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DRIP S. Card, Ed.
Internet-Draft A. Wiethuechter
Intended status: Informational AX Enterprize
Expires: 19 April 2021 R. Moskowitz
HTT Consulting
A. Gurtov
Linköping University
16 October 2020
Drone Remote Identification Protocol (DRIP) Requirements
draft-ietf-drip-reqs-05
Abstract
This document defines terminology and requirements for Drone Remote
Identification Protocol (DRIP) Working Group protocols to support
Unmanned Aircraft System Remote Identification and tracking (UAS RID)
for security, safety and other purposes. Complementing external
technical standards as regulator-accepted means of compliance with
UAS RID regulations, DRIP will:
facilitate use of existing Internet resources to support UAS RID
and to enable enhanced related services;
enable online and offline verification that UAS RID information is
trustworthy.
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 19 April 2021.
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Copyright Notice
Copyright (c) 2020 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.
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 Simplified BSD License text
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provided without warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction (Informative) . . . . . . . . . . . . . . . . . 2
1.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Concerns and Constraints . . . . . . . . . . . . . . . . 6
1.3. DRIP Scope . . . . . . . . . . . . . . . . . . . . . . . 7
2. Terms and Definitions . . . . . . . . . . . . . . . . . . . . 8
2.1. Requirements Terminology . . . . . . . . . . . . . . . . 8
2.2. Definitions . . . . . . . . . . . . . . . . . . . . . . . 8
3. UAS RID Problem Space . . . . . . . . . . . . . . . . . . . . 16
3.1. Network RID . . . . . . . . . . . . . . . . . . . . . . . 17
3.2. Broadcast RID . . . . . . . . . . . . . . . . . . . . . . 19
3.3. DRIP Focus . . . . . . . . . . . . . . . . . . . . . . . 22
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 22
4.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.2. Identifier . . . . . . . . . . . . . . . . . . . . . . . 24
4.3. Privacy . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.4. Registries . . . . . . . . . . . . . . . . . . . . . . . 26
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27
6. Security Considerations . . . . . . . . . . . . . . . . . . . 27
7. Privacy and Transparency Considerations . . . . . . . . . . . 29
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 29
8.1. Normative References . . . . . . . . . . . . . . . . . . 29
8.2. Informative References . . . . . . . . . . . . . . . . . 30
Appendix A. Discussion and Limitations . . . . . . . . . . . . . 32
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 33
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 34
1. Introduction (Informative)
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1.1. Motivation
Many considerations (especially safety and security) necessitate
Unmanned Aircraft Systems (UAS) Remote Identification and tracking
(RID).
Unmanned Aircraft (UA) may be fixed wing Short Take-Off and Landing
(STOL), rotary wing (e.g., helicopter) Vertical Take-Off and Landing
(VTOL), or hybrid. They may be single- or multi-engine. The most
common today are multicopters: rotary wing, multi engine. The
explosion in UAS was enabled by hobbyist development, for
multicopters, of advanced flight stability algorithms, enabling even
inexperienced pilots to take off, fly to a location of interest,
hover, and return to the take-off location or land at a distance.
UAS can be remotely piloted by a human (e.g., with a joystick) or
programmed to proceed from GNSS waypoint to waypoint in a weak form
of autonomy; stronger autonomy is coming. UA are "low observable":
they typically have small radar cross sections; they make noise quite
noticeable at short range but difficult to detect at distances they
can quickly close (500 meters in under 17 seconds at 60 knots); they
typically fly at low altitudes (for the small UAS to which RID
applies in the US, under 400 feet AGL); they are highly maneuverable
so can fly under trees and between buildings.
UA can carry payloads including sensors, cyber and kinetic weapons,
or can be used themselves as weapons by flying them into targets.
They can be flown by clueless, careless or criminal operators. Thus
the most basic function of UAS RID is "Identification Friend or Foe"
(IFF) to mitigate the significant threat they present. Numerous
other applications can be enabled or facilitated by RID: consider the
importance of identifiers in many Internet protocols and services.
The general scenario is illustrated in Figure 1.
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UA1 UA2
x x x x
xxxxx xxxxx
General x x Public
Public xxxxx xxxxx Safety
Observer x x Observer
x x
x x ---------+ +---------- x x
x x | | x x
| |
+ +
xxxxxxxxxx
x x
+----------+x Internet x+------------+
| x x |
UA1 x | xxxxxxxxxx | x UA2
Pilot xxxxx + + + xxxxx Pilot
Operator x | | | x Operator
x | | | x
x x | | | x x
x x | | | x x
| | |
+----------+ | | | +----------+
| |------+ | +-------| |
| Public | | | Private |
| Registry | +-----+ | Registry |
| | | DNS | | |
+----------+ +-----+ +----------+
Figure 1: "General UAS RID Scenario"
Note the absence of any links to/from the UA in Figure 1. This is
because UAS RID and other connectivity involving the UA varies as
described below.
Inherently, any responsible Observer of UA must classify them, as
illustrated notionally in Figure 2. For basic airspace Situational
Awareness (SA), an Observer who classifies an UAS: as Taskable, can
ask it to do something useful; as Low Concern, can reasonably assume
it is not malicious, and would cooperate with requests to modify its
flight plans for safety concerns that arise; as High Concern or
Unidentified, can focus surveillance on it. These classes are not
standard, but derive from first principles.
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xxxxxxx +--------------+
x x No | |
x ID? x+---->| UNIDENTIFIED |
x x | |
xxxxxxx +--------------+
+
| Yes
v
xxxxxxx
x x
+---------+x TYPE? x+----------+
| x x |
| xxxxxxx |
| + |
v v v
+--------------+ +--------------+ +--------------+
| | | | | |
| TASKABLE | | LOW CONCERN | | HIGH CONCERN |
| | | | | |
+--------------+ +--------------+ +--------------+
Figure 2: "Notional UAS Classification"
An ID is not an end in itself; it exists to enable lookups and
provision of services complementing mere identification.
Using UAS RID to facilitate vehicular (V2X) communications and
applications such as Detect And Avoid (DAA), which would impose
tighter latency bounds than RID itself, is an obvious possibility,
explicitly contemplated in the United States (US) Federal Aviation
Administration (FAA) Notice of Proposed Rule Making [NPRM]. However,
applications of RID beyond RID itself, including DAA, have been
explicitly declared out of scope in ASTM International, Technical
Committee F38 (UAS), Subcommittee F38.02 (Aircraft Operations), Work
Item WK65041, working group discussions, based on a distinction
between RID as a security standard vs DAA as a safety application.
Although dynamic establishment of secure communications between the
Observer and the UAS pilot seems to have been contemplated by the FAA
UAS ID and Tracking Aviation Rulemaking Committee (ARC) in their
[Recommendations], it is not addressed in any of the subsequent
proposed regulations or technical specifications.
[Opinion1] and [WG105] cite the Direct Remote Identification
previously required and specified, explicitly stating that whereas
Direct RID is primarily for security purposes, "Electronic
Identification" (or the "Network Identification Service" in the
context of U-space) is primarily for safety purposes (e.g. air
traffic management, especially hazards deconfliction) and also is
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allowed to be used for other purposes such as support of efficient
operations. These emerging standards allow the security and safety
oriented systems to be separate or merged. In addition to mandating
both Broadcast and Network one-way to Observers, they will use V2V to
other UAS (also likely to and/or from some manned aircraft). These
reflect the broad scope of the EU U-space concept, as being developed
in the Single European Sky ATM Research (SESAR) Joint Undertaking,
whose U-space architectural principles are outlined in [InitialView].
