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Versions: (draft-moskowitz-hierarchical-hip) 00 01 02

HIP                                                         R. Moskowitz
Internet-Draft                                            HTT Consulting
Intended status: Standards Track                                 S. Card
Expires: 19 April 2020                                   A. Wiethuechter
                                                           AX Enterprize
                                                         17 October 2019


                      Hierarchical HITs for HIPv2
                draft-moskowitz-hip-hierarchical-hit-02

Abstract

   This document describes using a hierarchical HIT to facilitate large
   deployments of managed devices.  Hierarchical HITs differ from HIPv2
   flat HITs by only using 64 bits for mapping the Host Identity,
   freeing 32 bits to bind in a hierarchy of Registering Entities that
   provide services to the consumers of hierarchical HITs.

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 19 April 2020.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   Please review these documents carefully, as they describe your rights
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   extracted from this document must include Simplified BSD License text




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   as described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terms and Definitions . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Requirements Terminology  . . . . . . . . . . . . . . . .   3
     2.2.  Definitions . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Problem Space . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Meeting the future of Mobile Devices in a public
           space . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.2.  Semi-permanency of Identities . . . . . . . . . . . . . .   4
     3.3.  Managing a large flat address space . . . . . . . . . . .   4
     3.4.  Defense against fraudulent HITs . . . . . . . . . . . . .   4
   4.  The Hierarchical Host Identity Tag (HHIT) . . . . . . . . . .   4
     4.1.  HHIT prefix . . . . . . . . . . . . . . . . . . . . . . .   5
     4.2.  HHIT Suite IDs  . . . . . . . . . . . . . . . . . . . . .   5
     4.3.  The Hierarchy ID (HID)  . . . . . . . . . . . . . . . . .   5
       4.3.1.  The Registered Assigning Authority (RAA)  . . . . . .   5
       4.3.2.  The Hierarchical HIT Domain Authority (HDA) . . . . .   6
       4.3.3.  Example of the HID DNS  . . . . . . . . . . . . . . .   6
       4.3.4.  HHIT DNS Retrieval  . . . . . . . . . . . . . . . . .   6
       4.3.5.  Changes to ORCHIDv2 to support Hierarchical
               HITs  . . . . . . . . . . . . . . . . . . . . . . . .   7
       4.3.6.  Collision risks with Hierarchical HITs  . . . . . . .   7
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   8
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Appendix A.  Calculating Collision Probabilities  . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   This document expands on HIPv2 [RFC7401] to describe the structure of
   a hierarchical HIT (HHIT).  Some of the challenges for large scale
   deployment addressed by HHITs are presented.  The basics for the
   hierarchical HIT registries are defined here.

   Separate documents will further expand on the registry service and
   how a device can advertise its availability and services provided.







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2.  Terms and Definitions

2.1.  Requirements Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.  `

2.2.  Definitions

   HDA (Hierarchical HIT Domain Authority):  The 14 bit field
      identifying the HIT Domain Authority under an RAA.

   HID (Hierarchy ID):  The 32 bit field providing the HIT Hierarchy ID.

   RAA (Registered Assigning Authority):  The 18 bit field identifying
      the Hierarchical HIT Assigning Authority.

3.  Problem Space

3.1.  Meeting the future of Mobile Devices in a public space

   Public safety may impose a "right to know" what devices are in a
   public space.  Public space use may only be permitted to devices that
   meet an exacting "who are you" query.  This implies a device identity
   that can be quickly validated by public safety personal and even the
   general public in many situations.

   Many proposals for mobile device identities are nothing more than a
   string of bits.  These may provide information about the device but
   provide no assurance that the identity associated with a device
   really belongs to a particular device.  Further they may impose a
   slow, complex method to discover the device owner to those with
   appropriate authorization.

   The Host Identity Tag (HIT) from the Host Identity Protocol (HIP)
   provides a self-asserting Identity through a public key signing
   operation using the Host Identity's (HI) private key.

