Layered Exported Authenticators in TLS
draft-hoyland-tls-layered-exported-authenticator-00

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Internet Engineering Task Force                          J. Hoyland, Ed.
Internet-Draft                      Royal Holloway, University of London
Intended status: Standards Track                           June 25, 2018
Expires: December 27, 2018

                 Layered Exported Authenticators in TLS
          draft-hoyland-tls-layered-exported-authenticator-00

Abstract

   This document describes an extension that allows for Exported
   Authenticators (EAs) to authenticate each other.  The extension
   includes a reference to a previous EA.  An EA containing this
   extension constitues an attestation of the authenticity of the
   referenced EA.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on December 27, 2018.

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   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Internet-Draft       Layered Exported Authenticators           June 2018

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Extension Format  . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   Exported Authenticators (EAs)[EA] provide a method for authenticating
   one party of a Transport Layer Security (TLS) communication to the
   other after the session has been established.  EAs are defined for
   TLS 1.3[TLS13] and TLS 1.2 with extended master secret, RFC 7627
   [RFC7627].  Multiple EAs sent on the same channel do not prove joint
   authentication.  They prove that the sender is individually
   authoritative over each certificate, but not jointly authoritative
   over all certificates.  By including this extension a sender can
   prove joint authentication.  This extension can be included in
   CertificateRequest messages and Certificate messages.

   Joint authentication could be used, for example, to securely update
   pinned certificates.  When a client connects to a server for which it
   has a pinned certificate, the server could send the new certificate
   to be pinned, and then bind the previously pinned certificate to it.
   This proves to the client that the server is jointly authoritative
   over both certificates.  To defeat this mechanism an attacker is
   required to both compromise the key of the old certificate and
   improperly obtain a certificate from the PKI.

   Another potential use is to provide proof that a certificate has been
   accepted.  Because EAs do not have a response mechanism, the sender
   of an EA does not know the receiver's view of its authentication
   status.  By using this extension to reference EAs sent by its peer, a
   party can prove to its peer that it has accepted a particular
   certificate.

   By constructing a chain of referenced EAs complex joint
   authentication properties can be achieved.

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1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
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