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DRIP R. Moskowitz
Internet-Draft HTT Consulting
Intended status: Standards Track S. Card
Expires: 6 November 2020 A. Wiethuechter
AX Enterprize
A. Gurtov
Linköping University
5 May 2020
UAS Remote ID
draft-moskowitz-drip-uas-rid-01
Abstract
This document describes using Hierarchical Host Identity Tags (HHITs)
as a self-asserting and thereby trustable Identifier for use as the
UAS Remote ID. HHITs include explicit hierarchy to provide
registration discovery for 3rd-party ID assertion. Further, HHITs
can also be used elsewhere in the UTM architecture to facilitate UAS
communications.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 6 November 2020.
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terms and Definitions . . . . . . . . . . . . . . . . . . . . 3
2.1. Requirements Terminology . . . . . . . . . . . . . . . . 3
2.2. Definitions . . . . . . . . . . . . . . . . . . . . . . . 3
3. Hierarchical HITs as Remote ID . . . . . . . . . . . . . . . 5
3.1. Hierarchy in ORCHID generation . . . . . . . . . . . . . 5
3.2. Hierarchical HIT Registry . . . . . . . . . . . . . . . . 5
3.3. Remote ID Authentication using HHITs . . . . . . . . . . 6
4. UAS ID HHIT in DNS . . . . . . . . . . . . . . . . . . . . . 6
5. Other UTM uses of HHITs . . . . . . . . . . . . . . . . . . . 7
6. DRIP Requirements addressed . . . . . . . . . . . . . . . . . 7
7. ASTM Considerations . . . . . . . . . . . . . . . . . . . . . 7
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
9. Security Considerations . . . . . . . . . . . . . . . . . . . 7
9.1. Hierarchical HIT Trust . . . . . . . . . . . . . . . . . 8
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
11. Normative References . . . . . . . . . . . . . . . . . . . . 8
12. Informative References . . . . . . . . . . . . . . . . . . . 9
Appendix A. EU U-Space RID Privacy Considerations . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
This document describes the use of Hierarchical HITs (HHITs)
[hierarchical-hit] as self-asserting and thereby a trustable
Identifier for use as the UAS Remote ID. HHITs include explicit
hierarchy to provide registration discovery for 3rd-party ID
assertion.
The Drip Requirements [drip-requirements] describe a UAS ID as a
"unique (ID-4), non-spoofable (ID-5), and identify a registry where
the ID is listed (ID-2)"; all within a 20 character Identifier (ID-
1).
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HITs are statistically unique through the cryptograhic hash feature
of second-preimage resistance. The cryptograhically-bound addition
of the Hierarchy and HHIT Registries [hhit-registries] provide
complete, global HHIT uniqueness. This is in contrast to general IDs
(e.g. a UUID or device serial number) as the subject in an X.509
certificate. All CAs within a PKI would have to check each other for
duplicate (possibly fraudulent) IDs to approach this assurance of
uniqueness.
Hierarchical HITs are valid, though non-routable, IPv6 addresses. As
such, they fit in many ways within various IETF technologies.
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
CAA
Civil Aeronautics Administration. Two CAAs are the US Federal
Aviation Administration (FAA) and European Union Aviation Safety
Agency (EASA).
C2
Command and Control. A set of organizational and technical
attributes and processes that employs human, physical, and
information resources to solve problems and accomplish missions.
Previously primarily used in military contexts.
CS-RID
Crowd Sourced Remote Identification. An optional DRIP WG service
that gateways Broadcast RID to Network RID, and supports
verification of RID positon/velocity claims with independent
measurements (e.g. by multilateration), via a SDSP.
GCS
Ground Control Station. The part of the UAS that the remote pilot
uses to exercise C2 over the UA, whether by remotely exercising UA
flight controls to fly the UA, by setting GPS waypoints, or
otherwise directing its flight.
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HI
Host Identity. The public key portion of an asymmetric keypair
from HIP.
HIP
Host Identity Protocol. The origin of HI, HIT, and HHIT, required
for DRIP. Optional full use of HIP enables additional DRIP
functionality.
HHIT
Hierarchical Host Identity Tag. A HIT with extra information not
found in a standard HIT.
HIT
Host Identity Tag. A 128 bit handle on the HI. HITs are valid
IPv6 addresses.
