Drone Remote Identification Protocol (DRIP) Architecture
draft-ietf-drip-arch-16
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 9434.
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|
|---|---|---|---|
| Authors | Stuart W. Card , Adam Wiethuechter , Robert Moskowitz , Shuai Zhao , Andrei Gurtov | ||
| Last updated | 2021-10-25 (Latest revision 2021-07-25) | ||
| Replaces | draft-card-drip-arch | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
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| Stream | WG state | In WG Last Call | |
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| Document shepherd | Daniel Migault | ||
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| Telechat date | (None) | ||
| Responsible AD | Éric Vyncke | ||
| Send notices to | daniel.migault@ericsson.com |
draft-ietf-drip-arch-16
drip S. Card
Internet-Draft A. Wiethuechter
Intended status: Informational AX Enterprize
Expires: 28 April 2022 R. Moskowitz
HTT Consulting
S. Zhao (Editor)
Tencent
A. Gurtov
Linköping University
25 October 2021
Drone Remote Identification Protocol (DRIP) Architecture
draft-ietf-drip-arch-16
Abstract
This document describes an architecture for protocols and services to
support Unmanned Aircraft System Remote Identification and tracking
(UAS RID), plus RID-related communications. This architecture
adheres to the requirements listed in the DRIP Requirements document.
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 28 April 2022.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
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and restrictions with respect to this document. Code Components
extracted from this document must include Simplified BSD License text
as described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Overview of Unmanned Aircraft System (UAS) Remote ID (RID)
and Standardization . . . . . . . . . . . . . . . . . . . 3
1.2. Overview of Types of UAS Remote ID . . . . . . . . . . . 4
1.2.1. Broadcast RID . . . . . . . . . . . . . . . . . . . . 4
1.2.2. Network RID . . . . . . . . . . . . . . . . . . . . . 5
1.3. Overview of USS Interoperability . . . . . . . . . . . . 7
1.4. Overview of DRIP Architecture . . . . . . . . . . . . . . 8
2. Terms and Definitions . . . . . . . . . . . . . . . . . . . . 9
2.1. Architecture Terminology . . . . . . . . . . . . . . . . 9
2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 9
2.3. Additional Definitions . . . . . . . . . . . . . . . . . 10
3. Claims, Assertions, Attestations, and Certificates . . . . . 10
4. HHIT as the DRIP Entity Identifier . . . . . . . . . . . . . 11
4.1. UAS Remote Identifiers Problem Space . . . . . . . . . . 11
4.2. HHIT as A Trustworthy DRIP Entity Identifier . . . . . . 12
4.3. HHIT for DRIP Identifier Registration and Lookup . . . . 13
4.4. HHIT as a Cryptographic Identifier . . . . . . . . . . . 13
5. DRIP Identifier Registration and Registries . . . . . . . . . 14
5.1. Public Information Registry . . . . . . . . . . . . . . . 14
5.1.1. Background . . . . . . . . . . . . . . . . . . . . . 14
5.1.2. DNS as the Public DRIP Identifier Registry . . . . . 14
5.2. Private Information Registry . . . . . . . . . . . . . . 14
5.2.1. Background . . . . . . . . . . . . . . . . . . . . . 14
5.2.2. EPP and RDAP as the Private DRIP Identifier
Registry . . . . . . . . . . . . . . . . . . . . . . 15
5.2.3. Alternative Private DRIP Registry methods . . . . . . 15
6. DRIP Identifier Trust . . . . . . . . . . . . . . . . . . . . 15
7. Harvesting Broadcast Remote ID messages for UTM Inclusion . . 16
7.1. The CS-RID Finder . . . . . . . . . . . . . . . . . . . . 16
7.2. The CS-RID SDSP . . . . . . . . . . . . . . . . . . . . . 17
8. DRIP Contact . . . . . . . . . . . . . . . . . . . . . . . . 17
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
10. Security Considerations . . . . . . . . . . . . . . . . . . . 18
11. Privacy & Transparency Considerations . . . . . . . . . . . . 19
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
12.1. Normative References . . . . . . . . . . . . . . . . . . 19
12.2. Informative References . . . . . . . . . . . . . . . . . 19
Appendix A. Overview of Unmanned Aircraft Systems (UAS) Traffic
Management (UTM) . . . . . . . . . . . . . . . . . . . . 22
A.1. Operation Concept . . . . . . . . . . . . . . . . . . . . 23
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A.2. UAS Service Supplier (USS) . . . . . . . . . . . . . . . 23
A.3. UTM Use Cases for UAS Operations . . . . . . . . . . . . 24
Appendix B. Automatic Dependent Surveillance Broadcast
(ADS-B) . . . . . . . . . . . . . . . . . . . . . . . . . 24
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 25
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25
1. Introduction
This document describes an architecture for protocols and services to
support Unmanned Aircraft System Remote Identification and tracking
(UAS RID), plus RID-related communications. The architecture takes
into account both current (including proposed) regulations and non-
IETF technical standards.
The architecture adheres to the requirements listed in the DRIP
Requirements document [I-D.ietf-drip-reqs].
1.1. Overview of Unmanned Aircraft System (UAS) Remote ID (RID) and
Standardization
UAS Remote Identification (RID) is an application enabler for a UAS
to be identified by Unmanned Aircraft Systems Traffic Management
(UTM) and UAS Service Supplier (USS) (Appendix A) or third parties
entities such as law enforcement. Many considerations (e.g., safety)
dictate that UAS be remotely identifiable.
Civil Aviation Authorities (CAAs) worldwide are mandating UAS RID.
CAAs currently promulgate performance-based regulations that do not
specify techniques, but rather cite industry consensus technical
standards as acceptable means of compliance.
