Drone Remote Identification Protocol (DRIP) Architecture
draft-ietf-drip-arch-25
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 9434.
|
|
|---|---|---|---|
| Authors | Stuart W. Card , Adam Wiethuechter , Robert Moskowitz , Shuai Zhao , Andrei Gurtov | ||
| Last updated | 2022-07-23 | ||
| Replaces | draft-card-drip-arch | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews |
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Ready w/issues
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| Additional resources | Mailing list discussion | ||
| Stream | WG state | Submitted to IESG for Publication | |
| Associated WG milestones |
|
||
| Document shepherd | Daniel Migault | ||
| Shepherd write-up | Show Last changed 2022-01-31 | ||
| IESG | IESG state | Became RFC 9434 (Informational) | |
| Consensus boilerplate | Yes | ||
| Telechat date |
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Has enough positions to pass. |
||
| Responsible AD | Éric Vyncke | ||
| Send notices to | daniel.migault@ericsson.com | ||
| IANA | IANA review state | Version Changed - Review Needed |
draft-ietf-drip-arch-25
drip S. Card
Internet-Draft A. Wiethuechter
Intended status: Informational AX Enterprize
Expires: 26 January 2023 R. Moskowitz
HTT Consulting
S. Zhao (Editor)
Tencent
A. Gurtov
Linköping University
25 July 2022
Drone Remote Identification Protocol (DRIP) Architecture
draft-ietf-drip-arch-25
Abstract
This document describes an architecture for protocols and services to
support Unmanned Aircraft System (UAS) Remote Identification (RID)
and tracking, plus UAS RID-related communications. This architecture
adheres to the requirements listed in the DRIP Requirements document
(RFC9153).
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
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 26 January 2023.
Copyright Notice
Copyright (c) 2022 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
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
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Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Overview of Unmanned Aircraft System (UAS) Remote ID (RID)
and Standardization . . . . . . . . . . . . . . . . . . . 3
1.2. Overview of Types of UAS Remote ID . . . . . . . . . . . 4
1.2.1. Broadcast RID . . . . . . . . . . . . . . . . . . . . 5
1.2.2. Network RID . . . . . . . . . . . . . . . . . . . . . 5
1.3. Overview of USS Interoperability . . . . . . . . . . . . 7
1.4. Overview of DRIP Architecture . . . . . . . . . . . . . . 8
2. Terms and Definitions . . . . . . . . . . . . . . . . . . . . 10
2.1. Additional Abbreviations . . . . . . . . . . . . . . . . 11
2.2. Additional Definitions . . . . . . . . . . . . . . . . . 11
3. HHIT as the DRIP Entity Identifier . . . . . . . . . . . . . 12
3.1. UAS Remote Identifiers Problem Space . . . . . . . . . . 12
3.2. HHIT as A Trustworthy DRIP Entity Identifier . . . . . . 13
3.3. HHIT for DRIP Identifier Registration and Lookup . . . . 14
3.4. HHIT as a Cryptographic Identifier . . . . . . . . . . . 15
4. DRIP Identifier Registration and Registries . . . . . . . . . 15
4.1. Public Information Registry . . . . . . . . . . . . . . . 15
4.1.1. Background . . . . . . . . . . . . . . . . . . . . . 15
4.1.2. DNS as the Public DRIP Identifier Registry . . . . . 16
4.2. Private Information Registry . . . . . . . . . . . . . . 16
4.2.1. Background . . . . . . . . . . . . . . . . . . . . . 16
4.2.2. EPP and RDAP as the Private DRIP Identifier
Registry . . . . . . . . . . . . . . . . . . . . . . 16
4.2.3. Alternative Private DRIP Registry methods . . . . . . 16
5. DRIP Identifier Trust . . . . . . . . . . . . . . . . . . . . 17
6. Harvesting Broadcast Remote ID messages for UTM Inclusion . . 18
6.1. The CS-RID Finder . . . . . . . . . . . . . . . . . . . . 19
6.2. The CS-RID SDSP . . . . . . . . . . . . . . . . . . . . . 19
7. DRIP Contact . . . . . . . . . . . . . . . . . . . . . . . . 19
8. Security Considerations . . . . . . . . . . . . . . . . . . . 20
8.1. Private Key Physical Security . . . . . . . . . . . . . . 20
8.2. Post Quantum Computing . . . . . . . . . . . . . . . . . 21
8.3. Denial Of Service (DOS) Protection . . . . . . . . . . . 21
9. Privacy & Transparency Considerations . . . . . . . . . . . . 21
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 22
10.1. Normative References . . . . . . . . . . . . . . . . . . 22
10.2. Informative References . . . . . . . . . . . . . . . . . 22
Appendix A. Overview of Unmanned Aircraft Systems (UAS) Traffic
Management (UTM) . . . . . . . . . . . . . . . . . . . . 26
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A.1. Operation Concept . . . . . . . . . . . . . . . . . . . . 26
A.2. UAS Service Supplier (USS) . . . . . . . . . . . . . . . 27
A.3. UTM Use Cases for UAS Operations . . . . . . . . . . . . 27
Appendix B. Automatic Dependent Surveillance Broadcast
(ADS-B) . . . . . . . . . . . . . . . . . . . . . . . . . 28
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28
1. Introduction
This document describes an architecture for protocols and services to
support Unmanned Aircraft System (UAS) Remote Identification (RID)
and tracking, plus RID-related communications. The architecture
takes into account both current (including proposed) regulations and
non-IETF technical standards.
The architecture adheres to the requirements listed in the DRIP
Requirements document [RFC9153]. The requirements document provides
an extended introduction to the problem space and use cases.
Further, it frames the DRIP Entity Tag (DET) [I-D.ietf-drip-rid]
within the architecture.
1.1. Overview of Unmanned Aircraft System (UAS) Remote ID (RID) and
Standardization
UAS Remote Identification (RID) is an application that enables a UAS
to be identified by Unmanned Aircraft Systems Traffic Management
(UTM) and UAS Service Supplier (USS) (Appendix A) or third party
entities such as law enforcement. Many considerations (e.g., safety)
dictate that a UAS be remotely identifiable.
Civil Aviation Authorities (CAAs) worldwide are mandating UAS RID.
CAAs currently promulgate performance-based regulations that do not
specify techniques, but rather cite industry consensus technical
standards as acceptable means of compliance.
USA Federal Aviation Administration (FAA)
The FAA published a Notice of Proposed Rule Making [NPRM] in 2019
and thereafter published a "Final Rule" in 2021 [FAA_RID],
imposing requirements on UAS manufacturers and operators, both
commercial and recreational. The rule states that Automatic
Dependent Surveillance Broadcast (ADS-B) Out and transponders
cannot be used to satisfy the UAS RID requirements on UAS to which
the rule applies (see Appendix B).