   Although the HIT provides a "trust me, I am me" claim, it does not
   provide an assertion as to why the claim should be trusted and any
   additional side information about the device.  The later could be
   distributed directly from the device in a secure manner, but again
   there is no 3rd-party assertion of such a claim.





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3.2.  Semi-permanency of Identities

   A device Identity has some degree of permanency.  A device creates
   its identity and registers it to some 3rd-party that will assert a
   level of trust for that identity.  A device may have multiple
   identities to use in different contexts, and it may deprecate an
   identity for any number of reasons.  The asserting 3rd-party may
   withdraw its assertion of an identity for any number of reasons.  An
   identity system needs to facilitate all of this.

3.3.  Managing a large flat address space

   For HITs to be successfully used by a large population of mobile
   devices, it must support an Identity per device; potentially 10
   billion Identities.  Perhaps a Distributed Hash Table [RFC6537] can
   scale this large.  There is still the operational challenges in
   establishing such a world-wide DHT implementation and how RVS
   [RFC8004] works with such a large population.  There is also the
   challenge of how to turn this into a viable business.  How can
   different controlling jurisdictions operate in such an environment?

   Even though the probability of collisions with 7B HITs (one HIT per
   person) in a 96 bit flat address space is 3.9E-10, it is still real.
   How are collisions managed?  It is also possible that weak key
   uniqueness, as has been shown in deployed TLS certificates
   [WeakKeys], results in a much greater probability of collisions.
   Thus resolution of collisions needs to be a feature in a global
   namespace.

3.4.  Defense against fraudulent HITs

   How can a host protect against a fraudulent HIT?  That is, a second
   pre-image attack on the HI hash that produces the HIT.  A strong
   defense would require every HIT/HI registered and openly verifiable.
   This would best be done as part of the R1 and I2 validation.  Or any
   other message that is signed by the HI private key.

4.  The Hierarchical Host Identity Tag (HHIT)

   The Hierarchical HIT (HHIT) is a small but important enhancement over
   the flat HIT space.  By adding two levels of hierarchical
   administration control, the HHIT provides for device registration/
   ownership, thereby enhancing the trust framework for HITs.

   HHITs represent the HI in only a 64 bit hash and uses the other 32
   bits to create a hierarchical administration organization for HIT
   domains.  Hierarchical HITs are ORCHIDs [RFC7343].  The change in
   construction rules are in Section 4.3.5.



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   A HHIT is built from the following fields:

   *  28 bit IANA prefix

   *  4 bit HIT Suite ID

   *  32 bit Hierarchy ID (HID)

   *  64 bit ORCHID hash

4.1.  HHIT prefix

   A unique 28 bit prefix for HHITs would be ideal.  It would clearly
   separate the flat-space HIT processing from HHIT processing.
   However, the prefix is the domain of ORCHIDs [RFC7343], and cannot be
   changed directly here.  Proposing a unique prefix to simplify
   Section 4.2 is in scope of this draft.

4.2.  HHIT Suite IDs

   The HIT Suite IDs specifies the HI and hash algorithms.  Any HIT
   Suite ID can be used for HHITs, provided that the prefix for HHITs is
   different from flat space HITs.  Without a unique prefix Section 4.1,
   additional HIT Suite IDs would be needed for HHITs.  This would risk
   exhausting the limited Suite ID space of only 15 IDs.

4.3.  The Hierarchy ID (HID)

   The Hierarchy ID (HID) provides the structure to organize HITs into
   administrative domains.  HIDs are further divided into 2 fields:

   *  14 bit Registered Assigning Authority (RAA)

   *  18 bit Hierarchical HIT Domain Authority (HDA)

4.3.1.  The Registered Assigning Authority (RAA)

   An RAA is a business or organization that manages a registry of HDAs.
   For example, the Federal Aviation Authority (FAA) could be an RAA.

