Internet DRAFT - draft-ietf-drip-arch
draft-ietf-drip-arch
drip S. Card
Internet-Draft A. Wiethuechter
Intended status: Informational AX Enterprize
Expires: 6 September 2023 R. Moskowitz
HTT Consulting
S. Zhao (Editor)
Intel
A. Gurtov
Linköping University
5 March 2023
Drone Remote Identification Protocol (DRIP) Architecture
draft-ietf-drip-arch-31
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
(RFC 9153).
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 6 September 2023.
Copyright Notice
Copyright (c) 2023 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.
Card, et al. Expires 6 September 2023 [Page 1]
Internet-Draft DRIP Architecture March 2023
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 UAS RID and its 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 Cryptographic Identifier . . . . . . . . . . . 13
3.3. HHIT as A Trustworthy DRIP Entity Identifier . . . . . . 13
3.4. HHIT for DRIP Identifier Registration and Lookup . . . . 15
4. DRIP Identifier Registration and Registries . . . . . . . . . 15
4.1. Public Information Registry . . . . . . . . . . . . . . . 15
4.1.1. Background . . . . . . . . . . . . . . . . . . . . . 16
4.1.2. Public DRIP Identifier Registry . . . . . . . . . . . 16
4.2. Private Information Registry . . . . . . . . . . . . . . 16
4.2.1. Background . . . . . . . . . . . . . . . . . . . . . 16
4.2.2. Information Elements . . . . . . . . . . . . . . . . 17
4.2.3. Private DRIP Identifier Registry Methods . . . . . . 17
4.2.4. Alternative Private DRIP Registry Methods . . . . . . 17
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 . . . . . . . . . . . . . . . . . . . . . . . . 20
8. Security Considerations . . . . . . . . . . . . . . . . . . . 21
8.1. Private Key Physical Security . . . . . . . . . . . . . . 21
8.2. Quantum Resistant Cryptography . . . . . . . . . . . . . 21
8.3. Denial Of Service (DoS) Protection . . . . . . . . . . . 22
8.4. Spoofing & Replay Protection . . . . . . . . . . . . . . 22
8.5. Timestamps & Time Sources . . . . . . . . . . . . . . . . 22
9. Privacy & Transparency Considerations . . . . . . . . . . . . 23
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 23
10.1. Normative References . . . . . . . . . . . . . . . . . . 23
10.2. Informative References . . . . . . . . . . . . . . . . . 24
Card, et al. Expires 6 September 2023 [Page 2]
Internet-Draft DRIP Architecture March 2023
Appendix A. Overview of Unmanned Aircraft Systems (UAS) Traffic
Management (UTM) . . . . . . . . . . . . . . . . . . . . 28
A.1. Operation Concept . . . . . . . . . . . . . . . . . . . . 28
A.2. UAS Service Supplier (USS) . . . . . . . . . . . . . . . 29
A.3. UTM Use Cases for UAS Operations . . . . . . . . . . . . 29
Appendix B. Automatic Dependent Surveillance Broadcast
(ADS-B) . . . . . . . . . . . . . . . . . . . . . . . . . 30
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 31
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] and illustrates how all of them can
be met, except for GEN-7 QoS, which is left for future work. The
requirements document provides an extended introduction to the
problem space and use cases. Further, this architecture document
frames the DRIP Entity Tag (DET) [I-D.ietf-drip-rid] within the
architecture.
1.1. Overview of UAS RID and its Standardization
UAS RID is an application that enables UAS to be identified by UAS
Traffic Management (UTM) and UAS Service Suppliers (USS) (Appendix A)
and third party entities such as law enforcement. Many
considerations (e.g., safety and security) dictate that 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).
Card, et al. Expires 6 September 2023 [Page 3]
Internet-Draft DRIP Architecture March 2023
European Union Aviation Safety Agency (EASA)
In pursuit of the "U-space" concept of a single European airspace
safely shared by manned and unmanned aircraft, 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 U-space regulations.
American Society for Testing and Materials (ASTM)
ASTM International, Technical Committee F38 (UAS), Subcommittee
F38.02 (Aircraft Operations), Work Item WK65041, developed the
ASTM [F3411-22a] 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. [F3411-22a] is the technical standard
basis of the [F3586-22] "Means Of Compliance" (MOC) accepted by
the FAA as per [MOC-NOA] to the FAA's UAS RID final rule [FAA_RID]
and is expected to be accepted by some other CAAs.
