Drone Remote Identification Protocol
(DRIP) RequirementsAX Enterprize4947 Commercial DriveYorkvilleNY13495USAstu.card@axenterprize.comAX Enterprize4947 Commercial DriveYorkvilleNY13495USAadam.wiethuechter@axenterprize.comHTT ConsultingOak ParkMI48237USArgm@labs.htt-consult.comLinköping UniversityIDALinköping58183Swedengurtov@acm.org
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DRIPRFCRequest for CommentsI-DInternet-DraftDRIP
This document defines the 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.
Introduction (Informative)Overall Context
Many considerations (especially safety and security) dictate that
UAS be remotely identifiable. Any Observer with responsibilities
involving aircraft inherently must classify Unmanned Aircraft (UA)
situationally according to basic considerations, as illustrated
notionally in
below. 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 reasons; as High Concern or Unidentified,
is worth focused surveillance.
Civil Aviation Authorities (CAAs) worldwide are mandating Unmanned
Aircraft System Remote Identification and tracking (UAS RID). The
European Union Aviation Safety Agency (EASA) has published and Regulations. The United
States (US) Federal Aviation Administration (FAA) has published a
Notice of Proposed Rule Making and has described the key role that UAS RID
plays in UAS Traffic Management (UTM) in (especially Section 2.6). 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 International, Technical Committee F38 (UAS), Subcommittee
F38.02 (Aircraft Operations), Work Item WK65041, developed ASTM
F3411-19 Standard
Specification for Remote ID and Tracking (early drafts are freely
available as
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, to be
received in real time by local Observers.
The same information must be provided via both means. 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 frequency with 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 GCS 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 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.
specifies three UAS ID
types:
A static, manufacturer assigned, hardware serial number per
ANSI/CTA-2063-A "Small Unmanned Aerial System Serial Numbers"
.
A CAA assigned (presumably static) ID.
A UTM system assigned UUID , which can but need not be dynamic.
The EU allows only Type 1. The US allows Types 1 and 3, but
requires Type 3 IDs (if used) each to be used only once (for a
single UAS flight, which in the context of UTM is called an
"operation"). The EU also requires an operator registration number
(an additional identifier distinct from the UAS ID) that can be
carried in an optional
Operator ID message. As yet apparently there are no CAA proposals
to use Type 2.
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.
and 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 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).
Security oriented UAS RID regulations essentially have 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, especially location. Safety oriented UAS RID has
stronger requirements. Aviation community SDOs set a higher bar for
safety than for security, especially with respect to reliability.
Intended Use
An ID is not an end in itself; it exists to enable lookups and
provision of services complementing mere identification.
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.
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.
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 FAA NPRM. However, applications of
RID beyond RID itself have been omitted from ; DAA has been explicitly
declared out of scope in ASTM 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 , it is not addressed in any of the subsequent
proposed regulations or technical specifications.
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 , 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.
UA onboard RID devices are severely constrained in Cost ($), Size,
Weight and Power ($SWaP). Cost is a significant impediment to the
necessary near-universal adoption of UAS send and Observer receive
RID capabilities. $SWaP 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 $SWaP 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.
Despite work by regulators and Standards Development Organizations
(SDOs), there are substantial gaps in UAS standards generally and
UAS RID specifically.
catalogs UAS related standards, ongoing standardization activities
and gaps (as of early 2020); Section 7.8 catalogs those related
specifically to UAS RID.
Given not only packet payload length and bandwidth, but also
processing and storage within the $SWaP constraints of very small
(e.g. consumer toy) UA, heavyweight cryptographic security
protocols are infeasible, yet trustworthiness of UAS RID
information is essential. Under , 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 ) is desirable.
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, 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 . 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. Potential follow-on goals may
extend beyond providing timely and trustworthy identification data,
to using it to enable identity-oriented networking of UAS.
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 and elaborated in other DRIP documents; this
document describes only relevant requirements and defines
terminology for the set of DRIP documents.
Terms and DefinitionsRequirements 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 when, and only when, they
appear in all capitals, as shown here.
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. 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 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)".
$SWaP
Cost, Size, Weight and Power. (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. Also known as "self-separation".
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."
Authentication Message
Message Type 2.
Provides framing for authentication data, only. Optional
per but may be
required by regulations.
Basic ID Message
Message Type 0.
Provides UA Type, UAS ID Type and UAS ID, only. Mandatory
per .
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
European Union Aviation Safety Agency (EASA).
C2
Command and Control. A set of organizational and technical
attributes and processes that employs human, physical, and
information resources to solve problems and accomplish
missions. Previously primarily used in military contexts.