Observer
Referred to in some UAS documents as a "user", but there are also
other classes of RID users; "observer" is preferred here to denote
an individual who has observed an UA and needs to know something
about it, starting with its RID.
RID
Remote ID. A unique identifier found on all UA to be used in
communication and in regulation of UA operation.
UA
Unmanned Aircraft. In this document UA's are typically thought of
as drones of commercial or military variety. This is a very
strict definition which can be relaxed to include any and all
aircraft that are unmanned.
UAS
Unmanned Aircraft System. Composed of Unmanned Aircraft and all
required on-board subsystems, payload, control station, other
required off-board subsystems, any required launch and recovery
equipment, all required crew members, and C2 links between UA and
the control station.
USS
UAS Service Supplier. Provide UTM services to support the UAS
community, to connect Operators and other entities to enable
information flow across the USS network, and to promote shared
situational awareness among UTM participants. (From FAA UTM
ConOps V1, May 2018).
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UTM
UAS Traffic Management. A "traffic management" ecosystem for
uncontrolled operations that is separate from, but complementary
to, Air Traffic Management (ATM) systems for manned aircraft.
3. Hierarchical HITs as Remote ID
Hierarchical HITs are a refinement on the Host Identity Tag (HIT) of
HIPv2 [RFC7401]. HHITs require a new ORCHID mechanism as described
in [new-orchid]. HHITs for UAS ID also use the new EdDSA/SHAKE128
HIT suite defined in [new-hip-crypto] (requirements GEN-2). This
hierarchy, cryptographically embedded within the HHIT, provides the
information for finding the UA's HHIT registry (ID-3).
The current ASTM [F3411-19] supports three types of UAS IDs, namely
the [CTA2063A] serial number, CAA registration ID, and UTM-provided
UUID session ID. For HHITs to be used effectively as UAS IDs,
F3411-19 SHOULD add HHIT as the fourth UAS ID type.
3.1. Hierarchy in ORCHID generation
ORCHIDS, as defined in [RFC7343], do not cryptographically bind the
IPv6 prefix nor the Orchid Generation Algorithm (OGA) ID to the hash
of the HI. The justification then was attacks against these fields
are DOS attacks against protocols using them.
HHITs, as defined in [new-orchid], cryptographically bind all content
in the ORCHID though the hashing function. Thus a recipient of a
HHIT that has the underlying HI can directly act on all content in
the HHIT. This is especially important to using the hierarchy to
find the HHIT Registry.
3.2. Hierarchical HIT Registry
HHITs are registered to Hierarchical HIT Domain Authorities (HDAs) as
described in [hhit-registries]. This registration process ensures
UAS ID global uniqueness (ID-4). It also provides the mechanism to
create UAS Public/Private data associated with the HHIT UAS ID (GEN-4
and GEN-5).
The 2 levels of hierarchy within the HHIT allows for CAAs to have
their own Registered Assigning Authority (RAA) for their National Air
Space (NAS). Within the RAA, the CAAs can delegate HDAs as needed.
There may be other RAAs allowed to operate within a given NAS; this
is a policy decision by the CAA.
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3.3. Remote ID Authentication using HHITs
The EdDSA25519 Host Identity (HI) underlying the HHIT is used for the
Message Wrapper, Sec 4.1 [drip-auth] (requirements GEN-2). It and
the HDA's HI/HHIT are used for the Offline Claim, sec 4.3 [drip-auth]
(requirements GEN-3). These messages also establish that the UA owns
the HHIT and that no other UA can assert ownership of the HHIT (GEN-
1).
The number of HDAs authorized to register UAs within an NAS
determines the size of the HDA credential cache a device processing
the Offline Authentication. This cache contains the HDA's HI/HHIT
and HDA meta-data; it could be very small.
4. UAS ID HHIT in DNS
There are 2 approaches for storing and retrieving the HHIT from DNS.
These are:
* As FQDNs in the .aero TLD.
* Reverse DNS lookups as IPv6 addresses per [RFC8005].
The HHIT can be used to construct an FQDN that points to the USS that
has the Public/Private information for the UA (GEN-4 and GEN-5). For
example the USS for the HHIT 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.uas.areo IN PTR foo.uss.areo.