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
study [TR-23.755] and specification [TS-23.255] focus 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 [F3411-22a].
Card, et al. Expires 6 September 2023 [Page 4]
Internet-Draft DRIP Architecture March 2023
1.2.1. Broadcast RID
[F3411-22a] 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
[F3411-22a], 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.
Card, et al. Expires 6 September 2023 [Page 5]
Internet-Draft DRIP Architecture March 2023
* 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
Card, et al. Expires 6 September 2023 [Page 6]
Internet-Draft DRIP Architecture March 2023
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 USS. Subscribed Net-RID DPs then
forward RID information via the Internet to subscribed Observer
devices. Regulations require and [F3411-22a] describes UAS RID data
elements that must be transported end-to-end from the UAS to the
subscribed Observer devices.
[F3411-22a] 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 [F3411-22a] 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.
Card, et al. Expires 6 September 2023 [Page 7]
Internet-Draft DRIP Architecture March 2023
+------+ +----------+ +------+
| 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). Multiple UAS are
shown, each with its own UA controlled by its own GCS, potentially
using the same or different USS, with the UA potentially
communicating directly with each other (V2V) especially for low
latency safety related purposes (DAA).
Card, et al. Expires 6 September 2023 [Page 8]
Internet-Draft DRIP Architecture March 2023
*************** ***************
* 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 [F3411-22a] and other external
standards, to satisfy UAS RID requirements.
Card, et al. Expires 6 September 2023 [Page 9]
Internet-Draft DRIP Architecture March 2023
This document outlines the DRIP architecture in the context of the
UAS RID architecture. This includes closing the gaps between the
CAAs' Concepts of Operations and [F3411-22a] 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 required by GEN-1
(Section 3), especially but not exclusively for use as single-
use session IDs.
- Mechanisms to leverage the Domain Name System (DNS [RFC1034]),
for registering and publishing public and private information
(see Section 4.1 and Section 4.2) as required by REG-1 and REG-
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 DIME (Section 4 and Section 5) as required by GEN-2.
- 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 (personal data protection)
(Section 9).
This document should serve as a main point of entry into the set
of IETF documents addressing the basic DRIP requirements.
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.
Card, et al. Expires 6 September 2023 [Page 10]
Internet-Draft DRIP Architecture March 2023
This document uses terms defined in [RFC9153].
Some of the acronyms have plural forms that remain the same as their
singular forms, e.g., UAS can expand to Unmanned Aircraft System
(singular) or Unmanned Aircraft Systems (plural), as appropriate for
the context. This usage is consistent with Section 2.2 of [RFC9153].
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 "Claim", "Evidence", "Endorsement",
and "Certificate" as used in DRIP. A DRIP certificate has a
different context compared with security certificates and Public Key
Infrastructure used in X.509.
Claim:
A claim shares the same definition as a claim in RATS [RFC9334];
it is a piece of asserted information, sometimes in the form of a
name/value pair. It could also been seen as a predicate (e.g., "X
is Y", "X has property Y", and most importantly "X owns Y" or "X
is owned by Y").
Evidence:
Evidence in DRIP borrows the same definition as in RATS [RFC9334];
that is, a set of claims.
Endorsement:
An Endorsement is inspired from RATS [RFC9334]; it is a secure
(i.e. signed) statement vouching the integrity and veracity of
evidence.
Certificate:
Card, et al. Expires 6 September 2023 [Page 11]
Internet-Draft DRIP Architecture March 2023
A certificate in DRIP is an endorsement, strictly over identity
information, signed by a third party. This third party should be
one with no stake in the endorsement over which it is signing.
DRIP Identity Management Entity (DIME):
An entity that performs functions similar to a domain registrar/
registry. A DIME vets Claims and/or Evidence from a registrant
and delivers back Endorsements and/or Certificates in response.
It is a high-level entity in the DRIP registration/provisioning
process that can hold the role of HDA, RAA, or root of trust
(typically the HHIT prefix owner or DNS apex owner) for DETs.
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 [F3411-22a] 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 DIME 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 registration
discovery (managed by a DRIP Identity Management Entity (DIME)) to
either yield the HI for a 3rd-party (seeking UAS ID endorsement)
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 Broadcast RID, especially its support for Bluetooth 4,
imposes severe constraints. A previous revision of the ASTM UAS RID,
F3411-19, allowed a UAS ID of types (1, 2, and 3), each of 20 bytes.
