Wireless Network Security

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Wireless Network Security

• Bureau of National Security (BNS)
• Brad Bargabus
• Minh Nguyen
• Nirdesh Shukla
• CMPE 209 Richard Sinn

2
Introduction

• What is it?
• to prevent unauthorized access to a wireless
  network.
• Why we need it?
• communication media is the airwaves.
• companies are reluctant to integrate wireless
  without security.

3
History
4
No Security

• Unsafe to implement for home usage
• Vulnerable to packet sniffing, illegal activates,
  and network takeover.
• Hotspots offer NO SECURITY.
• Password protected for logging in but packets are
  not encrypted.
• Unfeasible for hotspot providers to give everyone
  a personal VPN login.
• Avoid entering personal information (E-mail, Bank
  Accounts, chat conversations).

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WEP (Wired Equivalence Protection)

• 40-bit pre-shared key combined with 24-bit
  Initiation Vector (IV).
• Data encryption using RC4 stream cipher.
• IV is changed incrementally or pseudo-randomly
• No rules set for how to determine the IV.
• CRC-32 is used to as a checksum for data
  integrity.

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WEP Frame
7
WEP Weaknesses

• Keystream recycle over time becomes high with
  only 224 (16 mil.) combinations.
• Approx. 9000 weak IV values.
• Weak keys can be used to reveal keystream bytes
  5-10 of the time.
• Parts of the Keystream can be guessed.
• CRC is linear and should only be used to check
  data accuracy, not data integrity. MD5 or SHA-1
  much better.
• No authentication

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End of WEP

• Vulnerable to passive and active attacks.
• Increasing keystream size and IV size only delays
  key cracking, not prevent.
• Applications widely available on the internet to
  crack keys within minutes.
• WPA-PSK developed to replace WEP.

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WPA (TKIP) Features

• 128-bit Temporal Key (TK), 48-bit IV, RC4
  encryption.
• Base key is negotiated between AP and users using
  session secret, random numbers, and MAC
  addresses.
• New key is generated every 10,000 packets.
• IV is used as the counter and is incremented
  every packet, not sent as plaintext.
• Message Integrity Check (MIC)

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WPA Security Improvements

• Difficult to guess current IV and TK.
• Weak Key attack prevented by hashed counter and
  changing base keys.
• Replay attacks prevented by counter.
• Packet modification prevented by MIC.

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PSK (Pre-shared Key)

• 256-bit key, up to 32 characters.
• 4 way handshaking using hashed frames.
• Vulnerable to dictionary attacks if key less than
  20 characters.
• Tools available to help pick a strong key
  (Diceware)

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WPA2 (AES)

• Developed in 2004
• 256-bit block ciphers
• Based on PKI
• Initial Converted into 256-bit blocks.
• SubByte Each byte through 8-bit lookup
  tables.
• ShiftRows Shift each row in the block by an
  offset.
• MixColumns Each column 4-bytes are mixed.
• AddRoundKey Each block is XOR with subkey.

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EAP (Extensible Authentication Protocol)

• EAP-TLS
• EAP-TTLS
• EAP-PEAP
• PEAPv0 MSCHAPv2
• PEAPv1 GTC
• EAP-LEAP
• EAP-MD5

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EAP-TLS (Transport-Layer Security)

• Most secure EAP method today
• Based on RFC 5216 (standard)
• Certificates
• User-side certificates
• Server-side certificates
• Problem
• Need to provide user-side certificates for all
  the employees

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EAP-TLS (Transport-Layer Security)
Station
Access Point
Radius Server
Client Hello
Client Hello
Server Hello
Server Hello
ClientKeyExchange
ClientKeyExchange
Master Key
Master Key
ChangeCipherSpec
ChangeCipherSpec
EAP-SUCCESS
EAP-SUCCESS
Data
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EAP-TTLS (Tunneled TLS)

• Developed by Funk
• Client authenticates via username / password
• No need for user-side certificates

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EAP-PEAP (Protected EAP)

• Similar to EAP-TTLS
• Client needs username / password
• PEAPv0
• Developed by Microsoft, Cisco, RSA Security
• Uses MSCHAPv2 as outer auth. method
• PEAPv1
• Developed by Cisco
• Uses GTC (Challenge-Response)

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EAP-LEAP (Lightweight EAP)

• Developed by Cisco
• No outer authentication method
• Client authenticates via username / password
• Server does not authenticate to client
• Rarely used since Microsoft does not support
  EAP-LEAP in ZeroConfig.

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EAP-MD5

• Least secure EAP method
• MD5 hash of password

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Conclusion

• Network administrator should aware about attacks
  and how to restrict them
• WLAN devices should be secured using at least WEP
  security
• Use a closed network that does not broadcast
  the SSID
• Check and monitor the wireless network for
  weakness and compromise
• Personnel should be trained about wireless
  network security

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• Questions?