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Versions: 00 01
DRIP R. Moskowitz
Internet-Draft HTT Consulting
Intended status: Standards Track S. Card
Expires: March 31, 2021 A. Wiethuechter
AX Enterprize
A. Gurtov
Linköping University
September 27, 2020
Secure UAS Network RID and C2 Transport
draft-moskowitz-drip-secure-nrid-c2-01
Abstract
This document provides the mechanisms for secure transport of UAS
Network-RemoteID and Command-and-Control messaging. Both HIP and
DTLS based methods are described.
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
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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 March 31, 2021.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terms and Definitions . . . . . . . . . . . . . . . . . . . . 3
2.1. Requirements Terminology . . . . . . . . . . . . . . . . 3
2.2. Definitions . . . . . . . . . . . . . . . . . . . . . . . 3
3. Network RID endpoints . . . . . . . . . . . . . . . . . . . . 4
3.1. N-RID from the UA . . . . . . . . . . . . . . . . . . . . 5
3.2. N-RID from the GCS . . . . . . . . . . . . . . . . . . . 5
3.3. N-RID from the Operator . . . . . . . . . . . . . . . . . 5
3.4. UAS Identity . . . . . . . . . . . . . . . . . . . . . . 5
4. Command and Control . . . . . . . . . . . . . . . . . . . . . 6
5. Secure Transports . . . . . . . . . . . . . . . . . . . . . . 6
5.1. HIPv2 for Secure Transport . . . . . . . . . . . . . . . 6
5.2. DTLS for Secure Transport . . . . . . . . . . . . . . . . 7
5.3. Ciphers for Secure Transport . . . . . . . . . . . . . . 7
5.4. HIP and DTLS contrasted and compared . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
9. Normative References . . . . . . . . . . . . . . . . . . . . 9
10. Informative References . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
This document defines mechanisms to provide secure transport for the
ASTM Network Remote ID [F3411-19] (N-RID) and Command and Control
(C2) messaging.
A secure transport for C2 is critical for UAS Beyond visual line of
sight (BVLOS) operations.
Two options for secure transport are provided: HIPv2 [RFC7401] and
DTLS [DTLS-1.3-draft]. These options are generally defined and their
applicability is compared and contrasted. It is up to N-RID and C2
to select which is preferred for their situation.
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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
B-RID
Broadcast Remote ID. A method of sending RID messages as 1-way
transmissions from the UA to any Observers within radio range.
BVLOS
Beyond visual line of sight. An adjectival phrase describing any
information transfer that does not travel via LOS communications.
CAA
Civil Aeronautics Administration. An example is the Federal
Aviation Administration (FAA) in the United States of America.
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.
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.
N-RID
Network Remote ID. A method of sending RID messages via the
Internet connection of the UAS directly to the UTM.
NETSP
UAS Network RID Service Provider. System component that compiles
information from various sources (and methods) in its given
service area. Usually a USS.
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RID
Remote ID. A unique identifier found on all UA to be used in
communication and in regulation of UA operation.
UA
Unmanned Aircraft. In this document UA's are typically though of
as drones of commercial or military variety. This is a very
strict definition which can be relaxed to include any and all
aircraft that are unmanned.
UAS
Unmanned Aircraft System. Composed of Unmanned Aircraft and 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
the control station.
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. A "traffic management" ecosystem for
uncontrolled operations that is separate from, but complementary
to, the FAA's Air Traffic Management (ATM) system.
3. Network RID endpoints
The FAA defines the Network Remote ID endpoints as a USS Network
Service Provider (NETSP) and the UAS. Both of these are rather
nebulous items and what they actually are will impact how
communications flow between them.
The NETSP may be provided by the same entity serving as the UAS
Service Provider (USS). This simplifies a number of aspects of the
N-RID communication flow. An Operator is expected to register a
mission with the USS. If this is done via the GCS and the GCS is the
source (directly of acting as a gateway), this could set up the
secure connection for N-RID. The NETSP is likely to be stable in the
network, that is its IP address will not change during a mission.
