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Versions: (draft-mandyam-rats-eat) 00 01 02 03 04 05 06

RATS Working Group                                            G. Mandyam
Internet-Draft                                Qualcomm Technologies Inc.
Intended status: Standards Track                            L. Lundblade
Expires: June 4, 2021                                Security Theory LLC
                                                          M. Ballesteros
                                                           J. O'Donoghue
                                              Qualcomm Technologies Inc.
                                                       December 01, 2020

                   The Entity Attestation Token (EAT)


   An Entity Attestation Token (EAT) provides a signed (attested) set of
   claims that describe state and characteristics of an entity,
   typically a device like a phone or an IoT device.  These claims are
   used by a relying party to determine how much it wishes to trust the

   An EAT is either a CWT or JWT with some attestation-oriented claims.
   To a large degree, all this document does is extend CWT and JWT.



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 June 4, 2021.

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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
   (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 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  . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.1.  CWT, JWT and UCCS . . . . . . . . . . . . . . . . . . . .   5
     1.2.  CDDL  . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     1.3.  Entity Overview . . . . . . . . . . . . . . . . . . . . .   5
     1.4.  EAT Operating Models  . . . . . . . . . . . . . . . . . .   6
     1.5.  What is Not Standardized  . . . . . . . . . . . . . . . .   7
       1.5.1.  Transmission Protocol . . . . . . . . . . . . . . . .   7
       1.5.2.  Signing Scheme  . . . . . . . . . . . . . . . . . . .   8
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   8
   3.  The Claims  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     3.1.  Token ID Claim (cti and jti)  . . . . . . . . . . . . . .   9
     3.2.  Timestamp claim (iat) . . . . . . . . . . . . . . . . . .  10
     3.3.  Nonce Claim (nonce) . . . . . . . . . . . . . . . . . . .  10
       3.3.1.  nonce CDDL  . . . . . . . . . . . . . . . . . . . . .  10
     3.4.  Universal Entity ID Claim (ueid)  . . . . . . . . . . . .  11
       3.4.1.  ueid CDDL . . . . . . . . . . . . . . . . . . . . . .  13
     3.5.  Origination Claim (origination) . . . . . . . . . . . . .  13
       3.5.1.  origination CDDL  . . . . . . . . . . . . . . . . . .  13
     3.6.  OEM Identification by IEEE (oemid)  . . . . . . . . . . .  14
       3.6.1.  oemid CDDL  . . . . . . . . . . . . . . . . . . . . .  14
     3.7.  Hardware Version Claims (hardware-version-claims) . . . .  14
     3.8.  Software Description and Version  . . . . . . . . . . . .  15
     3.9.  The Security Level Claim (security-level) . . . . . . . .  15
       3.9.1.  security-level CDDL . . . . . . . . . . . . . . . . .  16
     3.10. Secure Boot Claim (secure-boot) . . . . . . . . . . . . .  16
       3.10.1.  secure-boot CDDL . . . . . . . . . . . . . . . . . .  16
     3.11. Debug Status Claim (debug-status) . . . . . . . . . . . .  16
       3.11.1.  Enabled  . . . . . . . . . . . . . . . . . . . . . .  17
       3.11.2.  Disabled . . . . . . . . . . . . . . . . . . . . . .  17
       3.11.3.  Disabled Since Boot  . . . . . . . . . . . . . . . .  18
       3.11.4.  Disabled Permanently . . . . . . . . . . . . . . . .  18