Security oriented UAS RID essentially has two goals: enable the
general public to obtain and record an opaque ID for any observed UA,
which they can then report to authorities; enable authorities, from
such an ID, to look up information about the UAS and its operator.
Safety oriented UAS RID has stronger requirements. Aviation
community SDOs set a higher bar for safety than for security,
especially with respect to reliability.
1.2. Concerns and Constraints
Disambiguation of multiple UA flying in close proximity may be very
challenging, even if each is reporting its identity, position and
velocity as accurately as it can. As the origin of all information
in UAS RID is self-reports from operators, there are possibilities
not only of unintentional error, but also of intentional
falsification, of this data.
Minimal specified information must be made available to the public;
access to other data, e.g., UAS operator Personally Identifiable
Information (PII), must be limited to strongly authenticated
personnel, properly authorized per policy. The balance between
privacy and transparency remains a subject for public debate and
regulatory action; DRIP can only offer tools to expand the achievable
trade space and enable trade-offs within that space. [F3411-19]
specifies only how to get the UAS ID to the Observer: how the
Observer can perform these lookups, and how the registries first can
be populated with information, is unspecified.
The need for near-universal deployment of UAS RID is pressing. This
implies the need to support use by Observers of already ubiquitous
mobile devices (typically smartphones and tablets). Anticipating
likely CAA requirements to support legacy devices, especially in
light of [Recommendations], [F3411-19] specifies that any UAS sending
Broadcast RID over Bluetooth must do so over Bluetooth 4, regardless
of whether it also does so over newer versions; as UAS sender devices
and Observer receiver devices are unpaired, this implies extremely
short "advertisement" (beacon) frames.
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Wireless data links on the UA are challenging due to low altitude
flight amidst structures and foliage over terrain, as well as the
severe Cost, Size, Weight and Power (CSWaP) constraints of devices
onboard UA. CSWaP is a burden not only on the designers of new UA
for production and sale, but also on owners of existing UA that must
be retrofit. Radio Controlled (RC) aircraft modelers, "hams" who use
licensed amateur radio frequencies to control UAS, drone hobbyists,
and others who custom build UAS, all need means of participating in
UAS RID, sensitive to both generic CSWaP and application-specific
considerations.
To accommodate the most severely constrained cases, all these
conspire to motivate system design decisions, especially for the
Broadcast RID data link, which complicate the protocol design
problem: one-way links; extremely short packets; and Internet-
disconnected operation of UA onboard devices. Internet-disconnected
operation of Observer devices has been deemed by ASTM F38.02 too
infrequent to address, but for some users is important and presents
further challenges.
As RID must often operate with limited bandwidth, short packet
payload length limits, and one-way links, heavyweight cryptographic
security protocols or even simple cryptographic handshakes are
infeasible, yet trustworthiness of UAS RID information is essential.
Under [F3411-19], even the most basic datum, the UAS ID string
(typically number) itself can be merely an unsubstantiated claim.
Observer devices being ubiquitous, thus popular targets for malware
or other compromise, cannot be generally trusted (although the user
of each device is compelled to trust that device, to some extent); a
"fair witness" functionality (inspired by [Stranger]) is desirable.
Despite work by regulators and Standards Development Organizations
(SDOs), there are substantial gaps in UAS standards generally and UAS
RID specifically. [Roadmap] catalogs UAS related standards, ongoing
standardization activities and gaps (as of early 2020); Section 7.8
catalogs those related specifically to UAS RID. DRIP will address
the most fundamental of these gaps, as foreshadowed above.
1.3. DRIP Scope
DRIP's initial goal is to make RID immediately actionable, in both
Internet and local-only connected scenarios (especially emergencies),
in severely constrained UAS environments, balancing legitimate (e.g.,
public safety) authorities' Need To Know trustworthy information with
UAS operators' privacy. By "immediately actionable" is meant
information of sufficient precision, accuracy, timeliness, etc. for
an Observer to use it as the basis for immediate decisive action,
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whether that be to trigger a defensive counter-UAS system, to attempt
to initiate communications with the UAS operator, to accept the
presence of the UAS in the airspace where/when observed as not
requiring further action, or whatever, with potentially severe
consequences of any action or inaction chosen based on that
information. For further explanation of the concept of immediate
actionability, see [ENISACSIRT]. Note that UAS RID must achieve near
universal adoption, but DRIP can add value even if only selectively
deployed, as those with jurisdiction over more sensitive airspace
volumes may set a higher than generally mandated RID bar for flight
in those volumes. Providing timely trustworthy identification data
is also prerequisite to identity-oriented networking.
DRIP (originally Trustworthy Multipurpose Remote Identification, TM-
RID) potentially could be applied to verifiably identify other types
of registered things reported to be in specified physical locations,
but the urgent motivation and clear initial focus is UAS. Existing
Internet resources (protocol standards, services, infrastructure, and
business models) should be leveraged. A natural Internet based
architecture for UAS RID conforming to proposed regulations and
external technical standards is described in a companion architecture
document [drip-architecture] and elaborated in other DRIP documents;
this document describes only relevant requirements and defines
terminology for the set of DRIP documents.
2. Terms and Definitions
2.1. Requirements Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2.2. Definitions
This section defines a set of terms expected to be used in DRIP
documents. This list is meant to be the DRIP terminology reference.
Some of the terms listed below are not used in this document.
[RFC4949] provides a glossary of Internet security terms that should
be used where applicable. In the UAS community, the plural form of
acronyms generally is the same as the singular form, e.g. Unmanned
Aircraft System (singular) and Unmanned Aircraft Systems (plural) are
both represented as UAS. On this and other terminological issues, to
encourage comprehension necessary for adoption of DRIP by the
intended user community, that community's norms are respected herein,
and definitions are quoted in cases where they have been found in
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that community's documents. Most of the listed terms are from that
community (even if specific source documents are not cited); any that
are DRIP-specific or invented by the authors of this document are
marked "(DRIP)".
AAA
Attestation, Authentication, Authorization, Access Control,
Accounting, Attribution, Audit, or any subset thereof (uses differ
by application, author and context). (DRIP)
ABDAA
AirBorne DAA. Accomplished using systems onboard the aircraft
involved. Supports "self-separation" (remaining "well clear" of
other aircraft) and collision avoidance.
ADS-B
Automatic Dependent Surveillance - Broadcast. "ADS-B Out"
equipment obtains aircraft position from other on-board systems
(typically GNSS) and periodically broadcasts it to "ADS-B In"
equipped entities, including other aircraft, ground stations and
satellite based monitoring systems.
AGL
Above Ground Level. Relative altitude, above the variously
defined local ground level, typically of an UA, measured in feet
or meters. Should be explicitly specified as either barometric
(pressure) or geodetic (GNSS).
ATC
Air Traffic Control. Explicit flight direction to pilots from
ground controllers. Contrast with ATM.
