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57th IETF WIEN, Austria, July 13-18, 2003 “EAP Secured Smartcard Channel”

This draft proposes the EAP-SSC protocol for secure messaging using smartcards. It introduces single EAP types, multiple sub-types, and symmetric or asymmetric key exchange procedures. The protocol supports session key exchange and validation, shared secret, common certification authority, and robust security mechanisms based on SHA-1 digest, 3DES, and AES.

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57th IETF WIEN, Austria, July 13-18, 2003 “EAP Secured Smartcard Channel”

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  1. 57th IETFWIEN, Austria, July 13-18, 2003“EAP Secured Smartcard Channel” Pascal Urien, Mesmin DANDJINOU ENST Pascal.Urien@enst.fr Draft-urien-EAP-SSC-00.txt

  2. EAP-SSC at a glance • Use of a single EAP type. • Introduction of multiple sub-types. • Symmetric or Asymmetric Key Exchange Procedures. • Two working phases: • Session Key (SK) Exchange & Validation • Shared Secret. • Common Certification Authority. • Secure Messaging. • Simple, but robust, security mechanisms, based on • SHA-1 digest • 3DES, AES • Secure messaging could be used to exchange messages with embedded repositories in smartcards.

  3. EAP-SSC Overview Smartcard Supplicant Authenticator RADIUS server Embedded Repository EAP EAP / 7816 EAP / LAN EAP / RADIUS ISO 7816 802.1x RADIUS SSC messages EAP Secured Smartcard Channel

  4. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Code | Identifier | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Sub-Type | Flags |Message Length +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Message Length (cont) | ..Payload .. | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Digest | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ EAP header EAP-SSC PDU L = Length of the message included M = More fragments S = Start E = End Flags 7 6 5 4 3 2 1 0 +-+-+-+-+-+-+-+-+ |L M S E D C X R| +-+-+-+-+-+-+-+-+ D = Digest(Code, Identifier, Length, Type, Sub-Type, Flags, Message Length, Payload, SK) C = Ciphered (Payload) X = Sequence of X.509 Certificate(s) R = Reserved EAP-SSC PDUs

  5. Key Production – Symmetric Case r2= 2nd random number r1=1st random number Session Key D=SHA-1 s=shared secret Sub-Type = 1, Start, r1 (20 bytes) SK = D(r1 | r2 | s) r2 (20 bytes) XOR D(r1 | s) SK = D(r1 | r2 | s ) M1, D1(M1 | SK) D1 = D(M1 | SK) D1 = D(M1 | SK) M2, D2(M2 |D1 | SK) Mi, Di Di = D(Mi | Di-1 | SK) Mi+1,Di+1 Di = D(Mi | Di-1 | SK) End, Mj, Dj EAP-Success SK Production & Validation Secure Messaging

  6. Key Production – Asymmetric Case C1, C2: Optional Sequence of X.509 Certificates r1, r2: Integer r1=1st random number D= SHA-1 r2= 2nd random number Sub-Type = 2, Start, Seq:C1, Int: r1 SK = D(r1 | r2) Seq:C2, Int:r2K1public, Int:D0K2private SK = D(r1 |r2 ) Session Key M1 , D1(M1 | SK) D1 = D(M1 | SK) D1 = D(M1, SK) M2 , D2(M2 | D1 | SK) Mi, Di Di = D(Mi | Di-1 | SK) Mi+1, Di+1 Di = D(Mi | Di-1 | SK) End Mj, Dj EAP-Success SK Production & Validation Secure Messaging

  7. Secure Messaging • All messages Mi are ended by a digest value Di. SK(r1, r2 [,s]) D1 = D(M1, SK) i>2, Di = D(Mi, Di-1, SK) • Message format is not yet defined. r1, r2 [,s] SK M2,D2 Mi,Di M3,D3 M1,D1

  8. Future Work • Random number format rules, for the asymmetric case. • Messages Ciphering • 3DES • AES • Messages Format

  9. Questions ?

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