TMRID                                                       R. Moskowitz
Internet-Draft                                            HTT Consulting
Intended status: Standards Track                                 S. Card
Expires: 3 September 2020                                A. Wiethuechter
                                                           AX Enterprize
                                                            2 March 2020

                        Crowd Sourced Remote ID


   This document describes using the ASTM Broadcast Remote ID (B-RID)
   specification in a "crowd sourced" smart phone environment to provide
   much of the FAA mandated Network Remote ID (N-RID) functionality.
   This crowd sourced B-RID data will use multi-lateration to add a
   level of reliability in the location data on the Unmanned Aircraft

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

   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 3 September 2020.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Simplified BSD License text

Moskowitz, et al.       Expires 3 September 2020                [Page 1]

Internet-Draft                   CS-RID                       March 2020

   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Draft Status  . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terms and Definitions . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Requirements Terminology  . . . . . . . . . . . . . . . .   3
     2.2.  Definitions . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Problem Space . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  Meeting the needs of Network ID . . . . . . . . . . . . .   5
     3.2.  Trustworthiness of Proxied Data . . . . . . . . . . . . .   6
     3.3.  Defense against fraudulent RID Messages . . . . . . . . .   6
   4.  The Finder - SPDP Security Relationship . . . . . . . . . . .   6
   5.  The CS-RID Messages . . . . . . . . . . . . . . . . . . . . .   7
     5.1.  CS-RID MESSAGE TYPE . . . . . . . . . . . . . . . . . . .   7
     5.2.  The CS-RID B-RID Proxy Message  . . . . . . . . . . . . .   7
       5.2.1.  CS-RID ID . . . . . . . . . . . . . . . . . . . . . .   8
     5.3.  CS-RID Finder Registration  . . . . . . . . . . . . . . .   8
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
     7.1.  Privacy Concerns  . . . . . . . . . . . . . . . . . . . .   9
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   9
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .   9
   10. Informative References  . . . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   This document defines a mechanism to capture the ASTM Broadcast
   Remote ID messages (B-RID) [WK65041] on any Internet connected device
   that receives them and can forward them to the SPDP(s) responsible
   for the geographic area the UA and receivers are in.  This will
   create a ecosystem that will meet most if not all data collection
   requriments that CAAs are placing on Network Remote ID (N-RID).

   These Internet connected devices are herein called "Finders", as they
   find UAs by listening for B-RID messages.  The Finders are B-RID
   forwarding proxies.  Their potentially limited spacial view of RID
   messages could result in bad decisions on what messages to send to
   the SPDP and which to drop.  The SPDP will make any filtering
   decisions in what it forwards to the UTM(s).

   Finders can be smartphones, tablets, or any computing platform with
   Internet connectivity that can meet the requirements defined in this
   document.  It is not expected, nor necessary, that Finders have any
   information about a UAS beyond the content in the B-RID messages.

Moskowitz, et al.       Expires 3 September 2020                [Page 2]

Internet-Draft                   CS-RID                       March 2020

   Finders MAY only need a loose association with the SPDP(s).  They may
   only have the SPDP's Public Key and FQDN.  It would use these, along
   with the Finder's Public Key to use ECIES, or other security methods,
   to send the messages in a secure manner to the SPDP.  The SPDP MAY
   require a stronger relationship to the Finders.  This may range from
   the Finder's Public Key being registered to the SPDP with other
   information so that the SPDP has some level of trust in the Finders
   to requiring transmissions be sent over long-lived transport
   connections like ESP or DTLS.

   This document has minimal information about the actions of SPDPs.  In
   general the SPDP is out of scope of this document.  That said, the
   SPDPs should not simply proxy B-RID messages to the UTM(s).  They
   should perform some minimal level of filtering and content checking
   before forwarding those messages that pass these tests in a secure
   manner to the UTM(s).

   An SPDP SHOULD only forward Authenticated B-RID messages like those
   defined in [tmrid-auth] to the UTM(s).  Further, the SPDP SHOULD
   validate the Remote ID (RID) and the Authentication signature before
   forwarding anything from the UA.

   When 3 or more Finders are reporting to an SPDP on a specific UA, the
   SPDP is in a unique position to perform multilateration on these
   messages and compute the Finder's view of the UA location to compare
   with the UA Location/Vector messages.  This check against the UA's
   location claims is both a validation on the UA's reliability as well
   as the trustworthiness of the Finders.  Other than providing data to
   allow for multilateration, this SPDP feature is out of scope of this

1.1.  Draft Status

   This draft was pushed out, in a largely raw state to meet the FAA's
   NPRM for "Remote Identification of Unmanned Aircraft Systems" comment
   filing deadline of March 2, 2020.

2.  Terms and Definitions

2.1.  Requirements Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "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.

Moskowitz, et al.       Expires 3 September 2020                [Page 3]

Internet-Draft                   CS-RID                       March 2020

2.2.  Definitions

      Broadcast Remote ID.  A method of sending RID messages as 1-way
      transmissions from the UA to any Observers within radio range.