ATM
Air Traffic Management. A broader functional and geographic scope
and/or a higher layer of abstraction than ATC. "The dynamic,
integrated management of air traffic and airspace including air
traffic services, airspace management and air traffic flow
management - safely, economically and efficiently - through the
provision of facilities and seamless services in collaboration
with all parties and involving airborne and ground-based
functions." [ICAOATM]
Authentication Message
[F3411-19] Message Type 2. Provides framing for authentication
data, only. Optional per [F3411-19] but may be required by
regulations.
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Basic ID Message
[F3411-19] Message Type 0. Provides UA Type, UAS ID Type and UAS
ID, only. Mandatory per [F3411-19].
B-LOS
Beyond Line Of Sight (LOS). Term to be avoided due to ambiguity.
See LOS.
BV-LOS
Beyond Visual Line Of Sight (V-LOS). See V-LOS.
CAA
Civil Aviation Authority. Two examples are the United States
Federal Aviation Administration (FAA) and the Japan Civil Aviation
Bureau.
CSWaP
Cost, Size, Weight and Power.
C2
Command and Control. Previously mostly used in military contexts.
In the UAS context, typically refers to the RF data link over
which the GCS controls the UA.
DAA
Detect And Avoid, formerly Sense And Avoid (SAA). A means of
keeping aircraft "well clear" of each other and obstacles for
safety. "The capability to see, sense or detect conflicting
traffic or other hazards and take the appropriate action to comply
with the applicable rules of flight." [ICAOUAS]
Direct RID
Direct Remote Identification. "a system that ensures the local
broadcast of information about a UA in operation, including the
marking of the UA, so that this information can be obtained
without physical access to the UA". [Delegated] Corresponds
roughly to the Broadcast RID portion of [NPRM] Standard RID.
DSS
Discovery and Synchronization Service. Formerly Inter-USS. The
UTM system overlay network backbone. Most importantly, it enables
one USS to learn which other USS have UAS operating in a given 4-D
airspace volume, for deconfliction of planned and Network RID
surveillance of active operations. [F3411-19]
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EUROCAE
European Organisation for Civil Aviation Equipment. Aviation SDO,
originally European, now with broader membership. Cooperates
extensively with RTCA.
GBDAA
Ground Based DAA. Accomplished with the aid of ground based
functions.
GCS
Ground Control Station. The part of the UAS that the remote pilot
uses to exercise C2 over the UA, whether by remotely exercising UA
flight controls to fly the UA, by setting GPS waypoints, or
otherwise directing its flight.
GNSS
Global Navigation Satellite System. Satellite based timing and/or
positioning with global coverage, often used to support
navigation.
GPS
Global Positioning System. A specific GNSS, but in the UAS
context, the term is typically misused in place of the more
generic term GNSS.
GRAIN
Global Resilient Aviation Interoperable Network. ICAO managed
IPv6 overlay internetwork per IATF, dedicated to aviation (but not
just aircraft). Currently in design.
IATF
International Aviation Trust Framework. ICAO effort to develop a
resilient and secure by design framework for networking in support
of all aspects of aviation.
ICAO
International Civil Aviation Organization. A United Nations
specialized agency that develops and harmonizes international
standards relating to aviation.
LAANC
Low Altitude Authorization and Notification Capability. Supports
ATC authorization requirements for UAS operations: remote pilots
can apply to receive a near real-time authorization for operations
under 400 feet in controlled airspace near airports. US partial
stopgap until UTM comes.
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Limited RID
A mode of operation that must use Network RID, must not use
Broadcast RID, and must provide pilot/GCS location only (not UA
location). This mode is only allowed for UA that neither require
(due to e.g. size) nor are equipped for Standard RID, operated
within V-LOS and within 400 feet of the pilot, below 400 feet AGL,
etc. [NPRM]
Location/Vector Message
[F3411-19] Message Type 1. Provides UA location, altitude,
heading, speed and status. Mandatory per [F3411-19].
LOS
Line Of Sight. An adjectival phrase describing any information
transfer that travels in a nearly straight line (e.g.
electromagnetic energy, whether in the visual light, RF or other
frequency range) and is subject to blockage. A term to be avoided
due to ambiguity, in this context, between RF-LOS and V-LOS.
MSL
Mean Sea Level. Relative altitude, above the variously defined
mean sea level, typically of an UA (but in [NPRM] also for a GCS),
measured in feet or meters. Should be explicitly specified as
either barometric (pressure) or geodetic (GNSS).
Net-RID DP
Network RID Display Provider. [F3411-19] logical entity that
aggregates data from Net-RID SPs as needed in response to user
queries regarding UAS operating within specified airspace volumes,
to enable display by a user application on a user device.
Potentially could provide not only information sent via UAS RID
but also information retrieved from UAS RID registries, or
information beyond UAS RID. Under [NPRM], not recognized as a
distinct entity, but a service provided by USS, including Public
Safety USS that may exist primarily for this purpose rather than
to manage any subscribed UAS.
Net-RID SP
Network RID Service Provider. [F3411-19] logical entity that
collects RID messages from UAS and responds to NetRID-DP queries
for information on UAS of which it is aware. Under [NPRM], the
USS to which the UAS is subscribed ("Remote ID USS").
Network Identification Service
EU regulatory requirement for Network RID. [Opinion1] and [WG105]
Corresponds roughly to the Network RID portion of [NPRM] Standard
RID.
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Observer
An entity (typically but not necessarily an individual human) who
has directly or indirectly observed an UA and wishes to know
something about it, starting with its ID. An observer typically
is on the ground and local (within V-LOS of an observed UA), but
could be remote (observing via Network RID or other surveillance),
operating another UA, aboard another aircraft, etc. (DRIP)
Operation
A flight, or series of flights of the same mission, by the same
UAS, separated by at most brief ground intervals. (inferred from
UTM usage, no formal definition found)
Operator
"A person, organization or enterprise engaged in or offering to
engage in an aircraft operation." [ICAOUAS]
Operator ID Message
[F3411-19] Message Type 5. Provides CAA issued Operator ID, only.
Operator ID is distinct from UAS ID. Optional per [F3411-19] but
may be required by regulations.
PIC
Pilot In Command. "The pilot designated by the operator, or in
the case of general aviation, the owner, as being in command and
charged with the safe conduct of a flight." [ICAOUAS]
PII
Personally Identifiable Information. In this context, typically
of the UAS Operator, Pilot In Command (PIC) or Remote Pilot, but
possibly of an Observer or other party.
Remote Pilot
A pilot using a GCS to exercise proximate control of an UA.
Either the PIC or under the supervision of the PIC. "The person
who manipulates the flight controls of a remotely-piloted aircraft
during flight time." [ICAOUAS]
RF
Radio Frequency. Noun or adjective, e.g. "RF link."
RF-LOS
RF LOS. Typically used in describing a direct radio link between
a GCS and the UA under its control, potentially subject to
blockage by foliage, structures, terrain or other vehicles, but
less so than V-LOS.
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RTCA
Radio Technical Commission for Aeronautics. US aviation SDO.
Cooperates extensively with EUROCAE.
Self-ID Message
[F3411-19] Message Type 3. Provides a 1 byte descriptor and 23
byte ASCII free text field, only. Expected to be used to provide
context on the operation, e.g. mission intent. Optional per
[F3411-19] but may be required by regulations.
