Provision Security For Wireless Mesh Networks
Celia Li Computer Science and Engineering York University
Outline
Overview of Wireless Mesh Networks (WMNs) Overview of network security Literature review and research directions Access control Authentication Group key management Conclusion
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Outline
Overview of Wireless Mesh Networks (WMNs) Overview of network security Literature review and research directions Access control Authentication Group key management Conclusion
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Wireless Mesh Networks (WMNs)
Object 83
Wireless Mesh Router Stationary in most cases No power or computation constrains Self-organized, self-configured Providing multi-hop connectivity Wireless Mesh Clients
Varying degrees of mobility Having energy autonomy, computation & transmission constrains PDA, laptops, pocket PCs, cell phones
Network Gateways / Access Points
Acting both as Internet routers and wireless mesh routers
Applications of WMNs Disaster recovery, security surveillance, Internet access in rural areas, municipal and metropolitan networking 4
Advantages of WMNs
Low cost installation
In hard-to-wire areas or building (e.g., water surface, mountains)
Large-scale deployment Reliability
If some nodes are down, packets can be delivered via adjacent nodes due to the mesh structure Self-configuration and self-healing
Self-management
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WMNs vs. Wireline Networks
Object 10
In wireline networks Wired routers can be physically protected
In WMNs Wireless routers are not physically protected easily if deployed outside.
Low cost deployment Vulnerable to security attacks
e.g.
eavesdropping, jamming, denial of service
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Lower bandwidth, higher error rate
WMNs vs. Wireless Local Area Networks (WLANs)
In WLANs
In WMNs
Only a small number of selected mesh routers (gateways) require wired interafce
Each access point has to have a wired interface
1-hop wireless connection
Multi-hop routing
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WMNs vs. Mobile Ad-hoc Networks
Similarity
Both operate in a wireless multi-hop routing fashion. Each node forwards data packets on behalf of other nodes.
In MANETs
Nodes are mobile or portable
In WMNs
Mesh routers are stationary in most cases
With power or computational constraints
No power or computational constraints
Dynamic network topology
Mesh clients' mobility does not affect network topology
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Outline
Overview of Wireless Mesh Networks (WMNs) Overview of network security Literature review and research directions Access control Authentication Group key management Conclusion
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Security Property
Confidentiality
Content of a message is accessible only to authorized users Data cannot be modified without being detected A node can be sure of the identity of the peer node it is communicating with. Neither the sender nor the receiver of a message is able to deny the transmission/reception. Authorized actions can in fact take place
Integrity
Authenticity
Non-repudiation
Availability
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Security Provision is Challenging in WMNs
Lower bandwidth and higher error rate of wireless channels Limited power supply, memory or computing capability of mesh clients Mobility of mesh clients Vulnerable to security attacks
e.g., eavesdropping, traffic analysis or denial of service
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Network Security Issues
Access control
Only authorized actions (e.g., membership enrollment, data transmission) can be performed. Ability to identify the members of the group (senders & receivers) Converting data into a form that cannot be easily understood by unauthorized people Generation, exchange, storage, safeguarding and replacement of keys Ensures that a message is eventually delivered to all legitimate nodes within a reasonable amount of time, despite nodes that may corrupt, drop or misroute the message.
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Authentication
Encryption
Key management
Secure routing
Security Requirements
Computation cost Mutual authentication between router and client Fast and secure handover operation Efficient and secure multicast communication Secure routing Service availability
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Our Research Focus
Security provision in WMNs: Access control Authentication Key management Group key management
To provide secure distributions & handling of cryptographic keying materials in a multicast group
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Outline
Overview of Wireless Mesh Networks (WMNs) Overview of network security Literature review and research directions Access control Authentication Group key management Conclusion
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Classification of Access Control
Access control operates against two risks
Unauthorized access to system resources Improper use of system resources
1.
Access Control List (ACL)
A list of permissions attached to an object Who or what is allowed to access the object What operations are allowed to be performed on the object E.g., entry (Alice, delete) for file XYZ
2.
Mandatory Access Control (MAC)
Assigning security labels or classifications to system resources Giving access using the defined levels E.g., top secret, secret, classified, unclassified
3.
Role-based Access Control (RBAC)
Enforcing access to computer or network resources based on the roles of individual users within an enterprise Assigning privileges to arbitrary roles Assigning roles to real users 16
Access Control List (ACL)
In ACL, every piece of data, database or application has a list of users associated with it.
Advantages
Simple, easy, straightforward
Good for small-size organizations Disadvantages Difficult, time consuming, error prone when access control list becomes large
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Mandatory Control List (MAC)
MAC enforces access control based on the security labels attached to users and objects.
Two principles for user access
Read down access Write up access Used for government and military users
Application
Disadvantages
Not flexible
Not suitable for commercial applications
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Role-based Access Control (RBAC)
RBAC is based on organization structure User-role-privilege Assign roles to users Each role associates with a set of privileges or objects Role hierarchies Constraints Mutual exclusive roles Cardinality Prerequisite roles Advantages Offering flexibility Simplifying access control administration Reducing management cost
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Security Principles for Access Control
Least privilege
Given no more privileges than necessary to perform a job No single individual be allowed to execute all transactions within the set. E.g., initiating a payment vs. authorizing a payment. Defining permissions at a higher level rather than on read/write/ execute E.g., defining permissions as credit/debit for an account object.
