drip S. Card
Internet-Draft A. Wiethuechter
Intended status: Informational AX Enterprize
Expires: 28 November 2021 R. Moskowitz
HTT Consulting
S. Zhao (Editor)
Tencent
A. Gurtov
Linköping University
27 May 2021
Drone Remote Identification Protocol (DRIP) Architecture
draft-ietf-drip-arch-13
Abstract
This document describes an architecture for protocols and services to
support Unmanned Aircraft System Remote Identification and tracking
(UAS RID), plus RID-related communications. This architecture
satisfies the requirements listed in the DRIP requirements document.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 28 November 2021.
Copyright Notice
Copyright (c) 2021 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/
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Please review these documents carefully, as they describe your rights
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and restrictions with respect to this document. Code Components
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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 . . . . . . . . . . . . . . . . . . . . 4
1.2.2. Network RID . . . . . . . . . . . . . . . . . . . . . 5
1.3. Overview of USS Interoperability . . . . . . . . . . . . 6
1.4. Overview of DRIP Architecture . . . . . . . . . . . . . . 7
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 9
3. Definitions and Abbreviations . . . . . . . . . . . . . . . . 9
3.1. Additional Definitions . . . . . . . . . . . . . . . . . 9
3.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 9
3.3. Claims, Assertions, Attestations, and Certificates . . . 10
4. HHIT for DRIP Entity Identifier . . . . . . . . . . . . . . . 11
4.1. UAS Remote Identifiers Problem Space . . . . . . . . . . 11
4.2. HIT as A Trustworthy DRIP Entity Identifier . . . . . . . 12
4.3. HHIT for DRIP Identifier Registration and Lookup . . . . 13
4.4. HHIT for DRIP Identifier Cryptographic . . . . . . . . . 14
5. DRIP Identifier Registration and Registries . . . . . . . . . 14
5.1. Public Information Registry . . . . . . . . . . . . . . . 14
5.1.1. Background . . . . . . . . . . . . . . . . . . . . . 14
5.1.2. Proposed Approach . . . . . . . . . . . . . . . . . . 14
5.2. Private Information Registry . . . . . . . . . . . . . . 15
5.2.1. Background . . . . . . . . . . . . . . . . . . . . . 15
5.2.2. Proposed Approach . . . . . . . . . . . . . . . . . . 15
6. Harvesting Broadcast Remote ID messages for UTM Inclusion . . 15
6.1. The CS-RID Finder . . . . . . . . . . . . . . . . . . . . 16
6.2. The CS-RID SDSP . . . . . . . . . . . . . . . . . . . . . 16
7. Privacy for Broadcast PII . . . . . . . . . . . . . . . . . . 16
8. Security Considerations . . . . . . . . . . . . . . . . . . . 17
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
10.1. Normative References . . . . . . . . . . . . . . . . . . 17
10.2. Informative References . . . . . . . . . . . . . . . . . 18
Appendix A. Overview of Unmanned Aircraft Systems (UAS) Traffic
Management (UTM) . . . . . . . . . . . . . . . . . . . . 20
A.1. Operation Concept . . . . . . . . . . . . . . . . . . . . 21
A.2. UAS Service Supplier (USS) . . . . . . . . . . . . . . . 21
A.3. UTM Use Cases for UAS Operations . . . . . . . . . . . . 22
A.4. Automatic Dependent Surveillance Broadcast (ADS-B) . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23
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1. Introduction
This document describes an architecture for protocols and services to
support Unmanned Aircraft System Remote Identification and tracking
(UAS RID), 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 [I-D.ietf-drip-reqs].
1.1. Overview of Unmanned Aircraft System (UAS) Remote ID (RID) and
Standardization
UAS Remote Identification (RID) is an application enabler for a UAS
to be identified by Unmanned Aircraft Systems Traffic Management
(UTM) and UAS Service Supplier (USS) (Appendix A) or third parties
entities such as law enforcement. Many considerations (e.g., safety)
dictate that UAS be remotely identifiable. Civil Aviation
Authorities (CAAs) worldwide are mandating UAS RID. For example, the
European Union Aviation Safety Agency (EASA) has published
[Delegated] and [Implementing] Regulations.
CAAs currently promulgate performance-based regulations that do not
specify techniques, but rather cite industry consensus technical
standards as acceptable means of compliance.
