802.11 Network Security Architecture

1. 802.11 Network Security Architecture Security Fundamentals Encryption Protocols Robust Security

2. Main Idea • The main function of Wi-Fi is to act as a portal to access the network infrastructure. • Network Administration spend considerable effort and resources to have a secure infrastructure • However, if the wireless AP is left open to access, then it becomes a security risk for the whole network

3. What to secure • Only authorized users should pass thru the wireless portal. • Only authenticated users should access network resources and services • Consequently, they need to be validated and authenticated to access the wireless network. • Afterward, the users might have to validate their network identity and rights with a directory system. • Monitoring of client activities can be enforced with a Wireless Intrusion Detection System WIDS. • Policies are implemented and enforced by the directory system. (This is regardless of wireless access)

4. The 5 Components of Wi-Fi Security

5. IEEE 802.11 Security • There are five (5) components to Wi-Fi Security: • Privacy of the data (encryption or ciphering) • Authentication, Authorization, and Accounting • Segmentation • Monitoring • Policing

6. Components of Wi-Fi Security Privacy

7. Privacy • Frames available in open space are susceptible to be listened to. • Frame payloads need to be ciphered. • Cipher algorithms are used to encrypt the data • 802.11 Management Frames are not ciphered • 802.11 Control Frames are not ciphered • 802.11 User Frames Payload should be ciphered

8. Privacy • A Cipher is an algorithm used to encrypt the data • Two major algorithms are: • RC4 • Ron’s Coder or Rivest’s Cipher • Stream Cipher • Systems such as WEP and TKIP use Rivest • AES Advanced Encryption Standard • Rijndael Coder • Block Cipher (128,192, 256 bits) • CCMP uses Rijndael

9. Ciphering protocols WEP

10. Wireless Encryption Privacy • WEP no longer has a value as a protection mechanism. • WEP is only used as a historical reference in the development of ciphering systems. • However, its basic knowledge help to understand how security protocols should or should not be designed.

11. Wireless Encryption Privacy Summary: • WEP is a stream cipher • The cipher algorithm is based on RC4 (Ron’s code or Rivest Cipher) • WEP was meant to provide: • Confidentiality • Access Control • Data Integrity • WEP is no longer considered secure enough

12. Wireless Encryption Privacy • WEP Confidentiality: • Data is ciphered in streams based on a secret, shared key • Access Control • Data Integrity • WEP Access Control: • It is used in authentication (verification of user identity and credentials) to grant authorization (access to network resources and services)

13. Wireless Encryption Privacy • WEP Data Integrity: • An Integrity Check Value is calculated on the data before encryption and used to prevent data from being altered

14. WEP Confidentiality Confidentiality • Stream Cipher RC4 • RC4 generates a pseudorandom stream of bits called the keystream • The cipher creates the keystream by doing permutations • The permutation is initialized with a key • This stream is combined with the plaintext using an x-or operation

15. WEP Confidentiality and Integrity Integrity • Integrity Check Value CRC-32 checksum is added to the cipher text • x32 + x26 + x23 + x22 + x16 + x12 + x11 + x10 + x8 + x7 + x5 + x4 + x2 + x + 1

16. WEP Structure • A word of 64 bits = 40 bit key + 24 bit Initialization Vector IV • A word of 128 bits = 104 bits + 24 IV • The IV is chosen by the wireless NIC card out of 224 = 16,777,216 combinations • The IV is sent in clear-text and it changes in every frame

17. The Problem with WEP • The single secret key is a word of 40-bit which is shared among the Access Point and all wireless clients. • Additionally there is an Initialization Vector IV 24-bit long intended to be a unique (part of the) key per packet. • The two pieces are XOR combined to form a unique RC4 key stream. • This RC4 key stream is used for ciphering and deciphering

18. The Problem with WEP • Both the sender and receiver must have the same RC4 secret key • The secret component is manually entered in all the participant devices • But the IV must be exchanged somehow. • The IV is exchanged in plain text

19. WEP Cipher Diagram Block

20. Cracking WEP • Cracking WEP keys has become so popular (it is a hobby) that the system is not even taken seriously anymore. • It has been conclusively proven that: • By sniffing (Tool Aircrack-ng) long enough • Having the software to crack it • The key can be obtained

21. Breaking WEP • There are two well known effective attacks on WEP: • Collision: • FMS attacks:

22. Breaking WEP • Collision Attacks: • IV are used to change the value of every key stream, producing a unique key stream for every cipher text packet sent. • Since the IV is 24-bits long there are 224 = 16,777,216 unique IV possibilities. • It is a matter of capturing traffic long enough to start getting repeated IV numbers • If two packets, that have the same IV, are XORed, then the clear text is returned • It is a matter of running all the cipher text against each other

23. Breaking WEP • Flurer, Mantin, Shamir FMS Attacks: • Some IV are weaker values than others • The first byte of the IV is used to estimate a key • The key is tested on cipher text repeatedly • Tools such as AirCrack and AirSnort use FMS

24. IEEE 802.11i Stronger Security for Wi-Fi

25. Summary of Encryption Methods BLOCK CIPHERS STREAM CIPHERS Cipher takes bit by bit for processing. Weaker, but cheaper to implement. Example algorithm: Rivest Code Example cipher system: RC4 Example cipher system: TKIP • Cipher takes blocks of bits for processing. • Stronger, better system. • Example algorithm: Rijndael. • Example cipher system: AES • Example cipher system: CCMP (derived from AES)