Federal Aviation Administration (FAA)
The FAA published a Notice of Proposed Rule Making [NPRM] in 2019
and thereafter published the "Final Rule" in 2021 [FAA_RID].
Under the Final Rule, UAS manufacturers, producers, and commercial
and recreational UAS drone pilots must comply with the final
rule's requirements.
In FAA's final rule, it is clearly stated that Automatic
Dependent Surveillance Broadcast (ADS-B) Out and transponders
can not be used to serve the purpose of an remote
identification. More details about ADS-B can be found in
Appendix B.
European Union Aviation Safety Agency (EASA)
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The EASA has published the [Delegated] in 2019 to provide
regulations for unmanned aircraft systems (UAS) and on third-
country operators of UAS and followed with implementation
regulation on the rules and procedures for the operation of
unmanned aircraft Regulations [Implementing].
American Society for Testing and Materials (ASTM)
ASTM International, Technical Committee F38 (UAS), Subcommittee
F38.02 (Aircraft Operations), Work Item WK65041, developed the
ASTM [F3411-19] Standard Specification for Remote ID and Tracking.
ASTM defines one set of RID information and two means, MAC-layer
broadcast and IP-layer network, of communicating it. If an UAS
uses both communication methods, the same information must be
provided via both means. [F3411-19] is cited by FAA in its RID
final rule [FAA_RID] as "a potential means of compliance" to a
Remote ID rule.
The 3rd Generation Partnership Project (3GPP)
With release 16, the 3GPP completed the UAS RID requirement study
[TS-22.825] and proposed a set of use cases in the mobile network
and the services that can be offered based on RID. Release 17
specification focuses on enhanced UAS service requirements and
provides the protocol and application architecture support that
will be applicable for both 4G and 5G networks.
1.2. Overview of Types of UAS Remote ID
1.2.1. Broadcast RID
[F3411-19] defines a set of RID messages for direct, one-way,
broadcast transmissions from the UA over Bluetooth or Wi-Fi. These
are currently defined as MAC-Layer messages. Internet (or other Wide
Area Network) connectivity is only needed for UAS registry
information lookup by Observers using the directly received UAS ID.
Broadcast RID should be functionally usable in situations with no
Internet connectivity.
The minimum Broadcast RID data flow is illustrated in Figure 1.
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+------------------------+
| Unmanned Aircraft (UA) |
+-----------o------------+
|
|
|
| app messages directly over
| one-way RF data link (no IP)
|
|
v
+------------------o-------------------+
| Observer's device (e.g., smartphone) |
+--------------------------------------+
Figure 1
Broadcast RID provides information only about UA (unmanned aircraft)
within direct RF LOS, typically similar to visual Light-Of-Sight
(LOS), with a range on the order of 1 km. This information may be
'harvested' from received broadcasts and made available via the
Internet (see Section 7), enabling surveillance of areas too large
for local direct visual observation or direct RF link based ID (e.g.
around airports, public gatherings, and other sensitive areas).
1.2.2. Network RID
[F3411-19] defines a Network Remote ID (Net-RID) data dictionary and
data flow for Internet based information delivery. This data flow is
emitted from an UAS via unspecified means (but at least in part over
the Internet) to a Net-RID Service Provider (Net-RID SP). A Net-RID
SP provides the RID data to Net-RID Display Providers (Net-RID DP).
It is the Net-RID DP that responds to queries from Observer's Net-RID
device (expected typically, but not specified exclusively, to be web-
based) specifying airspace volumes of interest. Net-RID depends upon
internet connectivity to fulfill Observer's queries to the Net-RID
DP. The summary of Net-RID data flows work as follows:
* The UA's RID data is generated from a UAS which consists of UAs
and GCSs.
* The GCS or UA (e.g. BVLOS and autonomous operation) provides the
UA's RID data to a Net-RID SP via a secure internet connection.
* Net-RID DP as a Net-RID SP subscriber satisfies the Observer's
query request via a secure internet connection.
The minimum Net-RID data flow is illustrated in Figure 2:
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+-------------+ ******************
| UA | * Internet *
+--o-------o--+ * *
| | * *
| | * * +------------+
| '--------*--(+)-----------*-----o |
| * | * | |
| .--------*--(+)-----------*-----o NET-RID SP |
| | * * | |
| | * .------*-----o |
| | * | * +------------+
| | * | *
| | * | * +------------+
| | * '------*-----o |
| | * * | NET-RID DP |
| | * .------*-----o |
| | * | * +------------+
| | * | *
| | * | * +------------+
+--o-------o--+ * '------*-----o Observer's |
| GCS | * * | Device |
+-------------+ ****************** +------------+
Figure 2
Command and Control (C2) must flow from the GCS to the UA via some
path, currently (in the year of 2021) typically a direct RF link, but
with increasing beyond Visual Line of Sight (BVLOS) operations
expected often to be wireless links at either end with the Internet
between.
Telemetry (at least UA's position and heading) flows from the UA to
the GCS via some path, typically the reverse of the C2 path. Thus,
RID information pertaining to both the GCS and the UA can be sent, by
whichever has Internet connectivity, to the Net-RID SP, typically the
USS managing the UAS operation.
The Net-RID SP forwards RID information via the Internet to
subscribed Net-RID DP, typically USS. Subscribed Net-RID DP forward
RID information via the Internet to subscribed Observer devices.
Regulations require and [F3411-19] describes RID data elements that
must be transported end-to-end from the UAS to the subscribed
Observer devices.
[F3411-19] prescribes the protocols between the Net-RID SP, Net-RID
DP, and the Discovery and Synchronization Service (DSS). It also
prescribes data elements (in JSON) between Observer and USS. DRIP
could address standardization of secure protocols between the UA and
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GCS (over direct wireless and Internet connection), between the UAS
and the Net-RID SP, and/or between the Net-RID DP and Observer
devices.