Standard RID
A mode of operation that must use both Network RID (if Internet
connectivity is available at the time in the operating area) and
Broadcast RID (always and everywhere), and must provide both
pilot/GCS location and UA location. This mode is required for UAS
that exceed the allowed envelope (e.g. size, range) of Limited RID
and for all UAS equipped for Standard RID (even if operated within
parameters that would otherwise permit Limited RID). [NPRM] The
Broadcast RID portion corresponds roughly to EU Direct RID; the
Network RID portion corresponds roughly to EU Network
Identification Service.
SDO
Standards Development Organization. ASTM, IETF, et al.
SDSP
Supplemental Data Service Provider. An entity that participates
in the UTM system, but provides services beyond those specified as
basic UTM system functions. E.g., provides weather data.
[FAACONOPS]
System Message
[F3411-19] Message Type 4. Provides general UAS information,
including remote pilot location, multiple UA group operational
area, etc. Optional per [F3411-19] but may be required by
regulations.
U-space
EU concept and emerging framework for integration of UAS into all
classes of airspace, specifically including high density urban
areas, sharing airspace with manned aircraft. [InitialView]
UA
Unmanned Aircraft. In popular parlance, "drone". "An aircraft
which is intended to operate with no pilot on board." [ICAOUAS]
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UAS
Unmanned Aircraft System. Composed of UA, all required on-board
subsystems, payload, control station, other required off-board
subsystems, any required launch and recovery equipment, all
required crew members, and C2 links between UA and control
station. [F3411-19]
UAS ID
UAS identifier. Although called "UAS ID", unique to the UA,
neither to the operator (as some UAS registration numbers have
been and for exclusively recreational purposes are continuing to
be assigned), nor to the combination of GCS and UA that comprise
the UAS. Maximum length of 20 bytes. [F3411-19]
UAS ID Type
UAS Identifier type index. 4 bits, see Section 3, Paragraph 5 for
currently defined values 0-3. [F3411-19]
UAS RID
UAS Remote Identification and tracking. System to enable
arbitrary Observers to identify UA during flight.
UAS RID Verifier Service
System component designed to handle the authentication
requirements of RID by offloading verification to a web hosted
service. [F3411-19]
USS
UAS Service Supplier. "A USS is an entity that assists UAS
Operators with meeting UTM operational requirements that enable
safe and efficient use of airspace" and "... provide services to
support the UAS community, to connect Operators and other entities
to enable information flow across the USS Network, and to promote
shared situational awareness among UTM participants" per
[FAACONOPS].
UTM
UAS Traffic Management. "A specific aspect of air traffic
management which manages UAS operations safely, economically and
efficiently through the provision of facilities and a seamless set
of services in collaboration with all parties and involving
airborne and ground-based functions." [ICAOUTM] In the US, per
FAA, a "traffic management" ecosystem for "uncontrolled" low
altitude UAS operations, separate from, but complementary to, the
FAA's ATC system for "controlled" operations of manned aircraft.
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V2V
Vehicle-to-Vehicle. Originally communications between
automobiles, now extended to apply to communications between
vehicles generally. Often, together with Vehicle-to-
Infrastructure (V2I) etc., generalized to V2X.
V-LOS
Visual LOS. Typically used in describing operation of an UA by a
"remote" pilot who can clearly directly (without video cameras or
any other aids other than glasses or under some rules binoculars)
see the UA and its immediate flight environment. Potentially
subject to blockage by foliage, structures, terrain or other
vehicles, more so than RF-LOS.
3. UAS RID Problem Space
Civil Aviation Authorities (CAAs) worldwide are mandating UAS RID.
The European Union Aviation Safety Agency (EASA) has published
[Delegated] and [Implementing] Regulations. The US FAA has described
the key role that UAS RID plays in UAS Traffic Management (UTM) in
[NPRM] and [FAACONOPS] (especially Section 2.6 of the latter). CAAs
currently (2020) promulgate performance-based regulations that do not
specify techniques, but rather cite industry consensus technical
standards as acceptable means of compliance.
ASTM developed a widely cited Standard Specification for Remote ID
and Tracking [F3411-19] (early drafts are freely available as
[OpenDroneID] specifications). It defines two means of UAS RID:
Network RID defines a set of information for UAS to make available
globally indirectly via the Internet, through servers that can be
queried by Observers.
Broadcast RID defines a set of messages for UA to transmit locally
directly one-way over Bluetooth or Wi-Fi (without IP or any other
protocols between the data link and application layer), to be
received in real time by local Observers.
UAS using both means must send the same UAS RID application layer
information via each per [F3411-19] and [NPRM]. The presentation may
differ, as Network RID defines a data dictionary, whereas Broadcast
RID defines message formats (which carry items from that same data
dictionary). The interval (or rate) at which it is sent may differ,
as Network RID can accommodate Observer queries asynchronous to UAS
updates (which generally need be sent only when information, such as
location, changes), whereas Broadcast RID depends upon Observers
receiving UA messages at the time they are transmitted. Network RID
depends upon Internet connectivity in several segments from the UAS
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to each Observer. Broadcast RID should need Internet (or other Wide
Area Network) connectivity only for UAS registry information lookup
using the directly locally received UAS Identifier (UAS ID) as a key.
Broadcast RID does not assume IP connectivity of UAS; messages are
encapsulated by the UA without IP, directly in Bluetooth or WiFi link
layer frames.
[F3411-19] specifies three UAS ID types:
TYPE-1 A static, manufacturer assigned, hardware serial number per
ANSI/CTA-2063-A "Small Unmanned Aerial System Serial Numbers"
[CTA2063A].
TYPE-2 A CAA assigned (generally static) ID, like the registration
number of a manned aircraft.
TYPE-3 A UTM system assigned UUID [RFC4122], which can but need not
be dynamic.
Per [Delegated], the EU allows only Type 1. Per [NPRM], the US
allows Types 1 and 3, but requires Type 3 IDs (if used) each to be
used only once as a "Session ID" (for a single UAS flight, which in
the context of UTM is called an "operation"). Per [Delegated], the
EU also requires an operator registration number (an additional
identifier distinct from the UAS ID) that can be carried in an
[F3411-19] optional Operator ID message. Per [NPRM], the US allows
but does not require that operator registration numbers be sent. As
yet apparently there are no CAA public proposals to use Type 2.
3.1. Network RID
x x UA
xxxxx ********************
| * ------*---+------------+
| * / * | NET_Rid_SP |
| * ------------/ +---*--+------------+
| RF */ | *
| * INTERNET | * +------------+
| /* +---*--| NET_Rid_DP |
| / * +----*--+------------+
+ / * | *
x / ****************|*** x
xxxxx | xxxxx
x +------- x
x x
x x Operator's GCS Observer x x
x x x x
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Figure 3: "Network RID Information Flow"
Note the data flow typically originates on or at least passes through
the Ground Control Station (GCS), rather than comes direct from the
UA as in Broadcast RID (below), and makes up to 3 trips through the
Internet, implying use of IP (and other middle layer protocols) on
those trips, but not necessarily on the UA-GCS link (if indeed the
Network RID data even flows across that link).