European Union Aviation Safety Agency (EASA)
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The EASA published a [Delegated] regulation in 2019 imposing
requirements on UAS manufacturers and third-country operators,
including but not limited to UAS RID requirements. The same year,
EASA also published an [Implementing] regulation laying down
detailed rules and procedures for UAS operations and operating
personnel which then was updated in 2021 [Implementing_update]. A
Notice of Proposed Amendment [NPA] was published in 2021 to
provide more information about the development of acceptable means
of compliance and guidance material to support the U-space
regulation.
American Society for Testing and Materials (ASTM)
ASTM International, Technical Committee F38 (UAS), Subcommittee
F38.02 (Aircraft Operations), Work Item WK65041, developed the
ASTM [F3411-19] Standard Specification for Remote ID and Tracking.
ASTM defines one set of UAS RID information and two means, MAC-
layer broadcast and IP-layer network, of communicating it. If an
UAS uses both communication methods, the same information must be
provided via both means. [F3411-19] is cited by the FAA in its
UAS RID final rule [FAA_RID] as "a potential means of compliance"
to a Remote ID rule.
The 3rd Generation Partnership Project (3GPP)
With release 16, the 3GPP completed the UAS RID requirement study
[TS-22.825] and proposed a set of use cases in the mobile network
and services that can be offered based on UAS RID. The Release 17
specification focuses on enhanced UAS service requirements and
provides the protocol and application architecture support that
will be applicable for both 4G and 5G networks. The study of
Further Architecture Enhancement for Uncrewed Aerial Vehicles
(UAV) and Urban Air Mobility (UAM) [FS_AEUA] in release 18 further
enhances the communication mechanism between UAS and USS/UTM. The
DRIP Entity Tag in Section 3 may be used as the 3GPP CAA-level UAS
ID for Remote Identification purposes.
1.2. Overview of Types of UAS Remote ID
This specification introduces two types of UAS Remote ID defined in
ASTM [F3411-19].
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1.2.1. Broadcast RID
[F3411-19] defines a set of UAS RID messages for direct, one-way,
broadcast transmissions from the UA over Bluetooth or Wi-Fi. These
are currently defined as MAC-Layer messages. Internet (or other Wide
Area Network) connectivity is only needed for UAS registry
information lookup by Observers using the directly received UAS ID.
Broadcast RID should be functionally usable in situations with no
Internet connectivity.
The minimum Broadcast RID data flow is illustrated in Figure 1.
+------------------------+
| Unmanned Aircraft (UA) |
+-----------o------------+
|
| app messages directly over
| one-way RF data link (no IP)
|
v
+------------------o-------------------+
| Observer's device (e.g., smartphone) |
+--------------------------------------+
Figure 1
Broadcast RID provides information only about unmanned aircraft (UA)
within direct Radio Frequency (RF) Line-Of-Sight (LOS), typically
similar to Visual LOS (VLOS), with a range up to approximately 1 km.
This information may be 'harvested' from received broadcasts and made
available via the Internet, enabling surveillance of areas too large
for local direct visual observation or direct RF link-based ID (see
Section 6).
1.2.2. Network RID
[F3411-19], using the same data dictionary that is the basis of
Broadcast RID messages, defines a Network Remote Identification (Net-
RID) data flow as follows.
* The information to be reported via UAS RID is generated by the
UAS. Typically some of this data is generated by the UA and some
by the GCS (Ground Control Station), e.g., their respective Global
Navigation Satellite System (GNSS) derived locations.
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* The information is sent by the UAS (UA or GCS) via unspecified
means to the cognizant Network Remote Identification Service
Provider (Net-RID SP), typically the USS under which the UAS is
operating if participating in UTM.
* The Net-RID SP publishes via the Discovery and Synchronization
Service (DSS) over the Internet that it has operations in various
4-D airspace volumes (Section 2.2 of [RFC9153]), describing the
volumes but not the operations.
* An Observer's device, which is expected, but not specified, to be
web-based, queries a Network Remote Identification Display
Provider (Net-RID DP), typically also a USS, about any operations
in a specific 4-D airspace volume.
* Using fully specified web-based methods over the Internet, the
Net-RID DP queries all Net-RID SPs that have operations in volumes
intersecting that of the Observer's query for details on all such
operations.
* The Net-RID DP aggregates information received from all such Net-
RID SPs and responds to the Observer's query.
The minimum Net-RID data flow is illustrated in Figure 2:
+-------------+ ******************
| UA | * Internet *
+--o-------o--+ * *
| | * * +------------+
| '--------*--(+)-----------*-----o |
| * | * | |
| .--------*--(+)-----------*-----o Net-RID SP |
| | * * | |
| | * .------*-----o |
| | * | * +------------+
| | * | *
| | * | * +------------+
| | * '------*-----o |
| | * * | Net-RID DP |
| | * .------*-----o |
| | * | * +------------+
| | * | *
| | * | * +------------+
+--o-------o--+ * '------*-----o Observer's |
| GCS | * * | Device |
+-------------+ ****************** +------------+
Figure 2
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Command and Control (C2) must flow from the GCS to the UA via some
path. Currently (in the year 2022) this is typically a direct RF
link; however, with increasing Beyond Visual Line of Sight (BVLOS)
operations, it is expected often to be a wireless link at either end
with the Internet between.
Telemetry (at least the UA's position and heading) flows from the UA
to the GCS via some path, typically the reverse of the C2 path.
Thus, UAS RID information pertaining to both the GCS and the UA can
be sent, by whichever has Internet connectivity, to the Net-RID SP,
typically the USS managing the UAS operation.
The Net-RID SP forwards UAS RID information via the Internet to
subscribed Net-RID DPs, typically USSs. Subscribed Net-RID DPs then
forward RID information via the Internet to subscribed Observer
devices. Regulations require and [F3411-19] describes UAS RID data
elements that must be transported end-to-end from the UAS to the
subscribed Observer devices.
[F3411-19] prescribes the protocols between the Net-RID SP, Net-RID
DP, and the DSS. It also prescribes data elements (in JSON) between
the Observer and the Net-RID DP. DRIP could address standardization
of secure protocols between the UA and GCS (over direct wireless and
Internet connection), between the UAS and the Net-RID SP, and/or
between the Net-RID DP and Observer devices.
Informative note: Neither link layer protocols nor the use of
links (e.g., the link often existing between the GCS and the
UA) for any purpose other than carriage of UAS RID information
is in the scope of [F3411-19] Network RID.
