1. Implementing Wireless LAN Security

2. Objectives List wireless security solutions
Tell the components of the transitional security model
Describe the personal security model
List the components that make up the enterprise security model

3. Wireless Security Solutions
IEEE a and b standards included WEP specification
Vulnerabilities quickly realized
Organizations implemented “quick fixes”
Did not adequately address encryption and authentication
IEEE and Wi-Fi Alliance started working on comprehensive solutions
IEEE i and Wi-Fi Protected Access (WPA)
Foundations of today’s wireless security

4. WEP2
Attempted to overcome WEP limitations by adding two new security enhancements
WEP key increased to 128 bits
Kerberos authentication
User issued “ticket” by Kerberos server
Presents ticket to network for a service
Used to authenticate user
No more secure than WEP
Collisions still occur
New dictionary-based attacks available

5. Dynamic WEP Solves weak IV problem by rotating keys frequently
More difficult to crack encrypted packet
Uses different keys for unicast and broadcast traffic
Unicast WEP key unique to each user’s session
Dynamically generated and changed frequently
Broadcast WEP key must be same for all users on a particular subnet and AP

6. Dynamic WEP (continued)B
Should be B
Should be A

7. Dynamic WEP (continued)
Can be implemented without upgrading device drivers or AP firmware
No-cost and minimal effort to deploy
Does not protect against man-in-the-middle attacks
Susceptible to DoS attacks

8. IEEE 802.11i Provides solid wireless security model
Robust security network (RSN)
Addresses both encryption and authentication
Encryption accomplished by replacing RC4 with a block cipher
Manipulates entire block of plaintext at one time
Block cipher used is Advanced Encryption Standard (AES)
Three step process
Second step consists of multiple rounds of encryption

9. IEEE i (continued)

10. IEEE i (continued)
IEEE i authentication and key management is accomplished by IEEE 802.1x standard
Implements port security
Blocks all traffic on port-by-port basis until client authenticated using credentials stored on authentication server
Key-caching: Stores information from a device on the network, for faster re-authentication (In the case when a user roams away and returns)
Pre-authentication: Allows a device to become authenticated to an AP before moving to it (Current AP will forward authentication info to the roamed-to AP

11. IEEE i (continued)

12. Wi-Fi Protected Access (WPA)
Subset of i that addresses encryption and authentication
Temporal Key Integrity Protocol (TKIP): Replaces WEP’s encryption key with 128-bit per-packet key
Dynamically generates new key for each packet
Prevents collisions
Authentication server can use 802.1x to produce unique master key for user sessions
Creates automated key hierarchy and management system

13. Wi-Fi Protected Access (continued)
Message Integrity Check (MIC): Designed to prevent attackers from capturing, altering, and resending data packets
Replaces CRC from WEP
CRC does not adequately protect data integrity
Authentication accomplished via IEEE 802.1x or pre-shared key (PSK) technology
PSK passphase serves as seed for generating keys

14. Wi-Fi Protected Access (continued)
Message Integrity Check (MIC)

15. Wi-Fi Protected Access 2 (WPA2)
Second generation of WPA security
Based on final IEEE i standard
Uses AES for data encryption
Supports IEEE 802.1x authentication or PSK technology
Allows both AES and TKIP clients to operate in same WLAN (This is useful is case of having legacy devices that can not support AES).

16. Summary of Wireless Security Solutions
Wi-Fi Alliance categorizes WPA and WPA2 by modes that apply to personal use and to larger enterprises
Security timeline

17. Summary of Wireless Security Solutions (continued)
Wi-Fi modes
AES
802.1x
Wireless security solutions

18. Transitional Security Model
Transitional wireless implementation
Should be temporary
Until migration to stronger wireless security possible
Should implement basic level of security for a WLAN
Including authentication and encryption

19. Authentication: Shared Key Authentication
Uses WEP keys
Networks that support multiple devices should use all four keys
Same key should not be designated as default on each device

20. Authentication: SSID Beaconing
Turn off SSID beaconing by configuring APs to not include it
Beaconing the SSID is default mode for all APs
Good practice to use cryptic SSID
Should not provide any information about the location or type of equipment to attackers

21. Authentication: MAC Address Filtering

22. WEP Encryption
Although vulnerabilities exist, should be turned on if no other options for encryption are available
Use longest WEP key available
May prevent script kiddies or “casual” eavesdroppers from attacking
Transitional security model

23. Personal Security Model
Designed for single users or small office home office (SOHO) settings
Generally 10 or fewer wireless devices
Two sections:
WPA: Older equipment
WPA2: Newer equipment

24. WPA Personal Security: PSK Authentication
Uses passphrase (PSK) that is manually entered to generate the encryption key
PSK used a seed for creating encryption keys
Key must be created and entered in AP and also on any wireless device (“shared”) prior to (“pre”) the devices communicating with AP

25. WPA Personal Security: TKIP Encryption
TKIP is a substitute for WEP encryption
Fits into WEP procedure with minimal change
Device starts with two keys:
128-bit temporal key
64-bit MIC
Three major components to address vulnerabilities:
MIC
IV sequence
TKIP key mixing
TKIP required in WPA

26. WPA Personal Security: TKIP Encryption (continued)
TKIP/MIC process

27. WPA2 Personal Security: PSK Authentication
PSK intended for personal and SOHO users without enterprise authentication server
Provides strong degree of authentication protection
PSK keys automatically changed (rekeyed) and authenticated between devices after specified period of time or after set number of packets transmitted (rekey interval)
Employs consistent method for creating keys
Uses shared secret entered at AP and devices
Random sequence of at least 20 characters or 24 hexadecimal digits