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       3.11.5.  Disabled Fully and Permanently . . . . . . . . . . .  18
       3.11.6.  debug-status CDDL  . . . . . . . . . . . . . . . . .  18
     3.12. Including Keys  . . . . . . . . . . . . . . . . . . . . .  18
     3.13. The Location Claim (location) . . . . . . . . . . . . . .  19
       3.13.1.  location CDDL  . . . . . . . . . . . . . . . . . . .  19
     3.14. The Uptime Claim (uptime) . . . . . . . . . . . . . . . .  20
       3.14.1.  uptime CDDL  . . . . . . . . . . . . . . . . . . . .  20
     3.15. The Intended Use Claim (intended-use) . . . . . . . . . .  20
       3.15.1.  intended-use CDDL  . . . . . . . . . . . . . . . . .  21
     3.16. The Submodules Part of a Token (submods)  . . . . . . . .  21
       3.16.1.  Two Types of Submodules  . . . . . . . . . . . . . .  21  Non-token Submodules . . . . . . . . . . . . . .  21  Nested EATs  . . . . . . . . . . . . . . . . . .  22  Unsecured JWTs and UCCS Tokens as Submodules . .  23
       3.16.2.  No Inheritance . . . . . . . . . . . . . . . . . . .  23
       3.16.3.  Security Levels  . . . . . . . . . . . . . . . . . .  23
       3.16.4.  Submodule Names  . . . . . . . . . . . . . . . . . .  24
       3.16.5.  submods CDDL . . . . . . . . . . . . . . . . . . . .  24
   4.  Endorsements and Verification Keys  . . . . . . . . . . . . .  24
   5.  Encoding  . . . . . . . . . . . . . . . . . . . . . . . . . .  24
     5.1.  Common CDDL Types . . . . . . . . . . . . . . . . . . . .  24
     5.2.  CDDL for CWT-defined Claims . . . . . . . . . . . . . . .  24
     5.3.  JSON  . . . . . . . . . . . . . . . . . . . . . . . . . .  25
       5.3.1.  JSON Labels . . . . . . . . . . . . . . . . . . . . .  25
       5.3.2.  JSON Interoperability . . . . . . . . . . . . . . . .  25
     5.4.  CBOR  . . . . . . . . . . . . . . . . . . . . . . . . . .  25
       5.4.1.  CBOR Interoperability . . . . . . . . . . . . . . . .  25
     5.5.  Collected CDDL  . . . . . . . . . . . . . . . . . . . . .  26
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  26
     6.1.  Reuse of CBOR Web Token (CWT) Claims Registry . . . . . .  26
     6.2.  Claim Characteristics . . . . . . . . . . . . . . . . . .  27
       6.2.1.  Interoperability and Relying Party Orientation  . . .  27
       6.2.2.  Operating System and Technology Neutral . . . . . . .  27
       6.2.3.  Security Level Neutral  . . . . . . . . . . . . . . .  28
       6.2.4.  Reuse of Extant Data Formats  . . . . . . . . . . . .  28
       6.2.5.  Proprietary Claims  . . . . . . . . . . . . . . . . .  28
     6.3.  Claims Registered by This Document  . . . . . . . . . . .  28
   7.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .  29
     7.1.  UEID Privacy Considerations . . . . . . . . . . . . . . .  29
     7.2.  Location Privacy Considerations . . . . . . . . . . . . .  30
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  30
     8.1.  Key Provisioning  . . . . . . . . . . . . . . . . . . . .  30
       8.1.1.  Transmission of Key Material  . . . . . . . . . . . .  30
     8.2.  Transport Security  . . . . . . . . . . . . . . . . . . .  31
     8.3.  Multiple EAT Consumers  . . . . . . . . . . . . . . . . .  31
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  32
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  32
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  34

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   Appendix A.  Examples . . . . . . . . . . . . . . . . . . . . . .  36
     A.1.  Very Simple EAT . . . . . . . . . . . . . . . . . . . . .  36
     A.2.  Example with Submodules, Nesting and Security Levels  . .  36
   Appendix B.  UEID Design Rationale  . . . . . . . . . . . . . . .  36
     B.1.  Collision Probability . . . . . . . . . . . . . . . . . .  36
     B.2.  No Use of UUID  . . . . . . . . . . . . . . . . . . . . .  38
   Appendix C.  Changes from Previous Drafts . . . . . . . . . . . .  39
     C.1.  From draft-rats-eat-01  . . . . . . . . . . . . . . . . .  39
     C.2.  From draft-mandyam-rats-eat-00  . . . . . . . . . . . . .  39
     C.3.  From draft-ietf-rats-eat-01 . . . . . . . . . . . . . . .  39
     C.4.  From draft-ietf-rats-eat-02 . . . . . . . . . . . . . . .  40
     C.5.  From draft-ietf-rats-eat-03 . . . . . . . . . . . . . . .  40
     C.6.  From draft-ietf-rats-eat-04 . . . . . . . . . . . . . . .  40
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  41

1.  Introduction

   Remote device attestation is a fundamental service that allows a
   remote device such as a mobile phone, an Internet-of-Things (IoT)
   device, or other endpoint to prove itself to a relying party, a
   server or a service.  This allows the relying party to know some
   characteristics about the device and decide whether it trusts the

   Remote attestation is a fundamental service that can underlie other
   protocols and services that need to know about the trustworthiness of
   the device before proceeding.  One good example is biometric
   authentication where the biometric matching is done on the device.
   The relying party needs to know that the device is one that is known
   to do biometric matching correctly.  Another example is content
   protection where the relying party wants to know the device will
   protect the data.  This generalizes on to corporate enterprises that
   might want to know that a device is trustworthy before allowing
   corporate data to be accessed by it.

   The notion of attestation here is large and may include, but is not
   limited to the following:

   o  Proof of the make and model of the device hardware (HW)

   o  Proof of the make and model of the device processor, particularly
      for security-oriented chips

   o  Measurement of the software (SW) running on the device

   o  Configuration and state of the device

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   o  Environmental characteristics of the device such as its GPS

   TODO: mention use for Attestation Evidence and Results.

1.1.  CWT, JWT and UCCS

   For flexibility and ease of imlpementation in a wide variety of
   environments, EATs can be either CBOR [RFC7049] or JSON [ECMAScript]
   format.  This specification simultaneously describes both formats.

   An EAT is either a CWT as defined in [RFC8392], a UCCS as defined in
   [UCCS.Draft], or a JWT as defined in [RFC7519].  This specification
   extends those specifications with additional claims for attestation.

   The identification of a protocol element as an EAT, whether CBOR or
   JSON format, follows the general conventions used by CWT, JWT and
   UCCS.  Largely this depends on the protocol carrying the EAT.  In
   some cases it may be by content type (e.g., MIME type).  In other
   cases it may be through use of CBOR tags.  There is no fixed
   mechanism across all use cases.

