1. WiMAX安全子層於嵌入式系統下之探討與實現
The research and implementation of WiMAX security subsystem over an embedded system
Advisor: Dr. Kai-Wei Ke
Speaker: Yen-Jen Chen
Date: /24/2008

2. Outline Introduction IEEE 802.16-2004 Security Sublayer Implementation
Overview of d Security
Overview of e Security
IEEE Security Sublayer Implementation
System Architecture
Subsystem design
System flow
System over embedded system
System test
Conclusion and Future Work
References

3. Outline Introduction IEEE 802.16-2004 Security Sublayer Implementation
Overview of d Security
Overview of e Security
IEEE Security Sublayer Implementation
System Architecture
Subsystem design
System flow
System over embedded system
System test
Conclusion and Future Work
References

4. MAC Privacy Sub-layer Provides secure communication
Data encrypted with cipher clock chaining mode of DES
Prevents theft of service
SSs authenticated by BS using key management protocol

5. IEEE 802.16 Security Architecture

6. IEEE Security Process

7. Authentication Key lifetime: 1 to 70 days , usually 7days
SS →BS: Cert(Manufacturer(SS))
SS →BS: Cert(SS) | Capabilities | SAID
BS →SS: RSA-Encrypt(PubKey(SS), AK) | Lifetime | SeqNo | SAIDList

8. Key Derivation KEK = Truncate-128(SHA1(((AK| 044) xor 5364)
Downlink HMAC key = SHA1((AK|044) xor 3A64)
Uplink HMAC key = SHA1((AK|044) xor 5C64)

9. Data Key Exchange

10. Data Encryption

11. IEEE 802.16 Security Process BS SS
認證資訊(authentication information) X.509 certificate
AK exchange
授權請求(authorization request) X.509 certificate, capability, Basic CID
1.確認SS身分
2.產生AK, 並用憑證中的public key將之加密
授權答覆(authorization reply) encrypted AK, SAIDs, SQNAK,…
將AK解開
密鑰請求(key request) SAID, HMAC-Digest,…
TEK exchange (每一個資料傳輸連線都必須先做此動作)
1.利用SHA演算法驗證HMAC-Digest
2.產生TEK
3.由AK產生KEK用以加密TEK
密鑰答覆(key reply) encrypted TEK, CBC IV, HMAC-Digest,…
1.利用SHA驗證HMAC-Digest
2.由AK計算出KEK以解開TEK
資料交換(利用TEK加密)
HMAC-Digest：用以驗證資料的完整性

12. Outline Introduction IEEE 802.16-2004 Security Sublayer Implementation
Overview of d Security
Overview of e Security
IEEE Security Sublayer Implementation
System Architecture
Subsystem design
System flow
System over embedded system
System test
Conclusion and Future Work
References

13. Security Architecture

14. WiMAX PKMv2 Protocol

15. EAP authentication protocol
EAP is a authentication framework not a specially authentication mechanism
the four methods in e
RSA based authentication
One level EAP based authentication
Two level EAP based authentication
RSA based authentication followed by EAP authentication

16. EAP authentication protocol
RSA based authentication
Use the PKMv2 RSA-Request、PKMv2 RSA-Reply、PKMv2 RSA-Reject、PKMv2 RSA-acknowledgement messages to get pre-PAK
Using the public key of SS to encrypt the pre-PAK and send back to SS
pre-PAK generates the PAK (Primary Authorization key) and EIK(EAP integrity Key)
PAK generates the AK

17. EAP authentication protocol (Cont.)
RSA based authentication
EIK|PAK <= Dot16KDF (pre-PAK,SS MAC address | BSID | ”EIK+PAK” , 320)
AK<= Dot16KDF (PAK,SS MAC address | BSID | PAK|”AK” , 160)

18. EAP authentication protocol (Cont.)
One level EAP based authentication
Using the authentication exchange message to get MSK (Master session key)
PMK<= truncate(MSK,160)
AK<=Dot16KDF(PMK,SS MAC Address | BSID | “AK”,160)

19. EAP authentication protocol (Cont.)
Two level EAP based authentication
SS sent the PKEv2 EAP Start to BS
The first EAP negotiation will begin between BS and SS included the message of PKMv2 Transfer2(MSK)
After that BS will send the EAP-Success or EAP-failure.
If BS sent the EAP-Success then BS will send the PKMv2_EAP_Complete encrypted by EIK immediate
If SS gets the EIK and PMK successful then SS can verify the message
Otherwise the SS might get the EAP-failure or get no respond to show that BS is failure to authentication

20. EAP authentication protocol (Cont.)
Two level EAP based authentication
After SS finished the first EAP negotiation successful ,the SS will send “PKMv2 Authenticated EAP Start” to start the second EAP negotiation
When BS got this message, BS will check the message by EIK.
If BS check ok then BS will start the second EAP negotiation, otherwise BS will think the Authenticated failure.
The related messages of PKM is protected by EIK in the second EAP negotiation
If BS and SS competed second EAP negotiation, then BS and SS can get the AK form PMK( pairwise authorization key) and PMK2