In the UAS context, typically refers to the link between
GCS and UA over which the former controls the latter.
DAA
Detect And Avoid, formerly Sense And Avoid (SAA). A means
of keeping aircraft "well clear" of each other for safety.
Direct RID
Direct Remote Identification. Per , "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". Requirement
could be met with ASTM Broadcast RID: Basic ID message with
UAS ID Type 1; Location/Vector message; Operator ID
message; System Message. Corresponds roughly to the
Broadcast RID portion of FAA 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
and surveillance; but it also supports other functions.
E2E
End to End.
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 this
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.
Limited RID
Per the FAA NPRM, 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.
Location/Vector Message
Message Type 1.
Provides UA location, altitude, heading and speed, only.
Mandatory per .
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 FAA NPRM
also for a GCS), measured in or meters. Should be
explicitly specified as either barometric (pressure) or
geodetic (GNSS).
Net-RID DP
Network RID Display Provider. 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,
regarding subscribed USS. Under the FAA 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. Logical entity that collects
RID messages from UAS and responds to NetRID-DP queries for
information on UAS of which it is aware. Under the FAA
NPRM, the USS to which the UAS is subscribed ("Remote ID
USS").
Network Identification Service
EU regulatory requirement for Network RID. Requirement
could be met with ASTM Network RID: Basic ID message with
UAS ID Type 1; Location/Vector message; Operator ID
message; System Message. Corresponds roughly to the
Network RID portion of FAA NPRM Standard RID.
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, in the same airspace volume, separated by at most
brief ground intervals.
Operator
"A person, organization or enterprise engaged in or
offering to engage in an aircraft operation."
Operator ID Message
Message Type 5.
Provides CAA issued Operator ID, only. Operator ID is
distinct from UAS ID. Optional per 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."
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.
RF-LOS
RF LOS. Typically used in describing operation of 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.
RTCA
Radio Technical Commission for Aeronautics. US aviation
SDO. Cooperates extensively with EUROCAE.
Self-ID Message
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 unless required by
the cognizant CAA. Optional per but may be required by regulations.
Standard RID
Per the FAA NPRM, 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). 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.
System Message
Message Type 4.
Provides general UAS information, including remote pilot
location, multiple UA group operational area, etc. Optional
per 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.
UA
Unmanned Aircraft. An aircraft which is intended to operate
with no pilot on board. In popular parlance, "drone".
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.
UAS ID
UAS identifier. Although called "UAS ID", unique to the UA:
neither to the operator (as previous registration numbers
have been assigned), nor to the combination of GCS and UA
that comprise the UAS. Per : maximum length of 20 bytes; see for currently
defined values.
UAS ID Type
Identifier type index. Per , 4 bits, values 0-3 already specified.
UAS RID
UAS Remote Identification. System for identifying UA during
flight by other parties.
UAS RID Verification Service
System component designed to handle the authentication
requirements of RID by offloading verification to a web
hosted service.
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 .
UTM
UAS Traffic Management. Per ICAO, "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." 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.
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.
UAS RID Problem Space
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.
Network RID from the UA itself (rather than from its GCS) and
Broadcast RID require one or more wireless data links from the UA,
but such communications are challenging due to $SWaP constraints
and low altitude flight amidst structures and foliage over terrain.
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.
Network RID
Network RID is essentially publish-subscribe-query. 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 containing that UAS operation, their USS
learns, via the UTM Discovery and Synchronization Service (DSS),
that USS#1 has such operations. Observers or other interested
parties can then subscribe, via their USS, which serves as a
Network RID Display Provider (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, which in turn
will deliver the surveillance 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).
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 coverage of an
airspace 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 . It is presumed that IETF
efforts supporting Broadcast RID (see next section) can be easily
generalized for Network RID.
Broadcast RID 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 , 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 as
Bluetooth Legacy).
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).
DRIP Focus
DRIP will focus on making information obtained via UAS RID
immediately usable:
by making it trustworthy (despite the severe constraints
of Broadcast RID);
by enabling verification that an UAS is registered, 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);
by facilitating independent reports of UA’s aeronautical data
(location, velocity, etc.) to confirm or refute the operator
self-reports upon which UAS RID and UTM tracking are based;
by enabling instant establishment, by authorized parties,
of secure communications with the remote pilot.
Any UA can assert any ID using the 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 have suggested using
the MAC addresses, but these may be randomized by the operating
system stack to avoid the adversarial correlation problems of
static identifiers.
The 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.