1.2.  CDDL

   This specification uses CDDL, [RFC8610], as the primary formalism to
   define each claim.  The implementor then interprets the CDDL to come
   to either the CBOR [RFC7049] or JSON [ECMAScript] representation.  In
   the case of JSON, Appendix E of [RFC8610] is followed.  Additional
   rules are given in Section 5.3.2 of this document where Appendix E is
   insufficient.  (Note that this is not to define a general means to
   translate between CBOR and JSON, but only to define enough such that
   the claims defined in this document can be rendered unambiguously in

   The CWT specification was authored before CDDL was available and did
   not use it.  This specification includes a CDDL definition of most of
   what is described in [RFC8392].

1.3.  Entity Overview

   An "entity" can be any device or device subassembly ("submodule")
   that can generate its own attestation in the form of an EAT.  The
   attestation should be cryptographically verifiable by the EAT
   consumer.  An EAT at the device-level can be composed of several
   submodule EAT's.  It is assumed that any entity that can create an
   EAT does so by means of a dedicated root-of-trust (RoT).

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   Modern devices such as a mobile phone have many different execution
   environments operating with different security levels.  For example,
   it is common for a mobile phone to have an "apps" environment that
   runs an operating system (OS) that hosts a plethora of downloadable
   apps.  It may also have a TEE (Trusted Execution Environment) that is
   distinct, isolated, and hosts security-oriented functionality like
   biometric authentication.  Additionally, it may have an eSE (embedded
   Secure Element) - a high security chip with defenses against HW
   attacks that can serve as a RoT.  This device attestation format
   allows the attested data to be tagged at a security level from which
   it originates.  In general, any discrete execution environment that
   has an identifiable security level can be considered an entity.

1.4.  EAT Operating Models

   TODO: Rewrite (or eliminate) this section in light of the RATS
   architecture draft.

   At least the following three participants exist in all EAT operating
   models.  Some operating models have additional participants.

   The Entity.  This is the phone, the IoT device, the sensor, the sub-
      assembly or such that the attestation provides information about.

   The Manufacturer.  The company that made the entity.  This may be a
      chip vendor, a circuit board module vendor or a vendor of finished
      consumer products.

   The Relying Party.  The server, service or company that makes use of
      the information in the EAT about the entity.

   In all operating models, the manufacturer provisions some secret
   attestation key material (AKM) into the entity during manufacturing.
   This might be during the manufacturer of a chip at a fabrication
   facility (fab) or during final assembly of a consumer product or any
   time in between.  This attestation key material is used for signing

   In all operating models, hardware and/or software on the entity
   create an EAT of the format described in this document.  The EAT is
   always signed by the attestation key material provisioned by the

   In all operating models, the relying party must end up knowing that
   the signature on the EAT is valid and consistent with data from
   claims in the EAT.  This can happen in many different ways.  Here are
   some examples.

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   o  The EAT is transmitted to the relying party.  The relying party
      gets corresponding key material (e.g. a root certificate) from the
      manufacturer.  The relying party performs the verification.

   o  The EAT is transmitted to the relying party.  The relying party
      transmits the EAT to a verification service offered by the
      manufacturer.  The server returns the validated claims.

   o  The EAT is transmitted directly to a verification service, perhaps
      operated by the manufacturer or perhaps by another party.  It
      verifies the EAT and makes the validated claims available to the
      relying party.  It may even modify the claims in some way and re-
      sign the EAT (with a different signing key).

   All these operating models are supported and there is no preference
   of one over the other.  It is important to support this variety of
   operating models to generally facilitate deployment and to allow for
   some special scenarios.  One special scenario has a validation
   service that is monetized, most likely by the manufacturer.  In
   another, a privacy proxy service processes the EAT before it is
   transmitted to the relying party.  In yet another, symmetric key
   material is used for signing.  In this case the manufacturer should
   perform the verification, because any release of the key material
   would enable a participant other than the entity to create valid
   signed EATs.

1.5.  What is Not Standardized

   The following is not standardized for EAT, just the same they are not
   standardized for CWT or JWT.

1.5.1.  Transmission Protocol

   EATs may be transmitted by any protocol the same as CWTs and JWTs.
   For example, they might be added in extension fields of other
   protocols, bundled into an HTTP header, or just transmitted as files.
   This flexibility is intentional to allow broader adoption.  This
   flexibility is possible because EAT's are self-secured with signing
   (and possibly additionally with encryption and anti-replay).  The
   transmission protocol is not required to fulfill any additional
   security requirements.

   For certain devices, a direct connection may not exist between the
   EAT-producing device and the Relying Party.  In such cases, the EAT
   should be protected against malicious access.  The use of COSE and
   JOSE allows for signing and encryption of the EAT.  Therefore, even
   if the EAT is conveyed through intermediaries between the device and

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   Relying Party, such intermediaries cannot easily modify the EAT
   payload or alter the signature.