Informative note: Neither link layer protocols nor the use of
links (e.g., the link often existing between the GCS and the
UA) for any purpose other than carriage of RID information is
in the scope of [F3411-19] Network RID.
1.3. Overview of USS Interoperability
With Net-RID, there is direct communication between the UAS and its
USS. With Broadcast-RID and UTM, the UAS Operator has either pre-
filed a 4D space volume for USS operational knowledge and/or
Observers can be providing information about observed UA to a
Surveillance Supplemental Data Service Provider (SDSP). USS exchange
information via a Discovery and Synchronization Service (DSS) so all
USS collectively have knowledge about all activities in a 4D
airspace.
The interactions among Observer, UA, and USS are shown in Figure 3.
+----------+
| Observer |
+----------+
/ \
/ \
+------+ +------+
| UAS1 | | UAS2 |
+------+ +------+
\ /
\ /
+----------+
| Internet |
+----------+
/ \
/ \
+------+ +------+
| USS1 | <-------> | USS2 |
+------+ +------+
\ /
\ /
+------+
| DSS |
+------+
Figure 3
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1.4. Overview of DRIP Architecture
The requirements document [I-D.ietf-drip-reqs] provides an extended
introduction to the problem space and use cases. Only a brief
summary of that introduction is restated here as context, with
reference to the general UAS RID usage scenarios shown in Figure 4.
General x x Public
Public xxxxx xxxxx Safety
Observer x x Observer
x x
x x ---------+ +---------- x x
x x | | x x
| |
UA1 x x | | +------------ x x UA2
xxxxx | | | xxxxx
| + + + |
| xxxxxxxxxx |
| x x |
+----------+x Internet x+------------+
UA1 | x x | UA1
Pilot x | xxxxxxxxxx | x Pilot
Operator xxxxx + + + xxxxx Operator
GCS1 x | | | x GCS2
x | | | x
x x | | | x x
x x | | | x x
| | |
+----------+ | | | +----------+
| |------+ | +-------| |
| Public | | | Private |
| Registry | +-----+ | Registry |
| | | DNS | | |
+----------+ +-----+ +----------+
Figure 4
DRIP is meant to leverage existing Internet resources (standard
protocols, services, infrastructures, and business models) to meet
UAS RID and closely related needs. DRIP will specify how to apply
IETF standards, complementing [F3411-19] and other external
standards, to satisfy UAS RID requirements.
This document outlines the DRIP architecture in the context of the
UAS RID architecture. This includes presenting the gaps between the
CAAs' Concepts of Operations and [F3411-19] as it relates to the use
of Internet technologies and UA direct RF communications. Issues
include, but are not limited to:
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- Design of trustworthy remote ID and trust in RID messages
(Section 4)
- Mechanisms to leverage Domain Name System (DNS: [RFC1034]),
Extensible Provisioning Protocol (EPP [RFC5731]) and
Registration Data Access Protocol (RDAP) ([RFC7482]) for
publishing public and private information (see Section 5.1 and
Section 5.2).
- Harvesting broadcast RID messages for UTM inclusion
(Section 7).
- Privacy in RID messages (PII protection) (Section 11).
2. Terms and Definitions
2.1. Architecture 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 above.
2.2. Abbreviations
DSS: Discovery & Synchronization Service
EdDSA: Edwards-Curve Digital Signature Algorithm
GCS: Ground Control Station
HHIT: Hierarchical HIT
HIP: Host Identity Protocol
HIT: Host Identity Tag
RID: Remote ID
Net-RID SP: Network RID Service Provider
Net-RID DP: Network RID Display Provider.
PII: Personally Identifiable Information
RF: Radio Frequency
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SDSP: Supplemental Data Service Provider
UA: Unmanned Aircraft
UAS: Unmanned Aircraft System
USS: UAS Service Supplier
UTM: UAS Traffic Management
2.3. Additional Definitions
This document uses terms defined in [I-D.ietf-drip-reqs].
3. Claims, Assertions, Attestations, and Certificates
This section introduces the terms "Claims", "Assertions",
"Attestations", and "Certificates" as used in DRIP. DRIP certificate
has a different context compared with security certificates and
Public Key Infrastructure used in X.509.
Claims:
A claim in DRIP is a predicate (e.g., "X is Y", "X has property
Y", and most importantly "X owns Y" or "X is owned by Y").
Assertions:
An assertion in DRIP is a set of claims. This definition is
borrowed from JWT [RFC7519] and CWT [RFC8392].
Attestations:
An attestation in DRIP is a signed assertion. The signer may be
the claimant or a related party with stake in the assertion(s).
Under DRIP this is normally used when an entity asserts a
relationship with another entity, along with other information,
and the asserting entity signs the assertion, thereby making it an
attestation.
Certificates:
A certificate in DRIP is an attestation, strictly over identity
information, signed by a third party. This third party should be
one with no stake in the attestation(s) its signing over.
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4. HHIT as the DRIP Entity Identifier
This section describes the DRIP architectural approach to meeting the
basic requirements of a DRIP entity identifier within external
technical standard ASTM [F3411-19] and regulatory constraints. It
justifies and explains the use of Hierarchical Host Identity Tags
(HHITs) as self-asserting IPv6 addresses suitable as a UAS ID type
and more generally as trustworthy multipurpose remote identifiers.
Self-asserting in this usage is given the Host Identity (HI), the
HHIT ORCHID construction and a signature of the HHIT by the HI can
both be validated. The explicit registration hierarchy within the
HHIT provides registry discovery (managed by a Registrar) to either
yield the HI for 3rd-party (who is looking for ID attestation)
validation or prove the HHIT and HI have uniquely been registered.
