1. Meeting Reports  A new delegation-based authentication protocol for use in portable communication systems IEEE Transactions on Wireless Communications, Volume 4, Issue 1, Jan. 2005 Page(s):57 – 64 Wei-Bin Lee; Chang-Kuo Yeh 95/12/13 H.H. Ou

2. A new delegation-based authentication protocol for use in portable communication systems 95/12/13Meeting Reports by H.H. Ou2 Paper Goals  Portable Communication Systems (PCSs) Wireless Secrecy, Authenticity, Integrity, Nonrepudiation  RSA have above characteristics but.. Complicated Periodical changing Public-Key  Author ’ s Methods User identity privacy Nonrepudiation Mutual authentication Efficient key management

3. A new delegation-based authentication protocol for use in portable communication systems 95/12/13Meeting Reports by H.H. Ou3 Main Concepts (1/2)  GSM Original GSM  Advantages Secret-key system Long-term secret key  Drawbacks No nonrepudiation Identity privacy can not keep No security protection between VLR and HLR MS can not authenticate VLR Public-Key system GSM Protocols  Advantages Nonrepudiation Mutual authentication  Drawbacks Complex computation MS must retrieve CRL Public-key of MS should be updated periodically Real identity of MS is revealed because the public key is necessary for verification

4. A new delegation-based authentication protocol for use in portable communication systems 95/12/13Meeting Reports by H.H. Ou4 Main Concepts (2/2)  Delegation Proxy signature

5. A new delegation-based authentication protocol for use in portable communication systems 95/12/13Meeting Reports by H.H. Ou5 Author ’ s Protocol (On-line authentication process) x: private key of HLR v: public key of HLR k: random by HLR K: g k mod p, pseudonym of MS σ: x+kK, secret key shared by MS, HLR t, n1, n2, m1: random number C1: session key used by VLR, MS l: prepared for VLR to verify MS for offline VLR verify MS generate session key MS verify VLR Prevent replay ?

6. A new delegation-based authentication protocol for use in portable communication systems 95/12/13Meeting Reports by H.H. Ou6 Author ’ s Protocol (Off-line authentication process)

7. A new delegation-based authentication protocol for use in portable communication systems 95/12/13Meeting Reports by H.H. Ou7 Comments MSTSMS HomeTS Home n2, ID TS r M, s M, K, n1, ID MH check s M Calculate r T, s T n1, n2, n3, K, ID TS, TD TH, r T, s T n4 check s T Calculate C1, l Calculate r M, s M [n3, n4, n5, ID TS, C1, l]K MTH, n5, ID MH Check n5 (TS, MS Home) [[n3, C1, l]β, n5]K MTH [n3, C1, l]β, [n1, m1] σ [n1, m1] σ Check n5 (TS Home) check n3 Store l Check n1 Calculate C1