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Separation of duty
Data abstraction
Access Control in Wireline Networks
Access control lists (ACLs) Does not support three security principles Least privilege Separation of duties Data abstraction Costly and prone to error Role-based access control (RBAC) Support three security principles Used to establish trust relationships for strangers on the Internet Flexible, simplifying access control administration, reducing management cost
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Access Control in Wireless Networks
ACLs in Wireless Metropolitan Networks Based on packet marking & packet filtering Checking an access control list (ACL) to decide how to process packets Supporting network roaming RBAC in WLANs Implemented with time and location constraints Strength of authentication and encryption is chosen according to the role of the user
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Access Control for WMNs
Previous work is not readily applicable to WMNs Access control that relies on access control list (ACL) is no longer effective Role-base access control (RBAC) is not suitable for multiple mesh domains Desired properties of access control in WMNs Fast access control for handover Flexibility Manageability Low communication overhead
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Research Directions
Developing an extended rolebased access control (ERBAC) model for WMNs Designing ERBAC for intradomain access control
A role assignment algorithm A role certificate generation and verification method A role mapping algorithm A role negotiation protocol
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Designing ERBAC for Inter-Domain access control
Outline
Overview of Wireless Mesh Networks (WMN) Overview of network Security Literature Review and Research Directions Access Control Authentication Group Key Management Conclusion
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Classification of Authentication (1/3)
Authentication is the process of proving one's identity to someone else Type of cryptography Symmetric key authentication Public key authentication Involvement of trusted third party Without trusted third party With trusted third party Reciprocity of authentication One-way authentication Mutual authentication (two-way)
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Classification of Authentication of (2/3)
Type cryptography
Symmetric key authentication
AB: M BA: EKab(M) A: DKab(EKab(M))=M AB: M BA: EB_private(M) A: DB_public(EB_private(M))=M
Verifying identity based on a secret key shared between the participants Based on a public-private key pair Private key for signing Public key for verification
Public key authentication
Comparison
Symmetric key authentication
Efficient Less Hard
Public key authentication
Strong
security complex
demanding computationally
Mathematically
to distribute shared keys in advance
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Classification of Authentication (3/3)
Involvement of trusted third party Without trusted third party Two parties trust each other With trusted third party Two parties do not fully trust each other Involves a trusted third party Reciprocity of authentication One-way authentication Only one party needs to authenticate the other Mutual authentication (two-way) Both parties authenticate each other
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Authentication Properties
Mutual authentication Two-way authentication process between a client and an authentication server Identity privacy Hiding identity of a client Identity: username of a client, instead of the physical address. Reply attack resistance Sending the previously submitted data of a legitimate user back to the authenticator. Counter measures: timestamp, sequence number, unique nonce (challenge/response) Fast reconnect For wireless local area networks (WLANs) Providing seamless connections when roaming occurs Reusing the credentials from previous access point 29
Authentication Protocols in Wireline Networks
Symmetric Key
One-pass unilateral Without trusted third authentication Two-pass unilateral party authentication Three-pass mutual authentication
Public key
One-pass unilateral authentication Two-pass unilateral authentication Three-pass mutual authentication Needham Schroeder authentication Secure socket layer (SSL) authentication
With trusted Needham Schroeder authentication third party
Kerberos authentication
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SSL (secure socket layer) vs. Kerberos
SSL
Type of cryptography Trusted third party Mutual authentication Reply attack resistance Identity privacy Applications Public Key Yes, Asynchronous, Rely on certificate Optional Yes Yes
Kerberos
Symmetric Key Yes, Synchronous, Rely on authentication server Yes Yes No
Large variable user Networked environment where base that is not known all services and users are in advance, e.g., web known in advance Not free, patented material Free open source
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Source
Authentication Protocols in WLANs
Symmetric Key Authentication Lightweight Extensible Authentication Protocol (LEAP) Kerberos Public Key Authentication EAP-Transport Layer Security (EAP-TLS) LEAP Kerberos Symmetric Key Yes Yes Yes No Yes EAP-TLS Public key Yes Yes Yes No No
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Type of cryptography Trusted third party Mutual authentication Reply attack resistance Identity privacy Fast reconnect
Symmetric Key No Yes No No No
Authentication for WMNs
Previous work is not readily applicable to WMNs Public key authentication Time consuming and computationally intense Symmetric key authentication Does not provide efficient methods to handle handover latency
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Research Directions
Goals Reducing the authentication latency Handling multiple domain authentication Designing an authentication ticketing scheme
Supporting ticket generation, verification, revocation Defending against ticket duplication, forgery, modification Supporting both intra and inter domain authentication Supporting mutual authentication (client-router, router-router) Supporting fast handoff
Designing extended Kerberos protocol for Intra-Domain
Designing extended Kerberos protocol for Inter-Domain
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Outline
Overview of Wireless Mesh Networks (WMN) Overview of network Security Literature Review and Research Directions Access Control Authentication Group Key Management Conclusion
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Group Key Management (GKM)
Multicast: An efficient way for group communications Important applications of multicast Pay-per-view movies, audio/video conference, distant learning, multiplayer online game, online chat group Secure multicast communication requires Group Key Management To provide secure distributions & handling of cryptographic keying materials Group Key A piece of secret information that is known only to the current group members Used to encrypt messages Membership changes trigger rekeying process Join: a new group key must prevent a new member from decoding previous messages Leave: a new group key must prevent former group members from decoding future messages Group Key Management Problem How to ensure that only authorized users have access to the group key
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Requirements for Group Key Management (1)
Group key secrecy
Computationally infeasible for a passive adversary to discover a group key Evicted users cannot learn any future keys New users should not have access to any old keys Disclosure of a key does not compromise other keys.
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Forward secrecy
Backward secrecy
Key independency
Requirements for Group Key Management (2)
Scalability (1-affects-n)
A membership change should affect only a small subset of members Providing a recovery mechanism for missing rekeying messages From both inside and out...