Authentication and Key Agreement Schemes for Network Applications 在電腦網路應用環境中的身份認證與金鑰協議技術之研究

1. Authentication and Key Agreement Schemes for Network Applications在電腦網路應用環境中的身份認證與金鑰協議技術之研究 Advisor: Dr. Chin-Chen Chang Student: Hao-Chuan Tsai Date: 12.30.2010 Department of Computer Science and Information Engineering, National Chung Cheng University

2. Outline • Part I: Authentication Scheme with Key Agreement • three party authenticated key agreement • Part II: Anonymous Authentication Scheme for Wireless Networks

3. Part I: Authentication Scheme with Key Agreement

4. User Authentication • Goal: • Convince system of your identity before it can act on your behalf • Methods • Who you are • What you know • What you have

5. 1.025cm 1.923cm 5.39cm 8.56cm User Authentication (cont.) • What you have • Verify identity based on possession of some object • Magnetic Card • Smart Card (IC Card)

6. User Authentication (cont.) • Who you are • verify identity based on your physical characteristics or involuntary response patterns known as biometrics • characteristics used include: • signature (usually dynamic) • fingerprint • hand geometry • face or body profile • speech • retina pattern • always have tradeoff between false rejection and false acceptance

7. User Authentication (cont.) • What you know • Birthday, School name, Blood type, or Salary ? • Meaningful Secrets ? • Meaningless Secrets (Passwords) ! • Traditional Password Mechanism • Procedure: • 1. Prompt user for a login name and password • 2. Verify identity by checking that password is correct • Passwords in the System: • May be stored in clear mode • May be stored in cipher mode: Encrypted or One-Way Hashed • Passwords should be selected with care to reduce risk of exhaustive search • One problem with traditional passwords is caused by eavesdropping their transfer over an insecure network

8. User Authentication (cont.) • Password Practice • Password Complexity Criteria • At least 7 characters long. • Does not contain your User Name, Real Name, or Company Name. • Does not contain a complete dictionary word. • Is significantly different from previous passwords. • Contains characters from each of the following groups: • uppercase letters • lowercase letters • numerals • symbols found on the keyboard.

9. Key Establishment • Create Session Keys • Key transport • A session key is selected by one communication party and is distributed to others in some way • Key agreement • A session key is established by the cooperating of all communication parties

10. Three-Party Authenticated Key Agreement (3PAKA) Drawbacks of 2PAKA • Given N parties • there are N(N-1)/2 (=nC2) secret keys that should be established • each party should securely store N-1 secret keys • Awkward for larger-scale networks • Inflexible (difficult to add, update, or delete a party) • Example • If N = 6, then there are 6(6-1)/2 = 15 secret keys should be established in advance.

11. Three-Party Authenticated Key Agreement (3PAKA) (cont.) • An authenticated key agreement protocol is an interactive method for two or more parties to determine session keys based on their secret keys or public/private keys. Trusted server Authentication Authentication Key agreement / key exchange SK Secure communication

12. Typical 3PAKA

13. Weaknesses of Typical 3PAKA • Impersonation attacks • Impersonate clients or the server • Man-in-the-middle attacks • On-line password guessing attacks • Off-line password guessing attacks • The most powerful attack

14. The Proposed 3PAKA (1/4) • The server needs to authenticate the communication clients explicitly • The established session key would not revealed to either the server or others • Round efficiency

15. The Proposed 3PAKA (2/4) • Initial phase • The server computes • And then the server computes • Server also finds a value rc to satisfy the equation and computes

16. The Proposed 3PAKA (3/4) 2. S 1. A B

17. compute compute The Proposed 3PAKA (4/4) S 3 retrieve derive 4 A B

18. Part I I : Anonymous Authentication Scheme for Wireless Networks

19. Roaming path Scenario

20. Architecture • Multiple regional domain • Each domain is operated under a different administration • HLR (Home Location Register) • HLR is used to denote the home domain, the home domain server, and the home location register, concurrently. • A subscriber has only one home as his administrative domain • One who desiring to contact MS must consult his HLR. • VLR (Visiting Location Register) • VLR is used to denote the visiting domain, the visiting domain server, and the visiting location register, concurrently. • When a subscriber roams into a visited domain, he should initially establish a residence within that domain.

21. VLR needs to ensure that MS is currently in good status. VLR HLR MS IMSI IMSI, VLR Computes: SRES1 = A3(Ki, RAND1), Kc1 = A8(Ki, RAND1) SRES2 = A3(Ki, RAND2), Kc2 = A8(Ki, RAND2) … SRESn = A3(Ki, RANDn), Kcn = A8(Ki, RANDn) IMSI, (RAND1, SRES1, Kc1), (RAND2, SRES2, Kc2), …, (RANDn , SRESn, Kcn). RAND1 (Unspecified Secure Channel) Multiple on-the-fly triplets should be on-line generated and transferred in batch to the VLR. Then, VLR can use them in successive authentication flows with the roaming MS. Computes: (inside SIM) SRES1 = A3(Ki, RAND1) Kc1 = A8(Ki, RAND1) SRES1 Computes: enc_with_ A5(Kc1, TMSI) enc_with_ A5(Kc1, TMSI) Decrypts: enc_with_ A5(Kc1, TMSI) MS establishes a temporary residence in the visited domain.

22. VLR MS TMSI RANDm Computes: (inside SIM) SRESm = A3(Ki, RANDm) Kcm = A8(Ki, RANDm) SRESm enc_with_A5(Kcm, messages) VLR MS TMSI, RANDm Computes: (inside SIM) SRESm= A3(Ki, RANDm) Kcm = A8(Ki, RANDm) SRESm enc_with_A5(Kcm, messages) When MS makes a call, the origination protocol is then invoked to authenticate himself to VLR and establish a session key.

23. Authentication in Wireless Mobile Networks (cont.)

24. Authentication in Wireless Mobile Networks

25. Authentication in Wireless Mobile Networks (cont.)

26. Authentication in Wireless Mobile Networks (cont.) • The main problems we suffer • Impersonation Attack • Attackers can impersonate either MS or FA to obtain secret information • Personal Privacy Problem • The identity of MS can be revealed to others

27. Authentication in Wireless Mobile Networks (cont.) • The proposed scheme has the following characteristics • Provide mutual authentication • A mobile client and the communicating entities can be authentic • An established session key would not revealed to either the uninvolved servers or others • Diverting the most complicated operations to either the HLR or VLR • The risk of compromising the secret information stored on HLR is reduced • Ensure anonymity

28. Authentication in Wireless Mobile Networks (cont.) • Initial phase • Sh chooses a long-term private key xsh. ( YSh=xshG) • Sh generates a unique master secret for an MS, where • Sh also generates the self-verified items • Eventually, Sh computes as the master delegation key

29. Authentication in Wireless Mobile Networks (cont.) • It is worth noting that, if the secrets are generated by the home network for which the public key is YSh, an MS can verify the secrets successfully since

30. Authentication in Wireless Mobile Networks (cont.)

31. Security Requirements

32. Performance Comparisons

33. Future works • Cloud Computing

34. Thanks for your attention