1.3. Overview of USS Interoperability
With Net-RID, there is direct communication between each UAS and its
USS. Multiple USS exchange information with the assistance of a DSS
so all USS collectively have knowledge about all activities in a 4D
airspace. The interactions among an Observer, multiple UAS, and
their USS are shown in Figure 3.
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+------+ +----------+ +------+
| UAS1 | | Observer | | UAS2 |
+---o--+ +-----o----+ +--o---+
| | |
******|*************|************|******
* | | | *
* | +---o--+ | *
* | .------o USS3 o------. | *
* | | +--o---+ | | *
* | | | | | *
* +-o--o-+ +--o--+ +-o--o-+ *
* | o----o DSS o-----o | *
* | USS1 | +-----+ | USS2 | *
* | o----------------o | *
* +------+ +------+ *
* *
* Internet *
****************************************
Figure 3
1.4. Overview of DRIP Architecture
Figure 4 illustrates a global UAS RID usage scenario. Broadcast RID
links are not shown as they reach from any UA to any listening
receiver in range and thus would obscure the intent of the figure.
Figure 4 shows, as context, some entities and interfaces beyond the
scope of DRIP (as currently (2022) chartered).
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*************** ***************
* UAS1 * * UAS2 *
* * * *
* +--------+ * DAA/V2V * +--------+ *
* | UA o--*----------------------------------------*--o UA | *
* +--o--o--+ * * +--o--o--+ *
* | | * +------+ Lookups +------+ * | | *
* | | * | GPOD o------. .------o PSOD | * | | *
* | | * +------+ | | +------+ * | | *
* | | * | | * | | *
* C2 | | * V2I ************ V2I * | | C2 *
* | '-----*--------------* *--------------*-----' | *
* | * * * * | *
* | o====Net-RID===* *====Net-RID===o | *
* +--o--+ * * Internet * * +--o--+ *
* | GCS o-----*--------------* *--------------*-----o GCS | *
* +-----+ * Registration * * Registration * +-----+ *
* * (and UTM) * * (and UTM) * *
*************** ************ ***************
| | |
+----------+ | | | +----------+
| Public o---' | '---o Private |
| Registry | | | Registry |
+----------+ | +----------+
+--o--+
| DNS |
+-----+
DAA: Detect And Avoid
GPOD: General Public Observer Device
PSOD: Public Safety Observer Device
V2I: Vehicle-to-Infrastructure
V2V: Vehicle-to-Vehicle
Figure 4
Informative note: see [RFC9153] for detailed definitions.
DRIP is meant to leverage existing Internet resources (standard
protocols, services, infrastructures, and business models) to meet
UAS RID and closely related needs. DRIP will specify how to apply
IETF standards, complementing [F3411-19] and other external
standards, to satisfy UAS RID requirements.
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This document outlines the DRIP architecture in the context of the
UAS RID architecture. This includes presenting the gaps between the
CAAs' Concepts of Operations and [F3411-19] as it relates to the use
of Internet technologies and UA direct RF communications. Issues
include, but are not limited to:
- Design of trustworthy remote identifiers (Section 3).
- Mechanisms to leverage the Domain Name System (DNS [RFC1034]),
Extensible Provisioning Protocol (EPP [RFC5731]) and
Registration Data Access Protocol (RDAP) ([RFC9082]) for
publishing public and private information (see Section 4.1 and
Section 4.2).
- Specific authentication methods and message payload formats to
enable verification that Broadcast RID messages were sent by
the claimed sender (Section 5) and that the sender is in the
claimed registry (Section 4 and Section 5).
- Harvesting Broadcast RID messages for UTM inclusion, with the
optional DRIP extension of Crowd Sourced Remote ID (CS-RID,
Section 6), using the DRIP support for gateways required by
GEN-5 [RFC9153].
- Methods for instantly establishing secure communications
between an Observer and the pilot of an observed UAS
(Section 7), using the DRIP support for dynamic contact
required by GEN-4 [RFC9153].
- Privacy in UAS RID messages (PII protection) (Section 9).
2. Terms and Definitions
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.
To encourage comprehension necessary for adoption of DRIP by the
intended user community, the UAS community's norms are respected
herein.
This document uses terms defined in [RFC9153].
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2.1. Additional Abbreviations
DET: DRIP Entity Tag
EdDSA: Edwards-Curve Digital Signature Algorithm
HHIT: Hierarchical HIT
HI: Host Identity
HIP: Host Identity Protocol
HIT: Host Identity Tag
2.2. Additional Definitions
This section introduces the terms "Claims", "Assertions",
"Attestations", and "Certificates" as used in DRIP. A DRIP
certificate has a different context compared with security
certificates and Public Key Infrastructure used in X.509.
Claims:
A claim in DRIP is a predicate (e.g., "X is Y", "X has property
Y", and most importantly "X owns Y" or "X is owned by Y").
Assertions:
An assertion in DRIP is a set of claims. This definition is
borrowed from JWT [RFC7519] and CWT [RFC8392].
Attestations:
An attestation in DRIP is a signed assertion. The signer may be
the claimant or a related party with a stake in the assertion(s).
Under DRIP this is normally used when an entity asserts a
relationship with another entity, along with other information,
and the asserting entity signs the assertion, thereby making it an
attestation.
Certificates:
A certificate in DRIP is an attestation, strictly over identity
information, signed by a third party. This third party should be
one with no stake in the attestation(s) over which it is signing.
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3. HHIT as the DRIP Entity Identifier
This section describes the DRIP architectural approach to meeting the
basic requirements of a DRIP entity identifier within external
technical standard ASTM [F3411-19] and regulatory constraints. It
justifies and explains the use of Hierarchical Host Identity Tags
(HHITs) [I-D.ietf-drip-rid] as self-asserting IPv6 addresses suitable
as a UAS ID type and, more generally, as trustworthy multipurpose
remote identifiers.
Self-asserting in this usage means that, given the Host Identity
(HI), the HHIT ORCHID construction (see section 3.5 of
[I-D.ietf-drip-rid]) and a signature of the registry on the HHIT and
HI, the HHIT can be verified by the receiver as a trusted UAS ID.
The explicit registration hierarchy within the HHIT provides registry
discovery (managed by a Registrar) to either yield the HI for a 3rd-
party (seeking UAS ID attestation) validation or prove that the HHIT
and HI have been registered uniquely.
3.1. UAS Remote Identifiers Problem Space
A DRIP entity identifier needs to be "Trustworthy" (see DRIP
Requirement GEN-1, ID-4 and ID-5 in [RFC9153]). This means that
given a sufficient collection of UAS RID messages, an Observer can
establish that the identifier claimed therein uniquely belongs to the
claimant. To satisfy DRIP requirements and maintain important
security properties, the DRIP identifier should be self-generated by
the entity it names (e.g., a UAS) and registered (e.g., with a USS,
see Requirements GEN-3 and ID-2).