Further, provides 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 GCS location to look for the remote
pilot. An observer with Internet connectivity 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.
Thus complementing 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.
RequirementsGeneral
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.
Provable Binding: DRIP MUST enable binding all other messages from the same
actual current sender to the UAS ID asserted in the Basic ID
message.
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.
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.
Gateway: DRIP MUST enable Broadcast RID -> 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).
Finger: DRIP MUST enable dynamically establishing, with AAA,
per policy, E2E strongly encrypted communications with the UAS
RID sender and entities looked up from the UAS ID, including at
least the remote pilot and USS.
QoS: DRIP MUST enable policy based specification of performance
and reliability parameters, such as maximum message
transmission intervals and delivery latencies.
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).
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.
Multicast: DRIP SHOULD support multicast for efficient
and flexible publish-subscribe notifications, e.g., of UAS
reporting positions in designated sensitive airspace volumes.
Management: DRIP SHOULD support monitoring of the health
and coverage of Broadcast and Network RID services.
Requirements imposed either by regulation or in are not reiterated here, but
drive many of the numbered requirements listed here. E.g. 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. Note that the "provable binding" requirement
addresses the MAC address correlation problem of noted above. Note that the
"gateway" requirement is the only instance in which DRIP transports
messages; most of DRIP
pertains to the authentication of such messages and the identifier
carried within them.
Identifier
Length: The DRIP (UAS) entity (remote) identifier must be no
longer than 20 bytes (per to fit in a Bluetooth 4 advertisement
payload).
Registry ID: The DRIP identifier MUST be sufficient to
identify a registry in which the (UAS) entity identified
therewith is listed.
Entity ID: The DRIP identifier MUST be sufficient to
enable lookup of other data associated with the (UAS) entity
identified therewith in that registry.
Uniqueness: The DRIP identifier MUST be unique within a
to-be-defined scope.
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).
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.
Note that Registry ID and Entity ID 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.
Privacy
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).
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.
Encrypted Storage: DRIP SHOULD facilitate selective strong
encryption of private data at rest in such a manner that only
authorized actors can recover it.
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.
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 (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.?
Registries
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
of the party submitting the query.
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 of the party submitting the
query.
Provisioning: DRIP MUST enable provisioning registries with
static information on the UAS and its operator, dynamic
information on its current operation within the 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.
AAA Policy: DRIP MUST enable closing the AAA-policy registry
loop by governing AAA per registered policies and administering
policies only via AAA.
IANA Considerations
This document does not make any IANA request.
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
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
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] 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 and more broadly .
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.
ReferencesNormative ReferencesInformative ReferencesController-Pilot Data Link Communication SecuritySmall Unmanned Aerial Systems Serial NumbersANSICommission Delegated Regulation (EU) 2019/945 of 12 March 2019 on unmanned aircraft systems and on third-country operators of unmanned aircraft systems European Union Aviation Safety Agency (EASA) Actionable information for Security Incident ResponseEuropean Union Agency for Cybersecurity (ENISA)2015/0277 (COD) PE-CONS 2/18 European Parliament and Council Standard Specification for Remote ID and TrackingASTM InternationalOpen Drone IDIntel Corp.Doc 4444: Procedures for Air Navigation Services: Air Traffic Management International Civil Aviation Organization Unmanned Aircraft Systems Traffic Management (UTM) - A Common Framework with Core Principles for Global Harmonization, Edition 2 International Civil Aviation Organization Commission Implementing Regulation (EU) 2019/947 of 24 May 2019 on the rules and procedures for the operation of unmanned aircraft European Union Aviation Safety Agency (EASA)Notice of Proposed Rule Making on Remote Identification of Unmanned Aircraft SystemsUnited States Federal Aviation Administration (FAA)UAS ID and Tracking ARC Recommendations Final ReportFAA UAS Identification and Tracking Aviation Rulemaking CommitteeUTM Concept of Operations v2.0FAA Office of NextGenStandardization Roadmap for Unmanned Aircraft Systems draft v2.0American National Standards Institute (ANSI) Unmanned Aircraft Systems Standardization Collaborative (UASSC)Stranger in a Strange LandWG-105 draft Minimum Operational Performance Standards (MOPS) for Unmanned Aircraft System (UAS) Electronic Identification EUROCAE Opinion No 01/2020: High-level regulatory framework for the U-spaceEuropean Union Aviation Safety Agency (EASA)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
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 .
L-band Digital Aeronautical Communications System (LDACS) is being
standardized by ICAO and IETF for use in future civil aviation
. 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
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 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.