      Civil Aeronautics Administration.  An example is the Federal
      Aviation Administration (FAA) in the United States of America.

      Elliptic Curve Integrated Encryption Scheme.  A hybrid encryption
      scheme which provides semantic security against an adversary who
      is allowed to use chosen-plaintext and chosen-ciphertext attacks.

      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.

      In Internet connected device that can receive B-RID messages and
      forward them to a UTM.

      Referred to in other UAS documents as a "user", but there are also
      other classes of 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 RID.

      Multilateration (more completely, pseudo range multilateration) is
      a navigation and surveillance technique based on measurement of
      the times of arrival (TOAs) of energy waves (radio, acoustic,
      seismic, etc.) having a known propagation speed.

      Network RID Service Provider.  USS receiving Network RID messages
      from UAS (UA or GCS), storing for a short specified time, making
      available to NETDP.

      Network RID Display Provider.  Entity (might be USS) aggregating
      data from multiple NETSPs to answer query from observer (or other
      party) desiring Situational Awareness of UAS operating in a
      specific airspace volume.

Moskowitz, et al.       Expires 3 September 2020                [Page 4]

Internet-Draft                   CS-RID                       March 2020

      Network Remote ID.  A method of sending RID messages via the
      Internet connection of the UAS directly to the UTM.

      Remote ID.  A unique identifier found on all UA to be used in
      communication and in regulation of UA operation.

      Supplemental Data Service Provider.  Entity providing information
      that is allowed, but not required to be present in the UTM system.

      Unmanned Aircraft.  In this document UA's are typically though of
      as drones of commerical or military variety.  This is a very
      strict definition which can be relaxed to include any and all
      aircraft that are unmanned.

      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.

      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.

      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).

3.  Problem Space

3.1.  Meeting the needs of Network ID

   The Federal (US) Aviation Authority (FAA), in the December 31, 2019
   Remote ID Notice of Proposed Rulemaking (NPRM), is requiring
   "Standard" and "Limited" Remote ID.  Standard is when the UAS
   provides both Network and Broadcast RID.  Limited is when the UAS
   provides only Network RID.  The FAA has dropped their previous
   position on allowing for only Broadcast RID.  We can guess as to
   their reasons; they are not spelled out in the NPRM.  It may be that

Moskowitz, et al.       Expires 3 September 2020                [Page 5]

Internet-Draft                   CS-RID                       March 2020

   just B-RID does not meet the FAA's statutory UA tracking

   The UAS vendors have commented that N-RID places considerable demands
   on currently used UAS.  For some UAS like RC planes, meaningful N-RID
   (via the Pilot's smartphone) are of limited value.  A mechanism that
   can augment B-RID to provide N-RID would help all members of the UAS
   environment to provide safe operation and allow for new applications.

3.2.  Trustworthiness of Proxied Data

   When a proxy is introduced in any communication protocol, there is a
   risk of corrupted data and DOS attacks.

3.3.  Defense against fraudulent RID Messages



4.  The Finder - SPDP Security Relationship

   The SPDP(s) and Finders SHOULD use EDDSA keys as their trusted
   Identities.  The public keys SHOULD be registered Hierarchical HITS,
   [hierarchical-hit] and [hhit-registries].

   The SPDP uses some process (out of scope here) to register the
   Finders and there EDDSA Public Key.  During this registration, the
   Finder gets the SPDP's EDDSA Public Key.  These Public Keys allow for
   the following options for authenticated messaging from the Finder to
   the SPDP.

   1.  ECIES can be used with a unique nonce to authenticate each
       message sent from a Finder to the SPDP.

   2.  ECIES can be used at the start of some period (e.g. day) to
       establish a shared secret that is then used to authenticate each
       message sent from a Finder to the SPDP sent during that period.

   3.  HIPv2 [RFC7401] can be used to establish a session secret that is
       then used with ESP [RFC4303] to authenticate each message sent
       from a Finder to the SPDP.

   4.  DTLS [RFC5238] can be used to establish a secure connection that
       is then used to authenticate each message sent from a Finder to
       the SPDP.

Moskowitz, et al.       Expires 3 September 2020                [Page 6]

Internet-Draft                   CS-RID                       March 2020

5.  The CS-RID Messages

   The CS-RID messages between the Finders and the SPDPs primarily
   support the proxy role of the Finders in forwarding the B-RID
   messages.  There are also Finder registration and status messages.

   CS-RID information is represented in CBOR [RFC7049].  COSE [RFC8152]
   may be used for CS-RID MAC and COAP [RFC7252] for the CS-RID

   The following is a general representation of the content in the CS-
   RID messages.