However the Broadcast RID, especially its support for Bluetooth 4.x,
imposes severe constraints. The ASTM UAS RID [F3411-19] allows a UAS
ID of types 1, 2 and 3 of 20 bytes. [F3411-22a] add an additional
type 4 (Specific Session ID). Type 4 uses one byte to index the
Specific Session ID (leaving 19 bytes, see ID-1 of DRIP Requirement
[RFC9153]); Specific Session ID of value 1 is allocated to IETF DRIP
by ASTM. This new Specific Session ID will be standardized by IETF
and other standards development organizations (SDOs) as extensions to
ASTM UAS RID.
Likewise, the maximum ASTM UAS RID [F3411-19] Authentication Message
payload is 201 bytes for most authentication types. A type 5 is also
added in this revision for IETF and other SDOs to develop Specific
Authentication Methods as extensions to ASTM UAS RID. One byte out
of 201 bytes is consumed to index the sub-type which leaves only 200
for DRIP authentication payloads, including one or more DRIP entity
identifiers and associated authentication data.
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3.2. HHIT as A Trustworthy DRIP Entity Identifier
A Remote UAS ID that can be trustworthy for use in Broadcast RID can
be built from an asymmetric keypair. In this method, the UAS ID is
cryptographically derived directly from the public key. The proof of
UAS ID ownership (verifiable attestation, versus mere claim) is
guaranteed by signing this cryptographic UAS ID with the associated
private key. The association between the UAS ID and the private key
is ensured by cryptographically binding the public key with the UAS
ID; more specifically, the UAS ID results from the hash of the public
key. The public key is designated as the HI while the UAS ID is
designated as the HIT.
By construction, the HIT is statistically unique through the
mandatory use of cryptographic hash functions with second-preimage
resistance. The cryptographically-bound addition of the Hierarchy
and an HHIT registration process provide complete, global HHIT
uniqueness. This registration forces the attacker to generate the
same public key rather than a public key that generates the same
HHIT. This is in contrast to general IDs (e.g., a UUID or device
serial number) as the subject in an X.509 certificate.
A UA equipped for Broadcast RID MUST be provisioned not only with its
HHIT but also with the HI public key from which the HHIT was derived
and the corresponding private key, to enable message signature. A
UAS equipped for Network RID SHOULD be provisioned likewise; the
private key resides only in the ultimate source of Network RID
messages (i.e., on the UA itself if the GCS is merely relaying rather
than sourcing Network RID messages). Each Observer device SHOULD be
provisioned either with public keys of the DRIP identifier root
registries or certificates for subordinate registries.
HHITs can also be used throughout the USS/UTM system. Operators and
Private Information Registries, as well as other UTM entities, can
use HHITs for their IDs. Such HHITs can facilitate DRIP security
functions such as used with HIP to strongly mutually authenticate and
encrypt communications.
A self-attestation of a HHIT used as a UAS ID can be done in as
little as 84 bytes when Ed25519 [RFC8032] is used by only including
the 16-byte HHIT, a 4-byte timestamp, and the 64-byte Ed25519
signature.
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Ed25519 [RFC8032] is used as the HHIT Mandatory to Implement signing
algorithm as [RFC9153] GEN-1 and ID-5 can best be met by restricting
the HI to 32 bytes. A larger public key would rule out the offline
attestation feature that fits within the 200-byte Authentication
Message maximum length. Other algorithms that meet this 32 byte
constraint can be added as deemed needed.
A DRIP identifier can be assigned to a UAS as a static HHIT by its
manufacturer, such as a single HI and derived HHIT encoded as a
hardware serial number per [CTA2063A]. Such a static HHIT SHOULD
only be used to bind one-time use DRIP identifiers to the unique UA.
Depending upon implementation, this may leave a HI private key in the
possession of the manufacturer (see also Section 8).
In general, Internet access may be needed to validate Attestations or
Certificates. This may be obviated in the most common cases (e.g.,
attestation of the UAS ID), even in disconnected environments, by
prepopulating small caches on Observer devices with Registry public
keys and a chain of Attestations or Certificates (tracing a path
through the Registry tree). This is assuming all parties on the
trust path also use HHITs for their identities.
3.3. HHIT for DRIP Identifier Registration and Lookup
UAS RID needs a deterministic lookup mechanism that rapidly provides
actionable information about the identified UA. Given the size
constraints imposed by the Bluetooth 4 broadcast media, the UAS ID
itself needs to be a non-spoofable inquiry input into the lookup.
A DRIP registration process based on the explicit hierarchy within a
HHIT provides manageable uniqueness of the HI for the HHIT. The
hierarchy is defined in [I-D.ietf-drip-rid] and consists of 2-levels,
a Registered Assigning Authority (RAA) and then a Hierarchical HIT
Domain Authority (HDA). The registration within this hierarchy is
the defense against a cryptographic hash second pre-image attack on
the HHIT (e.g., multiple HIs yielding the same HHIT, see Requirement
ID-3 in [RFC9153]). A lookup of the HHIT into the registration data
provides the registered HI for HHIT proof of ownership. A first-
come-first-served registration for a HHIT provides deterministic
access to any other needed actionable information based on inquiry
access authority (more details in Section 4.2).
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3.4. HHIT as a Cryptographic Identifier
The only (known to the authors at the time of this writing) existing
types of IP address compatible identifiers cryptographically derived
from the public keys of the identified entities are Cryptographically
Generated Addresses (CGAs) [RFC3972] and Host Identity Tags (HITs)
[RFC7401]. CGAs and HITs lack registration/retrieval capability. To
provide this, each HHIT embeds plaintext information designating the
hierarchy within which it is registered and a cryptographic hash of
that information concatenated with the entity's public key, etc.
Although hash collisions may occur, the registrar can detect them and
reject registration requests rather than issue credentials, e.g., by
enforcing a first-claimed, first-attested policy. Pre-image hash
attacks are also mitigated through this registration process, locking
the HHIT to a specific HI.
4. DRIP Identifier Registration and Registries
DRIP registries hold both public and private UAS information (see
PRIV-1 in [RFC9153]) resulting from the DRIP identifier registration
process. Given these different uses, and to improve scalability,
security, and simplicity of administration, the public and private
information can be stored in different registries. This section
introduces the public and private information registries for DRIP
identifiers. This DRIP Identifier registration process satisfies the
following DRIP requirements defined in [RFC9153]: GEN-3, GEN-4, ID-2,
ID-4, ID-6, PRIV-3, PRIV-4, REG-1, REG-2, REG-3 and REG-4.