28. WPA2 Personal Security: AES-CCMP Encryption
WPA2 personal security model encryption accomplished via AES
AES-CCMP: Encryption protocol in i
CCMP based on Counter Mode with CBC-MAC of AES encryption algorithm
Cipher Block Chaining-Message Authentication Code
CBC-MAC provides data integrity
AES processes blocks of 128 bits
Cipher key length can be 128, 192 and 256 bits
Number of rounds can be 10, 12, and 14

29. WPA2 Personal Security: AES-CCMP Encryption (continued)
AES encryption/decryption computationally intensive
Better to perform in hardware
Personal security model

30. Enterprise Security Model
Most secure level of security that can be achieved today for wireless LANs
Designed for medium to large-size organizations
Intended for setting with authentication server
Like personal security model, divided into sections for WPA and WPA2
Additional security tools available to increase network protection

31. WPA Enterprise Security: IEEE 802.1x Authentication
Uses port-based authentication mechanisms
Network supporting 802.1x standard should consist of three elements:
Supplicant: Wireless device which requires secure network access
Authenticator: Intermediary device accepting requests from supplicant
Can be an AP or a switch
Authentication Server: Accepts requests from authenticator, grants or denies access

32. WPA Enterprise Security: IEEE 802.1x Authentication (continued)
802.1x protocol

33. WPA Enterprise Security: IEEE 802.1x Authentication (continued)
Supplicant is software on a client implementing 802.1x framework
Authentication server stores list of names and credentials of authorized users
Remote Authentication Dial-In User Service (RADIUS) typically used
Allows user profiles to be maintained in central database that all remote servers can share

34. WPA Enterprise Security: IEEE 802.1x Authentication (continued)
802.1x based on Extensible Authentication Protocol (EAP)
Several variations:
EAP-Transport Layer Security (EAP-TLS)
Lightweight EAP (LEAP)
EAP-Tunneled TLS (EAP-TTLS)
Protected EAP (PEAP)
Flexible Authentication via Secure Tunneling (FAST)
Each maps to different types of user logons, credentials, and databases used in authentication

35. WPA Enterprise Security: TKIP Encryption
TKIP is a “wrapper” around WEP
Provides adequate encryption mechanism for WPA enterprise security
Dovetails into existing WEP mechanism
Vulnerabilities may be exposed in the future

36. WPA2 Enterprise Security: IEEE 802.1x Authentication
Enterprise security model using WPA2 provides most secure level of authentication and encryption available on a WLAN
IEEE 802.1x is strongest type of wireless authentication currently available
Wi-Fi Alliance certifies WPA and WPA2 enterprise products using EAP-TLS (Transport Layer Security)

37. WPA2 Enterprise Security: AES-CCMP Encryption
AES: Block cipher that uses same key for encryption and decryption
Bits encrypted in blocks of plaintext
Calculated independently
block size of 128 bits
Three possible key lengths: 128, 192, and 256 bits
WPA2/802.11i uses128-bit key length
Includes four stages that make up one round
Each round is iterated 10 times

38. WPA2 Enterprise Security: AES-CCMP Encryption (continued)
Enterprise security model

39. Other Enterprise Security Tools: Virtual Private Network (VPN)
Virtual private network (VPN): Uses a public, unsecured network as if it were private, secured network
Two common types:
Remote-access VPN: User-to-LAN connection used by remote users
Site-to-site VPN: Multiple sites can connect to other sites over Internet
VPN transmissions are achieved through communicating with endpoints

40. Other Enterprise Security Tools: Virtual Private Network (continued)
Endpoint: End of tunnel between VPN devices
Can local software, dedicated hardware device, or even a firewall
VPNs can be used in WLAN setting
Tunnel though WLAN for added security
Enterprise trusted gateway: Extension of VPN
Pairs of devices create “trusted” VPN connection between themselves
Can protect unencrypted packets better than a VPN endpoint

41. Other Enterprise Security Tools: Wireless Gateway
AP equipped with additional functionality
Most APs are wireless gateways
Combine functionality of AP, router, network address translator, firewall, and switch
On enterprise level, wireless gateway may combine functionality of a VPN and an authentication server
Can provide increased security for connected APs

42. Other Enterprise Security Tools: Wireless Intrusion Detection System (WIDS)
Intrusion-detection system (IDS): Monitors activity on network and what the packets are doing
May perform specific function when attack detected
May only report information, and not take action
Wireless IDS (WIDS): Constantly monitors RF frequency for attacks
Based on database of attack signatures or on abnormal behavior
Wireless sensors lie at heart of WIDS
Hardware-based have limited coverage, software-based have extended coverage

43. Other Enterprise Security Tools: Captive Portal
Web page that wireless users are forced to visit before they are granted access to Internet
Used in one of the following ways:
Notify users of wireless policies and rules
Advertise to users specific services or products
Authenticate users against a RADIUS server
Often used in public hotspots

44. Summary
IEEE i and Wi-Fi Protected Access (WPA), have become the foundations of today’s wireless security
Dynamic WEP attempts to solve the weak initialization vector (IV) problem by rotating the keys frequently, making it much more difficult to crack the encrypted packet
The IEEE i standard provided a more solid wireless security model, such as the block cipher Advanced Encryption Standard (AES) and IEEE 802.1x port security

45. Summary (continued)
WPA is a subset of i and addresses both encryption and authentication
The transitional security model uses shared key authentication, turning off SSID beaconing, and implementing MAC address filtering
The personal security model is designed for single users or small office home office (SOHO) settings of generally 10 or fewer wireless devices and does not include an authentication server

46. Summary (continued)
The enterprise security model is intended for settings in which an authentication server is available; if an authentication server is not available the highest level of the personal security model should be used instead
Additional security tools that can supplement the enterprise security model to provide even a higher degree of security include virtual private networks, wireless gateways, wireless intrusion detection systems (WIDS), and captive portals