Federal Aviation Administration (FAA)
The FAA published a Notice of Proposed Rule Making [NPRM] in 2019
and whereafter published the "Final Rule" in 2021 [FAA_RID]. In
FAA's final rule, it is clearly stated that Automatic Dependent
Surveillance Broadcast (ADS-B) Out and transponders can not be
used to serve the purpose of an remote identification. More
details about ADS-B can be found in Appendix A.4.
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 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 FAA in its RID
final rule [FAA_RID] as "a potential means of compliance" to a
Remote ID rule.
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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 the services that can be offered based on RID. 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 network.
1.2. Overview of Types of UAS Remote ID
1.2.1. Broadcast RID
A set of RID messages are defined 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 locally directly received
UAS RID as a key. Broadcast RID should be functionally usable in
situations with no Internet connectivity.
The Broadcast RID is illustrated in Figure 1.
x x UA
xxxxx
|
|
| app messages directly over
| one-way RF data link (no IP)
|
|
+
x
xxxxx
x
x
x x Observer's device (e.g. smartphone)
x x
Figure 1
With Broadcast RID, an Observer is limited to their radio "visible"
airspace for UAS awareness and information. With queries sent over
the Internet using harvested RID (see Section 6), the Observer may
gain more information about those visible UAS.
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1.2.2. Network RID
A RID data dictionary and data flow for Network RID are defined in
[F3411-19]. This data flow is emitted from an UAS via unspecified
means (but at least in part over the Internet) to a Network Remote ID
Service Provider (Net-RID SP). A Net-RID SP provides the RID data to
Network Remote ID Display Providers (Net-RID DP). It is the Net-RID
DP that responds to queries from Network Remote ID Observers
(expected typically, but not specified exclusively, to be web-based)
specifying airspace volumes of interest. Network RID depends upon
connectivity, in several segments, via the Internet, from the UAS to
the Observer.
The Network RID is illustrated in Figure 2:
x x UA
xxxxx ********************
| \ * ------*---+------------+
| \ * / * | NET_RID_SP |
| \ * ------------/ +---*--+------------+
| RF \ */ | *
| * INTERNET | * +------------+
| /* +---*--| NET_RID_DP |
| / * +---*--+------------+
+ / * | *
x / *****************|*** x
xxxxx | xxxxx
x +------- x
x x
x x Operator (GCS) Observer x x
x x x x
Figure 2
Command and Control (C2) must flow from the GCS to the UA via some
path, currently (in the year of 2021) typically a direct RF link, but
with increasing BVLOS operations expected often to be wireless links
at either end with the Internet between. For all, but the simplest
hobby aircraft, telemetry (at least position and heading) flows from
the UA to the GCS via some path, typically the reverse of the C2
path. Thus, 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.
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The Net-RID SP forwards RID information via the Internet to
subscribed Net-RID DP, typically a USS. Subscribed Net-RID DP
forward RID information via the Internet to subscribed Observer
devices. Regulations require and [F3411-19] describes RID data
elements that must be transported end-to-end from the UAS to the
subscribed Observer devices.
[F3411-19] prescribes the protocols only between the Net-RID SP, Net-
RID DP, and the Discovery and Synchronization Service (DSS). DRIP
may also address standardization of protocols between the UA and GCS,
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 RID information is
in the scope of [F3411-19] Network RID.
1.3. Overview of USS Interoperability
Each UAS is registered to at least one USS. With Net-RID, there is
direct communication between the UAS and its USS. With Broadcast-
RID, the UAS Operator has either pre-filed a 4D space volume for USS
operational knowledge and/or Observers can be providing information
about observed UA to a USS. USS exchange information via a Discovery
and Synchronization Service (DSS) so all USS collectively have
knowledge about all activities in a 4D airspace.
The interactions among Observer, UA, and USS are shown in Figure 3.
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+----------+
| Observer |
+----------+
/ \
/ \
+-----+ +-----+
| UA1 | | UA2 |
+-----+ +-----+
\ /
\ /
+----------+
| Internet |
+----------+
/ \
/ \
+-------+ +-------+
| USS-1 | <-------> | USS-2 |
+-------+ +-------+
\ /
\ /
+------+
| DSS |
+------+
Figure 3
1.4. Overview of DRIP Architecture
The requirements document [I-D.ietf-drip-reqs] provides an extended
introduction to the problem space and use cases. Only a brief
summary of that introduction is restated here as context, with
reference to the general UAS RID usage scenarios shown in Figure 4.