1.5.2.  Signing Scheme

   The term "signing scheme" is used to refer to the system that
   includes end-end process of establishing signing attestation key
   material in the entity, signing the EAT, and verifying it.  This
   might involve key IDs and X.509 certificate chains or something
   similar but different.  The term "signing algorithm" refers just to
   the algorithm ID in the COSE signing structure.  No particular
   signing algorithm or signing scheme is required by this standard.

   There are three main implementation issues driving this.  First,
   secure non-volatile storage space in the entity for the attestation
   key material may be highly limited, perhaps to only a few hundred
   bits, on some small IoT chips.  Second, the factory cost of
   provisioning key material in each chip or device may be high, with
   even millisecond delays adding to the cost of a chip.  Third,
   privacy-preserving signing schemes like ECDAA (Elliptic Curve Direct
   Anonymous Attestation) are complex and not suitable for all use

   Over time to faciliate interoperability, some signing schemes may be
   defined in EAT profiles or other documents either in the IETF or

2.  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.

   This document reuses terminology from JWT [RFC7519], COSE [RFC8152],
   and CWT [RFC8392].

   Claim Name.  The human-readable name used to identify a claim.

   Claim Key.  The CBOR map key or JSON name used to identify a claim.

   Claim Value.  The value portion of the claim.  A claim value can be
      any CBOR data item or JSON value.

   CWT Claims Set.  The CBOR map or JSON object that contains the claims
      conveyed by the CWT or JWT.

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   Attestation Key Material (AKM).  The key material used to sign the
      EAT token.  If it is done symmetrically with HMAC, then this is a
      simple symmetric key.  If it is done with ECC, such as an IEEE
      DevID [IDevID], then this is the private part of the EC key pair.
      If ECDAA is used, (e.g., as used by Enhanced Privacy ID, i.e.
      EPID) then it is the key material needed for ECDAA.

3.  The Claims

   This section describes new claims defined for attestation.  It also
   mentions several claims defined by CWT and JWT that are particularly
   important for EAT.

   Note also: * Any claim defined for CWT or JWT may be used in an EAT
   including those in the CWT [IANA.CWT.Claims] and JWT IANA
   [IANA.JWT.Claims] claims registries.

   o  All claims are optional

   o  No claims are mandatory

   o  All claims that are not understood by implementations MUST be

   There are no default values or meanings assigned to absent claims
   other than they are not reported.  The reason for a claim's absence
   may be the implementation not supporting the claim, an inability to
   determine its value, or a preference to report in a different way
   such as a proprietary claim.

   CDDL along with text descriptions is used to define each claim
   indepdent of encoding.  Each claim is defined as a CDDL group (the
   group is a general aggregation and type definition feature of CDDL).
   In the encoding section Section 5, the CDDL groups turn into CBOR map
   entries and JSON name/value pairs.

   TODO: add paragraph here about use for Attestation Evidence and for

3.1.  Token ID Claim (cti and jti)

   CWT defines the "cti" claim.  JWT defines the "jti" claim.  These are
   equivalent to each other in EAT and carry a unique token identifier
   as they do in JWT and CWT.  They may be used to defend against re use
   of the token but are distinct from the nonce that is used by the
   relying party to guarantee freshness and defend against replay.

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3.2.  Timestamp claim (iat)

   The "iat" claim defined in CWT and JWT is used to indicate the date-
   of-creation of the token, the time at which the claims are collected
   and the token is composed and signed.

   The data for some claims may be held or cached for some period of
   time before the token is created.  This period may be long, even
   days.  Examples are measurements taken at boot or a geographic
   position fix taken the last time a satellite signal was received.
   There are individual timestamps associated with these claims to
   indicate their age is older than the "iat" timestamp.

   CWT allows the use floating-point for this claim.  EAT disallows the
   use of floating-point.  No token may contain an iat claim in float-
   point format.  Any recipient of a token with a floating-point format
   iat claim may consider it an error.  A 64-bit integer representation
   of epoch time can represent a range of +/- 500 billion years, so the
   only point of a floating-point timestamp is to have precession
   greater than one second.  This is not needed for EAT.

3.3.  Nonce Claim (nonce)

   All EATs should have a nonce to prevent replay attacks.  The nonce is
   generated by the relying party, the end consumer of the token.  It is
   conveyed to the entity over whatever transport is in use before the
   token is generated and then included in the token as the nonce claim.

   This documents the nonce claim for registration in the IANA CWT
   claims registry.  This is equivalent to the JWT nonce claim that is
   already registered.

   The nonce must be at least 8 bytes (64 bits) as fewer are unlikely to
   be secure.  A maximum of 64 bytes is set to limit the memory a
   constrained implementation uses.  This size range is not set for the
   already-registered JWT nonce, but it should follow this size
   recommendation when used in an EAT.

   Multiple nonces are allowed to accommodate multistage verification
   and consumption.