[F3411-22a] adds type 4, Specific Session ID, for other Standards
Card, et al. Expires 6 September 2023 [Page 12]
Internet-Draft DRIP Architecture March 2023
Development Organizations (SDOs) to extend ASTM UAS RID. Type 4 uses
one byte to index the Specific Session ID subtype, leaving 19 bytes
(see ID-1 of DRIP Requirements [RFC9153]). As described in Section 3
of [RFC9153], ASTM has allocated Specific Session ID subtype 1 to
IETF DRIP.
The maximum ASTM UAS RID Authentication Message payload is 201 bytes
each for Authentication Types 1, 2, 3, and 4. [F3411-22a] adds
Authentication Type 5 for other SDOs (including the IETF) to extend
ASTM UAS RID with Specific Authentication Methods (SAM). With type
5, one of the 201 bytes is consumed to index the SAM Type, leaving
only 200 bytes for DRIP authentication payloads, including one or
more DRIP entity identifiers and associated authentication data.
3.2. 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 DIME can detect them and
reject registration requests rather than issue credentials, e.g., by
enforcing a First Come First Served policy. Pre-image hash attacks
are also mitigated through this registration process, locking the
HHIT to a specific HI.
3.3. 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 endorsement, 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
Card, et al. Expires 6 September 2023 [Page 13]
Internet-Draft DRIP Architecture March 2023
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 DRIP enhanced Network RID MUST be provisioned
likewise; the private key resides only in the ultimate source of
Network RID messages. If the GCS is the source of the Network RID
messages; the GCS MUST hold the private key. If the UA is the source
of the Network RID messages and they are being relayed by the GCS;
the UA MUST hold the private key, just as a UA that directly connects
to the network rather than through its GCS.
Each Observer device functioning with Internet connectivity MAY be
provisioned either with public keys of the DRIP identifier root
registries or certificates for subordinate registries; each Observer
device that needs to operate without Internet connectivity at any
time MUST be so provisioned.
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-endorsement of a HHIT used as a UAS ID can be done in as
little as 88-bytes when Ed25519 [RFC8032] is used by only including
the 16-byte HHIT, two 4-byte timestamps, and the 64-byte Ed25519
signature.
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
endorsement 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).
Card, et al. Expires 6 September 2023 [Page 14]
Internet-Draft DRIP Architecture March 2023
In general, Internet access may be needed to validate Endorsements or
Certificates. This may be obviated in the most common cases (e.g.,
endorsement of the UAS ID), even in disconnected environments, by
pre-populating small caches on Observer devices with DIME public keys
and a chain of Endorsements or Certificates (tracing a path through
the DIME tree). This is assuming all parties on the trust path also
use HHITs for their identities.
3.4. 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]). The First Come First Served registration policy
is adequate.
A lookup of the HHIT into the DIME provides the registered HI for
HHIT proof of ownership and deterministic access to any other needed
actionable information based on inquiry access authority (more
details in Section 4.2).
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
Card, et al. Expires 6 September 2023 [Page 15]
Internet-Draft DRIP Architecture March 2023
4.1.1. Background
The public information registry provides trustable information such
as endorsements 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 endorsement signing operations). This public
information will be principally used by Observers of Broadcast RID
messages. Data on UAS 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.
4.1.2. Public DRIP Identifier Registry
A DRIP identifier MUST 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 DNSSEC to deliver public
information that is not inherently trustable (e.g., everything other
than endorsements).
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.
Card, et al. Expires 6 September 2023 [Page 16]
Internet-Draft DRIP Architecture March 2023
4.2.2. Information Elements
When a DET is used as a UA's Session ID, the corresponding
manufacturer assigned serial number MUST be stored in a Private
Information Registry that can be identified uniquely from the DET.
When a DET is used as either as UA's Session ID or as a UA's
manufacturer assigned serial number, and the operation is being flown
under UTM, the corresponding UTM system assigned Operational Intent
Identifier SHOULD be so stored. Other information MAY be so stored,
and often must to satisfy CAA regulations or USS operator policies.
4.2.3. Private DRIP Identifier Registry Methods
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 leveraging
aspects of 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].