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General x x Public
Public xxxxx xxxxx Safety
Observer x x Observer
x x
x x ---------+ +---------- x x
x x | | x x
| |
UA1 x x | | +------------ x x UA2
xxxxx | | | xxxxx
| + + + |
| xxxxxxxxxx |
| x x |
+----------+x Internet x+------------+
UA1 | x x | UA1
Pilot x | xxxxxxxxxx | x Pilot
Operator xxxxx + + + xxxxx Operator
GCS1 x | | | x GCS2
x | | | x
x x | | | x x
x x | | | x x
| | |
+----------+ | | | +----------+
| |------+ | +-------| |
| Public | | | Private |
| Registry | +-----+ | Registry |
| | | DNS | | |
+----------+ +-----+ +----------+
Figure 4
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.
This document outlines the UAS RID architecture into which DRIP must
fit and the architecture for DRIP itself. 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 ID and trust in RID messages
(Section 4)
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- Mechanisms to leverage Domain Name System (DNS: [RFC1034]),
Extensible Provisioning Protocol (EPP [RFC5731]) and
Registration Data Access Protocol (RDAP) ([RFC7482]) to provide
for private (Section 5.2) and public (Section 5.1) information
registry.
- Harvesting broadcast RID messages for UTM inclusion
(Section 6).
- Privacy in RID messages (PII protection) (Section 7).
2. Conventions
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 above.
3. Definitions and Abbreviations
3.1. Additional Definitions
This document uses terms defined in [I-D.ietf-drip-reqs].
3.2. Abbreviations
ADS-B: Automatic Dependent Surveillance Broadcast
DSS: Discovery & Synchronization Service
EdDSA: Edwards-Curve Digital Signature Algorithm
GCS: Ground Control Station
HHIT: Hierarchical HIT Registries
HIP: Host Identity Protocol
HIT: Host Identity Tag
RID: Remote ID
Net-RID SP: Network RID Service Provider
Net-RID DP: Network RID Display Provider.
PII: Personally Identifiable Information
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RF: Radio Frequency
SDSP: Supplemental Data Service Provider
UA: Unmanned Aircraft
UAS: Unmanned Aircraft System
USS: UAS Service Supplier
UTM: UAS Traffic Management
3.3. Claims, Assertions, Attestations, and Certificates
This section introduces the terms "Claims", "Assertions",
"Attestations", and "Certificates" as used in DRIP.
This is due to the term "certificate" having significant
technological and legal baggage associated with it, specifically
around X.509 certificates. These types of certificates and Public
Key Infrastructure invoke more legal and public policy considerations
than probably any other electronic communication sector. It emerged
as a governmental platform for trusted identity management and was
pursued in intergovernmental bodies with links into treaty
instruments.
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 a
claimant or a third party. 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.
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4. HHIT for DRIP Entity Identifier
This section describes the basic requirements of a DRIP entity
identifier per regulation constrains from ASTM [F3411-19] and
explains the use of Hierarchical Host Identity Tags (HHITs) as self-
asserting IPv6 addresses and thereby a trustable DRIP identifier for
use as the UAS Remote ID. HHITs self-attest to the included explicit
hierarchy that provides Registrar discovery for 3rd-party ID
attestation.
4.1. UAS Remote Identifiers Problem Space
A DRIP entity identifier needs to be "Trustworthy". This means that
within the framework of the RID messages, an Observer can establish
that the DRIP identifier used does uniquely belong to the UAS. That
the only way for any other UAS to assert this DRIP identifier would
be to steal something from within the UAS. The DRIP identifier is
self-generated by the UAS (either UA or GCS) and registered with the
USS.
The data communication of using Broadcast RID faces extreme
challenges due to the limitation of the demanding support for
Bluetooth. The ASTM [F3411-19] defines the basic RID message which
is expected to contain certain RID data and the Authentication
message. The Basic RID message has a maximum payload of 25 bytes and
the maximum size allocated by ASTM for the RID is 20 bytes and only 3
bytes are left unused. currently, the authentication maximum payload
is defined to be 201 bytes.
Standard approaches like X.509 and PKI will not fit these
constraints, even using the new EdDSA [RFC8032] algorithm cannot fit
within the maximum 201 byte limit, due in large measure to ASN.1
encoding format overhead.