3.3.1.  nonce CDDL

   {::include cddl/nonce.cddl}

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3.4.  Universal Entity ID Claim (ueid)

   UEID's identify individual manufactured entities / devices such as a
   mobile phone, a water meter, a Bluetooth speaker or a networked
   security camera.  It may identify the entire device or a submodule or
   subsystem.  It does not identify types, models or classes of devices.
   It is akin to a serial number, though it does not have to be

   UEID's must be universally and globally unique across manufacturers
   and countries.  UEIDs must also be unique across protocols and
   systems, as tokens are intended to be embedded in many different
   protocols and systems.  No two products anywhere, even in completely
   different industries made by two different manufacturers in two
   different countries should have the same UEID (if they are not global
   and universal in this way, then relying parties receiving them will
   have to track other characteristics of the device to keep devices
   distinct between manufacturers).

   There are privacy considerations for UEID's.  See Section 7.1.

   The UEID should be permanent.  It should never change for a given
   device / entity.  In addition, it should not be reprogrammable.
   UEID's are variable length.  All implementations MUST be able to
   receive UEID's that are 33 bytes long (1 type byte and 256 bits).
   The recommended maximum sent is also 33 bytes.

   When the entity constructs the UEID, the first byte is a type and the
   following bytes the ID for that type.  Several types are allowed to
   accommodate different industries and different manufacturing
   processes and to give options to avoid paying fees for certain types
   of manufacturer registrations.

   Creation of new types requires a Standards Action [RFC8126].

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   | Type | Type | Specification                                       |
   | Byte | Name |                                                     |
   | 0x01 | RAND | This is a 128, 192 or 256 bit random number         |
   |      |      | generated once and stored in the device. This may   |
   |      |      | be constructed by concatenating enough identifiers  |
   |      |      | to make up an equivalent number of random bits and  |
   |      |      | then feeding the concatenation through a            |
   |      |      | cryptographic hash function. It may also be a       |
   |      |      | cryptographic quality random number generated once  |
   |      |      | at the beginning of the life of the device and      |
   |      |      | stored. It may not be smaller than 128 bits.        |
   | 0x02 | IEEE | This makes use of the IEEE company identification   |
   |      | EUI  | registry. An EUI is either an EUI-48, EUI-60 or     |
   |      |      | EUI-64 and made up of an OUI, OUI-36 or a CID,      |
   |      |      | different registered company identifiers, and some  |
   |      |      | unique per-device identifier. EUIs are often the    |
   |      |      | same as or similar to MAC addresses. This type      |
   |      |      | includes MAC-48, an obsolete name for EUI-48. (Note |
   |      |      | that while devices with multiple network interfaces |
   |      |      | may have multiple MAC addresses, there is only one  |
   |      |      | UEID for a device) [IEEE.802-2001], [OUI.Guide]     |
   | 0x03 | IMEI | This is a 14-digit identifier consisting of an      |
   |      |      | 8-digit Type Allocation Code and a 6-digit serial   |
   |      |      | number allocated by the manufacturer, which SHALL   |
   |      |      | be encoded as byte string of length 14 with each    |
   |      |      | byte as the digit's value (not the ASCII encoding   |
   |      |      | of the digit; the digit 3 encodes as 0x03, not      |
   |      |      | 0x33). The IMEI value encoded SHALL NOT include     |
   |      |      | Luhn checksum or SVN information. [ThreeGPP.IMEI]   |

                      Table 1: UEID Composition Types

   UEID's are not designed for direct use by humans (e.g., printing on
   the case of a device), so no textual representation is defined.

   The consumer (the relying party) of a UEID MUST treat a UEID as a
   completely opaque string of bytes and not make any use of its
   internal structure.  For example, they should not use the OUI part of
   a type 0x02 UEID to identify the manufacturer of the device.  Instead
   they should use the oemid claim that is defined elsewhere.  The
   reasons for this are:

   o  UEIDs types may vary freely from one manufacturer to the next.

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   o  New types of UEIDs may be created.  For example, a type 0x07 UEID
      may be created based on some other manufacturer registration

   o  Device manufacturers are allowed to change from one type of UEID
      to another anytime they want.  For example, they may find they can
      optimize their manufacturing by switching from type 0x01 to type
      0x02 or vice versa.  The main requirement on the manufacturer is
      that UEIDs be universally unique.

3.4.1.  ueid CDDL

   {::include cddl/ueid.cddl}

3.5.  Origination Claim (origination)

   TODO: this claim is likely to be dropped in favor of Endorsement
   identifier and locators.

   This claim describes the parts of the device or entity that are
   creating the EAT.  Often it will be tied back to the device or chip
   manufacturer.  The following table gives some examples:

   | Name              | Description                                   |
   | Acme-TEE          | The EATs are generated in the TEE authored    |
   |                   | and configured by "Acme"                      |
   | Acme-TPM          | The EATs are generated in a TPM manufactured  |
   |                   | by "Acme"                                     |
   | Acme-Linux-Kernel | The EATs are generated in a Linux kernel      |
   |                   | configured and shipped by "Acme"              |
   | Acme-TA           | The EATs are generated in a Trusted           |
   |                   | Application (TA) authored by "Acme"           |

   TODO: consider a more structure approach where the name and the URI
   and other are in separate fields.

   TODO: This needs refinement.  It is somewhat parallel to issuer claim
   in CWT in that it describes the authority that created the token.