4.2.4. 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
supported. These alternative methods may be used by Net-RID DP with
specific customers.
5. DRIP Identifier Trust
While the DRIP entity identifier is self-asserting, it alone does not
provide the trustworthiness (non-repudiation, 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 cannot be proved merely by its
possessing a DRIP Entity Tag (DET) and broadcasting it as a claim
that it belongs to that sender. Sending data signed using that HI's
private key proves little, as it is subject to trivial replay attacks
using previously broadcast messages. Only sending the DET and a
signature on novel (i.e., frequently changing and unpredictable) data
that can be externally validated by the Observer (such as a signed
Location/Vector message, matching actually seeing the UA at the
location and time reported in the signed message) proves that the
observed UA possesses the private key and thus the claimed UAS ID.
Card, et al. Expires 6 September 2023 [Page 17]
Internet-Draft DRIP Architecture March 2023
The severe constraints of Broadcast RID make it challenging to
satisfy UAS RID requirements. 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.
A combination of different DRIP Authentication Messages enables an
Observer, without Internet connection (offline) or with (online), to
validate a UAS DRIP ID in real-time. Some messages must contain the
relevant registration of the UA's DRIP ID in the claimed DIME. Some
messages must contain sender signatures over both static (e.g.,
registration) and dynamically changing (e.g., current UA location)
data. Combining these two sets of information, an Observer can piece
together a chain of trust including real-time evidence to make a
determination on the UA's claims.
This process (combining the DRIP entity identifier, registries, and
authentication formats for Broadcast RID) can satisfy the following
DRIP requirements defined in [RFC9153]: GEN-1, GEN-2, GEN-3, ID-2,
ID-3, ID-4, and ID-5.
6. Harvesting Broadcast Remote ID messages for UTM Inclusion
ASTM anticipated that regulators would require both Broadcast RID and
Network RID for large UAS, 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).
Crowd-sourcing can be encouraged by quid pro quo, providing CS-RID
Surveillance Supplemental Data Service Provider (SDSP) outputs only
to CS-RID Finders. As Broadcast RID media have limited range,
gateways receiving messages claiming locations far from the gateway
can alert authorities or a Surveillance SDSP to the failed sanity
Card, et al. Expires 6 September 2023 [Page 18]
Internet-Draft DRIP Architecture March 2023
check possibly indicating intent to deceive. CS-RID 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).
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 Net-RID client. It would
present a new interface to a CS-RID SDSP, similar to but readily
distinguishable from that which a UAS (UA or GCS) presents to 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 present the same interface to a Net-
RID SP as does a Net-RID DP and to a Net-RID DP as does a Net-RID SP,
but its data source must be readily distinguishable as via Finders
rather than direct from the UAS itself.
Card, et al. Expires 6 September 2023 [Page 19]
Internet-Draft DRIP Architecture March 2023
7. DRIP Contact
One of the ways in which DRIP can enhance [F3411-22a] 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 DIME 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
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.
Card, et al. Expires 6 September 2023 [Page 20]
Internet-Draft DRIP Architecture March 2023
8. Security Considerations
The size of the public key hash in the HHIT is vulnerable to a second
preimage attack. It is well within current server array technology
to compute another key pair that hashes to the same HHIT (given the
current ORCHID construction hash length to fit UAS RID and IPv6
address constraints). Thus, if a receiver were to check HHIT/HI pair
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, online receivers should verify the
received HHIT and received HI with the HDA (typically USS) with which
the HHIT/HI pair purports to be registered. Online and offline
receivers can use a chain of received DRIP link endorsements from a
root of trust through the RAA and the HDA to the UA, e.g., as
described in [I-D.ietf-drip-auth] and [I-D.ietf-drip-registries].
Compromise of a DIME private key could do widespread harm
[I-D.ietf-drip-registries]. In particular, it would allow bad actors
to impersonate trusted members of said DIME. These risks are in
addition to those involving key management practices and will be
addressed as part of the DIME process. All DRIP public keys can be
found in DNS thus they can be revoked in DNS and users SHOULD check
DNS when available. Specific key revocation procedures are as yet to
be determined.
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. 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 storage of the private key.