Network RID is essentially publish-subscribe-query. In the typical
UTM context... First the UAS operator pushes an operation plan to the
USS that will serve that UAS for that operation, for deconfliction
with other operations. Assuming the plan receives approval and the
operation commences, that UAS periodically pushes location/status
updates to that USS (call it USS#1), which serves as the Network RID
Service Provider (Net-RID SP) for that operation. If users of any
other USS (whether they be other UAS operators or Observers) develop
an interest in any 4-D airspace volume intersecting the 4-D volume
containing that UAS operation, they query their own USS (call them
USS#2 through USS#n). Their USS query, via the UTM Discovery and
Synchronization Service (DSS), all other USS in the UTM system, and
learn that USS#1 has such operations. Observers or other interested
parties can then subscribe to track updates, via their own USS, which
serve as Network RID Display Providers (Net-RID DP) for that
surveillance session. The Net-RID SP (USS#1) will then publish
updates of the UAS position/status to all subscribed Net-RID DP
(USS#2 through USS#n), which in turn will deliver the information to
their users via unspecified (but expected to be web browser based)
means.
Network RID has several variants. The UA may have persistent onboard
Internet connectivity, in which case it can consistently source RID
information directly over the Internet. The UA may have intermittent
onboard Internet connectivity, in which case the GCS must source RID
information whenever the UA itself is offline. The UA may not have
Internet connectivity of its own, but have instead some other form of
communications to another node that can relay RID information to the
Internet; this would typically be the GCS (which to perform its
function must know where the UA is, although C2 link outages do
occur).
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The UA may have no means of sourcing RID information, in which case
the GCS must source it; this is typical under FAA NPRM Limited RID
proposed rules, which require providing the location of the GCS (not
that of the UA). In the extreme case, this could be the pilot using
a web browser/application to designate, to an UAS Service Supplier
(USS) or other UTM entity, a time-bounded airspace volume in which an
operation will be conducted; this may impede disambiguation of ID if
multiple UAS operate in the same or overlapping spatio-temporal
volumes.
In most cases in the near term, if the RID information is fed to the
Internet directly by the UA or GCS, the first hop data links will be
cellular Long Term Evolution (LTE) or Wi-Fi, but provided the data
link can support at least UDP/IP and ideally also TCP/IP, its type is
generally immaterial to the higher layer protocols. An UAS as the
ultimate source of Network RID information feeds an USS acting as a
Network RID Service Provider (Net-RID SP), which essentially proxies
for that and other sources; an observer or other ultimate consumer of
Network RID information obtains it from a Network RID Display
Provider (Net-RID DP), which aggregates information from multiple
Net-RID SPs to offer airspace Situational Awareness (SA) coverage of
a volume of interest. Network RID Service and Display providers are
expected to be implemented as servers in well-connected
infrastructure, accessible via typical means such as web APIs/
browsers.
Network RID is the more flexible and less constrained of the defined
UAS RID means, but is only partially specified in [F3411-19]. It is
presumed that IETF efforts supporting Broadcast RID (see next
section) can be easily generalized for Network RID.
3.2. Broadcast RID
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
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Figure 4: "Broadcast RID Information Flow"
Note the absence of the Internet from this information flow sketch.
This is because Broadcast RID is one-way direct transmission of
application layer messages over a RF data link (without IP or other
middle layer protocols) from the UA to local Observer devices.
Internet connectivity is involved only in what the Observer chooses
to do with the information received, such as verify signatures using
a web based verifier service and look up information in registries
using the UAS ID as the primary unique key.
Broadcast RID is conceptually similar to Automatic Dependent
Surveillance - Broadcast (ADS-B). However, for various technical and
other reasons, regulators including the EASA and FAA have not
indicated intent to allow, and FAA has proposed explicitly to
prohibit, use of ADS-B for UAS RID.
[F3411-19] specifies three Broadcast RID data links: Bluetooth 4.X;
Bluetooth 5.X Long Range; and Wi-Fi with Neighbor Awareness
Networking (NAN). For compliance with [F3411-19], an UA must
broadcast (using advertisement mechanisms where no other option
supports broadcast) on at least one of these; if broadcasting on
Bluetooth 5.x, it is also required concurrently to do so on 4.x
(referred to in [F3411-19] as Bluetooth Legacy). Future revisions
may allow other data links.
The selection of the Broadcast media was driven by research into what
is commonly available on 'ground' units (smartphones and tablets) and
what was found as prevalent or 'affordable' in UA. Further, there
must be an Application Programming Interface (API) for the observer's
receiving application to have access to these messages. As yet only
Bluetooth 4.X support is readily available, thus the current focus is
on working within the 26 byte limit of the Bluetooth 4.X "Broadcast
Frame" transmitted on beacon channels. After nominal overheads, this
limits the UAS ID string to a maximum length of 20 bytes, and
precludes the same frame carrying position, velocity and other
information that should be bound to the UAS ID, much less strong
authentication data. This requires segmentation ("paging") of longer
messages or message bundles ("Message Pack"), and/or correlation of
short messages (anticipated by ASTM to be done on the basis of
Bluetooth 4 MAC address, which is weak and unverifiable).
[F3411-19] Broadcast RID specifies several message types: Basic,
Location, Authentication, Self-ID, System and Operator ID. To
satisfy EASA and FAA proposed rules, all types are needed, except
Authentication and Self-ID.
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[F3411-19] Broadcast RID specifies very few quantitative performance
requirements: static information must be transmitted at least once
per 3 seconds; dynamic information (the Location message) must be
transmitted at least once per second and be no older than one second
when sent. [NPRM] proposes all information be sent at least once per
second.
[F3411-19] Broadcast RID transmits all information as cleartext
(ASCII or binary), so static IDs enable trivial correlation of
patterns of use, unacceptable in many applications, e.g., package
delivery routes of competitors.
Any UA can assert any ID using the [F3411-19] required Basic ID
message, which lacks any provisions for verification. The Position/
Vector message likewise lacks provisions for verification, and does
not contain the ID, so must be correlated somehow with a Basic ID
message: the developers of [F3411-19] have suggested using the MAC
addresses on the Broadcast RID data link, but these may be randomized
by the operating system stack to avoid the adversarial correlation
problems of static identifiers.
The [F3411-19] optional Authentication Message specifies framing for
authentication data, but does not specify any authentication method,
and the maximum length of the specified framing is too short for
conventional digital signatures and far too short for conventional
certificates. The one-way nature of Broadcast RID precludes
challenge-response security protocols (e.g., observers sending nonces
to UA, to be returned in signed messages). An observer would be
seriously challenged to validate the asserted UAS ID or any other
information about the UAS or its operator looked up therefrom.
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3.3. DRIP Focus
In addition to the gaps described above, there is a fundamental gap
in almost all current or proposed regulations and technical standards
for UAS RID. As noted above, ID is not an end in itself, but a
means. [F3411-19] etc. provide very limited choices for an observer
to communicate with the pilot, e.g., to request further information
on the UAS operation or exit from an airspace volume in an emergency.
The System Message provides the location of the pilot/GCS, so an
observer could physically go to the asserted location to look for the
remote pilot; this is at best slow, and may not be feasible -- what
if the pilot is on the opposite rim of a canyon, or there are
multiple UAS operators to be contacted whose GCS all lie in different
directions from the Observer? An observer with Internet connectivity
and access privileges could look up operator PII in a registry, then
call a phone number in hopes someone who can immediately influence
the UAS operation will answer promptly during that operation; this is
unreliable. Internet technologies can do much better than this.