4.1. UAS Remote Identifiers Problem Space
A DRIP entity identifier needs to be "Trustworthy" (See DRIP
Requirement GEN-1, ID-4 and ID-5 in [I-D.ietf-drip-reqs]). This
means that given a sufficient collection of RID messages, an Observer
can establish that the identifier claimed therein uniquely belongs to
the claimant: that the only way for any other entity to prove
ownership of that identifier would be to obtain information that
ought to be available only to the legitimate owner of the identifier
(e.g., a cryptographic private key).
To satisfy DRIP requirements and maintain important security
properties, the DRIP identifier should be self-generated by the
entity it names (e.g., a UAS) and registered (e.g., with a USS, see
Requirements GEN-3 and ID-2).
Broadcast RID, especially its support for Bluetooth 4, imposes severe
constraints. ASTM [F3411-19] allows a UAS ID of types 1, 2 and 3 of
20 bytes; the new type 4, created to enable Session IDs to be
standardized by IETF and other standard development organizations
(SDOs) as extensions to ASTM [F3411-19], consumes one of those bytes
to index the sub-type, leaving only 19 for the identifier (see
Requirement ID-1). Likewise, the maximum ASTM [F3411-19]
Authentication Message payload is 201 bytes for most authentication
types, but for type 5, created for IETF and other SDOs to develop
Specific Authentication Methods as extensions to ASTM [F3411-19], one
byte is consumed to index the sub-type, leaving only 200 for DRIP
authentication payloads, including one or more DRIP entity
identifiers and associated authentication data.
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4.2. HHIT as A Trustworthy DRIP Entity Identifier
A Remote ID that can be trustworthily used in the RID Broadcast mode
can be built from an asymmetric keypair. Rather than using a key
signing operation to claim ownership of an ID that does not guarantee
name uniqueness, in this method the ID is cryptographically derived
directly from the public key. The proof of ID ownership (verifiable
attestation, versus mere claim) is guaranteed by signing this
cryptographic ID with the associated private key. The association
between the ID and the private key is ensured by cryptographically
binding the public key with the ID, more specifically the ID results
from the hash of the public key. It is statistically hard for
another entity to create a public key that would generate (spoof) the
ID.
The basic HIT is designed statistically unique through the
cryptographic hash feature of second-preimage resistance. The
cryptographically-bound addition of the Hierarchy and an HHIT
registration process (e.g. based on Extensible Provisioning Protocol,
[RFC5730]) provide complete, global HHIT uniqueness. This
registration forces the attacker to generate the same public key
rather than a public key that generates the same HHIT. This is in
contrast to general IDs (e.g. a UUID or device serial number) as the
subject in an X.509 certificate.
A DRIP identifier can be assigned to a UAS as a static HHIT by its
manufacturer, such as a single HI and derived HHIT encoded as a
hardware serial number per [CTA2063A]. Such a static HHIT SHOULD
only be used to bind one-time use DRIP identifiers to the unique UA.
Depending upon implementation, this may leave a HI private key in the
possession of the manufacturer (more details in Section 10).
A UAS equipped for Broadcast RID SHOULD be provisioned not only with
its HHIT but also with the HI public key from which the HHIT was
derived and the corresponding private key, to enable message
signature. A UAS equipped for Network RID SHOULD be provisioned
likewise; the private key resides only in the ultimate source of
Network RID messages (i.e. on the UA itself if the GCS is merely
relaying rather than sourcing Network RID messages). Each Observer
device SHOULD be provisioned either with public keys of the DRIP
identifier root registries or certificates for subordinate
registries.
HHITs can also be used throughout the USS/UTM system. The Operators,
Private Information Registries, as well as other UTM entities, can
use HHITs for their IDs. Such HHITs can facilitate DRIP security
functions such as used with HIP to strongly mutually authenticate and
encrypt communications.
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A self-attestation of a HHIT used as a UAS ID can be done in as
little as 84 bytes, by avoiding an explicit encoding technology like
ASN.1 or Concise Binary Object Representation (CBOR [RFC8949]). This
attestation consists of only the HHIT, a timestamp, and the EdDSA
signature on them.
An Observer would need Internet access to validate a self-
attestations claim. A third-party Certificate can be validated via a
small credential cache in a disconnected environment. This third-
party Certificate is possible when the third-party also uses HHITs
for its identity and the UA has the public key and the Certificate
for that HHIT.
4.3. HHIT for DRIP Identifier Registration and Lookup
Remote ID needs a deterministic lookup mechanism that rapidly
provides actionable information about the identified UA. Given the
size constraints imposed by the Bluetooth 4 broadcast media, the UAS
ID itself needs to be a non-spoofable inquiry input into the lookup.
A DRIP registration process based on the explicit hierarchy within a
HHIT provides manageable uniqueness of the HI for the HHIT (defense
against a cryptographic hash second pre-image attach on the HHIT
(e.g. multiple HIs yielding the same HHIT, see Requirement ID-3). A
lookup of the HHIT into this registration data provides the
registered HI for HHIT proof. A first-come-first-serve registration
for a HHIT provides deterministic access to any other needed
actionable information based on inquiry access authority (more
details in Section 5.2).
4.4. HHIT as a Cryptographic Identifier
The only (known to the authors at the time of this writing) extant
types of IP address compatible identifiers cryptographically derived
from the public keys of the identified entities are Cryptographically
Generated Addresses (CGAs) [RFC3972] and Host Identity Tags (HITs)
[RFC7401]. CGAs and HITs lack registration/retrieval capability. To
provide this, each HHIT embeds plaintext information designating the
hierarchy within which it is registered and a cryptographic hash of
that information concatenated with the entity's public key, etc.
