Wireless Security
CSE497b - Spring 2007
Introduction Computer and Network Security Professor Jaeger
Wireless Networks
• Network supported by radio communications .. • Alphabet soup of
standards, most on 802.11 • .. destroys the illusion of a
Why you should fear Simon Byers ...
• Over the course of history radio frequencies have been enormously vulnerable to eavesdropping and manipulation.
• ASSUME: Everything you say on a wireless network is going to be heard and potentially manipulated by your adversaries.
Wireless LANs
• Access point networks (ranging to about 300 feet) • All devices connect to the central access point
• Pro: very easy to setup and maintain, simple protocols
• Con: reliability/speed drops as you get away from AP or contention increases.
Ad hoc Networks (a.k.a peer-to-peer)
• Devices collaboratively work together to support network communication
• Network topology changes in response to moving devices, e.g., bluetooth
• Pro: highly flexible and responsive to changes in environment
• Con: complex, subject to traffic manipulation by malicious peers
Devices
• Laptops (canonical wireless devices) • Desktops, mobile phones, ....
Attacks on Wireless Networks
• DOS
• Planted devices
• Hijacked connections • Eavesdropping
Threats
• This is an open network ...
• ... to which anyone can connect. • What security is necessary?
– Authentication? – Confidentiality? – Integrity? – Privacy? – DOS Protection? – Accountability (traceability)?
Security Mechanisms
• Note: this is just a network with different threats, so implementing security is very similar to network
security
• Authentication
– Q: What are you authenticating in a wireless network? – Methods: password/passphrase, smartcard, etc.
– Tools: radius, Kerberos, PKI services ....
• Confidentiality/Integrity
– Typically implemented via some transport protocol
Wireless Security Approaches
• MAC Authentication
• WEP (Wired Equivalent Privacy)
• 802.11i (WPA - Wifi Protected Access)
• EAP/LEAP (Extensible Authentication Protocol) • WAP (Wireless Application Protocol)
MAC Authentication
• Create a list of MAC addresses
– media access layer, e.g., ether 00:0a:95:d5:74:6a – Only these devices are allowed on network
• Attack
– Listen on network for MAC address use -- laptop
– Masquerade as that MAC address (easy to do, many devices programmable)
– ... can wait for it to go off line to avoid conflict, but not necessary
• ARP Security limitations
WEP (Wired Equivalent Privacy)
• Keys
– Pass-phrase converts 40 bits from passphrase, plus 24 bit initialization vector (or)
– 26 char hexadecimal + 24-bit IV = 128-bit WEP
– Ability to send packets is essentially authentication
• integrity used as authentication
Page CSE497b Introduction to Computer and Network Security - Spring 2007 - Professor Jaeger
The WEP Flaw (greatly simplified)
Page 14
Protocol
• Passphrase Key kp
• Initialization vector ivi
• Plaintext data d1, d2 (for separate blocks 1 and 2)
• Traffic Key kti = kp||ivi
• Ciphertext = E(kti, di) = RC4(kti) ⊕ di
Attack
• Assume iv1 = iv2
• Only 17 million IVs (224), so IV of two packets can be found (≈ one in 4096)
(RC4(kt1) ⊕ d1) ⊕ (RC4(kt1) ⊕ d2) = d1 ⊕ d2
1
Protocol
• Passphrase Key kp
• Initialization vector ivi
• Plaintext data d1, d2 (for separate blocks 1 and 2)
• Traffic Key kti = kp||ivi
• Ciphertext = E(kti, di) = RC4(kti) ⊕ di
Attack
• Assume iv1 = iv2
• Only 17 million IVs (224), so IV of two packets can be found (≈ one in 4096)
802.11i (WPA - Wifi Protected Access)
• Solution to problems with WEP • Two modes of operation
– Pre-shared key mode -- WEP like, shared key derived from single network passphrase
– Server mode -- uses 802.1X authentication server to authenticate/give unique keys to users
• Protocol fixes to WEP
– increase IV size to 48 bits
– TKIP - change keys every so often -- Temporal Key
Integrity Protocol
– improved integrity (stop using CRC and start using MAC) – WPA2: AES instead of RC4
WAP (Wireless Application Protocol)
• A set of protocols for implementing applications over thin (read wireless) pipes.
• Short version: a set of protocols to implement the web over wireless links as delivered to resource limited devices
– reduce overhead and flabby content (image rich HTML) – support limited presentation and content formats
• Wireless Markup Language (XML-based language)
– reduce the footprint of the rendering engine (browser)
• Security: WTLS
– SSL/TLS protocol -- public keys, key negotiation, etc.
EAP/LEAP
• Extensible Authentication Protocol
– Challenge response - auth. only
– Bolts onto other authentication mechanisms, e.g., Kerberos, RADIUS
– Passes authentication information onto other protocols (WEP, WAP)
– LEAP: Cisco implementation/modifications (security problems are possibly serious)
– Standards: EAP-MD5, EAP-TLS
– PEAP: RSA/Microsoft/Cisco standards for WPA/WPA2 protocols
Bluetooth
• A standard for building very small personal area networks (PANs)
• Connects just everything you can name: PDAs, phones, keyboards, mice, your car
• Very short range range network: 1 meter, 10 meters, 100 meters (rare)
• Advertised as solution to "too many cables" • Authentication
– "pairing" uses pass-phrase style authentication to establish relationship which is often stored
Bluetooth Security
• Everything really works off the PIN
• Attacks have progressively been successful at
identifying vulnerabilities in the way PINs are used, can be reverse engineered
• Privacy: know what is on and how public it is ... • Problem: Cambridgeshire, England
RFIDs
•
Radio Frequency Identification (RFID)•
identity-providing transponders•
Passive: no external power - backscatter (Walmart)•
Active: internal power (SpeedPass)•
History: a soviet listening device (1945), alied FoF (1939)•
Privacy/Security anyone?•
Q: How do you control who is accessing your information?•
A: You don’t (currently)•
Security measures•
Rolling code (one time tokens)NIST Evaluation
• Any vulnerability in a wired network is present in the wireless network
• Many new ones: protocols, systems more public and vulnerable
• Recommendations:
– Disable file and directory sharing – Turn off APs when not in use
– Use robust passwords, 128-bit encryption – Audit, audit, audit