3.5.1.  origination CDDL

   {::include cddl/origination.cddl}

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3.6.  OEM Identification by IEEE (oemid)

   The IEEE operates a global registry for MAC addresses and company
   IDs.  This claim uses that database to identify OEMs.  The contents
   of the claim may be either an IEEE MA-L, MA-M, MA-S or an IEEE CID
   [IEEE.RA].  An MA-L, formerly known as an OUI, is a 24-bit value used
   as the first half of a MAC address.  MA-M similarly is a 28-bit value
   uses as the first part of a MAC address, and MA-S, formerly known as
   OUI-36, a 36-bit value.  Many companies already have purchased one of
   these.  A CID is also a 24-bit value from the same space as an MA-L,
   but not for use as a MAC address.  IEEE has published Guidelines for
   Use of EUI, OUI, and CID [OUI.Guide] and provides a lookup services

   Companies that have more than one of these IDs or MAC address blocks
   should pick one and prefer that for all their devices.

   Commonly, these are expressed in Hexadecimal Representation
   [IEEE.802-2001] also called the Canonical format.  When this claim is
   encoded the order of bytes in the bstr are the same as the order in
   the Hexadecimal Representation.  For example, an MA-L like "AC-DE-48"
   would be encoded in 3 bytes with values 0xAC, 0xDE, 0x48.  For JSON
   encoded tokens, this is further base64url encoded.

3.6.1.  oemid CDDL

   {::include cddl/oemid.cddl}

3.7.  Hardware Version Claims (hardware-version-claims)

   The hardware version can be claimed at three different levels, the
   chip, the circuit board and the final device assembly.  An EAT can
   include any combination these claims.

   The hardware version is a simple text string the format of which is
   set by each manufacturer.  The structure and sorting order of this
   text string can be specified using the version-scheme item from

   The hardware version can also be given by a 13-digit European Article
   Number [EAN-13].  An EAN-13 is also known as an International Article
   Number or most commonly as a bar code.  This claim is the ASCII text
   representation of actual digits often printed with a bar code.  Use
   of this claim must comply with the EAN allocation and assignment
   rules.  For example, this requires the manufacturer to obtain a
   manufacture code from GS1.

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   Both the simple version string and EAN-13 versions may be included
   for the same hardware.

   {::include cddl/hardware-version.cddl}

3.8.  Software Description and Version

   TODO: Add claims that reference CoSWID.

3.9.  The Security Level Claim (security-level)

   This claim characterizes the device/entity ability to defend against
   attacks aimed at capturing the signing key, forging claims and at
   forging EATs.  This is done by
   defining four security levels as described below.  This is similar to
   the key protection types defined by the Fast Identity Online (FIDO)
   Alliance [FIDO.Registry]).

   These claims describe security environment and countermeasures
   available on the end-entity / client device where the attestation key
   reside and the claims originate.

   1 - Unrestricted  There is some expectation that implementor will
      protect the attestation signing keys at this level.  Otherwise the
      EAT provides no meaningful security assurances.

   2- Restricted  Entities at this level should not be general-purpose
      operating environments that host features such as app download
      systems, web browsers and complex productivity applications.  It
      is akin to the Secure Restricted level (see below) without the
      security orientation.  Examples include a Wi-Fi subsystem, an IoT
      camera, or sensor device.

   3 - Secure Restricted  Entities at this level must meet the criteria
      defined by FIDO Allowed Restricted Operating Environments
      [FIDO.AROE].  Examples include TEE's and schemes using
      virtualization-based security.  Like the FIDO security goal,
      security at this level is aimed at defending well against large-
      scale network / remote attacks against the device.

   4 - Hardware  Entities at this level must include substantial defense
      against physical or electrical attacks against the device itself.
      It is assumed any potential attacker has captured the device and
      can disassemble it.  Example include TPMs and Secure Elements.

   The entity should claim the highest security level it achieves and no
   higher.  This set is not extensible so as to provide a common
   interoperable description of security level to the relying party.  If

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   a particular implementation considers this claim to be inadequate, it
   can define its own proprietary claim.  It may consider including both
   this claim as a coarse indication of security and its own proprietary
   claim as a refined indication.

   This claim is not intended as a replacement for a proper end-device
   security certification schemes such as those based on FIPS 140
   [FIPS-140] or those based on Common Criteria [Common.Criteria].  The
   claim made here is solely a self-claim made by the Entity Originator.

3.9.1.  security-level CDDL

   {::include cddl/security-level.cddl}

3.10.  Secure Boot Claim (secure-boot)

   The value of true indicates secure boot is enabled.  Secure boot is
   considered enabled when base software, the firmware and operating
   system, are under control of the entity manufacturer identified in
   the oemid claimd described in Section 3.6.  This may because the
   software is in ROM or because it is cryptographically authenticated
   or some combination of the two or other.

3.10.1.  secure-boot CDDL

   {::include cddl/secure-boot.cddl}

3.11.  Debug Status Claim (debug-status)

   This applies to system-wide or submodule-wide debug facilities of the
   target device / submodule like JTAG and diagnostic hardware built
   into chips.  It applies to any software debug facilities related to
   root, operating system or privileged software that allow system-wide
   memory inspection, tracing or modification of non-system software
   like user mode applications.

