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Vancouver, November 2007. IETF 70 th – netlmm WG. EAP-Based Keying for IP Mobility Protocols. draft-vidya-eap-usrk-ip-mobility-01. Vidya Narayanan and Gerardo Giaretta. What is this about. The draft defines EAP-based key derivations for MIPv4, MIPv6, HMIPv6 and FMIPv6
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Vancouver, November 2007 IETF 70th – netlmm WG EAP-Based Keying for IP Mobility Protocols draft-vidya-eap-usrk-ip-mobility-01 Vidya Narayanan and Gerardo Giaretta
What is this about • The draft defines EAP-based key derivations for MIPv4, MIPv6, HMIPv6 and FMIPv6 • The key hierarchy and key derivations are based on the EMSK hierarchy defined in HOKEY • The USRK labels required for these protocols and derivation of keys needed between the MN and the corresponding mobility agents are described • Left to other individual documents to describe the exact signaling mechanisms that will trigger this keying process and enable
Motivation • IP mobility protocols require cryptographic key material for authentication of signaling messages • In a system where network access authentication is done using EAP, it is possible to derive keys for use in mobility protocols using the EMSK key hierarchy • This prevents the need for having any pre-configured key material being available for each of these protocols used • or running a separate security association protocol to establish the necessary keying material (e.g. running again an EAP exchange over IKEv2) • Considered at the time of MIPv6 bootstrapping DT but the EMSK hierarchy was not defined yet
HOKEY Background • Key generating EAP methods produce a Master Session Key (MSK) and an Extended Master Session Key (EMSK) • the MSK is provided to the lower layer • Several lower layers use the MSK in various different ways. • EMSK hierarchy defined in draft-ietf-hokey-emsk-hierarchy-01 • meant to be extensible to derive keys for various usages • Usage Specific Root Keys (USRK) and Domain Specific Root Keys (DSRK) may be derived from the EMSK • USRKs are meant to be defined for specific usages and the scope of the key will be determined by the EAP Server (or the home AAA server) of the peer • DSRKs are limited in scope to a specific domain and are meant to be distributed to local AAA servers in different domains • The DSRK may then be used to derive various Domain Specific USRKs (DS-USRK), which are defined for specific usages within the domain for which the DSRK is valid
EMSK/DSRK Mobility Root Key (MRK) Mobility Integrity Key (MIK) Mobility Usage Session Key (MUSK) Key hierarchy • MRK is calculated in accordance with the USRK derivation defined in draft-ietf-hokey-emsk-hierarchy-01 • may be derived from the EMSK or the DSRK, depending on whether the keys are being derived at the home domain or the local domain • MIK is the key used to protect any exchange between the MN and the server deriving the MRK, to prove possession of the MRK • used for authentication of messages between the MN and the server that derived the MRK • MUSK is the key that is delivered to a mobility agent for a particular mobility session between the MN and the agent • may be used to protect the mobility signaling messages between the MN and the mobility agent or to perform IKEv2 authentication to establish an IPsec security association
Key derivation • MRK = KDF(Key, Mobility Key Label, Optional Data, Length) • Key = EMSK or DSRK • Mobility Key Label = the specific label defined for the particular IP mobility protocol • Optional Data = NULL • Length = 2 byte unsigned integer in network byte order of the output key length in octets • Mobility Key Labels defined in the draft • MIP4: "Mobile IPv4 Root Key" • MIP6: "Mobile IPv6 Root Key" • HMIPv6: "Hierarchical Mobile IPv6 Root Key" • FMIPv6: "Fast Mobile IPv6 Root Key" • Based on the above labels, the following are the specific root keys defined for the various IP mobility protocols: • MIP4-RK = KDF (Key, "Mobile IPv4 Root Key", Optional Data, Length) • MIP6-RK = KDF (Key, "Mobile IPv6 Root Key", Optional Data, Length) • HMIP6-RK = KDF (Key, "Hierarchical Mobile IPv6 Root Key", Optional Data, Length) • FMIP6-RK = KDF (Key, "Fast Mobile IPv6 Root Key", Optional Data, Length)
MIPv4 bootstrapping example MN FA HA AAA EAP authentication for network access Agent Solicitation Agent Advertisement Generate MN-AAA key = MIK Generate MN-AAA key = MIK RRQ (MN-AAA Auth Ext) AAA request (RRQ, HA Request) Generate MN-HA key = MUSK AAA (RRQ,MN-HA key) AAA (RRP) AAA reply (RRP) RRP Generate MN-HA key = MUSK
Next steps • Looking for an AD sponsored RFC