   The RAA is a 14 bit field (16,384 RAAs) assigned by a numbers
   management organization, perhaps ICANN's IANA service.  An RAA must
   provide a set of services to allocate HDAs to organizations.  It must
   have a public policy on what is necessary to obtain an HDA.  The RAA
   need not maintain any HIP related services.  It must maintain a DNS
   zone minimally for discovering HID RVS servers.





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   This DNS zone may be a PTR for its RAA.  It may be a zone in a HHIT
   specific DNS zone.  Assume that the RAA is 100.  The PTR record could
   be constructed:

   100.hhit.arpa   IN PTR      raa.bar.com.

4.3.2.  The Hierarchical HIT Domain Authority (HDA)

   An HDA may be an ISP or any third party that takes on the business to
   provide RVS and other needed services for HIP enabled devices.

   The HDA is an 18 bit field (262,144 HDAs per RAA) assigned by an RAA.
   An HDA should maintain a set of RVS servers that its client HIP-
   enabled customers use.  How this is done and scales to the
   potentially millions of customers is outside the scope of this
   document.  This service should be discoverable through the DNS zone
   maintained by the HDA's RAA.

   An RAA may assign a block of values to an individual organization.
   This is completely up to the individual RAA's published policy for
   delegation.

4.3.3.  Example of the HID DNS

   HID related services should be discoverable via DNS.  For example the
   RVS for a HID could be found via the following.  Assume that the RAA
   is 100 and the HDA is 50.  The PTR record is constructed as:

       50.100.hhit.arpa   IN PTR      rvs.foo.com.

   The RAA is running its zone, 100.hhit.arpa under the hhit.arpa zone.

4.3.4.  HHIT DNS Retrieval

   The HDA SHOULD provide DNS retrieval per [RFC8005].  Assume that the
   RAA is 10 and the HDA is 20 and the HHIT is:

       2001:14:28:14:a3ad:1952:ad0:a69e

   The HHIT FQDN is:

       2001:14:28:14:a3ad:1952:ad0:a69e.20.10.hhit.arpa.

   The NS record for the HDA zone is constructed as:

       20.10.hhit.arpa   IN NS      registry.foo.com.





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   registry.foo.com returns a HIP RR with the HHIT and matching HI.  The
   HDA sets its policy on TTL for caching the HIP RR.  Optionally, the
   HDA may include RVS information.  Including RVS in the HIP RR may
   impact the TTL for the response.

4.3.5.  Changes to ORCHIDv2 to support Hierarchical HITs

   ORCHIDv2 [RFC7343] has a number of inputs including a Context ID
   (unique for HHITs), some header bits, the hash algorithm, and the
   public key.  The output is a 96 bit value.  Hierarchical HIT makes
   the following changes.  The HID is added as part of the header bits
   and the output is a 64 bit value, derived the same way as the 96 bit
   hash.

       Input      :=  HID | HOST_ID
       OGA ID     :=  4-bit Orchid Generation Algorithm identifier
                      The HHIT Suite ID
       Hash Input :=  Context ID | Input
                      Context ID = 0x00B5 A69C 795D F5D5
                                     F008 7F56 843F 2C40
       Prefix     :=  HIPv2 Prefix
                      Note: per section 4.1, this should be a different Prefix
       HID        :=  Hierarchy ID
       Hash       :=  Hash_function( Hash Input )
       Encode_64  :=  Same as Encode_96, but only 64 bits
       ORCHID     :=  Prefix | OGA ID | HID | Encode_64( Hash )

   Hierarchical HIT uses the same context as all other HIPv2 HIT Suites
   as they are clearly separated by the distinct HIT Suite ID.

4.3.6.  Collision risks with Hierarchical HITs

   The 64 bit hash size does have an increased risk of collisions over
   the 96 bit hash size used for the other HIT Suites.  There is a 0.01%
   probability of a collision in a population of 66 million.  The
   probability goes up to 1% for a population of 663 million.  See
   Appendix A for the collision probability formula.

   However, this risk of collision is within a single HDA.  Further, all
   HDAs are expected to provide a registration process for reverse
   lookup validation.  This registration process would reject a
   collision, forcing the client to generate a new HI and thus
   hierarchical HIT and reapplying to the registration process.