21. EAP authentication protocol (Cont.)
Two level EAP based authentication
EIK|PMK <= truncate (MSK,320)
PMK2 <= truncate(MSK,160)
AK <= Dot 16KDF(PMK + PMK2, SS MAC Address| BSID|” AK” , 160)

22. EAP authentication protocol (Cont.)
RSA based authentication followed by EAP authentication
First execute RSA-based authorization and execute the second round of Double EAP mode
EIK|PAK <= Dot16KDF(pre-PAK, SS MAC Address | BSID | “EIK+PAK”,320)
AK <= Dot16KDF(PAK⊕PMK, SS MAC Address| BSID |PAK “AK” 160)

23. Key hierarchy in the 802.16e TEK (Traffic Encryption Key)
TEK is generated by random number of BS
BS use the KEK to encrypt the TEK and send to SS
TEK is used to encrypt the message or data between BS and SS

24. Key hierarchy in the e

25. Key hierarchy in the e

26. Outline Introduction IEEE 802.16-2004 Security Sublayer Implementation
Overview of d Security
Overview of e Security
IEEE Security Sublayer Implementation
System Architecture
Subsystem design
System flow
System over embedded system
System test
Conclusion and Future Work
References

27. System Architecture

28. System Architecture Data Privacy subsystem Authentication subsystem
Get the data form different system
Verify the data if encrypt or decrypt
Dispatch the data to the subsystem
Authentication subsystem
Verify the certification
Add the relative information
Generate the AK (New one or Update old)
Key Management subsystem
Save the information of the key (TEK KEK HMAC etc.)
Use AK to Generate key (KEK HMAC)
Generate the TEK (New one or Update old)

29. Outline Introduction IEEE 802.16-2004 Security Sublayer Implementation
Overview of d Security
Overview of e Security
IEEE Security Sublayer Implementation
System Architecture
Subsystem design
System flow
System over embedded system
System test
Conclusion and Future Work
References

30. Subsystem design
Data Privacy Subsystem

31. Subsystem design
Authentication Subsystem

32. Subsystem design
Key management Subsystem

33. Outline Introduction IEEE 802.16-2004 Security Sublayer Implementation
Overview of d Security
Overview of e Security
IEEE Security Sublayer Implementation
System Architecture
Subsystem design
System flow
System over embedded system
System test
Conclusion and Future Work
References

34. System flow

35. System flow
Uplink Flow

36. System flow
Downlink Flow

37. Outline Introduction IEEE 802.16-2004 Security Sublayer Implementation
Overview of d Security
Overview of e Security
IEEE Security Sublayer Implementation
System Architecture
Subsystem design
System flow
System over embedded system
System test
Conclusion and Future Work
References

38. System over embedded system

39. System over embedded system
Central Controller Communication
Layered Communication

40. System over embedded system
Class Diagram

41. Outline Introduction IEEE 802.16-2004 Security Sublayer Implementation
Overview of d Security
Overview of e Security
IEEE Security Sublayer Implementation
System Architecture
Subsystem design
System flow
System over embedded system
System test
Conclusion and Future Work
References

42. System test

43. System test

44. System test
Note: 為SS端IP， 為BS端IP， 為relay node IP
Number 1047 and 1054，show that SS send the first cert to BS
Number 1060 and 1092，show that BS send the ACK to BS
Number 1259 and 1260，show that SS send the second cert to BS
Number 1454 and 1455，show that BS send the ACK to BS
Number 1998 and 1999，show that SS send the TEK-REQ to BS
Number 2458 and 2459，show that BS send the TEK to SS

45. Outline Introduction IEEE 802.16-2004 Security Sublayer Implementation
Overview of d Security
Overview of e Security
IEEE Security Sublayer Implementation
System Architecture
Subsystem design
System flow
System over embedded system
System test
Conclusion and Future Work
References

46. Conclusion and future work
The System success porting over embedded system
Provide the security sublayer module of d and part of e
Porting the CPS of MAC over embedded system
Add the authentication of e

47. Outline
Introduction
Overview of d Security
Overview of e Security
IEEE Security Sublayer Implementation System
System Architecture
Subsystem design
System flow
System over embedded system
System test
Conclusion and Future Work
References

48. References
IEEE Standard for Local and metropolitan area networks Part 16:Air Interface for Fixed Broadband Wireless Access Systems，IEEE Std
IEEE Standard for Local and metropolitan area networks Part 16:Air Interface for Fixed and Mobile Broadband Wireless Access Systems，IEEE Std e-2005
Johnson, David and Walker, Jesse of Intel (2004), “Overview of IEEE Security” ,published by the IEEE computer society
WiMAX 安全問題之研究 ,孫宏民、陳帥名、蕭英助 ,資通安全專論 T96006
IEEE e-2005 WiMAX安全子層初探, 邱錫彥;陳彥學;王瑞堂;劉家蓁, 電腦與通訊, 119期, 2007/03