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EAP-PAX draft-clacy-eap-pax-05

T. Charles Clancy clancy@cs.umd.edu Department of Computer Science University of Maryland, College Park Laboratory for Telecommunication Sciences US Department of Defense IETF 64, EMU BoF, November 10, 2005. EAP-PAX draft-clacy-eap-pax-05. Overview.

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EAP-PAX draft-clacy-eap-pax-05

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  1. T. Charles Clancy clancy@cs.umd.edu Department of Computer Science University of Maryland, College Park Laboratory for Telecommunication Sciences US Department of Defense IETF 64, EMU BoF, November 10, 2005 EAP-PAXdraft-clacy-eap-pax-05

  2. Overview • Basic shared-key mutual authentication method • Includes support for: • Ciphersuite extensibility • Provisioning with a weak key or password • Key management (deriving new authentication keys) with perfect forward secrecy (using Diffie-Hellman) • Identity protection / user anonymity • Authenticated data exchange (supports channel binding) • Provably secure

  3. Subprotocols: PAX_STD CLIENT SERVER A B, CID, MACCK(A, B, CID) MACCK(B, CID) ACK

  4. Changes since -04 • Completed full proof of security, publication pending, will be available online: http://www.cs.umd.edu/~clancy/eap-pax/ • Added support for the authenticated exchange of data, targeted at channel binding

  5. Subprotocols: PAX_SEC CLIENT SERVER M, PK or CertPK ENCPK(M, N, CID) A, MACN(M, CID) B, MACCK(A, B, CID) MACCK(B, CID) ACK

  6. Certificate Requirements • Use of certificate with PAX_SEC is RECOMMENDED

  7. Security Properties • Extensible Ciphersuite • MAC Primatives: • HMAC-SHA1 • AES-CBC-MAC • Public-Key Primatives: • RSA-OAEP-2048 • DH-3072, 256-bit exponents • Attack Resistance (dictionary, replay, negotiation) • Confidentiality (in ID protect mode)

  8. Provable Security • Random Oracle Model [Bellare 93] • Supported primitives all act like Random Oracles [Bellare 94, Bellare 96, Bellare 00] • Assume probabilistic, polynomial-time attacker • EAP-PAX is secure against: • passive attacks if: • PAX_STD without DH: Key O(2k) • PAX_STD with DH: Key O(1) • PAX_SEC without DH: Key O(2k) • PAX_SEC with DH: Key O(1) • active attacks if: • PAX_STD: Key O(2k), auth limit O(kn) • PAX_SEC with cert: Key O(kn), auth limit O(1) • PAX_SEC without cert: Key O(2k), auth limit O(kn)

  9. Channel Binding • Validate lower-layer EAP parameters during authentication • Need secure mechanism for exchanging parameters • What is needed? Confidentiality? Authenticity? • PAX provides authenticity, but not confidentiality (would require additional symmetric-key ciphersuite) • Attach “Authenticated Data Exchange” frames during authentication once keys have been derived

  10. Channel Binding CLIENT SERVER A B, CID, MAC, ADE(type1, value1) MAC, ADE(type2, value2) ACK, ADE(type3, value3) … ACK, ADE(typeN, valueN) ACK, ADE(typeN+1, valueN+1) … EAP-Success / EAP-Failure

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