The individual HHITs are potentially too numerous to actually store
in DNS. Rather the USS would provide the HHIT detail response.
The HHIT reverse lookup can be a standard IPv6 reverse look up, or it
can leverage off the HHIT structure. Assume that the RAA is 10 and
the HDA is 20 and the HHIT is:
2001:14:28:14:a3ad:1952:ad0:a69e
An HHIT reverse lookup would be to is:
2001:14:28:14:a3ad:1952:ad0:a69e.20.10.hhit.arpa.
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5. Other UTM uses of HHITs
HHITs can be used extensively within the UTM architecture beyond for
UA ID (and USS in UA ID registration and authentication). The GCS
SHOULD have its own HHIT as an ID. It could use this if it is the
source of Network Remote ID for securing the transport and for secure
C2 transport [drip-secure-nrid-c2].
Observers SHOULD have HHITs to facilitate UAS information retrieval
(e.g. for authorization to private UAS data). They could also use
their HHIT for establishing a HIP connection with the UA Pilot for
direct communications per authorization. Further, they can be used
by FINDER observers, [crowd-sourced-rid].
6. DRIP Requirements addressed
This document provides solutions to GEN 1 - 6 and ID 1 - 5.
7. ASTM Considerations
ASTM will need to make the following changes to the "UA ID" in the
Basic Message:
Type 4:
This document UA ID of Hierarchical HITs (see Section 3).
8. IANA Considerations
TBD
9. Security Considerations
The security considerations with Hierarchical HITs, most notably the
short hash of the HI, are discussed in [hierarchical-hit]. The
binding of the hierarchy to the hash of the HI is covered in
[new-orchid].
Cryptographically Generated Addresses (CGAs) provide a unique
assurance of uniqueness. This is two-fold. The address (in this
case the UAS ID) is a hash of a public key and a Registry hierarchy
naming. Collision resistance (more important that its implied
second-preimage resistance) makes it statistically challenging to
attacks. A registration process as in HHIT Registries
[hhit-registries] provides a level of assured uniqueness unattainable
without mirroring this approach.
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The second aspect of assured uniqueness is the digital signing
process of the HHIT by the HI private key and the further signing of
the HI public key by the Registry's key. This completes the
ownership process. The observer at this point does not know WHAT
owns the HHIT, but is assured, other than the risk of theft of the HI
private key, that this UAS ID is owned by something and is properly
registered.
9.1. Hierarchical HIT Trust
The HHIT UAS RID in the ASTM Basic Message (the actual Remote ID
message) does not provide any assertions of trust. The best that
might be done is 4 bytes truncated from a HI signing of the HHIT (the
UA ID field is 20 bytes and a HHIT is 16). It is in the ASTM
Authentication Messages as defined in [drip-auth] that provide all of
the actual ownership proofs. These claims include timestamps to
defend against replay attacks. But in themselves, they do not prove
which UA actually sent the message. They could have been sent by a
dog running down the street with a Broadcast Remote ID device
strapped to its back.
Proof of UA transmission comes when the Authentication Message
includes proofs for the Location/Vector Message and the observer can
see the UA or that information is validated by ground multilateration
[crowd-sourced-rid]. Only then does an observer gain full trust in
the HHIT Remote ID.
HHIT Remote IDs obtained via the Network Remote ID path provides a
different approach to trust. Here the UAS SHOULD be securely
communicating to the USS (see [drip-secure-nrid-c2]), thus asserting
HHIT RID trust.
10. Acknowledgments
Dr. Gurtov is an advisor on Cybersecurity to the Swedish Civil
Aviation Administration.
11. 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>.
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12. Informative References
[corus] CORUS, "U-space Concept of Operations", September 2019,
<https://www.sesarju.eu/node/3411>.
[crowd-sourced-rid]
Moskowitz, R., Card, S., and A. Wiethuechter, "Crowd
Sourced Remote ID", Work in Progress, Internet-Draft,
draft-moskowitz-drip-crowd-sourced-rid-03, 20 March 2020,
<https://tools.ietf.org/html/draft-moskowitz-drip-crowd-
sourced-rid-03>.
[CTA2063A] ANSI, "Small Unmanned Aerial Systems Serial Numbers",
September 2019.