Although hash collisions may occur, the registrar can detect them and
reject registration requests rather than issue credentials, e.g., by
enforcing a first-claimed, first-attested policy. Pre-image hash
attacks are also mitigated through this registration process, locking
the HHIT to a specific HI
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5. DRIP Identifier Registration and Registries
DRIP registries hold both public and private UAS information
resulting from the DRIP identifier registration process. Given these
different uses, and to improve scalability, security, and simplicity
of administration, the public and private information can be stored
in different registries. This section introduces the public and
private information registries for DRIP identifiers.
5.1. Public Information Registry
5.1.1. Background
The public registry provides trustable information such as
attestations of RID ownership and registration with the HDA
(Hierarchical HIT Domain Authority). Optionally, pointers to the
registries for the HDA and RAA (Registered Assigning
Authority)implicit in the RID can be included (e.g., for HDA and RAA
HHIT|HI used in attestation signing operations). This public
information will be principally used by Observers of Broadcast RID
messages. Data on UAS that only use Network RID, is available via an
Observer's Net-RID DP that would tend to directly provide all public
registry information. The Observer may visually "see" these Net-RID
UAS, but they may be silent to the Observer. The Net-RID DP is the
only source of information based on a query for an airspace volume.
5.1.2. DNS as the Public DRIP Identifier Registry
A DRIP identifier SHOULD be registered as an Internet domain name (at
an arbitrary level in the hierarchy, e.g. in .ip6.arpa). Thus DNS
can provide all the needed public DRIP information. A standardized
HHIT FQDN (Fully Qualified Domain Name) can deliver the HI via a HIP
RR (Resource Record) [RFC8005] and other public information (e.g.,
RRA and HDA PTRs, and HIP RVS (Rendezvous Servers) [RFC8004]). These
public information registries can use secure DNS transport (e.g. DNS
over TLS) to deliver public information that is not inherently
trustable (e.g. everything other than attestations).
5.2. Private Information Registry
5.2.1. Background
The private information required for DRIP identifiers is similar to
that required for Internet domain name registration. A DRIP
identifier solution can leverage existing Internet resources:
registration protocols, infrastructure, and business models, by
fitting into an ID structure compatible with DNS names. The HHIT
hierarchy can provide the needed scalability and management
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structure. It is expected that the private registry function will be
provided by the same organizations that run a USS, and likely
integrated with a USS. The lookup function may be implemented by the
Net-RID DPs.
5.2.2. EPP and RDAP as the Private DRIP Identifier Registry
A DRIP private information registry supports essential registry
operations (e.g. add, delete, update, query) using interoperable open
standard protocols. It can accomplish this by using the Extensible
Provisioning Protocol (EPP [RFC5730]) and the Registry Data Access
Protocol (RDAP RFC7480] [RFC7482] [RFC7483]). The DRIP private
information registry in which a given UAS is registered needs to be
findable, starting from the UAS ID, using the methods specified in
[RFC7484].
5.2.3. Alternative Private DRIP Registry methods
A DRIP private information registry might be an access controlled DNS
(e.g. via DNS over TLS). Additionally, WebFinger [RFC7033] can be
deployed. These alternative methods may be used by Net-RID DP with
specific customers.
6. DRIP Identifier Trust
While the DRIP entity identifier is self-asserting, it alone does not
provide the "trustworthiness" specified in [I-D.ietf-drip-reqs]. For
that it MUST be registered (under DRIP Registries) and be actively
used by the party (in most cases the UA). For Broadcast RID this is
a challenge to balance the original requirements of Broadcast RID and
the efforts needed to satisfy the DRIP requirements all under severe
constraints.
An optimization of different DRIP Authentication Messages allows an
Observer, offline or online, to be able to validate a UAS ID in real-
time. First is the sending of various BroadcastAttestastion's (over
DRIP Link Authentication Messages) containing the relevant registry
hierarchy from the Root all the way to the claimed Registry. Next is
sending DRIP Wrapper Authentication Messages that sign over
dynamically changing data (such as UA location data). Combining
these two sets of information an Observer can piece together a chain
of trust and real-time evidence to make their determination of the
UAs claims.
This process (combining the DRIP entity identifier, Registries and
Authentication Formats for Broadcast RID) can satisfy the following
DRIP requirement defined in [I-D.ietf-drip-reqs]: GEN-1, GEN-2, GEN-
3, ID-2, ID-3, ID-4 and ID-5.
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7. Harvesting Broadcast Remote ID messages for UTM Inclusion
ASTM anticipated that regulators would require both Broadcast RID and
Network RID for large UAS, but allow RID requirements for small UAS
to be satisfied with the operator's choice of either Broadcast RID or
Network RID. The EASA initially specified Broadcast RID for UAS of
essentially all UAS and is now also considering Network RID. The FAA
RID Final Rules [FAA_RID] permit only Broadcast RID for rule
compliance, but still encourage Network RID for complementary
functionality, especially in support of UTM.
One obvious opportunity is to enhance the architecture with gateways
from Broadcast RID to Network RID. This provides the best of both
and gives regulators and operators flexibility. It offers advantages
over either form of RID alone: greater fidelity than Network RID
reporting of planned area operations; surveillance of areas too large
for local direct visual observation and direct RF-LOS link based
Broadcast RID (e.g., a city or a national forest).