Thus complementing [F3411-19] with protocols enabling strong
authentication, preserving operator privacy while enabling immediate
use of information by authorized parties, is critical to achieve
widespread adoption of a RID system supporting safe and secure
operation of UAS.
DRIP will focus on making information obtained via UAS RID
immediately usable:
1. by making it trustworthy (despite the severe constraints of
Broadcast RID);
2. by enabling verification that an UAS is registered for RID, and
if so, in which registry (for classification of trusted operators
on the basis of known registry vetting, even by observers lacking
Internet connectivity at observation time);
3. by facilitating independent reports of UA aeronautical data
(location, velocity, etc.) to confirm or refute the operator
self-reports upon which UAS RID and UTM tracking are based;
4. by enabling instant establishment, by authorized parties, of
secure communications with the remote pilot.
4. Requirements
4.1. General
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GEN-1 Provable Ownership: DRIP MUST enable verification that the
UAS ID asserted in the Basic ID message is that of the actual
current sender of the message (i.e. the message is not a
replay attack or other spoof, authenticating e.g. by
verifying an asymmetric cryptographic signature using a
sender provided public key from which the asserted ID can be
at least partially derived), even on an observer device
lacking Internet connectivity at the time of observation.
GEN-2 Provable Binding: DRIP MUST enable binding all other
[F3411-19] messages from the same actual current sender to
the UAS ID asserted in the Basic ID message.
GEN-3 Provable Registration: DRIP MUST enable verification that the
UAS ID is in a registry and identification of which one, even
on an observer device lacking Internet connectivity at the
time of observation; with UAS ID Type 3, the same sender may
have multiple IDs, potentially in different registries, but
each ID must clearly indicate in which registry it can be
found.
GEN-4 Readability: DRIP MUST enable information (regulation
required elements, whether sent via UAS RID or looked up in
registries) to be read and utilized by both humans and
software.
GEN-5 Gateway: DRIP MUST enable Broadcast RID to Network RID
application layer gateways to stamp messages with precise
date/time received and receiver location, then relay them to
a network service (e.g. SDSP or distributed ledger), to
support three objectives: mark up a RID message with where
and when it was actually received (which may agree or
disagree with the self-report in the set of messages); defend
against replay attacks; and support optional SDSP services
such as multilateration (to complement UAS position self-
reports with independent measurements).
GEN-6 Finger: DRIP MUST enable dynamically establishing, with AAA,
per policy, end to end strongly encrypted communications with
the UAS RID sender and entities looked up from the UAS ID,
including at least the remote pilot and USS.
GEN-7 QoS: DRIP MUST enable policy based specification of
performance and reliability parameters, such as maximum
message transmission intervals and delivery latencies.
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GEN-8 Mobility: DRIP MUST support physical and logical mobility of
UA, GCS and Observers. DRIP SHOULD support mobility of
essentially all participating nodes (UA, GCS, Observers, Net-
RID SP, Net-RID DP, Private Registry, SDSP).
GEN-9 Multihoming: DRIP MUST support multihoming of UA and GCS, for
make-before-break smooth handoff and resiliency against path/
link failure. DRIP SHOULD support multihoming of essentially
all participating nodes.
GEN-10 Multicast: DRIP SHOULD support multicast for efficient and
flexible publish-subscribe notifications, e.g., of UAS
reporting positions in designated airspace volumes.
GEN-11 Management: DRIP SHOULD support monitoring of the health and
coverage of Broadcast and Network RID services.
Requirements imposed either by regulation or [F3411-19] are not
reiterated here, but drive many of the numbered requirements listed
here. The QoS requirement currently would be satisfied generally by
ensuring information refresh rates of at least 1 Hertz, with
latencies no greater than 1 second, at least 80% of the time; but
these numbers may change, so instead the DRIP requirement is that
they be user policy specifiable (which does not imply satisfiable in
all cases, but implies that when the specs are not met, appropriate
parties are notified). The "provable ownership" requirement
addresses the possibility that the actual sender is not the claimed
sender (i.e. is a spoofer). The "provable binding" requirement
addresses the MAC address correlation problem of [F3411-19] noted
above. The "provable registration" requirement may impose burdens
not only on the UAS sender and the Observer's receiver, but also on
the registry; yet it cannot depend upon the Observer being able to
contact the registry at the time of observing the UA. The
"readability" requirement may involve machine assisted format
conversions, e.g. from binary encodings. The "gateway" requirement
is the only instance in which DRIP transports [F3411-19] messages;
most of DRIP pertains to the authentication of such messages and the
identifier carried within them.
4.2. Identifier
ID-1 Length: The DRIP (UAS) entity (remote) identifier must be no
longer than 20 bytes (per [F3411-19] to fit in a Bluetooth 4
advertisement payload).
ID-2 Registry ID: The DRIP identifier MUST be sufficient to identify
a registry in which the (UAS) entity identified therewith is
listed.
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ID-3 Entity ID: The DRIP identifier MUST be sufficient to enable
lookup of other data associated with the (UAS) entity
identified therewith in that registry.
ID-4 Uniqueness: The DRIP identifier MUST be unique within the
global UAS RID identifier space from when it is first
registered therein until it is explicitly de-registered
therefrom (due to e.g. expiration after a specified lifetime
such as the FAA's proposed 6 months RID data retention period,
revocation by the registry, or surrender by the operator).
ID-5 Non-spoofability: The DRIP identifier MUST be non-spoofable
within the context of Remote ID broadcast messages (some
collection of messages provides proof of UA ownership of ID).
ID-6 Unlinkability: A DRIP UAS ID MUST NOT facilitate adversarial
correlation over multiple UAS operations; this may be
accomplished e.g. by limiting each identifier to a single use,
but if so, the UAS ID MUST support well-defined scalable timely
registration methods.
The DRIP identifier can be used at various layers: in Broadcast RID,
it would be used by the application running directly over the data
link; in Network RID, it would be used by the application running
over HTTPS (and possibly other protocols); and in RID initiated V2X
applications such as DAA and C2, it could be used between the network
and transport layers (with HIP or DTLS).
Registry ID (which registry the entity is in) and Entity ID (which
entity it is, within that registry) are requirements on a single DRIP
entity Identifier, not separate (types of) ID. In the most common
use case, the Entity will be the UA, and the DRIP Identifier will be
the UAS ID; however, other entities may also benefit from having DRIP
identifiers, so the Entity type is not prescribed here.
Whether a UAS ID is generated by the operator, GCS, UA, USS or
registry, or some collaboration thereamong, is unspecified; however,
there must be agreement on the UAS ID among these entities.
4.3. Privacy
PRIV-1 Confidential Handling: DRIP MUST enable confidential handling
of private information (i.e., any and all information
designated by neither cognizant authority nor the information
owner as public, e.g., personal data).
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PRIV-2 Encrypted Transport: DRIP MUST enable selective strong
encryption of private data in motion in such a manner that
only authorized actors can recover it. If transport is via
IP, then encryption MUST be end-to-end, at or above the IP
layer. DRIP MUST NOT encrypt safety critical data to be
transmitted over Broadcast RID in any situation where it is
unlikely that local observers authorized to access the
plaintext will be able to decrypt it or obtain it from a
service able to decrypt it. DRIP MUST NOT encrypt data when/
where doing so would conflict with applicable regulations or
CAA policies/procedures, i.e. DRIP MUST support configurable
disabling of encryption.