[drip-auth]
Wiethuechter, A., Card, S., and R. Moskowitz, "DRIP
Authentication Formats", Work in Progress, Internet-Draft,
draft-wiethuechter-drip-auth-00, 23 March 2020,
<https://tools.ietf.org/html/draft-wiethuechter-drip-auth-
00>.
[drip-requirements]
Card, S., Wiethuechter, A., and R. Moskowitz, "Drone
Remote Identification Protocol (DRIP) Requirements", Work
in Progress, Internet-Draft, draft-card-drip-reqs-02, 20
April 2020,
<https://tools.ietf.org/html/draft-card-drip-reqs-02>.
[drip-secure-nrid-c2]
Moskowitz, R., Card, S., Wiethuechter, A., and A. Gurtov,
"Secure UAS Network RID and C2 Transport", Work in
Progress, Internet-Draft, draft-moskowitz-drip-secure-
nrid-c2-00, 6 April 2020, <https://tools.ietf.org/html/
draft-moskowitz-drip-secure-nrid-c2-00>.
[F3411-19] ASTM International, "Standard Specification for Remote ID
and Tracking", February 2020,
<http://www.astm.org/cgi-bin/resolver.cgi?F3411>.
[hhit-registries]
Moskowitz, R., Card, S., and A. Wiethuechter,
"Hierarchical HIT Registries", Work in Progress, Internet-
Draft, draft-moskowitz-hip-hhit-registries-02, 9 March
2020, <https://tools.ietf.org/html/draft-moskowitz-hip-
hhit-registries-02>.
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[hierarchical-hit]
Moskowitz, R., Card, S., and A. Wiethuechter,
"Hierarchical HITs for HIPv2", Work in Progress, Internet-
Draft, draft-moskowitz-hip-hierarchical-hit-04, 3 March
2020, <https://tools.ietf.org/html/draft-moskowitz-hip-
hierarchical-hit-04>.
[new-hip-crypto]
Moskowitz, R., Card, S., and A. Wiethuechter, "New
Cryptographic Algorithms for HIP", Work in Progress,
Internet-Draft, draft-moskowitz-hip-new-crypto-04, 23
January 2020, <https://tools.ietf.org/html/draft-
moskowitz-hip-new-crypto-04>.
[new-orchid]
Moskowitz, R., Card, S., and A. Wiethuechter, "Using
cSHAKE in ORCHIDs", Work in Progress, Internet-Draft,
draft-moskowitz-orchid-cshake-00, 11 December 2019,
<https://tools.ietf.org/html/draft-moskowitz-orchid-
cshake-00>.
[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>.
[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>.
Appendix A. EU U-Space RID Privacy Considerations
EU is defining a future of airspace management known as U-space
within the Single European Sky ATM Research (SESAR) undertaking.
Concept of Operation for EuRopean UTM Systems (CORUS) project
proposed low-level Concept of Operations [corus] for UAS in EU. It
introduces strong requirements for UAS privacy based on European GDPR
regulations. It suggests that UAs are identified with agnostic IDs,
with no information about UA type, the operators or flight
trajectory. Only authorized persons should be able to query the
details of the flight with a record of access.
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Due to the high privacy requirements, a casual observer can only
query U-space if it is aware of a UA seen in a certain area. A
general observer can use a public U-space portal to query UA details
based on the UA transmitted "Remote identification" signal. Direct
remote identification (DRID) is based on a signal transmitted by the
UA directly. Network remote identification (NRID) is only possible
for UAs being tracked by U-Space and is based on the matching the
current UA position to one of the tracks.
The project lists "E-Identification" and "E-Registrations" services
as to be developed. These services can follow the privacy mechanism
proposed in this document. If an "agnostic ID" above refers to a
completely random identifier, it creates a problem with identity
resolution and detection of misuse. On the other hand, a classical
HIT has a flat structure which makes its resolution difficult. The
Hierarchical HITs provide a balanced solution by associating a
registry with the UA identifier. This is not likely to cause a major
conflict with U-space privacy requirements, as the registries are
typically few at a country level (e.g. civil personal, military, law
enforcement, or commercial).
Authors' Addresses
Robert Moskowitz
HTT Consulting
Oak Park, MI 48237
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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Andrei Gurtov
Linköping University
IDA
SE-58183 Linköping
Sweden
Email: gurtov@acm.org
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