These gateways could be pre-positioned (e.g. around airports, public
gatherings, and other sensitive areas) and/or crowd-sourced (as
nothing more than a smartphone with a suitable app is needed). As
Broadcast RID media have limited range, gateways receiving messages
claiming locations far from the gateway can alert authorities or a
SDSP to the failed sanity check possibly indicating intent to
deceive. Surveillance SDSPs can use messages with precise date/time/
position stamps from the gateways to multilaterate UA location,
independent of the locations claimed in the messages, which are
entirely operator self-reported in UAS RID and UTM, and thus are
subject not only to natural time lag and error but also operator
misconfiguration or intentional deception.
Further, gateways with additional sensors (e.g. smartphones with
cameras) can provide independent information on the UA type and size,
confirming or refuting those claims made in the RID messages. This
Crowd Sourced Remote ID (CS-RID) would be a significant enhancement,
beyond baseline DRIP functionality; if implemented, it adds two more
entity types.
7.1. The CS-RID Finder
A CS-RID Finder is the gateway for Broadcast Remote ID Messages into
the UTM. It performs this gateway function via a CS-RID SDSP. A CS-
RID Finder could implement, integrate, or accept outputs from, a
Broadcast RID receiver. However, it should not depend upon a direct
interface with a GCS, Net-RID SP, Net-RID DP or Network RID client.
It would present a TBD interface to a CS-RID SDSP, similar to but
readily distinguishable from that between a GCS and a Net-RID SP.
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7.2. The CS-RID SDSP
A CS-RID SDSP should appear (i.e. present the same interface) to a
Net-RID SP as a Net-RID DP. A CS-RID SDSP aggregates and processes
(e.g., estimates UA location using) information collected by CS-RID
Finders.
8. DRIP Contact
One of the ways in which DRIP is to enhance [F3411-19] with
immediately actionable information is by enabling an Observer to
instantly initiate secure communications with the UAS remote pilot,
Pilot In Command, operator, USS under which the operation is being
flown, or other entity potentially able to furnish further
information regarding the operation and its intent and/or to
immediately influence further conduct or termination of the operation
(e.g., land or otherwise exit an airspace volume). Such potentially
distracting communications demand strong "AAA" (Authentication,
Attestation, Authorization, Access Control, Accounting, Attribution,
Audit) per applicable policies (e.g., of the cognizant CAA).
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A DRIP entity identifier based on a HHIT as outlined in Section 4
embeds an identifier of the registry in which it can be found
(expected typically to be the USS under which the UAS is flying) and
the procedures outlined in Section 6 enable Observer verification of
that relationship. A DRIP entity identifier with suitable records in
public and private registries as outlined in Section 5 can enable
lookup not only of information regarding the UAS but also identities
of and pointers to information regarding the various associated
entities (e.g., the USS under which the UAS is flying an operation),
including means of contacting those associated entities (i.e.,
locators, typically IP addresses). An Observer equipped with HIP can
initiate a Base Exchange (BEX) and establish a Bound End to End
Tunnel (BEET) protected by IPsec Encapsulating Security Payload (ESP)
encryption to a likewise equipped and identified entity: the UA
itself, if operating autonomously; the GCS, if the UA is remotely
piloted and the necessary records have been populated in DNS;
likewise the USS, etc. Certain preconditions are necessary: each
party to the communication needs a currently usable means (typically
DNS) of resolving the other party's DRIP entity identifier to a
currently usable locator (IP address); and there must be currently
usable bidirectional IP (not necessarily Internet) connectivity
between the parties. Given a BEET, arbitrary standard higher layer
protocols can then be used for Observer to Pilot (O2P) communications
(e.g., SIP [RFC3261] et seq), V2X communications (e.g., [MAVLink]),
etc. This approach satisfies DRIP requirement GEN-6 Contact,
supports satisfaction of requirements [I-D.ietf-drip-reqs] GEN-8,
GEN-9, PRIV-2, PRIV-5 and REG-3, and is compatible with all other
DRIP requirements.
9. IANA Considerations
This document does not make any IANA request.
10. Security Considerations
The security provided by asymmetric cryptographic techniques depends
upon protection of the private keys. A manufacturer that embeds a
private key in an UA may have retained a copy. A manufacturer whose
UA are configured by a closed source application on the GCS which
communicates over the Internet with the factory may be sending a copy
of a UA or GCS self-generated key back to the factory. Keys may be
extracted from a GCS or UA. The RID sender of a small harmless UA
(or the entire UA) could be carried by a larger dangerous UA as a
"false flag." Compromise of a registry private key could do
widespread harm. Key revocation procedures are as yet to be
determined. These risks are in addition to those involving Operator
key management practices.
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11. Privacy & Transparency Considerations
Broadcast RID messages can contain Personally Identifiable
Information (PII). A viable architecture for PII protection would be
symmetric encryption of the PII using a session key known to the UAS
and its USS. Authorized Observers could obtain plaintext in either
of two ways. An Observer can send the UAS ID and the cyphertext to a
server that offers decryption as a service. An Observer can send the
UAS ID only to a server that returns the session key, so that
Observer can directly locally decrypt all cyphertext sent by that UA
during that session (UAS operation). In either case, the server can
be: a Public Safety USS; the Observer's own USS; or the UA's USS if
the latter can be determined (which under DRIP it can be, from the
UAS ID itself). PII can be protected unless the UAS is informed
otherwise. This could come as part of UTM operation authorization.
It can be special instructions at the start or during an operation.
PII protection MUST not be used if the UAS loses connectivity to the
USS. The UAS always has the option to abort the operation if PII
protection is disallowed.
12. References
12.1. Normative References
[I-D.ietf-drip-reqs]
Card, S. W., Wiethuechter, A., Moskowitz, R., and A.
