Slideshow of our Term Paper presentation on Wireless Network Security Domain.

1. Wireless
LAN
Security
Ajay K Mathias M120445CS
Govind M M120432CS
Johnes Jose M120088CS

2. Introduction
WEP
EAP Overview
Authenticated KEP
Conclusion

4. Wireless Networks
 Extension of Wired networks, without using
wires.
 IEEE 802.11 (1997)
 802.11b (1999), 802.11g (2003), 802.11n (2009)
 802.11i (2004)
2 Types : Adhoc & Infrastructural WLAN

5. Ad Hoc WLAN
• Connect with whichever station
• Hop Hop.. Hop Hop..
• No device in the middle.

6. Infrastructure WLAN
 Parties Involved
 Wireless
Station
 Access Point (AP)
 Ground Station
 Terms
 BSS / ESS
 SSID
 Beacon
 Probe Request, Response
 Associate Frame
Request, Response

8. Security in WLAN
 Main Point of Concern
 Multiple Options exists in Wired Networks.
 SSID / MAC based Authentication was
used, both of which were spoof-able.
 Common Attacks Possible
 Masquerading
 Man in the middle
 Dictionary Attacks
 Requirement : Privacy Equivalent to that
in Wired Networks

9. Wired Equivalent Privacy (WEP)
 Challenge Response Protocol
Random Nonce, C
Station Access
Point
Response, R
Initialization Vector, IV
R = C O KEYSTREAM(S, IV)
+

10. But…..!
 WEP had the following security Issues
 Monitor Challenge Response to compute
Keystream.
 Obtain S, using Dictionary Attack
 One side Authentication
Thus…..
A better protocol was required
 WPA

12. Post WEP security
 WPA (TKIP) – Temporal Key Integrity
Protocol
 WPA 2 (CCMP) – Counter mode CBC
MAC Protocol
 The authentication in both schemes same
 Authentication same as in 802.11i
 Former uses RC4 key-stream encryption
 Latter uses AES with cipher block chaining

13. AUTHENTICATION IN WPA
3 entities
 Supplication (Station)
 Authenticator (AP – Access Point)
 Authentication Server (AS)
 EAP (Extensible Authentication Protocol)
 Authentication, Authorization &
Accounting

14. 802.11i Protocol
Authentication
Supplicant Authenticator Server
802.11
Association
EAP/802.1X/RADIUS
Authentication
MSK
4-Way
Handshake
Group Key
Handshake
Data
Communication

15. AUTHENTICATION METHODS
 EAP – MD5
 EAP – TLS
 EAP – TTLS
 EAP – PEAP

16. EAP – MD5
 Basicform
 Challenge is to send MD5 of password
 Password not known to AP, AS
 Drawbacks:
 Replay attack possible with MD5(password)
 AP is not verified to the supplicant

17. EAP-TLS
 Uses SSL/TLS
 All Entities have Certificates & Pvt. keys
 Drawbacks:
 Infeasible for all stations to have certificates
 PKI required to communicate

18. EAP-TTLS
 Requires AP to have certificates
 AP can be verified by AS, supplicants
 Forms a secure tunnel through which
password can be sent
EAP-PEAP
 Similar
to EAP-TTLS
 Forms a secure tunnel
 Authentication of station to AS
independent

19. KEY AGREEMENT
 Two types of keys:
 TK (Temporal Key) [128]
 GTK (Group Transient Key) [128]
 PMK can be replaced by PSK (Pre Shared
Key) [256], but not secure
 TK and other keys are derived from PMK
(Pairwise Master Key) [256] by 4-way
handshake protocol

20. KEY HIERARCHY
MSK [256] : AS & Station
PMK [256] : AP (derived
from MSK)
PTK = f(PMK) [512]
PTK -> TK [128]
PTK -> KCK [128]
PTK -> KEK [128]

21. FOUR WAY HANDSHAKE
Calculate PTK
Calculate PTK
 PTK = prf (PMK,NA,NB,MACA,MACS)
 PTK = (TK, KCK, KEK)

23. EAP-SPEKE
 Simple Password-Authenticated
Exponential Key Exchange
 Diffie-Hellman based
 Authentication with session key
negotiation
 Mutual Authentication
 Withstands Man in the middle attack
 Withstands Replay attack

24. Supplicant Authenticator
A = gXa mod p A
g = f(pd) B = gXb mod p
Xa = secret key Xb = secret key
S(n1)
S= H(BXamod p) S = H(AXb mod p)
n1 = nonce n2 = nonce
S(n2)
Verify n1 Verify n2

25. EAP - SRP
 EAP-Secure Remote Password
 Borrows elements from other key
exchange protocol
 User ID and password-based
authentication

26. Supplicant Authenticator
B = (V+gXb) mod p
A = gXa mod p A, ID Xb = secret key
g = f(pd) V = gx mod p
Xa = secret key
x = H(Salt, pd)
ID = identifier
x = H(Salt, pd)
u = H(A, B)
S = (B-gx)Xa+ux mod p
K = H(S)
u = H(A, B)
S = (AVu) Xbmod p
K = H(S)
Verify n1

27. Improved EAP-SRP
A = gXa mod p
Ma = H(H(Pd) Xor H(g), H(ID), A) A,ID,Ma
B = (v + gXb) mod p
U = H(A, B)
S = (A.Vu)Xb mod p
K = H(s)
Mb = H(A, B, Ma, k)
Salt, Mb, B
U = H(A,B)
S = (B-gx)(Xa+Ux) mod p
K = H(S)
Mc = H(B, Mb, K)
Mc
Session Key
Mutual Authentication

28. • Mutual Authentication • Computationally
Pros
Cons
• No Cleartext Password Intensive
Exchange (Comparitively)
• Works against • Narrow domain of
Dictionary choosing primes.
Attacks, Password
Sniffing and Network (eg. Reqd : Prime p,q
Traffic Analysis Attacks such that p = 2q+1)
• Easier to setup, than
Dig Cert based
Authentication.

29. References
1. An Efficient Password Authenticated Key Exchange Protocol for
WLAN and WIMAX, AK Rai, V Kumar, S Mishra, ICWETT
2011
2. Extensible authentication
protocol, Adoba, B., Blunk, L., Vollbrecht, J., Carlson
, J. & Levkowetz, E., RFC 3748 2004
3. The SRP Authentication and Key Exchange System, T. Wu, RFC
2945 2000
4. Cryptography and Network Security, Bernard
Menesez, Cengage Solutions

30. Thank You…!