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5.  IANA Considerations

   Because HHIT use of ORCHIDv2 format is not compatible with [RFC7343],
   IANA is requested to allocated a new 28-bit prefix out of the IANA
   IPv6 Special Purpose Address Block, namely 2001:0000::/23, as per
   [RFC6890].

6.  Security Considerations

   A 64 bit hash space presents a real risk of second pre-image attacks.
   The HHIT Registry services effectively block attempts to "take over"
   a HHIT.  It does not stop a rogue attempting to impersonate a known
   HHIT.  This attack can be mitigated by the Responder using DNS to
   find the HI for the HHIT or the RVS for the HHIT that then provides
   the registered HI.

   The two risks with hierarchical HITs are the use of an invalid HID
   and forced HIT collisions.  The use of the "hhit.arpa."  DNS zone is
   a strong protection against invalid HIDs.  Querying an HDA's RVS for
   a HIT under the HDA protects against talking to unregistered clients.
   The Registry service has direct protection against forced or
   accidental HIT hash collisions.

7.  Acknowledgments

   The initial versions of this document were developed with the
   assistance of Xiaohu Xu and Bingyang Liu of Huawei.

   Sue Hares contributed to the clarity in this document.

8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

8.2.  Informative References

   [RFC6537]  Ahrenholz, J., "Host Identity Protocol Distributed Hash
              Table Interface", RFC 6537, DOI 10.17487/RFC6537, February
              2012, <https://www.rfc-editor.org/info/rfc6537>.



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   [RFC6890]  Cotton, M., Vegoda, L., Bonica, R., Ed., and B. Haberman,
              "Special-Purpose IP Address Registries", BCP 153,
              RFC 6890, DOI 10.17487/RFC6890, April 2013,
              <https://www.rfc-editor.org/info/rfc6890>.

   [RFC7343]  Laganier, J. and F. Dupont, "An IPv6 Prefix for Overlay
              Routable Cryptographic Hash Identifiers Version 2
              (ORCHIDv2)", RFC 7343, DOI 10.17487/RFC7343, September
              2014, <https://www.rfc-editor.org/info/rfc7343>.

   [RFC7401]  Moskowitz, R., Ed., Heer, T., Jokela, P., and T.
              Henderson, "Host Identity Protocol Version 2 (HIPv2)",
              RFC 7401, DOI 10.17487/RFC7401, April 2015,
              <https://www.rfc-editor.org/info/rfc7401>.

   [RFC8004]  Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
              Rendezvous Extension", RFC 8004, DOI 10.17487/RFC8004,
              October 2016, <https://www.rfc-editor.org/info/rfc8004>.

   [RFC8005]  Laganier, J., "Host Identity Protocol (HIP) Domain Name
              System (DNS) Extension", RFC 8005, DOI 10.17487/RFC8005,
              October 2016, <https://www.rfc-editor.org/info/rfc8005>.

   [WeakKeys] Heninger, N.H., Durumeric, Z.D., Wustrow, E.W., and J.A.H.
              Halderman, "Detection of Widespread Weak Keys in Network
              Devices", August 2012,
              <https://factorable.net/weakkeys12.extended.pdf>.

Appendix A.  Calculating Collision Probabilities

   The accepted formula for calculating the probability of a collision
   is:

       p = 1 - e^{-k^2/(2n)}


       P   Collision Probability
       n   Total possible population
       k   Actual population



Authors' Addresses

   Robert Moskowitz
   HTT Consulting
   Oak Park, MI 48237




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   United States of America

   Email: rgm@labs.htt-consult.com


   Stuart W. Card
   AX Enterprize
   4947 Commercial Drive
   Yorkville, NY 13495
   United States of America

   Email: stu.card@axenterprize.com


   Adam Wiethuechter
   AX Enterprize
   4947 Commercial Drive
   Yorkville, NY 13495
   United States of America

   Email: adam.wiethuechter@axenterprize.com






























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