4.1. Public Information Registry
4.1.1. Background
The public information registry provides trustable information such
as attestations of UAS RID ownership and registration with the HDA
(Hierarchical HIT Domain Authority). Optionally, pointers to the
registries for the HDA and RAA (Registered Assigning Authority)
implicit in the UAS RID can be included (e.g., for HDA and RAA
HHIT|HI used in attestation signing operations). This public
information will be principally used by Observers of Broadcast RID
messages. Data on UASs that only use Network RID, is available via
an Observer's Net-RID DP that would directly provide all public
registry information. The Net-RID DP is the only source of
information for a query on an airspace volume.
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4.1.2. DNS as the Public DRIP Identifier Registry
A DRIP identifier SHOULD be registered as an Internet domain name (at
an arbitrary level in the hierarchy, e.g., in .ip6.arpa). Thus DNS
can provide all the needed public DRIP information. A standardized
HHIT FQDN (Fully Qualified Domain Name) can deliver the HI via a HIP
RR (Resource Record) [RFC8005] and other public information (e.g.,
RAA and HDA PTRs, and HIP RVS (Rendezvous Servers) [RFC8004]). These
public information registries can use secure DNS transport (e.g., DNS
over TLS) to deliver public information that is not inherently
trustable (e.g., everything other than attestations).
This DNS entry for the HHIT can also provide a revocation service.
For example, instead of returning the HI RR it may return some record
showing that the HI (and thus HHIT) has been revoked.
4.2. Private Information Registry
4.2.1. Background
The private information required for DRIP identifiers is similar to
that required for Internet domain name registration. A DRIP
identifier solution can leverage existing Internet resources:
registration protocols, infrastructure, and business models, by
fitting into a UAS ID structure compatible with DNS names. The HHIT
hierarchy can provide the needed scalability and management
structure. It is expected that the private information registry
function will be provided by the same organizations that run a USS,
and likely integrated with a USS. The lookup function may be
implemented by the Net-RID DPs.
4.2.2. EPP and RDAP as the Private DRIP Identifier Registry
A DRIP private information registry supports essential registry
operations (e.g., add, delete, update, query) using interoperable
open standard protocols. It can accomplish this by using the
Extensible Provisioning Protocol (EPP [RFC5730]) and the Registry
Data Access Protocol (RDAP [RFC7480] [RFC9082] [RFC9083]). The DRIP
private information registry in which a given UAS is registered needs
to be findable, starting from the UAS ID, using the methods specified
in [RFC9224].
4.2.3. Alternative Private DRIP Registry methods
A DRIP private information registry might be an access-controlled DNS
(e.g., via DNS over TLS). Additionally, WebFinger [RFC7033] can be
deployed. These alternative methods may be used by Net-RID DP with
specific customers.
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5. DRIP Identifier Trust
While the DRIP entity identifier is self-asserting, it alone does not
provide the trustworthiness (non-repudiability, protection vs.
spoofing, message integrity protection, scalability, etc.) essential
to UAS RID, as justified in [RFC9153]. For that it MUST be
registered (under DRIP Registries) and be actively used by the party
(in most cases the UA). A sender's identity can not be proved by
only possessing a DRIP Entity Tag (DET) and broadcasting it as a
claim that it belongs to that sender. Even the sender using that
HI's private key to sign static data proves nothing as well, as it is
subject to trivial replay attacks. Only sending the DET and a
signature on frequently changing data that can be externally
validated by the Observer (such as a Location/Vector message matching
actually seeing the UA at that location) proves that the observed UA
possesses the claimed UAS ID.
For Broadcast RID, it is a challenge to balance the original
requirements of Broadcast RID and the efforts needed to satisfy the
DRIP requirements all under severe constraints. From received
Broadcast RID messages and information that can be looked up using
the received UAS ID in online registries or local caches, it is
possible to establish levels of trust in the asserted information and
the Operator.
Optimization of different DRIP Authentication Messages allows an
Observer, without Internet connection (offline) or with (online), to
be able to validate a UAS DRIP ID in real-time. First is the sending
of Broadcast Attestations (over DRIP Link Authentication Messages)
[I-D.ietf-drip-auth] containing the relevant registration of the UA's
DRIP ID in the claimed Registry. Next is sending DRIP Wrapper
Authentication Messages that sign over both static (e.g., above
registration) and dynamically changing data (such as UA location
data). Combining these two sets of information, an Observer can
piece together a chain of trust and real-time evidence to make their
determination of the UA's claims.
This process (combining the DRIP entity identifier, Registries and
Authentication Formats for Broadcast RID) can satisfy the following
DRIP requirement defined in [RFC9153]: GEN-1, GEN-2, GEN-3, ID-2, ID-
3, ID-4 and ID-5.
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6. Harvesting Broadcast Remote ID messages for UTM Inclusion
ASTM anticipated that regulators would require both Broadcast RID and
Network RID for large UASs, but allow UAS RID requirements for small
UAS to be satisfied with the operator's choice of either Broadcast
RID or Network RID. The EASA initially specified Broadcast RID for
essentially all UAS, and is now also considering Network RID. The
FAA UAS RID Final Rules [FAA_RID] permit only Broadcast RID for rule
compliance, but still encourage Network RID for complementary
functionality, especially in support of UTM.
One opportunity is to enhance the architecture with gateways from
Broadcast RID to Network RID. This provides the best of both and
gives regulators and operators flexibility. It offers advantages
over either form of UAS RID alone: greater fidelity than Network RID
reporting of planned area operations; surveillance of areas too large
for local direct visual observation and direct RF-LOS link based
Broadcast RID (e.g., a city or a national forest).
These gateways could be pre-positioned (e.g., around airports, public
gatherings, and other sensitive areas) and/or crowd-sourced (as
nothing more than a smartphone with a suitable app is needed). As
Broadcast RID media have limited range, gateways receiving messages
claiming locations far from the gateway can alert authorities or a
SDSP to the failed sanity check possibly indicating intent to
deceive. Surveillance SDSPs can use messages with precise date/time/
position stamps from the gateways to multilaterate UA location,
independent of the locations claimed in the messages, which are
entirely operator self-reported in UAS RID and UTM, and thus are
subject not only to natural time lag and error but also operator
misconfiguration or intentional deception.
Multilateration technologies use physical layer information, such as
precise Time Of Arrival (TOA) of transmissions from mobile
transmitters at receivers with a priori precisely known locations, to
estimate the locations of the mobile transmitters.
Further, gateways with additional sensors (e.g., smartphones with
cameras) can provide independent information on the UA type and size,
confirming or refuting those claims made in the UAS RID messages.
Section 6.1 and Section 6.2 define two additional entities that are
required to provide this Crowd Sourced Remote ID (CS-RID).
