Security in Wireless Residential Networks

1
Security in Wireless Residential Networks

• Prashant Krishnamurthy
• Joseph Kabara
• Tanapat Anusas-amornkul
• IEEE Transactions on Cosumer Electronics
• February 2002

2
Outline

• Introduction
• A brief overview of network security
• Security in wireless technologies for residential
  networking
• Characteristics of residential networks
• An approach ofr implementing security in WRNs
• Conclusions

3
Introduction

• Residential networking is expected to experience
  accelerating growth over the next few years.
• The residential networks will interconnect a wide
  variety of Internet appliances.
• WRNs must support a variety of devices, different
  types of traffic, different applications and be
  simple ton install, inexpensive, and easy to
  manage and modify.

4
Introduction (cont.)

• Breaching security in wireless networks by
  eavesdropping and masquerading is particularly
  easy.
• We provide a mechanism that can unify a security
  architecture for the home despite the diverse
  nature of the requirements, network , devices and
  protocols.
• We also provide a classification of the security
  issues and requirements in WRNs and provide a
  frame work that may be employed in WRNs for
  designing security services and mechanisms.

5
A brief overview of network security
Security Services
6
A brief overview of network security (cont.)

• Other security services ----
• Authorization
• Authentication
• Identification

7
A brief overview of network security (cont.)

• Encryption algorithms

• The strength of the encryption is dependent
  mostly on the size of the secret key.
• Encryption algorithms employed today are almost
  impossible to break except by brute force that
  involves searching through all possible keys.

8
A brief overview of network security (cont.)

• Encryption algorithms
• Hybrid encryption schemes tat use a public key
  algorithm for key exchange and secret key
  algorithms for bulk data transfer are currently
  in vogue

9
A brief overview of network security (cont.)
10
Security in wireless technologies for residential
networking

• Wireless technology is becoming the popular
  choice for networking in residences because of
  convenience.
• The greatest obstacle to networking in residences
  is the lack of structured wiring.
• Also, wireless networking provides mobility for
  consumer electronic devices.
• Lastly, wireless networking provides the ability
  to control or access networked devices.

11
Security in wireless technologies for residential
networking (cont.)

• Wired solutions inherently provide more security
  than wireless because they cannot be tapped
  easily.
• The most popular technologies in the market today
  and the ones likely to be deployed in the
  residential environment are the IEEE 802.11b and
  the Bluetooth standards.

12
Security in IEEE 802.11

• The 802.11 standard specifies a Wired Equivalent
  Protocol (WEP) mechanism for wireless security.
  The WEP can provide confidentiality, access
  control and message integrity services.
• An access point can be configured in 2 modes
• Open-system modeWEP data encryption
• Shared-key modeprovides WEP encryption and
  authentication
• Denial of service

13
Security in Bluetooth

• Bluetooth devices operate in an ad-hoc manner
  (peer-to-peer communication).
• Bluetooth specifications provide usage protection
  and information confidentiality.
• It has three modes of operation
• Non-secure mode
• Service-level mode
• Link-level security mode

14
Security in Bluetooth (cont.)

• Devices also can be classified into trusted and
  distrusted.
• Bluetooth uses
• two secret keys (128 bits for authentication and
  8-128 bits for encryption)
• A 128d-bit random number and the 48-bit MAC
  address of devices.

15
General technique for sharing keys in wireless
networks

• Most wireless networks employ identification
  schemes followed by hash algorithms to generate
  fresh keys that can be used with a secret key
  algorithm to provide various security services.
• Hashing a random number concatenated with a
  secret identifying parameter known only to the
  communicating parties can securely generate keys.
• Generally, the shared secret should be at least
  80 to 128 bits in length.

16
Characteristics of residential networks

• The lack of standardization, the different
  perspectives from which consumer devices are
  manufactured, and especially their varying
  capabilities and needs.
• This heterogeneity affects the requirements of
  any protocol or security mechanism used to
  support the network.

17
Heterogeneity of devices, their capabilities and
their requirements

• Electronic devices networked in residences are
  usually classified into two categories home
  automation and computer communications.
• Home automation mostly operate at low data rates.
• Computer with multimedia Internet appliances have
  the ability to download music or obtain video on
  demand over the Internet via broadband Internet
  service to the home.

18
Heterogeneity of devices, their capabilities and
their requirements (cont.)

• The device capabilities are vastly different with
  respect to implementation of security mechanisms.
• No single security mechanism can provide all
  possible security services and not all devices
  require the same level of sevurity.