8.2. Quantum Resistant Cryptography
There has been no effort as yet in DRIP to address post quantum
computing cryptography. Small UAS and Broadcast Remote ID
communications are so constrained that current post quantum computing
cryptography is not applicable. Fortunately, since a UA may use a
unique HHIT for each operation, the attack window can be limited to
the duration of the operation. One potential future DRIP use for
Card, et al. Expires 6 September 2023 [Page 21]
Internet-Draft DRIP Architecture March 2023
post quantum cryptography is for keypairs that have long usage lives,
but rarely if ever need to be transmitted over bandwidth constrained
links; such as for Serial Numbers or Operators. As the HHIT contains
the ID for the cryptographic suite used in its creation, a future
post quantum computing safe algorithm that fits Remote ID constraints
may readily be added. This is left for future work.
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. Also DOS
may be attempted with spoofing/replay attacks, for which see
Section 8.4.
8.4. Spoofing & Replay Protection
As noted in Section 5, spoofing is combatted by the intrinsic self-
attesting properties of HHITs plus their registration. Also as noted
in Section 5, to combat replay attacks, a receiver MUST NOT trust
that an observed UA is that identified in the Basic ID message (i.e.
possesses the corresponding private key) until it receives a complete
chain of endorsement links from a root of trust to the UA's leaf DET,
plus a signed message containing frequently changing, unpredictable
but sanity-checkable data (e.g., a Location/Vector message) and
verifies all the foregoing.
8.5. Timestamps & Time Sources
Section 6 and more fundamentally Section 3.3 both require timestamps.
In Broadcast RID messages, [F3411-22a] specifies both 32 bit Unix
style UTC timestamps (seconds since midnight going into the 1st day
of 2019 rather than 1970) and 16 bit relative timestamps (tenths of
seconds since the start of the most recent hour or other specified
event). [F3411-22a] requires that 16 bit timestamp accuracy,
relative to the time of applicability of the data being timestamped,
also be reported, with a worst allowable case of 1.5 seconds.
[F3411-22a] does not specify the time source, but GNSS is generally
assumed, as latitude, longitude and geodetic altitude must be
reported and most small UAS use GNSS for positioning and navigation.
Card, et al. Expires 6 September 2023 [Page 22]
Internet-Draft DRIP Architecture March 2023
Informative note: for example, to satisfy [FAA_RID], [F3586-22]
specifies tamper protection of the entire RID subsystem and use of
the US Government operated GPS. GPS has sub-microsecond accuracy
and 1.5 second precision. In this example, UA-sourced messages
can be assumed to have timestamp accuracy and precision of 1.5
seconds at worst.
GCS often have access to cellular LTE or other time sources better
than the foregoing, and such better time sources would be required to
support multilateration in Section 6, but such better time sources
cannot be assumed generally for purposes of security analysis.
9. Privacy & Transparency Considerations
Broadcast RID messages can contain personal data (Section 3.2 of
[RFC6973]) such as the operator ID and in most jurisdictions must
contain the pilot/GCS location. The DRIP architectural approach for
personal data protection is symmetric encryption of the personal data
using a session key known to the UAS and its USS, as follows.
Authorized Observers 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 just the UAS ID
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).
Personal data is protected unless the UAS is otherwise configured: as
part of DRIP-enhanced RID subsystem provisioning; as part of UTM
operation authorization; or via subsequent authenticated
communications from a cognizant authority. Personal data protection
MUST NOT be used if the UAS loses connectivity to its USS, as if the
UAS loses connectivity, Observers nearby likely also won't have
connectivity enabling decryption of the personal data. The UAS
always has the option to abort the operation if personal data
protection is disallowed, but if this occurs during flight, the UA
then MUST broadcast the personal data without protection until it
lands and is powered off. Note that normative language was used only
minimally in this section, as privacy protection requires refinement
of the DRIP architecture and specification of interoperable protocol
extensions, which are left for future DRIP documents.
10. References
10.1. Normative References
Card, et al. Expires 6 September 2023 [Page 23]
Internet-Draft DRIP Architecture March 2023
[F3411-22a]
ASTM International, "Standard Specification for Remote ID
and Tracking", July 2022,
<https://www.astm.org/f3411-22a.html>.
[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-37, 2 December 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-drip-
rid-37>.
[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>.
[F3586-22] ASTM International, "Standard Practice for Remote ID Means
of Compliance to Federal Aviation Administration
Regulation 14 CFR Part 89", July 2022,
<https://www.astm.org/f3586-22.html>.
