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EAP-POTP: An EAP method for One-Time Passwords. OTPS Workshop February 2006. EAP-POTP: A Primer. General EAP method for OTP tokens Provides mutual authentication Generates keying material Does not rely on tunnelling (provides privacy for OTP values) Enables fast session resumption
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EAP-POTP: An EAP method for One-Time Passwords OTPS Workshop February 2006
EAP-POTP: A Primer • General EAP method for OTP tokens • Provides mutual authentication • Generates keying material • Does not rely on tunnelling (provides privacy for OTP values) • Enables fast session resumption • EAP-POTP • Complements EAP-PEAP, EAP-TTLS, and EAP-FAST • May be used as a better alternative for an “inner” EAP method than EAP-GTC, PAP, CHAP, etc
Characteristics • Built on the principle of TLVs • 16 TLVs defined: Version, Server-Info, Resume, OTP, Confirm, Vendor-Specific, Counter, Time Stamp, Challenge, Keep Alive, Token Serial, User Identifier, NAK, New PIN, Protected, Crypto Algorithm
Profiles • The method is profiled for RSA SecurID – EAP-POTP RSA SecurID (EAP method 32) • Profiles for other OTP algorithms expected and desired • May be seen as a framework within a framework • EAP is a framework for many authentication mechanisms • POTP is a framework for OTP-based mechanisms within EAP
Recent Modifications • Draft 5 published in December 2005 • Derivation of a special session resumption key (SRK) at the same time as derivation of other keys such as the EMSK and the MSK • Avoids some issues identified with the use of the EMSK as a basis for the SRK • Parameterization of the hash, encryption, and MAC algorithms through a new "Crypto Algorithm TLV“ • Allows for cryptographic algorithm negotiation • Addition of a "Challenge TLV“ • When the challenge used in a challenge-response method otherwise would be unknown to the EAP server
The SRK K_MAC | K_ENC | MSK | EMSK | SRK =PBKDF2 (OTP, …) At session resumption: K_MAC | K_ENC | MSK | EMSK | SRK = PBKDF2 (SRK, …) SRK only used for session resumption (previously MSK was used, but was also used for session keys)
Current Status and Next Steps • Have asked for Designated Expert Review • Subsequent to this, or if no response from IETF EAP WG chairs, will ask for IETF Last-Call (for Informational RFC) • After OTPS participants’ confirmation • Interoperability event?