Gurtov, "Drone Remote Identification Protocol (DRIP)
Requirements", Work in Progress, Internet-Draft, draft-
ietf-drip-reqs-18, 8 September 2021,
<https://www.ietf.org/archive/id/draft-ietf-drip-reqs-
18.txt>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
12.2. Informative References
[CTA2063A] ANSI, "Small Unmanned Aerial Systems Serial Numbers",
2019.
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[Delegated]
European Union Aviation Safety Agency (EASA), "EU
Commission Delegated Regulation 2019/945 of 12 March 2019
on unmanned aircraft systems and on third-country
operators of unmanned aircraft systems", 2019.
[F3411-19] ASTM, "Standard Specification for Remote ID and Tracking",
2019.
[FAA_RID] United States Federal Aviation Administration (FAA),
"Remote Identification of Unmanned Aircraft", 2021,
<https://www.govinfo.gov/content/pkg/FR-2021-01-15/
pdf/2020-28948.pdf>.
[FAA_UAS_Concept_Of_Ops]
United States Federal Aviation Administration (FAA),
"Unmanned Aircraft System (UAS) Traffic Management (UTM)
Concept of Operations (V2.0)", 2020,
<https://www.faa.gov/uas/research_development/
traffic_management/media/UTM_ConOps_v2.pdf>.
[I-D.ietf-drip-rid]
Moskowitz, R., Card, S. W., Wiethuechter, A., and A.
Gurtov, "DRIP Entity Tag (DET) for Unmanned Aircraft
System Remote Identification (UAS RID)", Work in Progress,
Internet-Draft, draft-ietf-drip-rid-11, 20 October 2021,
<https://www.ietf.org/archive/id/draft-ietf-drip-rid-
11.txt>.
[Implementing]
European Union Aviation Safety Agency (EASA), "EU
Commission Implementing Regulation 2019/947 of 24 May 2019
on the rules and procedures for the operation of unmanned
aircraft", 2019.
[LAANC] United States Federal Aviation Administration (FAA), "Low
Altitude Authorization and Notification Capability", n.d.,
<https://www.faa.gov/uas/programs_partnerships/
data_exchange/>.
[MAVLink] "Micro Air Vehicle Communication Protocol", n.d..
[NPRM] United States Federal Aviation Administration (FAA),
"Notice of Proposed Rule Making on Remote Identification
of Unmanned Aircraft Systems", 2019.
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[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<https://www.rfc-editor.org/info/rfc1034>.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
DOI 10.17487/RFC3261, June 2002,
<https://www.rfc-editor.org/info/rfc3261>.
[RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)",
RFC 3972, DOI 10.17487/RFC3972, March 2005,
<https://www.rfc-editor.org/info/rfc3972>.
[RFC5730] Hollenbeck, S., "Extensible Provisioning Protocol (EPP)",
STD 69, RFC 5730, DOI 10.17487/RFC5730, August 2009,
<https://www.rfc-editor.org/info/rfc5730>.
[RFC5731] Hollenbeck, S., "Extensible Provisioning Protocol (EPP)
Domain Name Mapping", STD 69, RFC 5731,
DOI 10.17487/RFC5731, August 2009,
<https://www.rfc-editor.org/info/rfc5731>.
[RFC7033] Jones, P., Salgueiro, G., Jones, M., and J. Smarr,
"WebFinger", RFC 7033, DOI 10.17487/RFC7033, September
2013, <https://www.rfc-editor.org/info/rfc7033>.
[RFC7401] Moskowitz, R., Ed., Heer, T., Jokela, P., and T.
Henderson, "Host Identity Protocol Version 2 (HIPv2)",
RFC 7401, DOI 10.17487/RFC7401, April 2015,
<https://www.rfc-editor.org/info/rfc7401>.
[RFC7482] Newton, A. and S. Hollenbeck, "Registration Data Access
Protocol (RDAP) Query Format", RFC 7482,
DOI 10.17487/RFC7482, March 2015,
<https://www.rfc-editor.org/info/rfc7482>.
[RFC7483] Newton, A. and S. Hollenbeck, "JSON Responses for the
Registration Data Access Protocol (RDAP)", RFC 7483,
DOI 10.17487/RFC7483, March 2015,
<https://www.rfc-editor.org/info/rfc7483>.
[RFC7484] Blanchet, M., "Finding the Authoritative Registration Data
(RDAP) Service", RFC 7484, DOI 10.17487/RFC7484, March
2015, <https://www.rfc-editor.org/info/rfc7484>.
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[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<https://www.rfc-editor.org/info/rfc7519>.
[RFC8002] Heer, T. and S. Varjonen, "Host Identity Protocol
Certificates", RFC 8002, DOI 10.17487/RFC8002, October
2016, <https://www.rfc-editor.org/info/rfc8002>.
[RFC8004] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
Rendezvous Extension", RFC 8004, DOI 10.17487/RFC8004,
October 2016, <https://www.rfc-editor.org/info/rfc8004>.
[RFC8005] Laganier, J., "Host Identity Protocol (HIP) Domain Name
System (DNS) Extension", RFC 8005, DOI 10.17487/RFC8005,
October 2016, <https://www.rfc-editor.org/info/rfc8005>.
[RFC8032] Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital
Signature Algorithm (EdDSA)", RFC 8032,
DOI 10.17487/RFC8032, January 2017,
<https://www.rfc-editor.org/info/rfc8032>.
[RFC8392] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig,
"CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392,
May 2018, <https://www.rfc-editor.org/info/rfc8392>.
[RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", STD 94, RFC 8949,
DOI 10.17487/RFC8949, December 2020,
<https://www.rfc-editor.org/info/rfc8949>.
[TS-22.825]
3GPP, "Study on Remote Identification of Unmanned Aerial
Systems (UAS)", n.d.,
<https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=3527>.