This approach satisfies the following DRIP requirements defined in
[RFC9153]: GEN-5, GEN-11, and REG-1. As Broadcast messages are
inherently multicast, GEN-10 is met for local-link multicast to
multiple Finders (how multilateration is possible).
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6.1. The CS-RID Finder
A CS-RID Finder is the gateway for Broadcast Remote ID Messages into
UTM. It performs this gateway function via a CS-RID SDSP. A CS-RID
Finder could implement, integrate, or accept outputs from a Broadcast
RID receiver. However, it should not depend upon a direct interface
with a GCS, Net-RID SP, Net-RID DP or Network RID client. It would
present a new interface to a CS-RID SDSP, similar to but readily
distinguishable from that between a GCS and a Net-RID SP.
6.2. The CS-RID SDSP
A CS-RID SDSP aggregates and processes (e.g., estimates UA location
using multilateration when possible) information collected by CS-RID
Finders. A CS-RID SDSP should appear (i.e., present the same
interface) to a Net-RID SP as a Net-RID DP.
7. DRIP Contact
One of the ways in which DRIP can enhance [F3411-19] with immediately
actionable information is by enabling an Observer to instantly
initiate secure communications with the UAS remote pilot, Pilot In
Command, operator, USS under which the operation is being flown, or
other entity potentially able to furnish further information
regarding the operation and its intent and/or to immediately
influence further conduct or termination of the operation (e.g., land
or otherwise exit an airspace volume). Such potentially distracting
communications demand strong "AAA" (Authentication, Attestation,
Authorization, Access Control, Accounting, Attribution, Audit) per
applicable policies (e.g., of the cognizant CAA).
A DRIP entity identifier based on a HHIT as outlined in Section 3
embeds an identifier of the registry in which it can be found
(expected typically to be the USS under which the UAS is flying) and
the procedures outlined in Section 5 enable Observer verification of
that relationship. A DRIP entity identifier with suitable records in
public and private registries as outlined in Section 5 can enable
lookup not only of information regarding the UAS, but also identities
of and pointers to information regarding the various associated
entities (e.g., the USS under which the UAS is flying an operation),
including means of contacting those associated entities (i.e.,
locators, typically IP addresses).
A suitably equipped Observer could initiate a secure communication
channel, using the DET HI, to a similarly equipped and identified
entity: the UA itself, if operating autonomously; the GCS, if the UA
is remotely piloted and the necessary records have been populated in
DNS; the USS, etc. Assuming secure communication setup (e.g. via
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IPsec or HIP), arbitrary standard higher layer protocols can then be
used for Observer to Pilot (O2P communications (e.g., SIP [RFC3261]
et seq), V2X communications (e.g., [MAVLink]), etc. Certain
preconditions are necessary: each party needs a currently usable
means (typically DNS) of resolving the other party's DRIP entity
identifier to a currently usable locator (IP address); and there must
be currently usable bidirectional IP (not necessarily Internet)
connectivity between the parties. One method directly supported by
the use of HHITs as DRIP entity identifiers is initiation of a HIP
Base Exchange (BEX) and Bound End-to-End Tunnel (BEET).
This approach satisfies DRIP requirement GEN-6 Contact, supports
satisfaction of requirements [RFC9153] GEN-8, GEN-9, PRIV-2, PRIV-5
and REG-3, and is compatible with all other DRIP requirements.
8. Security Considerations
The size of the public key hash in the HHIT is vulnerable to a
second-image attack. It is well within current server array
technology to compute another key pair that hashes to the same HHIT.
Thus, if a receiver were to check HHIT validity only by verifying
that the received HI and associated information, when hashed in the
ORCHID construction, reproduce the received HHIT, an adversary could
impersonate a validly registered UA. To defend against this, on-line
receivers should verify the received HHIT and received HI with the
USS with which the HHIT purports to be registered. On-line and off-
line receivers can use a chain of received DRIP link attestations
from a root of trust through the RAA and the HDA to the UA, as
described, e.g., in [I-D.ietf-drip-auth] and
[I-D.ietf-drip-registries].
Compromise of a registry private key could do widespread harm
[I-D.ietf-drip-registries]. In particular, it would allow bad actors
to impersonate trusted members of said registry. Key revocation
procedures are as yet to be determined. These risks are in addition
to those involving Operator key management practices and will be
addressed as part of the registry process.
8.1. Private Key Physical Security
The security provided by asymmetric cryptographic techniques depends
upon protection of the private keys. It may be necessary for the GCS
to have the key pair to register the HHIT to the USS. Thus it may be
the GCS that generates the key pair and delivers it to the UA, making
the GCS a part of the key security boundary. Leakage of the private
key either from the UA or GCS to the component manufacturer is a
valid concern and steps need to be in place to ensure safe keeping of
the private key.
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Since it is possible for the UAS RID sender of a small harmless UA
(or the entire UA) to be carried by a larger dangerous UA as a "false
flag", it is out of scope to deal with secure store for the private
key.
8.2. Post Quantum Computing
There has been no effort, at this time, to address post quantum
computing cryptography. UAs and Broadcast Remote ID communications
are so constrained that current post quantum computing cryptography
is not applicable. Plus since a UA may use a unique HHIT for each
operation, the attack window could be limited to the duration of the
operation.
Finally, as the HHIT contains the ID for the cryptographic suite used
in its creation, a future post quantum computing safe algorithm that
fits the Remote ID constraints may readily be added.
8.3. Denial Of Service (DOS) Protection
Remote ID services from the UA use a wireless link in a public space.
As such, they are open to many forms of RF jamming. It is trivial
for an attacker to stop any UA messages from reaching a wireless
receiver. Thus it is pointless to attempt to provide relief from DOS
attacks as there is always the ultimate RF jamming attack. Subtle
DOS attacks of message content altering are not practical with the
basic message error correction provided. Finally, this whole
architecture is put forth to make DOS spoofing/replay attacks very
hard.
9. Privacy & Transparency Considerations
Broadcast RID messages can contain Personally Identifiable
Information (PII). A viable architecture for PII protection would be
symmetric encryption of the PII using a session key known to the UAS
and its USS. Authorized Observers could obtain plaintext in either
of two ways. An Observer can send the UAS ID and the cyphertext to a
server that offers decryption as a service. An Observer can send the
UAS ID only to a server that returns the session key, so that
Observer can directly locally decrypt all cyphertext sent by that UA
during that session (UAS operation). In either case, the server can
be: a Public Safety USS, the Observer's own USS, or the UA's USS if
the latter can be determined (which under DRIP it can be, from the
UAS ID itself). PII can be protected unless the UAS is informed
otherwise. This could come as part of UTM operation authorization.