This simplifies maintaining the N-RID communications.
The UAS component in N-RID may be either the UA, GCS, or the
Operator's Internet connected device (e.g. smartphone or tablet). In
all cases, mobility MUST be assumed. That is the IP address of this
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end of the N-RID communication will change during a mission. The
N-RID mechanism MUST support this. the UAS Identity for the secure
connection may vary based on the UAS endpoint.
3.1. N-RID from the UA
Some UA will be equipped with direct Internet access. These UA will
also tend to have multiple radios for their Internet access. Thus
multi-homing with "make before break" behavior is needed. This is on
top of any IP address changes on any of the interfaces while in use.
3.2. N-RID from the GCS
Many UA will lack direct Internet access, but their GCS may be so
connected. There are two sources for the GCS for the RID messages,
both from the UA. These are UA B-RID messages, or content from C2
messages that the GCS converts to RID message format. In either
case, the GCS may be mobile with changing IP addresses. The GCS may
be in a fast moving ground device (automobile), so it can have as
mobility demanding connection needs as the UA.
3.3. N-RID from the Operator
Many UAS will have no Internet connectivity, but the UA is sending
B-RID messages and the Operator has an Internet Connected device that
is receiving these B-RID messages. The Operator's device can act as
the proxy for these messages, turning them into N-RID messages.
3.4. UAS Identity
The UA MAY use its RID private key if the RID is a HHIT
[drip-uas-rid]. It may use some other Identity, based on the NETSP
policy.
The GCS or Operator smart device may have a copy of the UA
credentials and use them in the connection to the NETSP. In this
case, they are indistinguishable from the UA as seen from the NETSP.
Alternatively, they may use their own credentials with the NETSP
which would need some internal mechanism to tie that to the UA.
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4. Command and Control
Command and Control (C2) connection is between the UA and GCS. Often
this over a direct link radio. Some times, particularly for BVLOS,
it is via Internet connections. In either case C2 SHOULD be secure
from eavesdroppers and tampering. For design and implementation
consistency it is best to treat the direct link as a local link
Internet connection and use constrained networking compression
standards.
Both the UA and GCS need to be treated as fully mobile in the IP
networking sense. Either one can have its IP address change and both
could change at the same time (the double jump problem). It is
preferable to use a peer-to-peer (P2P) secure technology like HIPv2
[RFC7401].
5. Secure Transports
The raw RID and C2 messages will be wrapped in UDP. These UDP
packets will either be transported in ESP for the HPv2 approach or
DTLS application messages for DTLS. In both cases header compression
technologies SHOULD be used and negotiated based on policy.
For IPv6 over both WiFi and Bluetooth (or any other radio link),
Robust Header Compression (ROHC) [RFC5795] and/or Generic Header
Compression (6LoWAN-HGC) [RFC7400] can significantly reduce the per
packet transmission cost of IPv6. For Bluetooth, there is also IPv6
over Bluetooth LE [RFC7668] for more guidance.
Local link (direct radio) C2 security is possible with the link's MAC
layer security. Both WiFi and Bluetooth link security can provide
appropriate security, but this would not provide trustworthy multi-
homed security.
5.1. HIPv2 for Secure Transport
HIP has already been used for C2 mobility, managing the ongoing
connectivity over WiFi at start of mission, switching to LTE once out
of WiFi range, and returning to WiFi connectivity at the end of the
mission. This functionality is especially important for BVLOS.
HHITs are already defined for RID, and need only be added to the GCS
via HHIT Registration [hhit-registries] for C2 HIP.
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When the UA is the UAS endpoint for N-RID, and particularly when HIP
is used for C2, HIP for N-RID simplifies protocol use on the UA. The
NETSP endpoint may already support HIP if it is also the HHIT
Registrar. If the UA lacks any IP ability and the RID HHIT
registration was done via the GCS or Operator device, then they may
also be set for using HIP for N-RID.
