Wireless Security Models

Wireless Security Solutionsslide 5

• WEP suffers from serious weakness
• “Band-aid” solutions
  • WEP2 and Dynamic WEP
• Better solutions
  • IEEE 802.11i (WPA, WPA2)
  • Wi-Fi Protected Access (WPA)
  • Wi-Fi Protected Access 2 (WPA2)

IEEE 802.11islides 6–10

• IEEE 802.11i addresses the two weaknesses of wireless networks: encryption and authentication
• Encryption
  • Replaces the RC4 stream cipher algorithm with a block cipher
    • Manipulates an entire block of text at one time
  • 802.11i uses the Advanced Encryption Standard (AES)
    • Designed to be an encryption technique that is secure from attacks

• Authentication and key management
  • Accomplished by the IEEE 802.1x standard
    • Implements port security
    • Blocks all traffic on a port-by-port basis
      • Until the client is authenticated using credentials stored on an authentication server
• Key-caching
  • Stores information from a device on the network
  • If a user roams away and later returns
    • She/he does not need to re-enter all of the credentials

• Pre-authentication
  • Allows a device to become authenticated to an AP
    • Before moving into range of the AP
  • Device sends a pre-authentication packet to the AP the user is currently associated with
    • And the packet is then routed to a remote AP or APs
  • Allows for faster roaming between access points

Wi-Fi Protected Access (WPA)slides 11–14

• Subset of 802.11i and addresses both encryption and authentication
• Temporal Key Integrity Protocol (TKIP)
  • TKIP keys are known as per-packet keys
  • TKIP dynamically generates a new key for each packet that is created
  • Prevent collisions
    • Which was one of the primary weaknesses of WEP
• Authentication server can use 802.1x to produce a unique master key for that user session

• TKIP distributes the key to wireless devices and AP
  • Setting up an automated key hierarchy and management system
• WPA replaces the Cyclic Redundancy Check (CRC) with the Message Integrity Check (MIC)
  • Designed to prevent an attacker from capturing, altering, and resending data packets
  • Provides a strong mathematical function
  • Clients are de-authenticated and new associations are prevented for one minute if an MIC error occurs

• WPA authentication
  • Accomplished by using either IEEE 802.1x or preshared key (PSK) technology
• PSK authentication uses a passphrase to generate the encryption key
  • Passphrase must be entered on each access point and wireless device in advance
  • Serves as the seed for mathematically generating the encryption keys
• WPA was designed to address WEP vulnerabilities with minimum inconvenience

Wi-Fi Protected Access 2 (WPA2)slides 15–18

• Second generation of WPA security
• Based on the final IEEE 802.11i standard
• Uses the Advanced Encryption Standard (AES) for data encryption
• Supports IEEE 802.1x authentication or PSK technology
• WPA2 allows both AES and TKIP clients to operate in the same WLAN
  • This allows devices that only support TKIP (older devices) to connect using WPA, while newer devices connect using AES and WPA2.
  • Both types of clients share the same SSID (network name) but operate with their respective encryption protocols

• Wi-Fi Alliance wireless security models based on WPA and WPA2
  • WPA—Personal Security
  • WPA—Enterprise Security
  • WPA2—Personal Security
  • WPA2—Enterprise Security
• Transitional security model
  • Used as a “bridge” solution in situations where WPA or WPA2 security is not available
  • Intended as a temporary fix

Transitional Security Modelslide 19

• Should only be implemented as a temporary solution

Authenticationslides 20–23

• Shared key authentication
  • Should be used instead of open system authentication
  • Uses WEP keys for authentication
  • Based on a challenge-response scheme
• SSID beaconing
  • Should be turned off
  • May prevent a “casual” unauthorized user or novice attacker from capturing the SSID and entering the network
  • Use a hard-to-guess SSID in a WLAN

• MAC address filtering limitations
  • Managing a large number of MAC addresses is difficult
  • Does not provide an easy means to temporarily allow a guest user to access the network
  • WLANs initially exchange MAC addresses in cleartext
  • A MAC address can be “spoofed” or substituted
• DHCP restrictions
  • DHCP “leases” IP addresses to clients to use while they are connected to the network

WEP Encryptionslides 24–25

• Should be turned on
  • If no other options are available for encryption
• The longest WEP key available should be used for added security
  • Most vendors have the option of a 128-bit WEP key
• There is evidence that WEP passphrase generators may create predictable keys

Personal Security Modelslide 26

• Designed for single users or small office/home office (SOHO) settings
  • Generally, 10 or fewer wireless devices
• Intended for settings in which an authentication server is unavailable
• Divided into two parts, WPA and WPA2
  • WPA2 should always be used instead of WPA

WPA Personal Securityslides 27–29

• PSK authentication
  • Purchasing, installing, and managing an authentication server is costly
    • May require special technical skills
  • PSK functions
    • Used to authenticate the user
    • Plays a role in encryption
  • PSK vulnerabilities
    • Key management
    • Passphrases

WPA2 Personal Securityslides 30–32

• PSK authentication
  • PSK keys are automatically changed (called rekeying)
    • And authenticated between devices after a specified period
      • Known as the rekey interval
• AES-CCMP encryption
  • CCMP stands for Counter Mode CBC-MAC Protocol (Counter Mode with Cipher Block Chaining Message Authentication Code Protocol)
  • AES is used in WPA2 for data encryption
  • AES-CCMP is the encryption protocol in the 802.11i standard
    • CCMP is based upon the Counter Mode with CBC-MAC (CCM)

• AES-CCMP encryption
  • CCM provides data privacy
  • CBC-MAC provides data integrity and authentication
  • AES algorithm processes blocks of 128 bits
    • Length of the cipher keys and number of rounds can vary
  • It is recommended that AES encryption and decryption be performed in hardware

Enterprise Security Modelslide 33

• Most robust level of security
• Designed for medium to large-sized organizations
• Intended for settings in which an authentication server is available
• Divided into two parts, WPA and WPA2

WPA Enterprise Securityslides 34–37

• IEEE 802.1x authentication
  • Provides an authentication framework for all IEEE 802-based LANs
  • Elements
    • Supplicant
    • Authenticator
    • Authentication server
  • IEEE 802.1x supplicant
    • Software that implements the IEEE 802.1x framework
    • May be included in the client operating system or WNIC

• IEEE 802.1x authentication
  • Authentication server
    • Stores the list of the names and credentials of authorized users to verify their authenticity
    • Typically a Remote Authentication Dial-In User Service (RADIUS) server is used
      • Allows a company to maintain user profiles in a central database that all remote servers can share
    • Other options
      • Structured Query Language (SQL)
      • Lightweight Directory Access Protocol (LDAP)
      • Microsoft Active Directory

• TKIP encryption
  • Should be considered an interim WPA enterprise security solution
  • A more robust encryption protocol is AES-CCMP

WPA2 Enterprise Securityslides 38–40

• IEEE 802.1x authentication
  • Disadvantage
    • High cost involved with purchasing, installing, and maintaining an authentication server
• AES-CCMP encryption
  • A 128-bit key length is used
  • AES encryption includes four stages that make up one round
    • Each round is iterated 10 times

• Robust Secure Network (RSN)
• is a term used to describe a set of security features and protocols implemented in Wi-Fi networks to ensure robust protection against various security threats. RSN builds upon the security enhancements introduced in the IEEE 802.11i standard, which is commonly known as WPA2 (Wi-Fi Protected Access 2).
  • Uses dynamic negotiation of authentication and encryption algorithms
    • Between access points and wireless devices
  • RSNs evolve as vulnerabilities are exposed OR improved security is introduced