[U-Space] European Organization for the Safety of Air Navigation
(EUROCONTROL), "U-space Concept of Operations", 2019,
<https://www.sesarju.eu/sites/default/files/documents/u-
space/CORUS%20ConOps%20vol2.pdf>.
Appendix A. Overview of Unmanned Aircraft Systems (UAS) Traffic
Management (UTM)
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A.1. Operation Concept
The National Aeronautics and Space Administration (NASA) and FAA's
effort of integrating UAS's operation into the national airspace
system (NAS) led to the development of the concept of UTM and the
ecosystem around it. The UTM concept was initially presented in 2013
and version 2.0 was published in 2020 [FAA_UAS_Concept_Of_Ops].
The eventual concept refinement, initial prototype implementation and
testing were conducted by the UTM research transition team which is
the joint workforce by FAA and NASA. World efforts took place
afterward. The Single European Sky ATM Research (SESAR) started the
CORUS project to research its UTM counterpart concept, namely
[U-Space]. This effort is led by the European Organization for the
Safety of Air Navigation (Eurocontrol).
Both NASA and SESAR have published the UTM concept of operations to
guide the development of their future air traffic management (ATM)
system and ensure safe and efficient integration of manned and
unmanned aircraft into the national airspace.
The UTM comprises UAS operation infrastructure, procedures and local
regulation compliance policies to guarantee safe UAS integration and
operation. The main functionality of a UTM includes, but is not
limited to, providing means of communication between UAS operators
and service providers and a platform to facilitate communication
among UAS service providers.
A.2. UAS Service Supplier (USS)
A USS plays an important role to fulfill the key performance
indicators (KPIs) that a UTM has to offer. Such Entity acts as a
proxy between UAS operators and UTM service providers. It provides
services like real-time UAS traffic monitoring and planning,
aeronautical data archiving, airspace and violation control,
interacting with other third-party control entities, etc. A USS can
coexist with other USS to build a large service coverage map which
can load-balance, relay and share UAS traffic information.
The FAA works with UAS industry shareholders and promotes the Low
Altitude Authorization and Notification Capability [LAANC] program
which is the first system to realize some of the UTM envisioned
functionality. The LAANC program can automate the UAS operational
intent (flight plan) submission and application for airspace
authorization in real-time by checking against multiple aeronautical
databases such as airspace classification and fly rules associated
with it, FAA UAS facility map, special use airspace, Notice to Airmen
(NOTAM), and Temporary Flight Restriction (TFR).
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A.3. UTM Use Cases for UAS Operations
This section illustrates a couple of use case scenarios where UAS
participation in UTM has significant safety improvement.
1. For a UAS participating in UTM and taking off or landing in a
controlled airspace (e.g., Class Bravo, Charlie, Delta and Echo
in the United States), the USS under which the UAS is operating
is responsible for verifying UA registration, authenticating the
UAS operational intent (flight plan) by checking against
designated UAS facility map database, obtaining the air traffic
control (ATC) authorization and monitor the UAS flight path in
order to maintain safe margins and follow the pre-authorized
sequence of authorized 4-D volumes (route).
2. For a UAS participating in UTM and taking off or landing in an
uncontrolled airspace (ex. Class Golf in the United States),
pre-flight authorization must be obtained from a USS when
operating beyond-visual-of-sight (BVLOS). The USS either accepts
or rejects received operational intent (flight plan) from the
UAS. Accepted UAS operation may share its current flight data
such as GPS position and altitude to USS. The USS may keep the
UAS operation status near real-time and may keep it as a record
for overall airspace air traffic monitoring.
Appendix B. Automatic Dependent Surveillance Broadcast (ADS-B)
The ADS-B is the de jure technology used in manned aviation for
sharing location information, from the aircraft to ground and
satellite-based systems, designed in the early 2000s. Broadcast RID
is conceptually similar to ADS-B, but with the receiver target being
the general public on generally available devices (e.g. smartphones).
For numerous technical reasons, ADS-B itself is not suitable for low-
flying small UA. Technical reasons include but not limited to the
following:
1. Lack of support for the 1090 MHz ADS-B channel on any consumer
handheld devices
2. Weight and cost of ADS-B transponders on CSWaP constrained UA
3. Limited bandwidth of both uplink and downlink, which would likely
be saturated by large numbers of UAS, endangering manned aviation
Understanding these technical shortcomings, regulators worldwide have
ruled out the use of ADS-B for the small UAS for which UAS RID and
DRIP are intended.
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Acknowledgements
The work of the FAA's UAS Identification and Tracking (UAS ID)
Aviation Rulemaking Committee (ARC) is the foundation of later ASTM
and proposed IETF DRIP WG efforts. The work of ASTM F38.02 in
balancing the interests of diverse stakeholders is essential to the
necessary rapid and widespread deployment of UAS RID. IETF
volunteers who have contributed to this draft include Amelia
Andersdotter and Mohamed Boucadair.
Authors' Addresses
Stuart W. Card
AX Enterprize
4947 Commercial Drive
Yorkville, NY, 13495
United States of America
Email: stu.card@axenterprize.com
Adam Wiethuechter
AX Enterprize
4947 Commercial Drive
Yorkville, NY, 13495
United States of America
Email: adam.wiethuechter@axenterprize.com
Robert Moskowitz
HTT Consulting
Oak Park, MI, 48237
United States of America
Email: rgm@labs.htt-consult.com
Shuai Zhao
Tencent
2747 Park Blvd
Palo Alto, 94588
United States of America
Email: shuai.zhao@ieee.org
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Andrei Gurtov
Linköping University
IDA
SE-58183 Linköping Linköping
Sweden
Email: gurtov@acm.org
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