26. Summary of Encryption Methods • Rivest Cipher RC4 • Advanced Encryption System AES • Temporal Key Integrity Protocol TKIP • Counter Cipher Modewith Block Chaining Message Authentication Code Protocol CCMP

27. RC4 • Rivest Cipher RC4 • Stream Cipher • Weaker system

28. TKIP • Temporal Key Integrity Protocol TKIP • TKIP is based on RC4 cipher • TKIP has stronger mixing properties (confusion, replacement and diffusion)

29. AES • Advanced Encryption System AES • AES is based on a Block Cipher • The Algorithm is Rijndael • Provides stronger security than RC4 • CCMP is a derivation of this system

30. Advanced Encryption Standard (AES): • AES successor to DES as for December 2001 • AES uses an SKC scheme called Rijndael, a block cipher designed by Belgian cryptographers Joan Daemen and Vincent Rijmen. • The algorithm can use a variable block length and key length; the latest specification allowed any combination of keys lengths of 128, 192, or 256 bits and blocks of length 128 bits

31. CCMP • Counter Mode with Cipher Block Chaining Authentication Code Protocol • It uses AES-Rijndael algorithm • Keys of 128 bits and blocks of 128 bits • It is the default encryption method for 802.11i

32. Wireless Protected Access WPA

33. Wi-Fi Protected Access WPA • WPA was designed to address the problems presented by WEP • Characteristics: • Per packet key mixing • Message integrity check MIC or Michael • Extended IV with rules for reusing • Re-keying so same key is not used for a long time • Two deployment modes: • Personal (use of pre-shared key) • Enterprise (mutual authentication with RADIUS or any other Authentication Server)

34. Wi-Fi Protected Access WPA2 • Standard IEEE 802.11iincludes WPA2 for wireless security • WPA uses Temporal Key Integrity Protocol TKIP • but WPA2 uses a stronger form of encryption the Advanced Encryption Standard AES • Wi-Fi Alliance certifies Wi-Fi Products with respect WPA2 • Counter Mode with Cipher Block Chaining Message CCMP

35. 802.11 SECURITY AUTHENTICATION PROCESS

36. Authentication in Wireless • Authentication to get connected to the Access Point AP is not the same as Authentication to the resources in the network.

37. Open System Authentication • Basically, it connects the station client to the access point without any need for client identity or profile validation. • The AP can provide “Authentication to the Network Infrastructure” if it is configured to do so.

38. Shared Key Authentication • Uses a symmetric key to authenticate client stations. • Requires that the same static key be configured on both the station and the access point. • Both sides must run the same ciphering algorithm

39. Authentication by Shared Key Station Authentication (Key indicator enabled) Frame ACK Frame Challenge 128 bytes of clear text ACK Frame AP Challenge is sent back encrypted by Key AP deciphers and compares ACK Frame Authentication Response ACK Frame

40. Frame AUTHENTICATION STA should Authenticate with Shared Key with the AP IEEE 802.11 wireless LAN management frame Fixed parameters (6 bytes) Authentication Algorithm: Shared key (1) Authentication SEQ: 0x0002 Status code: Successful (0x0000) Tagged parameters (138 bytes) Challenge text Tag Number: 16 (Challenge text) Tag length: 128 Tag interpretation: Challenge text: C73FFDB3646E8AA9B62698C212926AAD6BA1F1718D69B0C0... Vendor Specific: Broadcom Tag Number: 221 (Vendor Specific) Tag length: 6 Vendor: Broadcom Tag interpretation: Not interpreted The AP challenges the Client to resolve the crypto-message The client would resolve the crypto-challenge if it has the same shared key and the algorithm Otherwise, it can not continue with the authentication

41. Authentication • The client station sends an Authentication Request Message to the Access Point. Request AP

42. Authentication • The AP replies with a Challenge Message Challenge AP

43. Authentication • The client station sends the Challenge encrypted with the WEP key Request AP

44. Authentication • The AP attempts to decrypt the ciphertext with its own WEP key • If the result matched the Challenge, then that means that the cipher was created with the same exact WEP key by the client (the client knows the right key) • A message of authentication accepted or denied is send to client Authentication Accepted or rejected AP

45. Components of Wi-Fi Security segmentation

46. Segmentation • Wireless Communications, in general, is assumed to be on the untrusted side of a network firewall • Clients must be restricted as to what resources they can access • This is done in different methods: • VLAN assignments • VPN • Firewall • RBAC Role Based Access Control

47. Components of Wi-Fi Security segmentation

48. 802.11x • Framework defines the roles and actions of the different entities (supplicant, authenticator and server) and how they work together. • A protocol is needed to carry on the conversation between the entities. • There are several protocols to accomplish just that:

49. 802.11x • A protocol is needed to carry on the conversation between the entities. • There are several protocols to accomplish just that: • EAP Extensible Authentication Protocol • PEAP Protected EAP • EAP with TLS Transport Layer Security • LEAP Cisco proprietary Light EAP • EAP-TTLS proprietary by Funk Software

50. Amendment 802.11i - 2004 • This revision to the standard 802.11 defines a Robust Security Network RSN. • This is to ensure that wireless access can be as secure as any other type of access. • Security related documents typically are put together as an umbrella or suite of actions, protocols, definitions and policies.