1. A flexible biometrics remote user authentication scheme Authors: Chu-Hsing Lin and Yi-Yi Lai Sources: Computer Standards & Interfaces, 27(1), pp.19-23, 2004. Adviser: Min-Shiang Hwang Speaker: Chun-Ta Li ( 李俊達 )

2. 2 Outline IntroductionIntroduction The Lee-Ryu-Yoo schemeThe Lee-Ryu-Yoo scheme Cryptanalysis of the Lee-Ryu-Yoo schemeCryptanalysis of the Lee-Ryu-Yoo scheme The proposed schemeThe proposed scheme ConclusionsConclusions CommentsComments

3. 3 Introduction Remote password authentication – [Lamport, 1981]Remote password authentication – [Lamport, 1981] –Insecure channel –User authentication (identity & password) Remote password authentication scheme using smart cards – [Hwang and Li, 2000]Remote password authentication scheme using smart cards – [Hwang and Li, 2000] –Based on ElGamal’s cryptosystem –Only one secret key without password table

4. 4 Introduction (cont.) Biometrics remote user authentication scheme using smart cards – [Lee et al., 2002]Biometrics remote user authentication scheme using smart cards – [Lee et al., 2002] –Based on ElGamal’s cryptosystem (two secret keys) –Smart card owner’s fingerprint Minutiae extraction – [Bae et al., 2000]Minutiae extraction – [Bae et al., 2000] Matching – [Ratha et al., 1996]Matching – [Ratha et al., 1996] Lin and Lai point out their scheme is vulnerable to masquerade attackLin and Lai point out their scheme is vulnerable to masquerade attack Lin and Lai propose a flexible scheme (change password)Lin and Lai propose a flexible scheme (change password)

5. 5 The Lee-Ryu-Yoo scheme Three phases in the Lee-Ryu-Yoo schemeThree phases in the Lee-Ryu-Yoo scheme –Registration phase (U i offers ID i and fingerprint of U i ) –Login phase (U i inserts smart card and offers ID i, PW i and fingerprint of U i ) – fingerprint verification [Jain et al. 1999] 1.Generate r using minutiae extracted from the imprint fingerprint 2.Compute C 1 = (ID i ) r mod P 3.Compute t = f(T ⊕ PW i ) mod (P-1) 4.Compute M = (ID i ) t mod P 5.Compute C 2 = M(PW i ) r mod P 6.Send the message C = (ID i, C 1, C 2, T) to the remote system Smart card: Smart card: f(.), P and U i ’s fingerprint data Secure channel

6. 6 The Lee-Ryu-Yoo scheme (cont.) –Authentication phase 1.The system check the validity of ID i 2.If (T` ﹣ T) ＞ △ T, rejects the login request 3.The system check the validity of equation as follows: C 2 (C 1 SK2 ) -1 mod P = (ID i ) SK1*f(T ⊕ PW i ) C 2 (C 1 SK2 ) -1 mod P = (ID i ) SK1*f(T ⊕ PW i ) = M(PW i ) r * (1/(ID i r ) SK2 ) mod P = M(PW i ) r * (1/(ID i r ) SK2 ) mod P = (ID i ) t (ID i ) SK2*r * (1/ID i r*SK1*SK2 ) mod P = (ID i ) t (ID i ) SK2*r * (1/ID i r*SK1*SK2 ) mod P = (ID i ) SK1*f(T ⊕ PW i ) * ID i SK1*SK2*r / ID i r*SK1*SK2 mod P = (ID i ) SK1*f(T ⊕ PW i ) * ID i SK1*SK2*r / ID i r*SK1*SK2 mod P ?