   This characterization assumes that debug facilities can be enabled
   and disabled in a dynamic way or be disabled in some permanent way
   such that no enabling is possible.  An example of dynamic enabling is
   one where some authentication is required to enable debugging.  An
   example of permanent disabling is blowing a hardware fuse in a chip.
   The specific type of the mechanism is not taken into account.  For
   example, it does not matter if authentication is by a global password
   or by per-device public keys.

   As with all claims, the absence of the debug level claim means it is
   not reported.  A conservative interpretation might assume the Not

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   Disabled state.  It could however be that it is reported in a
   proprietary claim.

   This claim is not extensible so as to provide a common interoperable
   description of debug status to the relying party.  If a particular
   implementation considers this claim to be inadequate, it can define
   its own proprietary claim.  It may consider including both this claim
   as a coarse indication of debug status and its own proprietary claim
   as a refined indication.

   The higher levels of debug disabling requires that all debug
   disabling of the levels below it be in effect.  Since the lowest
   level requires that all of the target's debug be currently disabled,
   all other levels require that too.

   There is no inheritance of claims from a submodule to a superior
   module or vice versa.  There is no assumption, requirement or
   guarantee that the target of a superior module encompasses the
   targets of submodules.  Thus, every submodule must explicitly
   describe its own debug state.  The verifier or relying party
   receiving an EAT cannot assume that debug is turned off in a
   submodule because there is a claim indicating it is turned off in a
   superior module.

   An individual target device / submodule may have multiple debug
   facilities.  The use of plural in the description of the states
   refers to that, not to any aggregation or inheritance.

   The architecture of some chips or devices may be such that a debug
   facility operates for the whole chip or device.  If the EAT for such
   a chip includes submodules, then each submodule should independently
   report the status of the whole-chip or whole-device debug facility.
   This is the only way the relying party can know the debug status of
   the submodules since there is no inheritance.

3.11.1.  Enabled

   If any debug facility, even manufacturer hardware diagnostics, is
   currently enabled, then this level must be indicated.

3.11.2.  Disabled

   This level indicates all debug facilities are currently disabled.  It
   may be possible to enable them in the future, and it may also be
   possible that they were enabled in the past after the target device/
   sub-system booted/started, but they are currently disabled.

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3.11.3.  Disabled Since Boot

   This level indicates all debug facilities are currently disabled and
   have been so since the target device/sub-system booted/started.

3.11.4.  Disabled Permanently

   This level indicates all non-manufacturer facilities are permanently
   disabled such that no end user or developer cannot enable them.  Only
   the manufacturer indicated in the OEMID claim can enable them.  This
   also indicates that all debug facilities are currently disabled and
   have been so since boot/start.

3.11.5.  Disabled Fully and Permanently

   This level indicates that all debug capabilities for the target
   device/sub-module are permanently disabled.

3.11.6.  debug-status CDDL

   {::include cddl/debug-status.cddl}

3.12.  Including Keys

   An EAT may include a cryptographic key such as a public key.  The
   signing of the EAT binds the key to all the other claims in the

   The purpose for inclusion of the key may vary by use case.  For
   example, the key may be included as part of an IoT device onboarding
   protocol.  When the FIDO protocol includes a pubic key in its
   attestation message, the key represents the binding of a user, device
   and relying party.  This document describes how claims containing
   keys should be defined for the various use cases.  It does not define
   specific claims for specific use cases.

   Keys in CBOR format tokens SHOULD be the COSE_Key format [RFC8152]
   and keys in JSON format tokens SHOULD be the JSON Web Key format
   [RFC7517].  These two formats support many common key types.  Their
   use avoids the need to decode other serialization formats.  These two
   formats can be extended to support further key types through their
   IANA registries.

   The general confirmation claim format [RFC8747], [RFC7800] may also
   be used.  It provides key encryption.  It also allows for inclusion
   by reference through a key ID.  The confirmation claim format may
   employed in the definition of some new claim for a a particular use

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   When the actual confirmation claim is included in an EAT, this
   document associates no use case semantics other than proof of
   posession.  Different EAT use cases may choose to associate further
   semantics.  The key in the confirmation claim MUST be protected the
   same as the key used to sign the EAT.  That is, the same, equivalent
   or better hardware defenses, access controls, key generation and such
   must be used.

3.13.  The Location Claim (location)

   The location claim gives the location of the device entity from which
   the attestation originates.  It is derived from the W3C Geolocation
   API [W3C.GeoLoc].  The latitude, longitude, altitude and accuracy
   must conform to [WGS84].  The altitude is in meters above the [WGS84]
   ellipsoid.  The two accuracy values are positive numbers in meters.
   The heading is in degrees relative to true north.  If the device is
   stationary, the heading is NaN (floating-point not-a-number).  The
   speed is the horizontal component of the device velocity in meters
   per second.

   When encoding floating-point numbers half-precision should not be
   used.  It usually does not provide enough precision for a geographic
   location.  It is not a requirement that the receiver of an EAT
   implement half-precision, so the receiver may not be able to decode
   the location.