An example of a technology that will fit within these limitations is
an enhancement of the Host Identity Tag (HIT) of HIPv2 [RFC7401]
using Hierarchical HITs (HHITs) for UAS RID is outlined in HHIT based
UAS RID [I-D.ietf-drip-rid]. As PKI with X.509 is being used in
other systems with which UAS RID must interoperate (e.g. Discovery
and Synchronization Service and any other communications involving
USS) mappings between the more flexible but larger X.509 certificates
and the HHIT-based structures must be devised. This could be as in
[RFC8002] or simply the HHIT as Subject Alternative Name (SAN) and no
Distinguished Name (DN).
A self-attestation of the HHIT RID can be done in as little as 84
bytes, by avoiding an explicit encoding technology like ASN.1 or
Concise Binary Object Representation (CBOR [RFC8949]). This
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compressed attestation consists of only the HHIT, a timestamp, and
the EdDSA signature on them. The HHIT prefix and suiteID provide
crypto agility and implicit encoding rules. Similarly, a self-
attestation of the Hierarchical registration of the RID (an
attestation of a RID third-party registration "certificate") can be
done in 200 bytes. Both these are detailed in UAS RID
[I-D.ietf-drip-rid].
An Observer would need Internet access to validate a self-
attestations claim. A third-party Certificate can be validated via a
small credential cache in a disconnected environment. This third-
party Certificate is possible when the third-party also uses HHITs
for its identity and the UA has the public key and the Certificate
for that HHIT.
4.2. HIT as A Trustworthy DRIP Entity Identifier
A Remote ID that can be trustworthily used in the RID Broadcast mode
can be built from an asymmetric keypair. Rather than using a key
signing operation to claim ownership of an ID that does not guarantee
name uniqueness, in this method the ID is cryptographically derived
directly from the public key. The proof of ID ownership (verifiable
attestation, versus mere claim) comes from signing this cryptographic
ID with the associated private key. It is statistically hard for
another entity to create a public key that would generate (spoof) the
ID.
HITs are so designed; they are statistically unique through the
cryptographic hash feature of second-preimage resistance. The
cryptographically-bound addition of the Hierarchy and an HHIT
registration process (e.g. based on Extensible Provisioning Protocol,
[RFC5730]) 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.
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4.3. HHIT for DRIP Identifier Registration and Lookup
Remote ID 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
Remote ID itself needs to be the inquiry input into the lookup. An
HHIT DRIP identifier contains cryptographically embedded registration
information. This HHIT registration hierarchy, along with the IPv6
prefix, is trustable and sufficient information that can be used to
perform such a lookup. Additionally, the IPv6 prefix can enhance the
HHITs use beyond the basic Remote ID function (e.g use in HIP,
[RFC7401]).
Therefore, a DRIP identifier can be represented as a HHIT. It can be
self-generated by a UAS (either UA or GCS) and registered with the
Private Information Registry (More details in Section 5.2) identified
in its hierarchy fields. Each DRIP identifier represented as an HHIT
can not be used more than once.
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 can 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 (more details in Section 8).
In another case, a UAS equipped for Broadcast RID can 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 can 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 can be provisioned either with public keys of the DRIP
identifier root registries or certificates for subordinate
registries.
HHITs can be used throughout the UAS/UTM system. The Operators,
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.
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4.4. HHIT for DRIP Identifier Cryptographic
The only (known to the authors of this document at the time of its
writing) extant fixed-length ID cryptographically derived from a
public key are the Host Identity Tag [RFC7401], HITs, and
Cryptographically Generated Addresses [RFC3972], CGAs. However, both
HITs and CGAs lack registration/retrieval capability. HHIT, on the
other hand, is capable of providing a cryptographic hashing function,
along with a registration process to mitigate the probability of a
hash collision (first registered, first allowed).
5. DRIP Identifier Registration and Registries
UAS registries can hold both public and private UAS information
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. A DRIP identifier is amenable to handling
as an Internet domain name (at an arbitrary level in the hierarchy).
It also can be registered in at least a pseudo-domain (e.g. .ip6.arpa
for reverse lookup), or as a sub-domain (for forward lookup). This
section introduces the public and private information registries for
DRIP identifiers.
5.1. Public Information Registry
5.1.1. Background
The public registry provides trustable information such as
attestations of RID ownership and HDA registration. Optionally,
pointers to the repositories for the HDA and RAA implicit in the 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 UAS that only
use Network RID, is only available via an Observer's Net-RID DP that
would tend to provide all public registry information directly. The
Observer can visually "see" these UAS, but they are silent to the
Observer; the Net-RID DP is the only source of information based on a
query for an airspace volume.