PRIV-3 Encrypted Storage: DRIP SHOULD facilitate selective strong
encryption of private data at rest in such a manner that only
authorized actors can recover it.
PRIV-4 Public/Private Designation: DRIP SHOULD facilitate
designation, by cognizant authorities and information owners,
which information is public and which private. By default,
all information required to be transmitted via Broadcast RID,
even when actually sent via Network RID, is assumed to be
public; all other information contained in registries for
lookup using the UAS ID is assumed to be private.
PRIV-5 Pseudonymous Rendezvous: DRIP MAY enable mutual discovery of
and communications among participating UAS operators whose UA
are in 4-D proximity, using the UAS ID without revealing
pilot/operator identity or physical location.
How information is stored on end systems is out of scope for DRIP.
Encouraging privacy best practices, including end system storage
encryption, by facilitating it with protocol design reflecting such
considerations, is in scope. Similar logic applies to methods for
designating information as public or private.
The privacy requirements above are for DRIP, neither for [F3411-19]
(which requires obfuscation of location to any Network RID subscriber
engaging in wide area surveillance, limits data retention periods,
etc. in the interests of privacy), nor for UAS RID in any specific
jurisdiction (which may have its own regulatory requirements). The
requirements above are also in a sense parameterized: who are the
"authorized actors", how are they designated, how are they
authenticated, etc.?
4.4. Registries
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REG-1 Public Lookup: DRIP MUST enable lookup, from the UAS ID, of
information designated by cognizant authority as public, and
MUST NOT restrict access to this information based on identity
or role of the party submitting the query.
REG-2 Private Lookup: DRIP MUST enable lookup of private information
(i.e., any and all information in a registry, associated with
the UAS ID, that is designated by neither cognizant authority
nor the information owner as public), and MUST, per policy,
enforce AAA, including restriction of access to this
information based on identity or role of the party submitting
the query.
REG-3 Provisioning: DRIP MUST enable provisioning registries with
static information on the UAS and its operator, dynamic
information on its current operation within the U-space / UTM
(including means by which the USS under which the UAS is
operating may be contacted for further, typically even more
dynamic, information), and Internet direct contact information
for services related to the foregoing.
REG-4 AAA Policy: DRIP MUST enable closing the AAA-policy registry
loop by governing AAA per registered policies and
administering policies only via AAA.
Registries are fundamental to RID. Only very limited information can
be Broadcast, but extended information is sometimes needed. The most
essential element of information sent is the UAS ID itself, the
unique key for lookup of extended information in registries. Beyond
designating the UAS ID as that unique key, the registry information
model is not specified herein, in part because regulatory
requirements for different registries (UAS operators and their UA,
each narrowly for UAS RID and broadly for U-space / UTM) and business
models for meeting those requirements are in flux. However those may
evolve, the essential registry functions remain the same, so are
specified herein.
5. IANA Considerations
This document does not make any IANA request.
6. Security Considerations
DRIP is all about safety and security, so content pertaining to such
is not limited to this section. Potential vulnerabilities of DRIP
include but are not limited to:
* Sybil attacks
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* Confusion created by many spoofed unsigned messages
* Processing overload induced by attempting to verify many spoofed
signed messages (where verification will fail but still consume
cycles)
* Malicious or malfunctioning registries
* Interception of (e.g. Man In The Middle attacks on) registration
messages
* UA impersonation through private key extraction, improper key
sharing or carriage of a small (presumably harmless) UA, e.g. as a
"false flag", by a larger (malicious) UA
It may be inferred from the Section 4.1 General requirements for
Provable Ownership, Provable Binding and Provable Registration,
together with the Section 4.2 Identifier requirements, that DRIP must
provide:
* message integrity / non-repudiation
* defense against replay attacks
* defense against spoofing
One approach to so doing involves verifiably binding the DRIP
identifier to a public key. Providing these security features,
whether via this approach or another, is likely to be especially
challenging for Observers without Internet connectivity at the time
of observation. E.g. checking the signature of a registry on a
public key certificate received via Broadcast RID in a remote area
presumably would require that the registry's public key had been
previously installed on the Observer's device, yet there may be many
registries and the Observer's device may be storage constrained, and
new registries may come on-line subsequent to installation of DRIP
software on the Observer's device. Thus there may be caveats on the
extent to which requirements can be satisfied in such cases, yet
strenuous effort should be made to satisfy them, as such cases, e.g.
firefighting in a national forest, are important.
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7. Privacy and Transparency Considerations
Privacy is closely related to but not synonymous with security, and
conflicts with transparency. Privacy and transparency are important
for legal reasons including regulatory consistency. [EU2018]
[EU2018] states "harmonised and interoperable national registration
systems... should comply with the applicable Union and national law
on privacy and processing of personal data, and the information
stored in those registration systems should be easily accessible."
Privacy and transparency (where essential to security or safety) are
also ethical and moral imperatives. Even in cases where old
practices (e.g. automobile registration plates) could be imitated,
when new applications involving PII (such as UAS RID) are addressed
and newer technologies could enable improving privacy, such
opportunities should not be squandered. Thus it is recommended that
all DRIP documents give due regard to [RFC6973] and more broadly
[RFC8280].
DRIP information falls into two classes: that which, to achieve the
purpose, must be published openly as cleartext, for the benefit of
any Observer (e.g., the basic UAS ID itself); and that which must be
protected (e.g., PII of pilots) but made available to properly
authorized parties (e.g., public safety personnel who urgently need
to contact pilots in emergencies). How properly authorized parties
are authorized, authenticated, etc. are questions that extend beyond
the scope of DRIP, but DRIP may be able to provide support for such
processes. Classification of information as public or private must
be made explicit and reflected with markings, design, etc.
Classifying the information will be addressed primarily in external
standards; herein it will be regarded as a matter for CAA, registry
and operator policies, for which enforcement mechanisms will be
defined within the scope of DRIP WG and offered. Details of the
protection mechanisms will be provided in other DRIP documents.
Mitigation of adversarial correlation will also be addressed.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
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8.2. Informative References
[cpdlc] Gurtov, A., Polishchuk, T., and M. Wernberg, "Controller-
Pilot Data Link Communication Security", MDPI
Sensors 18(5), 1636, 2018,
<https://www.mdpi.com/1424-8220/18/5/1636>.
[CTA2063A] ANSI, "Small Unmanned Aerial Systems Serial Numbers",
September 2019.
[Delegated]
European Union Aviation Safety Agency (EASA), "Commission
Delegated Regulation (EU) 2019/945 of 12 March 2019 on
unmanned aircraft systems and on third-country operators
of unmanned aircraft systems", March 2019.
[drip-architecture]
Card, S., Wiethuechter, A., Moskowitz, R., Zhao, S., and
A. Gurtov, "Drone Remote Identification Protocol (DRIP)
Architecture", Work in Progress, Internet-Draft, draft-
ietf-drip-arch-03, 13 July 2020,
<https://tools.ietf.org/html/draft-ietf-drip-arch-03>.
[ENISACSIRT]
European Union Agency for Cybersecurity (ENISA),
"Actionable information for Security Incident Response",
November 2014, <https://www.enisa.europa.eu/topics/csirt-
cert-services/reactive-services/copy_of_actionable-
information>.
[EU2018] European Parliament and Council, "2015/0277 (COD) PE-CONS
2/18", February 2018.
