My research topic on "Noordelijke Hogeschool Leeuwarden"

1. DEIOC
Authentication in wireless networks
Ludo Stoetenga
Chris van den Berg
Noordelijke Hogeschool Leeuwarden

2. DEIOC
Introduction
 ProjectObjectives
 Choices
– Network type
– Standards
 Types of Connections
 Encryption methods
 Conclusion

3. DEIOC
Project Objectives
 Investigate through documents and lecture
studies about the subject and write a
theoretical description about this.
 Implement one of the encryption methods in
a Java based environment.
 Write a document how we implemented the
authentications in Java.

4. DEIOC
Choices
 Network types
– TTP (Trusted Third Party)
– Location Limited
– Chain of Thrust
 Standards
– 802.11b (Wi-Fi)
– 802.16 (Broadband Wireless Metropolitan Area
Networks)

5. DEIOC
TTP (Trusted Third Party)
A server that is trusted by the clients
 The server defines the protocol for secure
connections.
TTP
Client A Client B

6. DEIOC
Wireless
There are two standards
802.11 802.16
 Wi-Fi  MAN
 Authentication  Authentication
– Open Key – Open Key
– Shared Key – Shared Key
 Encryption  Encryption
– RC4 – RSA
– TripleDES

7. DEIOC
Connections
 Client connect with the TTP for the first time
 Client connect with a different Client

8. DEIOC
Client connect with the TTP
Client TTP
Given a password (on a paper)
Agree on secret key by Diffie-Hellman key agreement
Send given password (encrypted with secret key)
Send new password (encrypted with secret key)

9. DEIOC
Client connect with a different Client
Client A Agree on Connection Client B
TTP
Get keys from the TTP encrypted with
Shared Secret key
Send data encrypted with the keys
provided by the TTP

10. DEIOC
Encryption methods
 Diffie-Hellman
key agreement
 Lamport Scheme
 RSA
 RC4
 TripleDES

11. DEIOC
Diffie-Hellman key agreement
A B
A and B agree on: P (prime) and G (1 > g > p)
Gen X (0 > x > p-1) Gx
Gen Y (0 > x > p-1)
Gy
A and B can both Compute Gxy
Gxy is the Shared secret Key

12. DEIOC
Lamport scheme
 Shared secret key
 40-bits key
Shared Secret Key
One way function New Shared Secret Key
Key (40 bits)

13. DEIOC
RSA
• 2 large primes P and Q
• Compute N = P * Q and F = (P-1)(Q-1) • N modules
• Select Random: E, 1 < E < F ( gcd(E,F)=1 ) • E Encryption exponent
• Select Unique: D, 1 < D < F ( E * D = 1 (mod F) • D Decryption Exponent
A B
Send N, E
C = ME mod N
M = CD mod N

14. DEIOC
RC4
A B
Shared secret Key
Encrypt Plain Text
with Secret Key Cipher Text
Decrypt Cipher text
with Secret Key
• RC4 uses a variable length key from 1 to 256 bytes
• The stream cipher uses swap and modulate operations to encrypt

15. DEIOC
DES
A B
Shared secret Key
Cipher Text
Encryption
L0 L1 L16
Input output
IP FP
R0 L0 + F(R0,key1) L15 + F(R15,key16)
 Decryption is simply the inverse of encryption, following the same steps
as above, but reversing the order in which the subkeys are applied.
 Blocksize is 64 bits

16. DEIOC
TripleDES
 Triple-DES is just DES with two 48-bit key array’s
applied in 3 rounds
Encryption
Encrypt (key 1) Decrypt (key 2) Encrypt (key 1)
Decryption
Decrypt (key 1) Encrypt (key 2) Decrypt (key 1)

17. DEIOC
Conclusion
 Encryption methods are not secure
– Methods are insecure
– Errors by programming
 Standards
– RC4
– RSA
– TripleDES