            (   CS-RID MESSAGE TYPE,
                CS-RID MESSAGE CONTENT,
                CS-RID MAC)




   Number   CS-RID Message Type
   ------   -----------------
   0        Reserved
   1        B-RID Forwarding
   2        Finder Registration

5.2.  The CS-RID B-RID Proxy Message

   The Finders add their own information to the B-RID messages,
   permitting the SPDP(s) to gain additional knowledge about the UA(s).
   The RID information is the B-RID message content plus the MAC
   address.  The MAC address is critical, as it is the only field that
   links a UA's B-RID messages together.  Only the ASTM Basic ID Message
   and possibly the Authentication Message contain the UAS ID field.

   The Finders add an SPDP assigned ID, a 64 bit timestamp, GPS
   information, and type of B-RID media to the B-RID message.  Both the
   timestamp and GPS information are for when the B-RID message(s) were
   received, not forwarded to the SPDP.  All this content is MACed using
   a key shared between the Finder and SPDP.

   The following is a representation of the content in the CS-RID

Moskowitz, et al.       Expires 3 September 2020                [Page 7]

Internet-Draft                   CS-RID                       March 2020

            (   CS-RID MESSAGE TYPE,
                CS-RID ID,
                RECEIVE TIMESTAMP,
                RECEIVE GPS,
                RECEIVE RADIO TYPE,
                B-RID MAC ADDRESS,
                B-RID MESSAGE,
                CS-RID MAC)


5.2.1.  CS-RID ID

   The CS-RID ID is the ID recognized by the SPDP.  This may be an HHIT
   Hierarchical HITs [hierarchical-hit], or any ID used by the SPDP.

5.3.  CS-RID Finder Registration

   The CS-RID Finder MAY use HIPv2 [RFC7401] with the SPDP to establish
   a Security Association and a shared secret to use for the CS-RID MAC
   generation.  In this approach, the HIPv2 mobility functionality and
   ESP [RFC4303] support are not used.

   When HIPv2 is used as above, the Finder Registration is a SPDP "wake
   up".  It is sent prior to the Finder sending any proxied B-RID
   messages to ensure that the SPDP is able to receive and process the

   In this usage, the CS-RID is the Finder HIT.  If the SPDP has lost
   state with the Finder, it initiates the HIP exchange with the Finder
   to reestablish HIP state and a new shared secret for the CS-RID B-RID
   Proxy Messages.  In this case the Finder Registration Message is:

            (   CS-RID MESSAGE TYPE,
                CS-RID ID,
                CS-RID MAC)

6.  IANA Considerations


7.  Security Considerations


Moskowitz, et al.       Expires 3 September 2020                [Page 8]

Internet-Draft                   CS-RID                       March 2020

7.1.  Privacy Concerns


8.  Acknowledgments

   The Crowd Sourcing idea in this document came from the Apple "Find My
   Device" presentation at the International Association for
   Cryptographic Research's Real World Crypto 2020 conference.

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,

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <>.

10.  Informative References

              Moskowitz, R., Card, S., and A. Wiethuechter,
              "Hierarchical HIT Registries", Work in Progress, Internet-
              Draft, draft-moskowitz-hip-hhit-registries-01, 17 October
              2019, <

              Moskowitz, R., Card, S., and A. Wiethuechter,
              "Hierarchical HITs for HIPv2", Work in Progress, Internet-
              Draft, draft-moskowitz-hip-hierarchical-hit-03, 16
              December 2019, <

   [RFC4303]  Kent, S., "IP Encapsulating Security Payload (ESP)",
              RFC 4303, DOI 10.17487/RFC4303, December 2005,

   [RFC5238]  Phelan, T., "Datagram Transport Layer Security (DTLS) over
              the Datagram Congestion Control Protocol (DCCP)",
              RFC 5238, DOI 10.17487/RFC5238, May 2008,

   [RFC7049]  Bormann, C. and P. Hoffman, "Concise Binary Object

Moskowitz, et al.       Expires 3 September 2020                [Page 9]

Internet-Draft                   CS-RID                       March 2020

              Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
              October 2013, <>.

   [RFC7252]  Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
              Application Protocol (CoAP)", RFC 7252,
              DOI 10.17487/RFC7252, June 2014,

   [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,

   [RFC8152]  Schaad, J., "CBOR Object Signing and Encryption (COSE)",
              RFC 8152, DOI 10.17487/RFC8152, July 2017,

              Wiethuechter, A., Card, S., and R. Moskowitz, "TM-RID
              Authentication Formats", Work in Progress, Internet-Draft,
              draft-wiethuechter-tmrid-auth-05, 18 February 2020,

   [WK65041]  ASTM, "Standard Specification for Remote ID and Tracking",
              September 2019.

Authors' Addresses

   Robert Moskowitz
   HTT Consulting
   Oak Park, MI 48237
   United States of America


   Stuart W. Card
   AX Enterprize
   4947 Commercial Drive
   Yorkville, NY 13495
   United States of America


   Adam Wiethuechter
   AX Enterprize

Moskowitz, et al.       Expires 3 September 2020               [Page 10]

Internet-Draft                   CS-RID                       March 2020

   4947 Commercial Drive
   Yorkville, NY 13495
   United States of America


Moskowitz, et al.       Expires 3 September 2020               [Page 11]