It can be special instructions at the start or during an operation.
PII protection MUST NOT be used if the UAS loses connectivity to the
USS. The UAS always has the option to abort the operation if PII
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protection is disallowed.
10. References
10.1. 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>.
[RFC9153] Card, S., Ed., Wiethuechter, A., Moskowitz, R., and A.
Gurtov, "Drone Remote Identification Protocol (DRIP)
Requirements and Terminology", RFC 9153,
DOI 10.17487/RFC9153, February 2022,
<https://www.rfc-editor.org/info/rfc9153>.
10.2. Informative References
[CTA2063A] ANSI, "Small Unmanned Aerial Systems Serial Numbers",
2019.
[Delegated]
European Union Aviation Safety Agency (EASA), "EU
Commission Delegated Regulation 2019/945 of 12 March 2019
on unmanned aircraft systems and on third-country
operators of unmanned aircraft systems", 2019,
<https://eur-lex.europa.eu/legal-content/EN/
TXT/?uri=CELEX%3A32019R0945>.
[F3411-19] ASTM International, "Standard Specification for Remote ID
and Tracking", February 2020,
<http://www.astm.org/cgi-bin/resolver.cgi?F3411>.
[F3411-22a]
ASTM International, "Standard Specification for Remote ID
and Tracking", July 2022,
<https://www.astm.org/f3411-22a.html>.
[FAA_RID] United States Federal Aviation Administration (FAA),
"Remote Identification of Unmanned Aircraft", 2021,
<https://www.govinfo.gov/content/pkg/FR-2021-01-15/
pdf/2020-28948.pdf>.
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[FAA_UAS_Concept_Of_Ops]
United States Federal Aviation Administration (FAA),
"Unmanned Aircraft System (UAS) Traffic Management (UTM)
Concept of Operations (V2.0)", 2020,
<https://www.faa.gov/uas/research_development/
traffic_management/media/UTM_ConOps_v2.pdf>.
[FS_AEUA] "Study of Further Architecture Enhancement for UAV and
UAM", 2021, <https://www.3gpp.org/ftp/tsg_sa/WG2_Arch/
TSGS2_147E_Electronic_2021-10/Docs/S2-2107092.zip>.
[I-D.ietf-drip-auth]
Wiethuechter, A., Card, S., and R. Moskowitz, "DRIP Entity
Tag Authentication Formats & Protocols for Broadcast
Remote ID", Work in Progress, Internet-Draft, draft-ietf-
drip-auth-15, 11 July 2022,
<https://www.ietf.org/archive/id/draft-ietf-drip-auth-
15.txt>.
[I-D.ietf-drip-registries]
Wiethuechter, A., Card, S., Moskowitz, R., and J. Reid,
"DRIP Entity Tag (DET) Registration & Lookup", Work in
Progress, Internet-Draft, draft-ietf-drip-registries-05,
11 July 2022, <https://www.ietf.org/archive/id/draft-ietf-
drip-registries-05.txt>.
[I-D.ietf-drip-rid]
Moskowitz, R., Card, S. W., Wiethuechter, A., and A.
Gurtov, "DRIP Entity Tag (DET) for Unmanned Aircraft
System Remote ID (UAS RID)", Work in Progress, Internet-
Draft, draft-ietf-drip-rid-30, 11 July 2022,
<https://www.ietf.org/archive/id/draft-ietf-drip-rid-
30.txt>.
[Implementing]
European Union Aviation Safety Agency (EASA), "EU
Commission Implementing Regulation 2019/947 of 24 May 2019
on the rules and procedures for the operation of unmanned
aircraft", 2019, <https://eur-lex.europa.eu/legal-
content/EN/TXT/?uri=CELEX%3A32019R0947>.
[Implementing_update]
European Union Aviation Safety Agency (EASA), "EU
COMMISSION IMPLEMENTING REGULATION (EU) 2021/664 of 22
April 2021 on a regulatory framework for the U-space",
2021, <https://eur-lex.europa.eu/legal-content/EN/
TXT/?uri=CELEX%3A32021R0664>.
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[LAANC] United States Federal Aviation Administration (FAA), "Low
Altitude Authorization and Notification Capability", n.d.,
<https://www.faa.gov/uas/programs_partnerships/
data_exchange/>.
[MAVLink] "Micro Air Vehicle Communication Protocol", 2021,
<http://mavlink.io/>.
[NPA] European Union Aviation Safety Agency (EASA), "Notice of
Proposed Amendment 2021-14 Development of acceptable means
of compliance and guidance material to support the U-space
regulation", 2021,
<https://www.easa.europa.eu/downloads/134303/en>.
[NPRM] United States Federal Aviation Administration (FAA),
"Notice of Proposed Rule Making on Remote Identification
of Unmanned Aircraft Systems", 2019.
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<https://www.rfc-editor.org/info/rfc1034>.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
DOI 10.17487/RFC3261, June 2002,
<https://www.rfc-editor.org/info/rfc3261>.
[RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)",
RFC 3972, DOI 10.17487/RFC3972, March 2005,
<https://www.rfc-editor.org/info/rfc3972>.
[RFC5730] Hollenbeck, S., "Extensible Provisioning Protocol (EPP)",
STD 69, RFC 5730, DOI 10.17487/RFC5730, August 2009,
<https://www.rfc-editor.org/info/rfc5730>.
[RFC5731] Hollenbeck, S., "Extensible Provisioning Protocol (EPP)
Domain Name Mapping", STD 69, RFC 5731,
DOI 10.17487/RFC5731, August 2009,
<https://www.rfc-editor.org/info/rfc5731>.
[RFC7033] Jones, P., Salgueiro, G., Jones, M., and J. Smarr,
"WebFinger", RFC 7033, DOI 10.17487/RFC7033, September
2013, <https://www.rfc-editor.org/info/rfc7033>.
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[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>.
[RFC7480] Newton, A., Ellacott, B., and N. Kong, "HTTP Usage in the
Registration Data Access Protocol (RDAP)", STD 95,
RFC 7480, DOI 10.17487/RFC7480, March 2015,
<https://www.rfc-editor.org/info/rfc7480>.
[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<https://www.rfc-editor.org/info/rfc7519>.
[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>.
[RFC8032] Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital
Signature Algorithm (EdDSA)", RFC 8032,
DOI 10.17487/RFC8032, January 2017,
<https://www.rfc-editor.org/info/rfc8032>.
[RFC8392] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig,
"CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392,
May 2018, <https://www.rfc-editor.org/info/rfc8392>.
[RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", STD 94, RFC 8949,
DOI 10.17487/RFC8949, December 2020,
<https://www.rfc-editor.org/info/rfc8949>.