Further, double jump and multi-homing support is mandatory for C2
mobility. This is inherent in the HIP design. The HIP address
update can be improved with [hip-fast-mobility].
5.2. DTLS for Secure Transport
DTLS is a good fit for N-RID for any of the possible UAS endpoints.
There are challenges in using it for C2. To use DTLS for C2, the GCS
will need to be the DTLS server. How does it 'push' commands to the
UA? How does it reestablish DTLS security if state is lost? And
finally, how is the double jump scenario handled?
All the above DTLS for C2 probably have solutions. None of them are
inherent in the DTLS design.
5.3. Ciphers for Secure Transport
The cipher choice for either HIP or DTLS depends, in large measure,
on the UAS endpoint. If the endpoint is computationally constrained,
the cipher computations become important. If any of the links are
constrained or expensive, then the over-the-wire cost needs to be
minimized. AES-CCM and AES-GCM are the preferred, modern, AEAD
ciphers.
For ESP with HIP [RFC7402], an additional 8 bytes can be trimmed by
using the Implicit IV for ESP option [RFC8750].
NIST is working on selecting a new lightweight cipher that may be the
best choice for use on a UA. The Keccak Keyak cipher in [new-crypto]
is a good "Green Cipher". The Implicit IV, above, can be used as the
Unique Value in the Keyak cipher, saving sending the UV in the ESP
(or DTLS) datagram.
5.4. HIP and DTLS contrasted and compared
This document specifies the use of DTLS 1.3 for its 0-RTT mobility
feature and improved (over 1.2) handshake. DTLS 1.3 is still an IETF
draft, so there is little data available to properly contrast it with
HIPv2. This section will be based on the current DTLS 1.2. The
basic client-server model is unchanged.
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The use of DTLS vs HIPv2 (both over UDP, HIP in IPsec ESP mode) has
own pros and cons. DTLS is currently at version 1.2 and based on TLS
1.2. It is a more common protocol than HIP, with many different
implementations available for various platforms and languages.
DTLS implements a client-server model, where the client initiates the
communication. In HIP, two parties are equal and either can be an
Initiator or Responder of the Base Exchange. HIP provides separation
between key management (base exchange) and secure transport (for
example IPsec ESP tunnel) while both parts are tightly coupled in
DTLS.
DTLS 1.2 still has quite chatty connection establishment taking 3-5
RTTs and 15 packets. HIP connection establishment requires 4 packets
(I1,R1,I2,R2) over 2 RTTs. This is beneficial for constrained
environments of UAs. HIPv2 supports cryptoagility with possibility
to negotiate cryptography mechanisms during the Base Exchange.
Both DTLS and HIP support mobility with a change of IP address.
However, in DTLS only client mobility is well supported, while in HIP
either party can be mobile. The double-jump problem (simultaneous
mobility) is supported in HIP with a help of Rendezvous Server (RVS)
[RFC8004]. HIP can implement secure mobility with IP source address
validation in 2 RTTs, and in 1 RTT with fast mobility extension.
One study comparing DTLS and IPsec-ESP performance concluded that
DTLS is recommended for memory-constrained applications while IPSec-
ESP for battery power-constrained [Vignesh].
6. IANA Considerations
TBD
7. Security Considerations
Designing secure transports is challenging. Where possible, existing
technologies SHOULD be used. Both ESP and DTLS have stood "the test
of time" against many attack scenarios. Their use here for N-RID and
C2 do not represent new uses, but rather variants on existing
depoyments.
The same can be said for both key establishment, using HIPv2 and
DTLS, and the actual cipher choice for per packet encryption and
authentication. N-RID and C2 do not present new challenges, rather
new opportunities to provide communications security using well
researched technologies.
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8. Acknowledgments
Stuart Card and Adam Wiethuechter provivded information on their use
of HIP for C2 at the Syracuse NY UAS test corridor. This, in large
measure, was the impetus to develop this document.
9. 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>.
