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Authentication and Key Agreement

Authentication and Key Agreement. Flexibility in credentials Modern, publically analysed/available cryptographic primitives Freshness guarantees PFS? Mutual authentication Identity hiding for supplicant/end-user No key re-use Fast re-key Fast handoff

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Authentication and Key Agreement

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  1. Authentication and Key Agreement • Flexibility in credentials • Modern, publically analysed/available cryptographic primitives • Freshness guarantees • PFS? • Mutual authentication • Identity hiding for supplicant/end-user • No key re-use • Fast re-key • Fast handoff • Efficiency not an overarching concern: • Protocol runs only 1/2^N-1 packets, on average • DOS resistance

  2. Credentials flexibility • Local security policy dictates types of credentials used by end-users • Legacy authentication compatibility extremely important in market • Examples: • username/password • Tokens (SecurID, etc) • X.509 certificates

  3. Algorithms • Algorithms must provide confidentiality and integrity of the authentication and key agreement. • Public-key encryption/signature • RSA • ECC • DSA • PFS support • D-H

  4. Freshness • Most cryptographic primitives require strong random material that is “fresh”. • Not a protocol issue, per se, but a design requirement nonetheless

  5. Mutual Authentication • Both sides of authentication/key agreement must be certain of identity of other party. • Symmetric RSA/DSA schemes (public-keys on both sides) • Asymmetric schemes • Legacy on end-user side • RSA/DSA on authenticator side

  6. Identity hiding • Important to hide end-user identity in some situations (public shared networks, for example). • DISTINCT from hiding MAC address • IPSEC has gone down this road, and has much experience. • Not as easy as it sounds—active attacks make it harder.

  7. Fast rekey/fast handoff • Ability to create fresh keying material without undergoing slow authentication path (requiring username/password again, for example). • In mobile environments, ability to transition without re-doing initial authentication.

  8. Efficiency • CPU efficiency not a serious concern, since this protocol will be used relatively infrequently. • On-the-wire efficiency may be important in low-bandwidth scenarios, but again protocol is not run that often, compared to MACsec.

  9. DOS resistance • Modern key-agreement protocols fertile ground for DOS attacks. • Look to other schemes (IKE, for example) to provide guidance. • No perfect anti-DOS schemes • Increase unpleasantnesss for attacker • Detect and throw away bogosity at the earliest, cheapest point in the protocol.

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