7. 7 Cryptanalysis of the Lee-Ryu-Yoo scheme A legal user U i (owns a pair of ID i and PW i )A legal user U i (owns a pair of ID i and PW i ) U i wants to masquerade another pair of valid (ID d, PW d ) without knowing the two secret keys SK1 and Sk2U i wants to masquerade another pair of valid (ID d, PW d ) without knowing the two secret keys SK1 and Sk2 –U i computes ID d = ID i q mod P –U i computes PW d = (ID d ) SK1*SK2 mod P = (ID i q mod P) SK1*SK2 mod P = (ID i q mod P) SK1*SK2 mod P = (ID i q ) SK1*SK2 mod P = (ID i q ) SK1*SK2 mod P = (ID i SK1*SK2 mod P) q mod P = (ID i SK1*SK2 mod P) q mod P = (PW i ) q mod P = (PW i ) q mod P

8. 8 The proposed scheme Three phases in Lin-Lai schemeThree phases in Lin-Lai scheme –Registration phase (U i offers ID i, PW i and fingerprint of U i ) 1.Compute PW i ` = h(PW i ⊕ S i ), where S i denotes U i ’s minutiae template 2.Compute Y i = (ID i Xs mod P) ⊕ PW i `, where Xs denotes the secret key kept securely in the system −Login phase (U i inserts smart card, imprint the fingerprint and offers PW i ) – fingerprint verification [Jain et al. 1999] Smart card Smart card: h(.), P, Y i, S i and ID i

9. 9 The proposed scheme (cont.) –Login phase 1.Generate r using minutiae extracted from the imprint fingerprint 2.Compute PW i ” = h(PW i ⊕ S i ) mod P 3.Compute Y i ` = Y i ⊕ PW i ” 4.Compute C 1 = (ID i ) r mod P 5.Compute M = h(Y i ` ⊕ T) mod P 6.Compute C 2 = M(Y i `) r mod P 7.Send the message C = (ID i, C 1, C 2, T) to the remote system

10. 10 The proposed scheme (cont.) –Authentication phase 1.The system check the validity of ID i 2.If (T` ﹣ T) ＞ △ T, rejects the login request 3.The system check the validity of equation as follows: C 2 (C 1 Xs ) -1 mod P = h((ID i Xs mod P) ⊕ T) mod P C 2 (C 1 Xs ) -1 mod P = h((ID i Xs mod P) ⊕ T) mod P ? h(Y i ⊕ h(PW i ⊕ S i ) ⊕ T)*(Y i ⊕ h(PW i ⊕ S i )) r * (1/(ID i ) rXs ) mod P = h(Y i ⊕ h(PW i ⊕ S i ) ⊕ T)*(Y i ⊕ h(PW i ⊕ S i )) r * (1/(ID i ) rXs ) mod P h(((ID i Xs mod P) ⊕ h(PW i ⊕ S i )) ⊕ h(PW i ⊕ S i ) ⊕ T)*(((ID i Xs mod P) ⊕ h(PW i ⊕ S i )) ⊕ h(PW i ⊕ S i )) r /(ID i ) rXs mod P = h(((ID i Xs mod P) ⊕ h(PW i ⊕ S i )) ⊕ h(PW i ⊕ S i ) ⊕ T)*(((ID i Xs mod P) ⊕ h(PW i ⊕ S i )) ⊕ h(PW i ⊕ S i )) r /(ID i ) rXs mod P

11. 11 The proposed scheme (cont.) –Change password (U i imprint his fingerprint, pass fingerprint verification, inputs old password PW i and the new password PW i *) 1.Compute PW i ” = h(PW i ⊕ S i ) mod P 2.Compute Y i ` = Y i ⊕ PW i ” = ID i Xs mod P 3.Compute new Y i * = Y i ` ⊕ h(PW i * ⊕ S i ) 4.Replace the old Y i with the new Y i * on the smart card

12. 12 Conclusions Presented a cryptanalysis of the Lee-Ryu- Yoo schemePresented a cryptanalysis of the Lee-Ryu- Yoo scheme Proposed an improved and flexible scheme that allows user to change their passwordProposed an improved and flexible scheme that allows user to change their password Needs only to maintain one secret key, without password tables and identity tablesNeeds only to maintain one secret key, without password tables and identity tables

13. 13 Comments Biometric keyBiometric key password-based authentication fingerprint-based authentication

14. 14 Comments (cont.) Biometric-based security applicationsBiometric-based security applications Biometric characteristics Network environments Information security Key authentication Key authentication Conference key Conference key Key hierarchy Key hierarchy E-Voting E-Voting … Internet Internet Distributed network Distributed network Mobile network Mobile network …