Multiple Key Exchanges in IKEv2
Post-Quantum
Post-Quantum
Quantum Secret
Cisco Systems
ISARA Corporation
Philips
ELVIS-PLUS
This document describes how to extend the Internet Key Exchange Protocol Version 2 (IKEv2) to allow multiple key exchanges to take place while computing a shared secret during a Security Association (SA) setup. The primary application of this feature in IKEv2 is the ability to perform one or more post-quantum key exchanges in conjunction with the classical (Elliptic Curve) Diffie-Hellman (EC)DH key exchange, so that the resulting shared key is resistant against quantum computer attacks. Since there is currently no post-quantum key exchange that is as well-studied as (EC)DH, performing multiple key exchanges with different post-quantum algorithms along with the well-established classical key exchange algorithms addresses this concern, since the overall security is at least as strong as each individual primitive. Another possible application for this extension is the ability to combine several key exchanges in situations when no single key exchange algorithm is trusted by both initiator and responder. This document utilizes the IKE_INTERMEDIATE exchange, by means of which multiple key exchanges are performed when an IKE SA is being established. It also introduces a new IKEv2 exchange IKE_FOLLOWUP_KE, which is used for the same purpose when the IKE SA is up (during rekeys or creating additional Child SAs). This document updates RFC7296 by renaming a transform type 4 from "Diffie-Hellman Group (D-H)" to "Key Exchange Method (KE)" and renaming a field in the Key Exchange Payload from "Diffie-Hellman Group Num" to "Key Exchange Method". It also renames an IANA registry for this transform type from "Transform Type 4 - Diffie- Hellman Group Transform IDs" to "Transform Type 4 - Key Exchange Method Transform IDs". These changes generalize key exchange algorithms that can be used in IKEv2.