19
Heterogeneous applications

• The applications supported on the network are
  also diverse. Each application will have security
  algorithms that are best suited for it.
• Multimedia Internet appliances that directly
  connect to the network cant tolerate delay or
  jitter.
• High data rate services will require algorithms
  that can encrypt very fast while low data rate
  services will be constrained by economic and
  power consumption factors.

20
Wireless security issues

• Modular exponentiation of 1024 bit numbers
  consumes the mobile terminals battery very
  quickly. (minimum required for public key
  protocols)
• Secret key algorithms require elaborate key
  management schemes, violating the ease of
  implementation requirement.
• Several handshakes -gt consumes battery power,
  bandwidth and time.

21
Summary

• Any solution must satisfy the following
  requirements
• The cost of implementing the security mechanism
  must not be prohibitive.
• The security mechanism must be simple to
  implement and maintain.
• There should be minimum changes to existing
  standards and products.
• The solution should be scaleable.
• The solution should be upgradeable.

22
An approach for implementing security in WRNs

• The primary concern in residential networks will
  be access control.
• We classify devices that connect to the WRN into
  categories. We also classify different levels of
  security assigned to these devices.
• We then layout an infrastructure with a universal
  access point that enforces security in the WRN by
  implementing algorithm agility and a containment
  security policy based on the category of device
  and its security level.

23
An approach for implementing security in WRNs
(cont.)

• Categories of WRN devices
• Low data rate low power fixed devices
• Low data rate high power fixed devices
• Low data rate low power mobile devices
• High data rate high power fixed devices
• High data rate low power mobile devices
• High data rate high power mobile devices

24
An approach for implementing security in WRNs
(cont.)

• Categories of security services
• No security
• Moderate security
• Wireline equivalent security
• High security
• Ultra-high security
• Critically high security

25
The architecture

• The architecture of a WRN can have two
  possibilities
• Ad hoc a topology
• An infrastructure-based network with an access
  point
• The second on is preferable because each device
  has to identify/authenticate itself with the
  access point.
• A device is identified by its physical address
  and a class that is determined based upon a tuple
  associated with it. The tuple consists of the
  device category and the security level.

26
The architecture (cont.)
27
The architecture (cont.)

• Authentication and access-control can be tied in
  together with a message authentication code.
• A message authentication code is represented as
  MAC ck(x) where x is the message and k is a
  shared secret key.
• There are two ways of implementing a MAC either
  encrypting a hash function or hashing together
  the message and the secret key.

28
The architecture (cont.)

• These two approaches ca be written as
• c1,k(x) ek (h (x))
• c2,k(x) h (k x)
• h () is the hash function,
• ek is a secret key encryption algorithm
• Both approaches are secure, but the second one is
  faster and hence preferred.
• A want to transmit a message to B, A will send
• y x ck(x)

29
Enforcement of security using algorithm agility
and containment at the access point

• The access point will implement algorithm-agile
  encryption and also have security mechanisms for
  containment based on the algorithm chosen.
• The algorithm-agile encryptor will allow the
  access point to determine what encryption
  algorithm is applied to an incoming request for
  access and relay, and act accordingly based on
  security policies associated with the connection.

30
Enforcement of security using algorithm agility
and containment at the access point (cont.)

• Containment refers to the ability of the network
  to keep certain security levels of information
  from leaking out of a particular region.
• Communication from a tuple consisting of a
  security level and device category shall be
  relayed only to another device with a tuple
  falling into the same class.
• The access point must ensure that no traffic from
  a low-security communication session is relayed
  to a high security device

31
An example of the security mechanism

• The music deviceDeva
• Its device categoryDc, security level SL
• An algorithm Alg, a nonce RN

32
An example of the security mechanism (cont.)
33
Advantages and limitations

• The advantage of this approach is that the
  security mechanism is simple to implement and
  maintain.
• The security mechanism is upgradeable. New
  algorithms and policies can be put in place,
  expanded, improved and customized as needed.
• The primary limitation is that this does not
  solve the simple denial of service attack
  although the access point can discard packets
  that are not part of the network.

34
Advantages and limitations (cont.)

• The access point is unlikely that several streams
  of devices will request service simultaneously.
• Also, the medium access control protocols of IEEE
  802.11 and Bluetooth prevent simultaneous access
  to the medium from several devices.
• It is possible that someone can hack into the
  access point.

35
Conclusions

• The cost of wiring a home for networking devices
  being prohibitive, the trend is towards an all
  wireless or hybrid wireless-wired networking
  solution.
• The complexity of the WRNs require a solution
  that can service a variety of security levels and
  different categories of devices.
• We have presented a systematic classification of
  WRN devices, security categories and discussed a
  solution based on algorithm agility and a
  containment based security policy.