Internet DRAFT - draft-card-drip-reqs
draft-card-drip-reqs
DRIP S. Card
Internet-Draft A. Wiethuechter
Intended status: Informational AX Enterprize
Expires: 22 October 2020 R. Moskowitz
HTT Consulting
20 April 2020
Drone Remote Identification Protocol (DRIP) Requirements
draft-card-drip-reqs-02
Abstract
This document defines the requirements for Drone Remote
Identification Protocol (DRIP) Working Group protocols and services
to support Unmanned Aircraft System Remote Identification (UAS RID).
Objectives include: complementing external technical standards as
regulator-accepted means of compliance with UAS RID regulations;
facilitating use of existing Internet resources to support UAS RID
and to enable enhanced related services; and enabling verification
that UAS RID information is trustworthy (to some extent, even in the
absence of Internet connectivity at the receiving node).
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 22 October 2020.
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terms and Definitions . . . . . . . . . . . . . . . . . . . . 5
2.1. Requirements Terminology . . . . . . . . . . . . . . . . 5
2.2. Definitions . . . . . . . . . . . . . . . . . . . . . . . 5
3. UAS RID Problem Space . . . . . . . . . . . . . . . . . . . . 10
3.1. Network RID . . . . . . . . . . . . . . . . . . . . . . . 11
3.2. Broadcast RID . . . . . . . . . . . . . . . . . . . . . . 12
3.3. DRIP Focus . . . . . . . . . . . . . . . . . . . . . . . 12
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 13
4.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.2. Identifier . . . . . . . . . . . . . . . . . . . . . . . 15
4.3. Privacy . . . . . . . . . . . . . . . . . . . . . . . . . 16
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
6. Security Considerations . . . . . . . . . . . . . . . . . . . 16
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
8.1. Normative References . . . . . . . . . . . . . . . . . . 17
8.2. Informative References . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction
Many safety and other considerations dictate that UAS be remotely
identifiable. Civil Aviation Authorities (CAAs) worldwide are
mandating UAS RID. The European Union Aviation Safety Agency (EASA)
has published [Delegated] and [Implementing] Regulations. The United
States (US) Federal Aviation Administration (FAA) has published a
Notice of Proposed Rule Making ([NPRM]). CAAs currently 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 [F3411-19] Standard Specification for Remote ID and
Tracking. It defines 2 means of UAS RID. Network RID defines a set
of information for UAS to make available globally indirectly via the
Internet. Broadcast RID defines a set of messages for Unmanned
Aircraft (UA) to transmit locally directly one-way over Bluetooth or
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Wi-Fi. Network RID depends upon Internet connectivity, in several
segments, from the UAS to the observer. Broadcast RID should need
Internet (or other Wide Area Network) connectivity only for UAS
registry information lookup using the directly locally received UAS
ID as a key. It is expected that the same information will be
provided via Broadcast and Network RID; in the US, the FAA NPRM so
specifies.
[F3411-19] specifies 3 UAS ID types. Type 1 is a static,
manufacturer assigned, hardware serial number per ANSI/CTA-2063-A
"Small Unmanned Aerial System Serial Numbers" [CTA2063A]. Type 2 is
a CAA assigned (presumably static) ID. Type 3 is a UAS Traffic
Management (UTM) system assigned UUID [RFC4122], 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"). [F3411-19] Broadcast RID transmits all information in
the clear as plaintext (ASCII or binary), so static IDs enable
trivial correlation of patterns of use, unacceptable in many
applications, e.g. package delivery routes of competitors.
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. [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.
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 [F3411-19]; 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 [Recommendations], it is not addressed in
any of the subsequent proposed regulations or technical
specifications.
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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 (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.
UA onboard RID devices are severely constrained in Size, Weight and
Power (SWaP). Cost is a significant impediment to the necessary
near-universal adoption of UAS send and observer receive RID
capabilities. 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.
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 [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]) may
be desirable.
DRIP's 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. DRIP (originally called 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 architecture for UAS
RID conforming to proposed regulations and external technical
standards will be described in a companion DRIP Architecture
document; this document describes only requirements.
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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
$SWaP
Cost, Size, Weight and Power.
AAA
Attestation, Authentication, Authorization, Access Control,
Accounting, Attribution, Audit.
ABDAA
AirBorne DAA. Also known as "self-separation".
