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A Secure Email System Based on Fingerprint Authentication Scheme

Author： Zhe Wu,Jie Tian,Liang Li, Cai-ping Jiang,Xin Yang

Prestented by Chia Jui Hsu Date： 2008-03-04

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Outline

• Introduction

• Fingerprint Authentication Scheme

• Implementation

• Manipulation

• Security Analysis

• Conclusion

• References

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Introduction

• Inherent shortcoming and flaw of PKI– Certificates are not easily located– There need strict online requirement– Validating policy is time-consuming and

difficult to administer– Certificates leak data and users must pre-

enroll

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• Inherent shortcoming and flaw of IBE– It is difficult in prove self-identity to Trust

Authority (TA) and authenticate email sender’s identity.

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• This paper proposes a new secure email system based on a fingerprint authentication scheme which combines fingerprint authentication technology with IBE scheme.

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Fingerprint Authentication Scheme

• Setup

• Encryption

• Decryption

• Verification

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Setup

• TA initializes a secure area• Constructs a supersingular elliptic curve s

atisfying Weil Diffie-Hellman (WDH)

• TA chooses three secrets s,u,v

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Encryption

• Step1– Usb-keyA authenticates A

• Step2– Usb-keyA generates A’s signature FPSA

• Step3– Obtains authentication data AUTHA

• Step4– CIPH1 = EncAB+Hash(EncAB)+AUTHA+r P‧

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Decryption

• When receiving the email from A, B computes the session key KAB with his private KAB of identifier and uses KAB to decrypt EncAB to get M.

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Verification

• When B wants to verify A's identity, TA provides online identity authentication service.

• Receiving AUTHA sent from B, TA first encrypts it and obtains A's onsite fingerprint summary bA , then verifies the signature FPSA by verification function Ver .

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• If Ver is true, TA matches bA with the registered fingerprint summary bA stored in database by function FPM . TA returns the matching result to B after encryption and signature. Finally, B verifies A's identity.

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Implementation

• TA

• Email-client

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TA

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User registration

• Step1– generate bA

• Step2– TA enrolls A’s identifier： IDA

• Step3– TA computes A’s fingerprint certificate CA

• Step4– TA computes A’s QFP-A and DFP-A

• Step5– TA writes the public params { P,PT-pub, Ppub

Ponline, H, H1, H2, Sig } and A's personal params { DFP-

A,,CA, RA, bA } into Usb-keyA, and handsover into A.

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Usb-key

• We integrate fingerprint sensor and USB token into one device called Usb-key. The Usb-key is able to capture and process fingerprint image. There is an independent time

• Besides, it also contains fingerprint summary matching algorithm and Identity-Based Signature algorithm (Sig and Ver ), and be able to be protected against duplication of private key of fingerprint.

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Online Secret-key distribution

• Step1(B→TA)– CIPH2=Cpri+Hash(Cpri)+c． P

• Step2– Use Ver and FPM to authenticate B’s identity

• Step3(TA→B)– CIPH3=Cback+Hash(Cback)

• Step4– B obtains his private key of identifier from TA

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Online Identity authentication

• B sends A's authentication data to TA. TA authenticates A's identity and returns matching result to B.

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Online Identifier update

• Assume B wants to update his identifier, he could apply to TA online for relevant service.

• B computes Cpri which also contains B's new string. Then B sends CIPH2 to TA. After authenticating B's identity, TA provides update service requested by B.

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• TA recomputes B's identifier and fingerprint certificate, encrypts them with the session key and obtains Cupdate, then returns CIPH4 to B where

CIPH4= Cupdate +Hash(Cupdate)

• B takes new idetifier and figerprint certificate instead of in Usb-keyB

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Email-client

• Local login authentication

• Encryption and decryption

• Intercommunication with Usb-key

• Intercommunication with TA

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Intercommunication with TA

• Private key of identifier distribution

• Email sender’s identity authentication

• Identifier update

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Manipulation

• Step1

• Step2

• Step3

• Step4

• Step5

• Step6

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Security Analysis

• C pretends B to ask TA for B’s private key of identifier

• Cpretends A to send an email to B

• B pretends A to send email to other users like D or TA

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C pretends B to ask TA for B’s private key of identifier

user C

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C pretends A to send an email to B

user C

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B pretends A to send email to other users like D or TA

user C

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Conclusion

• In the system, we user Usb-key to keep secret data and help completing relevant encryption process. Usb-key can only be used by its legitimate owner. Thus the system successfully combines cryptographic key with legitimate users.

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References

• http://ieeexplore.ieee.org/xpl/RecentCon.jsp?punumber=4258655

• http://zh.wikipedia.org/wiki/Wiki