10. Informative References
[drip-uas-rid]
Moskowitz, R., Card, S., Wiethuechter, A., and A. Gurtov,
"UAS Remote ID", Work in Progress, Internet-Draft, draft-
moskowitz-drip-uas-rid-06, August 17, 2020,
<https://tools.ietf.org/html/draft-moskowitz-drip-uas-rid-
06>.
[DTLS-1.3-draft]
Rescorla, E., Tschofenig, H., and N. Modadugu, "The
Datagram Transport Layer Security (DTLS) Protocol Version
1.3", Work in Progress, Internet-Draft, draft-ietf-tls-
dtls13-38, May 29, 2020,
<https://tools.ietf.org/html/draft-ietf-tls-dtls13-38>.
[F3411-19] ASTM International, "Standard Specification for Remote ID
and Tracking", February 2020,
<http://www.astm.org/cgi-bin/resolver.cgi?F3411>.
[hhit-registries]
Moskowitz, R., Card, S., and A. Wiethuechter,
"Hierarchical HIT Registries", Work in Progress, Internet-
Draft, draft-moskowitz-hip-hhit-registries-02, March 9,
2020, <https://tools.ietf.org/html/draft-moskowitz-hip-
hhit-registries-02>.
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[hip-fast-mobility]
Moskowitz, R., Card, S., and A. Wiethuechter, "Fast HIP
Host Mobility", Work in Progress, Internet-Draft, draft-
moskowitz-hip-fast-mobility-03, April 3, 2020,
<https://tools.ietf.org/html/draft-moskowitz-hip-fast-
mobility-03>.
[new-crypto]
Moskowitz, R., Card, S., and A. Wiethuechter, "New
Cryptographic Algorithms for HIP", Work in Progress,
Internet-Draft, draft-moskowitz-hip-new-crypto-05, July
26, 2020, <https://tools.ietf.org/html/draft-moskowitz-
hip-new-crypto-05>.
[RFC5795] Sandlund, K., Pelletier, G., and L-E. Jonsson, "The RObust
Header Compression (ROHC) Framework", RFC 5795,
DOI 10.17487/RFC5795, March 2010,
<https://www.rfc-editor.org/info/rfc5795>.
[RFC7400] Bormann, C., "6LoWPAN-GHC: Generic Header Compression for
IPv6 over Low-Power Wireless Personal Area Networks
(6LoWPANs)", RFC 7400, DOI 10.17487/RFC7400, November
2014, <https://www.rfc-editor.org/info/rfc7400>.
[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>.
[RFC7402] Jokela, P., Moskowitz, R., and J. Melen, "Using the
Encapsulating Security Payload (ESP) Transport Format with
the Host Identity Protocol (HIP)", RFC 7402,
DOI 10.17487/RFC7402, April 2015,
<https://www.rfc-editor.org/info/rfc7402>.
[RFC7668] Nieminen, J., Savolainen, T., Isomaki, M., Patil, B.,
Shelby, Z., and C. Gomez, "IPv6 over BLUETOOTH(R) Low
Energy", RFC 7668, DOI 10.17487/RFC7668, October 2015,
<https://www.rfc-editor.org/info/rfc7668>.
[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>.
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[RFC8750] Migault, D., Guggemos, T., and Y. Nir, "Implicit
Initialization Vector (IV) for Counter-Based Ciphers in
Encapsulating Security Payload (ESP)", RFC 8750,
DOI 10.17487/RFC8750, March 2020,
<https://www.rfc-editor.org/info/rfc8750>.
[Vignesh] Vignesh, K., "Performance analysis of end-to-end DTLS and
IPsec-based communication in IoT environments", Thesis
no. MSEE-2017: 42, 2017, <http://www.diva-
portal.org/smash/get/diva2:1157047/FULLTEXT02>.
Authors' Addresses
Robert Moskowitz
HTT Consulting
Oak Park, MI 48237
United States of America
Email: rgm@labs.htt-consult.com
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
Andrei Gurtov
Linköping University
IDA
SE-58183 Linköping
Sweden
Email: gurtov@acm.org
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