AGL
Above Ground Level. Relative altitude, above the variously
defined local ground level, typically of an UA, typically measured
in feet.
ATC
Air Traffic Control. Explicit flight direction to pilots from
ground controllers. Contrast with ATM.
ATM
Air Traffic Management. All systems that assist aircraft from
departure to landing. A broader functional and geographic scope
and/or a higher layer of abstraction than ATC.
Authentication Message
F3411 Message Type 2. Provides framing for authentication data,
only.
Basic ID Message
F3411 Message Type 0. Provides UA Type, UAS ID Type and UAS ID,
only.
CAA
Civil Aviation Authority. An example is the Federal Aviation
Administration (FAA) in the United States of America.
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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.
Mainly used in military contexts. In the UAS context, typically
refers to the link between GCS and UA over which the former
controls the latter. Out of scope for DRIP, even when this link
is used to provide UA location to the GCS or vice-versa, for
subsequent RID transmission.
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 [Delegated], "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.
E2E
End to End.
GBDAA
Ground Based DAA.
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.
GPS
Global Positioning System. In this context, misused in place of
Global Navigation Satellite System (GNSS) or more generally SATNAV
to refer generically to satellite based timing and/or positioning.
GRAIN
Global Resilient Aviation Information Network. An effort to
develop an international IPv6 overlay network with end-to-end
security supporting all aspects of aviation.
IATF
International Aviation Trust Framework. ICAO effort to develop a
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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
F3411 Message Type 1. Provides UA location, altitude, heading and
speed, only.
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 for a GCS),
typically measured in feet.
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. 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.
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Net-RID SP
Network RID Service Provider. Logical entity that participates in
Network RID and provides to NetRID-DPs information on UAS it
manages. 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
Referred to in other UAS RID documents as a "user", but there are
also other classes of UAS RID users, so we prefer "observer" to
denote an individual who has observed an UA and wishes to know
something about it, starting with its ID.
Operator ID Message
F3411 Message Type 5. Provides CAA issued Operator ID, only.
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.
RF
Radio Frequency. May be used as an adjective or as a noun; in the
latter case, typically means Radio Frequency energy.
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.
Self-ID Message
F3411 Message Type 3. Provides a 1 byte descriptor and 23 byte
ASCII free text field, only.
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
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(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.
SDSP
Supplemental Data Service Provider. An entity that participates
in the UTM system, but provides services beyond those specified as
basic UTM system functions.
System Message
F3411 Message Type 4. Provides general UAS information, including
remote pilot location, multiple UA group operational area, etc.
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 [F3411-19], maximum length of 20 bytes.
UAS ID Type
Identifier type index. Per [F3411-19], 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.
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USS
UAS Service Supplier. Provide UTM 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. (From FAA UTM
ConOps V1, May 2018).
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.
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
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 engine 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 Global
Positioning System (GPS) waypoint to waypoint in a weak form of
autonomy; stronger autonomy is coming. UA are "low observable": they
typically have a small radar cross section; 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
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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.
3.1. Network RID
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). 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 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 WiFi, but provided the data
link can support at least IP and ideally TCP, its type is generally
immaterial to the higher layer protocols. An UAS or other 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.
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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
[F3411-19] specifies 3 Broadcast RID data links: Bluetooth 4.X;
Bluetooth 5.X Long Range; and WiFi with Neighbor Awareness Networking
(NAN). For compliance with this standard, 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).
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).
3.3. DRIP Focus
DRIP WG will focus on making information obtained via UAS RID
immediately usable (for the observer to determine whether the UAS is
trusted to fly in the airspace volume where and when observed, to
establish communications whereby the observer can inquire of the
pilot as to intent and/or direct the pilot to exit from the volume,
etc.):
1. first by making it trustworthy (despite the severe constraints of
Broadcast RID);
2. second 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);
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3. third by enabling instant establishment, by authorized parties,
of secure communications with the remote pilot.
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, 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.
Further, [F3411-19] 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 [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.
4. Requirements
4.1. General
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).
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GEN-2 Provable Binding: DRIP MUST enable binding all other F3411
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 (with
UAS ID Type 3, the same sender may have multiple IDs,
potentially in different registries, but each ID should
clearly indicate in which registry it can be found).
GEN-4 Public Lookup: DRIP MUST enable lookup, from the UAS ID, of
information designated by cognizant authority as public.