5.1.2. Proposed Approach
A DRIP public information registry can respond to standard DNS
queries, in the definitive public Internet DNS hierarchy. If a DRIP
public information registry lists, in a HIP RR, any HIP RVS servers
for a given DRIP identifier, those RVS servers can restrict relay
services per AAA policy; this requires extensions to [RFC8004].
These public information registries can use secure DNS transport
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(e.g. DNS over TLS) to deliver public information that is not
inherently trustable (e.g. everything other than attestations).
5.2. Private Information Registry
5.2.1. 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 an ID structure compatible with DNS names. This implies
some sort of hierarchy, for scalability, and management of this
hierarchy. It is expected that the private registry function will be
provided by the same organizations that run USS, and likely
integrated with USS.
5.2.2. Proposed Approach
A DRIP private information registry can support essential Internet
domain name registry operations (e.g. add, delete, update, query)
using interoperable open standard protocols. It can also support the
Extensible Provisioning Protocol (EPP) and the Registry Data Access
Protocol (RDAP) with access controls. It might be listed in a DNS:
that DNS could be private; but absent any compelling reasons for use
of private DNS, a public DNS hierarchy needs to be in place. 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 [RFC7484]. A DRIP private information registry can also
support WebFinger as specified in [RFC7033].
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 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 UAS of
essentially all UAS and is now also considering Network RID. The FAA
RID Final Rules only specifies Broadcast RID for UAS, however, still
encourages Network RID for complementary functionality, especially in
support of UTM.
One obvious 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
considerable enhancement over some Network RID options such as only
reporting planned 4D operation space by the operator.
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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 may have
a natural time lag as it is), which are entirely operator self-
reported in UAS RID and UTM.
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 RID messages. This
Crowd Sourced Remote ID (CS-RID) would be a significant enhancement,
beyond baseline DRIP functionality; if implemented, it adds two more
entity types.
6.1. The CS-RID Finder
A CS-RID Finder is the gateway for Broadcast Remote ID Messages into
the 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 can not interface directly with
a GCS, Net-RID SP, Net-RID DP or Network RID client. It would
present a TBD interface to a CS-RID SDSP; this interface needs to be
based upon but readily distinguishable from that between a GCS and a
Net-RID SP.
6.2. The CS-RID SDSP
A CS-RID SDSP would appear (i.e. present the same interface) to a
Net-RID SP as a Net-RID DP. A CS-RID SDSP can not present a standard
GCS-facing interface as if it were a Net-RID SP. A CS-RID SDSP would
present a TBD interface to a CS-RID Finder; this interface can be
based upon but readily distinguishable between a GCS and a Net-RID
SP.
7. Privacy for Broadcast PII
Broadcast RID messages can contain PII. A viable architecture for
PII protection would be symmetric encryption of the PII using a key
known to the UAS and its USS. An authorized Observer could send the
encrypted PII along with the UAS ID (to entities such as USS of the
Observer, or to the UAS in which the UAS ID is registered if that can
be determined from the UAS ID itself or to a Public Safety USS) to
get the plaintext. Alternatively, the authorized Observer can
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receive the key to directly decrypt all future PII content from the
UA.
PII can be protected unless the UAS is informed otherwise. This
could come from operational instructions to even permit flying in a
space/time. It can be special instructions at the start or during an
operation. PII protection can not be used if the UAS loses
connectivity to the USS. The UAS always has the option to abort the
operation if PII protection is disallowed.
An authorized Observer can instruct a UAS via the USS that conditions
have changed mandating no PII protection or land the UA (abort the
operation).
8. Security Considerations
The security provided by asymmetric cryptographic techniques depends
upon protection of the private keys. A manufacturer that embeds a
private key in an UA may have retained a copy. A manufacturer whose
UA are configured by a closed source application on the GCS which
communicates over the Internet with the factory may be sending a copy
of a UA or GCS self-generated key back to the factory. Keys may be
extracted from a GCS or UA. The RID sender of a small harmless UA
(or the entire UA) could be carried by a larger dangerous UA as a
"false flag." Compromise of a registry private key could do
widespread harm. Key revocation procedures are as yet to be
determined. These risks are in addition to those involving Operator
key management practices.
