An IPv6 Prefix for Overlay Routable Cryptographic Hash Identifiers (ORCHID)
RFC 4843

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Network Working Group                                        P. Nikander
Request for Comments: 4843                 Ericsson Research Nomadic Lab
Category: Experimental                                       J. Laganier
                                                        DoCoMo Euro-Labs
                                                               F. Dupont
                                                                   CELAR
                                                              April 2007

                          An IPv6 Prefix for
        Overlay Routable Cryptographic Hash Identifiers (ORCHID)

Status of This Memo

   This memo defines an Experimental Protocol for the Internet
   community.  It does not specify an Internet standard of any kind.
   Discussion and suggestions for improvement are requested.
   Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   This document introduces Overlay Routable Cryptographic Hash
   Identifiers (ORCHID) as a new, experimental class of IPv6-address-
   like identifiers.  These identifiers are intended to be used as
   endpoint identifiers at applications and Application Programming
   Interfaces (API) and not as identifiers for network location at the
   IP layer, i.e., locators.  They are designed to appear as application
   layer entities and at the existing IPv6 APIs, but they should not
   appear in actual IPv6 headers.  To make them more like vanilla IPv6
   addresses, they are expected to be routable at an overlay level.
   Consequently, while they are considered non-routable addresses from
   the IPv6 layer point-of-view, all existing IPv6 applications are
   expected to be able to use them in a manner compatible with current
   IPv6 addresses.

   This document requests IANA to allocate a temporary prefix out of the
   IPv6 addressing space for Overlay Routable Cryptographic Hash
   Identifiers.  By default, the prefix will be returned to IANA in
   2014, with continued use requiring IETF consensus.

Nikander, et al.              Experimental                      [Page 1]
RFC 4843        Cryptographic Hash IDentifiers (ORCHID)       April 2007

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Rationale and Intent . . . . . . . . . . . . . . . . . . .  3
     1.2.  ORCHID Properties  . . . . . . . . . . . . . . . . . . . .  4
     1.3.  Expected use of ORCHIDs  . . . . . . . . . . . . . . . . .  4
     1.4.  Action Plan  . . . . . . . . . . . . . . . . . . . . . . .  4
     1.5.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Cryptographic Hash Identifier Construction . . . . . . . . . .  5
   3.  Routing Considerations . . . . . . . . . . . . . . . . . . . .  6
     3.1.  Overlay Routing  . . . . . . . . . . . . . . . . . . . . .  6
   4.  Collision Considerations . . . . . . . . . . . . . . . . . . .  7
   5.  Design Choices . . . . . . . . . . . . . . . . . . . . . . . .  9
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 11
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 11
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 11

1.  Introduction

   This document introduces Overlay Routable Cryptographic Hash
   Identifiers (ORCHID), a new class of IP address-like identifiers.
   These identifiers are intended to be globally unique in a statistical
   sense (see Section 4), non-routable at the IP layer, and routable at
   some overlay layer.  The identifiers are securely bound, via a secure
   hash function, to the concatenation of an input bitstring and a
   context tag.  Typically, but not necessarily, the input bitstring
   will include a suitably encoded public cryptographic key.

1.1.  Rationale and Intent

   These identifiers are expected to be used at the existing IPv6
   Application Programming Interfaces (API) and application protocols
   between consenting hosts.  They may be defined and used in different
   contexts, suitable for different overlay protocols.  Examples of
   these include Host Identity Tags (HIT) in the Host Identity Protocol
   (HIP) [HIP-BASE] and Temporary Mobile Identifiers (TMI) for Mobile
   IPv6 Privacy Extension [PRIVACYTEXT].

   As these identifiers are expected to be used along with IPv6
   addresses at both applications and APIs, co-ordination is desired to
   make sure that an ORCHID is not inappropriately taken for a vanilla
   IPv6 address and vice versa.  In practice, allocation of a separate
   prefix for ORCHIDs seems to suffice, making them compatible with IPv6
   addresses at the upper layers while simultaneously making it trivial
   to prevent their usage at the IP layer.