Card, et al. Expires 6 September 2023 [Page 24]
Internet-Draft DRIP Architecture March 2023
[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>.
[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. W., and R. Moskowitz, "DRIP
Entity Tag Authentication Formats & Protocols for
Broadcast Remote ID", Work in Progress, Internet-Draft,
draft-ietf-drip-auth-29, 15 February 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-drip-
auth-29>.
[I-D.ietf-drip-registries]
Wiethuechter, A. and J. Reid, "DRIP Entity Tag (DET)
Identity Management Architecture", Work in Progress,
Internet-Draft, draft-ietf-drip-registries-07, 5 December
2022, <https://datatracker.ietf.org/doc/html/draft-ietf-
drip-registries-07>.
[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>.
Card, et al. Expires 6 September 2023 [Page 25]
Internet-Draft DRIP Architecture March 2023
[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/>.
[MOC-NOA] United States Federal Aviation Administration (FAA),
"Accepted Means of Compliance; Remote Identification of
Unmanned Aircraft", August 2022,
<https://www.regulations.gov/document/FAA-2022-0859-0001>.
[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>.
[RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
Morris, J., Hansen, M., and R. Smith, "Privacy
Considerations for Internet Protocols", RFC 6973,
DOI 10.17487/RFC6973, July 2013,
<https://www.rfc-editor.org/info/rfc6973>.
Card, et al. Expires 6 September 2023 [Page 26]
Internet-Draft DRIP Architecture March 2023
[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>.
[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>.
[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>.
[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>.
[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>.
[RFC9334] Birkholz, H., Thaler, D., Richardson, M., Smith, N., and
W. Pan, "Remote ATtestation procedureS (RATS)
Architecture", RFC 9334, DOI 10.17487/RFC9334, January
2023, <https://www.rfc-editor.org/info/rfc9334>.
Card, et al. Expires 6 September 2023 [Page 27]
Internet-Draft DRIP Architecture March 2023
[TR-23.755]
3GPP, "Study on application layer support for Unmanned
Aerial Systems (UAS) (Release 17)", 2019,
<https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=3588>.
[TS-22.825]
3GPP, "Study on Remote Identification of Unmanned Aerial
Systems (UAS)", 2018,
<https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=3527>.
[TS-23.255]
3GPP, "Application layer support for Uncrewed Aerial
System (UAS) Functional architecture and information
flows; (Release 17)", 2020,
<https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=3843>.
[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.
Card, et al. Expires 6 September 2023 [Page 28]
Internet-Draft DRIP Architecture March 2023
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.
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)
Card, et al. Expires 6 September 2023 [Page 29]
Internet-Draft DRIP Architecture March 2023
from the UAS. An accepted UAS operation may, and in some cases
must, share its current flight data, such as GPS position and
altitude, to the USS. The USS may maintain (and provide to
authorized requestors) the UAS operation status near real-time in
the short term, and may retain at least some of it in the longer
term, e.g., for overall airspace air traffic monitoring.
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. Cost, Size, Weight and Power (CSWaP) requirements of ADS-B
transponders on CSWaP constrained UA
3. Limited bandwidth of both uplink and downlink, which would likely
be saturated by large numbers of UAS, 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 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,
Stephan Wenger, Kyle Rose, Roni Even, Thomas Fossati, Valery Smyslov,
Erik Kline, John Scudder, Murray Kucheraway, Robert Wilton, Roman
Daniliw, Warren Kumari, Zaheduzzaman Sarker and Dave Thaler for the
reviews and helpful positive comments. Thanks to Laura Welch for her
assistance greatly improving this document. Thanks to Dave Thaler
for showing our authors how to leverage the RATS model for
attestation in DRIP. Thanks to chairs Daniel Migault and Mohamed
Boucadair for direction of our team of authors and editor, some of
Card, et al. Expires 6 September 2023 [Page 30]
Internet-Draft DRIP Architecture March 2023
whom are relative newcomers to writing IETF documents. Thanks
especially to Internet Area Director Eric Vyncke for guidance and
support.
Authors' Addresses
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
Intel
2200 Mission College Blvd
Santa Clara, 95054
United States of America
Email: shuai.zhao@ieee.org
Andrei Gurtov
Linköping University
IDA
SE-58183 Linköping Linköping
Sweden
Email: gurtov@acm.org
Card, et al. Expires 6 September 2023 [Page 31]
