An Extension for Postquantum Security using Preshared Keys for IKEv2
draft-fluhrer-qr-ikev2-00

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Internet Engineering Task Force                               S. Fluhrer
Internet-Draft                                                 D. McGrew
Intended status: Informational                             P. Kampanakis
Expires: March 13, 2016                                    Cisco Systems
                                                      September 10, 2015

  An Extension for Postquantum Security using Preshared Keys for IKEv2
                       draft-fluhrer-qr-ikev2-00

Abstract

   This document describes an extension of IKEv2 to allow it to be
   resistant to a Quantum Computer, by using preshared keys

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Internet-Draft       Postquantum Security for IKEv2       September 2015

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Assumptions . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Exchanges . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Computing SKEYSEED  . . . . . . . . . . . . . . . . . . .   4
     3.2.  Verifying preshared key . . . . . . . . . . . . . . . . .   5
     3.3.  Child SAs . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Appendix A.  Discussion and Rationale . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   It is an open question whether or not it is feasible to build a
   quantum computer, but if it is, many of the cryptographic algorithms
   and protocols currently in use would be insecure.  A quantum computer
   would be able to solve DH and ECDH problems, and this would imply
   that the security of existing IKEv2 systems would be compromised.
   IKEv1 when used with preshared keys does not share this
   vulnerability, because those keys are one of the inputs to the key
   derivation function.  If the preshared key have sufficient entropy,
   then the resulting system is believed to be quantum resistant.

   This document describes a way to extend IKEv2 to have a similar
   property; assuming that the two end systems share a long secret key,
   then the resulting exchange is quantum resistant, that is, believed
   to be invulnerable to an attacker with a Quantum Computer.  By
   bringing postquantum security to IKEv2, this note removes the need to
   use an obsolete version of the Internet Key Exchange in order to
   achieve that security goal.

   The general idea is that we add an additional secret that is shared
   between the initiator and the responder; this secret is in addition
   to the authentication method that is already provided within IKEv2.
   We stir in this secret when generating the IKE keys (along with the
   parameters that IKEv2 normally uses); this secret adds quantum
   resistance to the exchange.

   It is important to minimize the changes to IKEv2.  The existing
   mechanisms to do authentication and key exchange remain in place
   (that is, we continue to do (EC)DH, and potentially a PKI
   authentication if configured).  This does not replace the
   authentication checks that the protocol does; instead, it is done as
   a parallel check.

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1.1.  Requirements Language
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