[F3411-19] ASTM International, "Standard Specification for Remote ID
and Tracking", February 2020,
<http://www.astm.org/cgi-bin/resolver.cgi?F3411>.
[FAACONOPS]
FAA Office of NextGen, "UTM Concept of Operations v2.0",
March 2020.
[I-D.maeurer-raw-ldacs]
Maeurer, N., Graeupl, T., and C. Schmitt, "L-band Digital
Aeronautical Communications System (LDACS)", Work in
Progress, Internet-Draft, draft-maeurer-raw-ldacs-06, 2
October 2020,
<https://tools.ietf.org/html/draft-maeurer-raw-ldacs-06>.
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[ICAOATM] International Civil Aviation Organization, "Doc 4444:
Procedures for Air Navigation Services: Air Traffic
Management", November 2016.
[ICAOUAS] International Civil Aviation Organization, "Circular 328:
Unmanned Aircraft Systems", February 2011.
[ICAOUTM] International Civil Aviation Organization, "Unmanned
Aircraft Systems Traffic Management (UTM) - A Common
Framework with Core Principles for Global Harmonization,
Edition 2", November 2019.
[Implementing]
European Union Aviation Safety Agency (EASA), "Commission
Implementing Regulation (EU) 2019/947 of 24 May 2019 on
the rules and procedures for the operation of unmanned
aircraft", May 2019.
[InitialView]
SESAR Joint Undertaking, "Initial view on Principles for
the U-space architecture", July 2019.
[NPRM] United States Federal Aviation Administration (FAA),
"Notice of Proposed Rule Making on Remote Identification
of Unmanned Aircraft Systems", December 2019.
[OpenDroneID]
Intel Corp., "Open Drone ID", March 2019,
<https://github.com/opendroneid/specs>.
[Opinion1] European Union Aviation Safety Agency (EASA), "Opinion No
01/2020: High-level regulatory framework for the U-space",
March 2020.
[Recommendations]
FAA UAS Identification and Tracking Aviation Rulemaking
Committee, "UAS ID and Tracking ARC Recommendations Final
Report", September 2017.
[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
Unique IDentifier (UUID) URN Namespace", RFC 4122,
DOI 10.17487/RFC4122, July 2005,
<https://www.rfc-editor.org/info/rfc4122>.
[RFC4949] Shirey, R., "Internet Security Glossary, Version 2",
FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,
<https://www.rfc-editor.org/info/rfc4949>.
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[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>.
[RFC8280] ten Oever, N. and C. Cath, "Research into Human Rights
Protocol Considerations", RFC 8280, DOI 10.17487/RFC8280,
October 2017, <https://www.rfc-editor.org/info/rfc8280>.
[Roadmap] American National Standards Institute (ANSI) Unmanned
Aircraft Systems Standardization Collaborative (UASSC),
"Standardization Roadmap for Unmanned Aircraft Systems
draft v2.0", April 2020, <https://share.ansi.org/Shared
Documents/Standards Activities/UASSC/
UASSC_20-001_WORKING_DRAFT_ANSI_UASSC_Roadmap_v2.pdf>.
[Stranger] Heinlein, R.A., "Stranger in a Strange Land", June 1961.
[WG105] EUROCAE, "WG-105 draft Minimum Operational Performance
Standards (MOPS) for Unmanned Aircraft System (UAS)
Electronic Identification", June 2020.
Appendix A. Discussion and Limitations
This document is largely based on the process of one SDO, ASTM.
Therefore, it is tailored to specific needs and data formats of this
standard. Other organizations, for example in EU, do not necessary
follow the same architecture.
The need for drone ID and operator privacy is an open discussion
topic. For instance, in the ground vehicular domain each car carries
a publicly visible plate number. In some countries, for nominal cost
or even for free, anyone can resolve the identity and contact
information of the owner. Civil commercial aviation and maritime
industries also have a tradition of broadcasting plane or ship ID,
coordinates and even flight plans in plain text. Community networks
such as OpenSky and Flightradar use this open information through
ADS-B to deploy public services of flight tracking. Many researchers
also use these data to perform optimization of routes and airport
operations. Such ID information should be integrity protected, but
not necessarily confidential.
In civil aviation, aircraft identity is broadcast by a device known
as transponder. It transmits a four-digit squawk code, which is
assigned by a traffic controller to an airplane after approving a
flight plan. There are several reserved codes such as 7600 which
indicate radio communication failure. The codes are unique in each
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traffic area and can be re-assigned when entering another control
area. The code is transmitted in plain text by the transponder and
also used for collision avoidance by a system known as Traffic alert
and Collision Avoidance System (TCAS). The system could be used for
UAS as well initially, but the code space is quite limited and likely
to be exhausted soon. The number of UAS far exceeds the number of
civil airplanes in operation.
The ADS-B system is utilized in civil aviation for each "ADS-B Out"
equipped airplane to broadcast its ID, coordinates and altitude for
other airplanes and ground control stations. If this system is
adopted for drone IDs, it has additional benefit with backward
compatibility with civil aviation infrastructure; then, pilots and
dispatchers will be able to see UA on their control screens and take
those into account. If not, a gateway translation system between the
proposed drone ID and civil aviation system should be implemented.
Again, system saturation due to large numbers of UAS is a concern.
Wi-Fi and Bluetooth are two wireless technologies currently
recommended by ASTM specifications due to their widespread use and
broadcast nature. However, those have limited range (max 100s of
meters) and may not reliably deliver UAS ID at high altitude or
distance. Therefore, a study should be made of alternative
technologies from the telecom domain (WiMAX, 5G) or sensor networks
(Sigfox, LORA). Such transmission technologies can impose additional
restrictions on packet sizes and frequency of transmissions, but
could provide better energy efficiency and range. In civil aviation,
Controller-Pilot Data Link Communications (CPDLC) is used to transmit
command and control between the pilots and ATC. It could be
considered for UAS as well due to long range and proven use despite
its lack of security [cpdlc].
L-band Digital Aeronautical Communications System (LDACS) is being
standardized by ICAO and IETF for use in future civil aviation
[I-D.maeurer-raw-ldacs]. It provides secure communication,
positioning and control for aircraft using a dedicated radio band.
It should be analyzed as a potential provider for UAS RID as well.
This will bring the benefit of a global integrated system creating a
global airspace use awareness.
Acknowledgments
The work of the FAA's UAS Identification and Tracking (UAS ID)
Aviation Rulemaking Committee (ARC) is the foundation of later ASTM
[F3411-19] and IETF DRIP efforts. The work of Gabriel Cox, Intel
Corp. and their Open Drone ID collaborators opened UAS RID to a wider
community. The work of ASTM F38.02 in balancing the interests of
diverse stakeholders is essential to the necessary rapid and
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widespread deployment of UAS RID. IETF volunteers who have
extensively reviewed or otherwise contributed to this document
include Amelia Andersdotter, Carsten Bormann, Mohamed Boucadair,
Toerless Eckert, Susan Hares, Mika Jarvenpaa, Daniel Migault,
Alexandre Petrescu, Saulo Da Silva and Shuai Zhao.
Authors' Addresses
Stuart W. Card (editor)
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
Andrei Gurtov
Linköping University
IDA
SE-58183 Linköping
Sweden
Email: gurtov@acm.org
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