GEN-5 Private Lookup: DRIP MUST enable lookup, with AAA, per
policy, 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).
GEN-6 Readability: DRIP MUST enable information to be read and
utilized by both humans and software.
GEN-7 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.
GEN-8 AAA Policy: DRIP MUST enable closing the AAA-policy registry
loop by governing AAA per registered policies and
administering policies only via AAA.
GEN-9 Finger (placeholder name): 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.
GEN-10 QoS: DRIP MUST enable policy based specification of
performance and reliability parameters, such as maximum
message transmission intervals and delivery latencies.
GEN-11 Mobility: DRIP MUST support physical and logical mobility of
UA, GCS and Observers. DRIP SHOULD support mobility of all
participating nodes.
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GEN-12 Multihoming: DRIP MUST support multihoming of UA, for make-
before-break smooth handoff and resiliency against path/link
failure. DRIP SHOULD support multihoming of all
participating nodes.
GEN-13 Multicast: DRIP SHOULD support multicast for efficient and
flexible publish-subscribe notifications, e.g. of UAS
reporting positions in designated sensitive airspace volumes.
GEN-14 Management: DRIP SHOULD support monitoring of the health and
coverage of Broadcast and Network RID services.
It is highly desirable that Broadcast RID receivers be able to stamp
messages with accurate date/time received and receiver location, then
relay them to a network service (e.g. SDSP or distributed ledger).
This supports 3 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 reply attacks; and
support optional SDSP services such as multilateration (to complement
UAS position self-reports with independent measurements).
4.2. Identifier
ID-1 Length: The DRIP [UAS] entity [remote] identifier must be no
longer than 20 bytes.
ID-2 Registry ID: The DRIP identifier MUST be sufficient to identify
a registry in which the [UAS] entity identified therewith is
listed.
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 a to-be-
defined scope.
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).
A DRIP UAS ID MUST NOT facilitate adversarial correlation of UAS
operational patterns; this may be accomplished e.g. by limiting each
identifier to a single use, but if so, the UAS ID MUST support
defined scalable timely registration methods.
Mechanisms standardized in DRIP WG MUST be capable of proving
ownership of a claimed UAS ID, and SHOULD be capable of doing so
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immediately on an observer device lacking Internet connectivity at
the time of observation.
Mechanisms standardized in DRIP WG MUST be capable of verifying that
messages claiming to have been sent from a UAS with a given UAS ID
indeed came from the claimed sender.
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).
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.
PRIV-3 Encrypted Storage: DRIP SHOULD enable selective strong
encryption of private data at rest in such a manner that only
authorized actors can recover it.
As satisfying these requirements may require that authorized actors
have e.g. Internet connectivity to a Remote ID USS to enable
decryption, and such connectivity cannot be assured, DRIP SHOULD
provide automatic fallback to plaintext transmission of safety-
critical information when necessary.
5. IANA Considerations
It is likely that an IPv6 prefix or other namespace will be needed;
this will be specified in other documents.
6. Security Considerations
DRIP is all about safety and security, so content pertaining to such
is not limited to this section. DRIP information must be divided
into 2 classes: that which, to achieve the purpose, must be published
openly in clear plaintext, for the benefit of any observer; 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). Details of the
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protection mechanisms will be provided in other documents.
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. Mitigation of
adversarial correlation will also be addressed.
7. 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 WG efforts. The work of ASTM F38.02 in
balancing the interests of diverse stakeholders is essential to the
necessary rapid and widespread deployment of UAS RID.
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>.
8.2. Informative References
[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.
[F3411-19] ASTM, "Standard Specification for Remote ID and Tracking",
December 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.
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[NPRM] United States Federal Aviation Administration (FAA),
"Notice of Proposed Rule Making on Remote Identification
of Unmanned Aircraft Systems", December 2019.
[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>.
[Stranger] Heinlein, R.A., "Stranger in a Strange Land", June 1961.
Authors' Addresses
Stuart W. Card
AX Enterprize
4947 Commercial Drive
Yorkville, NY 13495
United States of America
Email: stu.card@axenterprize.com
Adam Wiethuechter
AX Enterprize
4947 Commercial Drive
Yorkville, NY 13495
United States of America
Email: adam.wiethuechter@axenterprize.com
Robert Moskowitz
HTT Consulting
Oak Park, MI 48237
United States of America
Email: rgm@labs.htt-consult.com
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