSNs. The protocol divides the network into clusters. =Pros: Energy efficient=Cons: scheme did not discuss the anonymity level per transmission Karlof and Wagnerdiscussed attacks that can disrupt group routing in WSNs. It explains how each attack is executed.

26. 7. Open Challenges Integration of security services Deployment of SGC in heterogenous wireless networks Optimization of the group performance with respect to overheads and limited resources Extension to Ipv6 wireless networks

27. 8. Conclusion Wireless networks are less secure than wired networks. There are 6 groups of attacks, namely Data Integrity and Confidentiality Related Power Consumption Related Service Availability and Bandwidth Related Routing Related Identity Related Privacy Related SGC is studied with the known attacks

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