9. Acknowledgements
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. IETF
volunteers who have contributed to this draft include Amelia
Andersdotter and Mohamed Boucadair.
10. References
10.1. Normative References
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[I-D.ietf-drip-reqs]
Card, S. W., Wiethuechter, A., Moskowitz, R., and A.
Gurtov, "Drone Remote Identification Protocol (DRIP)
Requirements", Work in Progress, Internet-Draft, draft-
ietf-drip-reqs-12, 23 May 2021,
<https://www.ietf.org/archive/id/draft-ietf-drip-reqs-
12.txt>.
[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>.
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.
[F3411-19] ASTM, "Standard Specification for Remote ID and Tracking",
2019.
[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>.
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[I-D.ietf-drip-rid]
Moskowitz, R., Card, S. W., Wiethuechter, A., and A.
Gurtov, "UAS Remote ID", Work in Progress, Internet-Draft,
draft-ietf-drip-rid-07, 28 January 2021,
<https://www.ietf.org/archive/id/draft-ietf-drip-rid-
07.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.
[LAANC] United States Federal Aviation Administration (FAA), "Low
Altitude Authorization and Notification Capability", n.d.,
<https://www.faa.gov/uas/programs_partnerships/
data_exchange/>.
[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>.
[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>.
[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>.
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[RFC7482] Newton, A. and S. Hollenbeck, "Registration Data Access
Protocol (RDAP) Query Format", RFC 7482,
DOI 10.17487/RFC7482, March 2015,
<https://www.rfc-editor.org/info/rfc7482>.
[RFC7484] Blanchet, M., "Finding the Authoritative Registration Data
(RDAP) Service", RFC 7484, DOI 10.17487/RFC7484, March
2015, <https://www.rfc-editor.org/info/rfc7484>.
[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>.
[RFC8002] Heer, T. and S. Varjonen, "Host Identity Protocol
Certificates", RFC 8002, DOI 10.17487/RFC8002, October
2016, <https://www.rfc-editor.org/info/rfc8002>.
[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>.
[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>.
[TS-22.825]
3GPP, "UAS RID requirement study", 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)
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A.1. Operation Concept
The National Aeronautics and Space Administration (NASA) and FAAs'
effort of integrating UAS's operation into the national airspace
system (NAS) leads 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 is published in 2020 [FAA_UAS_Concept_Of_Ops].
The eventual development and implementation are conducted by the UTM
research transition team which is the joint workforce by FAA and
NASA. 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 the UTM concept of operations to
guide the development of their future air traffic management (ATM)
system and make sure safe and efficient integrations of manned and
unmanned aircraft into the national airspace.
The UTM composes of UAS operation infrastructure, procedures and
local regulation compliance policies to guarantee UAS's safe
integration and operation. The main functionality of a 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 a UTM has to offer. Such Entity acts as a
proxy between UAS operators and UTM service providers. It provides
services like real-time UAS traffic monitor and planning,
aeronautical data archiving, airspace and violation control,
interacting with other third-party control entities, etc. A USS can
coexist with other USS(s) to build a large service coverage map which
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 UTM envisioned
functionality. The LAANC program can automate the UAS's flight plan
application and approval process for airspace authorization in real-
time by checking against multiple aeronautical databases such as
airspace classification and fly rules associated with it, FAA UAS
facility map, special use airspace, Notice to Airman (NOTAM), and
Temporary Flight Rule (TFR).
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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 takeoff or land in a
controlled airspace (e.g., Class Bravo, Charlie, Delta and Echo
in United States), the USS where UAS is currently communicating
with is responsible for UAS's registration, authenticating the
UAS's fly plan by checking against designated UAS fly map
database, obtaining the air traffic control (ATC) authorization
and monitor the UAS fly path in order to maintain safe boundary
and follow the pre-authorized route.
2. For a UAS participating in UTM and take off or land in an
uncontrolled airspace (ex. Class Golf in the United States),
pre-fly authorization must be obtained from a USS when operating
beyond-visual-of-sight (BVLOS) operation. The USS either accepts
or rejects received intended fly plan from the UAS. Accepted UAS
operation may share its current fly data such as GPS position and
altitude to USS. The USS may keep the UAS operation status near
real-time and may keep it as a record for overall airspace air
traffic monitor.
A.4. 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 UA. Technical reasons include but 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 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.
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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
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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