[RFC9082] Hollenbeck, S. and A. Newton, "Registration Data Access
Protocol (RDAP) Query Format", STD 95, RFC 9082,
DOI 10.17487/RFC9082, June 2021,
<https://www.rfc-editor.org/info/rfc9082>.
[RFC9083] Hollenbeck, S. and A. Newton, "JSON Responses for the
Registration Data Access Protocol (RDAP)", STD 95,
RFC 9083, DOI 10.17487/RFC9083, June 2021,
<https://www.rfc-editor.org/info/rfc9083>.
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[RFC9224] Blanchet, M., "Finding the Authoritative Registration Data
Access Protocol (RDAP) Service", STD 95, RFC 9224,
DOI 10.17487/RFC9224, March 2022,
<https://www.rfc-editor.org/info/rfc9224>.
[TS-22.825]
3GPP, "Study on Remote Identification of Unmanned Aerial
Systems (UAS)", n.d.,
<https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=3527>.
[U-Space] European Organization for the Safety of Air Navigation
(EUROCONTROL), "U-space Concept of Operations", 2019,
<https://www.sesarju.eu/sites/default/files/documents/u-
space/CORUS%20ConOps%20vol2.pdf>.
Appendix A. Overview of Unmanned Aircraft Systems (UAS) Traffic
Management (UTM)
A.1. Operation Concept
The National Aeronautics and Space Administration (NASA) and FAA's
effort to integrate UAS operations into the national airspace system
(NAS) led to the development of the concept of UTM and the ecosystem
around it. The UTM concept was initially presented in 2013 and
version 2.0 was published in 2020 [FAA_UAS_Concept_Of_Ops].
The eventual concept refinement, initial prototype implementation,
and testing were conducted by the joint FAA and NASA UTM research
transition team. World efforts took place afterward. The Single
European Sky ATM Research (SESAR) started the CORUS project to
research its UTM counterpart concept, namely [U-Space]. This effort
is led by the European Organization for the Safety of Air Navigation
(Eurocontrol).
Both NASA and SESAR have published their UTM concepts of operations
to guide the development of their future air traffic management (ATM)
system and ensure safe and efficient integration of manned and
unmanned aircraft into the national airspace.
UTM comprises UAS operations infrastructure, procedures and local
regulation compliance policies to guarantee safe UAS integration and
operation. The main functionality of UTM includes, but is not
limited to, providing means of communication between UAS operators
and service providers and a platform to facilitate communication
among UAS service providers.
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A.2. UAS Service Supplier (USS)
A USS plays an important role to fulfill the key performance
indicators (KPIs) that UTM has to offer. Such an Entity acts as a
proxy between UAS operators and UTM service providers. It provides
services like real-time UAS traffic monitoring and planning,
aeronautical data archiving, airspace and violation control,
interacting with other third-party control entities, etc. A USS can
coexist with other USS to build a large service coverage map that can
load-balance, relay, and share UAS traffic information.
The FAA works with UAS industry shareholders and promotes the Low
Altitude Authorization and Notification Capability [LAANC] program,
which is the first system to realize some of the envisioned
functionality of UTM. The LAANC program can automate UAS operational
intent (flight plan) submission and application for airspace
authorization in real-time by checking against multiple aeronautical
databases such as airspace classification and operating rules
associated with it, FAA UAS facility map, special use airspace,
Notice to Airmen (NOTAM), and Temporary Flight Restriction (TFR).
A.3. UTM Use Cases for UAS Operations
This section illustrates a couple of use case scenarios where UAS
participation in UTM has significant safety improvement.
1. For a UAS participating in UTM and taking off or landing in
controlled airspace (e.g., Class Bravo, Charlie, Delta, and Echo
in the United States), the USS under which the UAS is operating
is responsible for verifying UA registration, authenticating the
UAS operational intent (flight plan) by checking against a
designated UAS facility map database, obtaining the air traffic
control (ATC) authorization, and monitoring the UAS flight path
in order to maintain safe margins and follow the pre-authorized
sequence of authorized 4-D volumes (route).
2. For a UAS participating in UTM and taking off or landing in
uncontrolled airspace (e.g., Class Golf in the United States),
pre-flight authorization must be obtained from a USS when
operating Beyond-Visual-Line-of-Sight (BVLOS). The USS either
accepts or rejects the received operational intent (flight plan)
from the UAS. Approved UAS operation may share its current
flight data such as GPS position and altitude to the USS. The
USS may keep the UAS operation status near real-time and may keep
it as a record for overall airspace air traffic monitoring.
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Appendix B. Automatic Dependent Surveillance Broadcast (ADS-B)
The ADS-B is the de jure technology used in manned aviation for
sharing location information, from the aircraft to ground and
satellite-based systems, designed in the early 2000s. Broadcast RID
is conceptually similar to ADS-B, but with the receiver target being
the general public on generally available devices (e.g.,
smartphones).
For numerous technical reasons, ADS-B itself is not suitable for low-
flying small UAS. Technical reasons include but are not limited to
the following:
1. Lack of support for the 1090 MHz ADS-B channel on any consumer
handheld devices
2. Weight and cost of ADS-B transponders on CSWaP (Cost, Size,
Weight, and Power) constrained UA
3. Limited bandwidth of both uplink and downlink, which would likely
be saturated by large numbers of UASs, endangering manned
aviation
Understanding these technical shortcomings, regulators worldwide have
ruled out the use of ADS-B for the small UAS for which UAS RID and
DRIP are intended.
Acknowledgments
The work of the FAA's UAS Identification and Tracking (UAS ID)
Aviation Rulemaking Committee (ARC) is the foundation of later ASTM
and proposed IETF DRIP WG efforts. The work of ASTM F38.02 in
balancing the interests of diverse stakeholders is essential to the
necessary rapid and widespread deployment of UAS RID. Thanks to
Alexandre Petrescu and Stephan Wenger for the helpful and positive
comments. Thanks to chairs Daniel Migault and Mohamed Boucadair for
direction of our team of authors and editor, some of whom are
newcomers to writing IETF documents. Laura Welch is also thanked for
her valuable review comments that led to great improvements of this
memo. Thanks especially to Internet Area Director Eric Vyncke for
guidance and support.
Authors' Addresses
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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
Robert Moskowitz
HTT Consulting
Oak Park, MI, 48237
United States of America
Email: rgm@labs.htt-consult.com
Shuai Zhao
Tencent
2747 Park Blvd
Palo Alto, 94588
United States of America
Email: shuai.zhao@ieee.org
Andrei Gurtov
Linköping University
IDA
SE-58183 Linköping Linköping
Sweden
Email: gurtov@acm.org
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