Wired Equivalent Privacy (WEP)

1. Wired Equivalent Privacy (WEP) Presented By Kavitha Devireddy Sapna Shankar

2. Agenda • Introduction -Kavitha • WEP • WEP Encryption • WEP Decryption • Problems with WEP • Various attacks on WEP -Sapna • Solutions for improving security of Wireless LAN • Conclusion

3. Introduction • wireless network connectivity is becoming very important part of computing environments. • Currently popular wireless network standard is 802.11, in this standard data is transmitted over radio waves. • In this transmissions interception and tampering becomes easy to anyone with a radio.

4. WEP • Wired Equivalent Privacy (WEP), a security protocol for wireless local area networks (WLANs) defined in the 802.11b standard. • LANs are more secure than WLANs. • WLANs, which are over radio waves are more vulnerable to tampering. • WEP provides security by encrypting data over radio waves. • WEP provides confidentiality and data integrity, and protects access to the network.

5. Plaintext Message CRC XOR Keystream=RC4(IV,k) Transmitted Data IVCiphertext WEP Encryption • WEP uses a 40bit length shared secret key. Fig: WEP Encryption frame

6. WEP Encryption Cont.. • First message data frame is checksummed, c(M). • plaintext(p) = message(M) + Checksum message(c(M)) • Keystream = RC4(IV, k). Here k is shared key. • ciphertext = plaintext XOR Keystream • The cipher text and the initialization vector (IV) are then transmitted via radio.

7. WEP Decryption • Decryption is reverse of encryption. • First receiver recreates the keystream, Keystream = RC4(IV, k). • Plaintext = Ciphertext XOR Keystream • This plain text is then divided into Message and checksum. • Checksum is then computed for the message and compared with the received checksum. • If (Original checksum != Computed checksum), then the message has been changed during transmission.

8. Problems with WEP • Key management: • WEP standard lacks good Key management that leads to poor quality. • IV reuse: • WEP's IV size is 24 bits. • WEP uses the same IV for different data packets. • An attacker can decrypt packets that were encrypted with the same IV. • Inappropriate Integrity check: • MD5 or SHA-1 algorithms are more suitable for cryptographic hash than CRC-32.

9. Various Attacks • passively attacking to decrypt traffic. • all wireless traffic can be intercepted by a passive intruder, until an IV collision occurs. • he can recover all the messages with same IV after recovering the entire plaintext for one of the messages. • actively attacking to inject traffic. • If the attacker knows plaintext of one encrypted message, he can change the plaintext to the new message by calculating CRC-32 and doing bit flips on the original encrypted message. • If the attacker sends the new packet to the access point, it will be accepted.

10. Various Attacks cont.. • actively attacking from both ends. • If the attacker guesses the headers of a packet, which includes destination IP address, he can flip relevant bits to make the destination system to send the packet to his own system and transmit it using some mobile station. • attacking using table of appropriate initialization vectors. • Here the attacker can build table of IVs, if he knows the plaintext for some packets. • Once he builds this table, he can decrypt all packets that are sent over the wireless link.

11. Solutions for improving security of Wireless LAN’s • Multiple Security measures along with WEP. • Using VPN. • Using Efficient key management techniques as an additional measure. • Using alternative encryption techniques like IPsec instead of WEP.

12. New Standards for improving security of Wireless LAN’s • 802.1X • 802.11i

13. 802.1X : Framework for Authentication • 802.1x is an open standard framework for authenticating wireless stations. • Authenticates the wireless stations with an authentication server via an access point. • EAP(Extensible Authentication Protocol )is used for message exchange to manage mutual authentication. • Dynamic distribution of encryption keys.

14. 802.11i • Standard is a solution to current security problems of WLAN’s. • 802.11i has two sections • 802.1x section provides authentication and key management for stations. • The second section, 802.11i, defines two data privacy protocols. • Temporal Key Integrity Protocol(TKIP) • Counter Mode/CBC MAC Protocol(CCMP)

15. Temporal Key Integrity Protocol(TKIP) • It is data encryption algorithm,provided for backward compatibility with devices using WEP and it is optional to implement. • TKIP resolves the key reuse in WEP by providing 128 bit “temporal key” in a dynamic way for securing data. • It uses the same RC4 algorithm as WEP does and it is not considered as a long term solution.

16. Counter Mode/CBC-MAC Protocol • It is mandatory for all devices implementing 802.11i standard. • Is an encryption algorithm based on AES. • Counter Mode provides confidentiality, integrity and protection against replay attacks. • CBC-MAC(Cipher Block Chaining message authentication code) provides authentication.

17. Conclusion • WEP does little to secure the WLAN’s from attackers. • Better to use WEP rather than not using any encryption. • New standards and specifications which will replace WEP can be expected to provide sufficient security for wireless LAN’s.