   The location may have been cached for a period of time before token
   creation.  For example, it might have been minutes or hours or more
   since the last contact with a GPS satellite.  Either the timestamp or
   age data item can be used to quantify the cached period.  The
   timestamp data item is preferred as it a non-relative time.

   The age data item can be used when the entity doesn't know what time
   it is either because it doesn't have a clock or it isn't set.  The
   entity must still have a "ticker" that can measure a time interval.
   The age is the interval between acquisition of the location data and
   token creation.

   See {#locationprivacyconsiderations} below.

3.13.1.  location CDDL

   {::include cddl/location.cddl}

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3.14.  The Uptime Claim (uptime)

   The "uptime" claim contains a value that represents the number of
   seconds that have elapsed since the entity or submod was last booted.

3.14.1.  uptime CDDL

   {::include cddl/uptime.cddl}

3.15.  The Intended Use Claim (intended-use)

   EAT's may be used in the context of several different applications.
   The intended-use claim provides an indication to an EAT consumer
   about the intended usage of the token.  This claim can be used as a
   way for an application using EAT to internally distinguish between
   different ways it uses EAT.

   1 - Generic  Generic attestation describes an application where the
      EAT consumer requres the most up-to-date security assessment of
      the attesting entity.  It is expected that this is the most
      commonly-used application of EAT.

   2- Registration  Entities that are registering for a new service may
      be expected to provide an attestation as part of the registration
      process.  This intended-use setting indicates that the attestation
      is not intended for any use but registration.

   3 - Provisioning  Entities may be provisioned with different values
      or settings by an EAT consumer.  Examples include key material or
      device management trees.  The consumer may require an EAT to
      assess device security state of the entity prior to provisioning.

   4 - Certificate Issuance (Certificate Signing Request)  Certifying
      authorities (CA's) may require attestations prior to the issuance
      of certificates related to keypairs hosted at the entity.  An EAT
      may be used as part of the certificate signing request (CSR).

   5 - Proof-of-Possession  An EAT consumer may require an attestation
      as part of an accompanying proof-of-possession (PoP) appication.
      More precisely, a PoP transaction is intended to provide to the
      recipient cryptographically-verifiable proof that the sender has
      posession of a key.  This kind of attestation may be neceesary to
      verify the security state of the entity storing the private key
      used in a PoP application.

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3.15.1.  intended-use CDDL

   intended-use = &(
       generic: 1,
       registration: 2,
       provisioning: 3,
       csr: 4,
       pop:  5

3.16.  The Submodules Part of a Token (submods)

   Some devices are complex, having many subsystems or submodules.  A
   mobile phone is a good example.  It may have several connectivity
   submodules for communications (e.g., Wi-Fi and cellular).  It may
   have subsystems for low-power audio and video playback.  It may have
   one or more security-oriented subsystems like a TEE or a Secure

   The claims for each these can be grouped together in a submodule.

   The submods part of a token are in a single map/object with many
   entries, one per submodule.  There is only one submods map in a
   token.  It is identified by its specific label.  It is a peer to
   other claims, but it is not called a claim because it is a container
   for a claim set rather than an individual claim.  This submods part
   of a token allows what might be called recursion.  It allows claim
   sets inside of claim sets inside of claims sets...

3.16.1.  Two Types of Submodules

   Each entry in the submod map is one of two types:

   o  A non-token submodule that is a map or object directly containing
      claims for the submodule.

   o  A nested EAT that is a fully formed, independently signed EAT
      token  Non-token Submodules

   This is simply a map or object containing claims about the submodule.

   It may contain claims that are the same as its surrounding token or
   superior submodules.  For example, the top-level of the token may
   have a UEID, a submod may have a different UEID and a further
   subordinate submodule may also have a UEID.

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   It is signed/encrypted along with the rest of the token and thus the
   claims are secured by the same Attester with the same signing key as
   the rest of the token.

   If a token is in CBOR format (a CWT or a UCCS), all non-token
   submodules must be CBOR format.  If a token in in JSON format (a
   JWT), all non-token submodules must be in JSON format.

   When decoding, this type of submodule is recognized from the other
   type by being a data item of type map for CBOR or type object for
   JSON.  Nested EATs

   This type of submodule is a fully formed secured EAT as defined in
   this document except that it MUST NOT be a UCCS or an unsecured JWT.
   A nested token that is one that is always secured using COSE or JOSE,
   usually by an independent Attester.  When the surrounding EAT is a
   CWT or secured JWT, the nested token becomes securely bound with the
   other claims in the surrounding token.

   It is allowed to have a CWT as a submodule in a JWT and vice versa,
   but this SHOULD be avoided unless necessary.  Surrounding EAT is CBOR format

   They type of an EAT nested in a CWT is determined by whether the CBOR
   type is a text string or a byte string.  If a text string, then it is
   a JWT.  If a byte string, then it is a CWT.

   A CWT nested in a CBOR-format token is always wrapped by a byte
   string for easier handling with standard CBOR decoders and token
   processing APIs that will typically take a byte buffer as input.

   Nested CWTs may be either a CWT CBOR tag or a CWT Protocol Message.
   COSE layers in nested CWT EATs MUST be a COSE_Tagged_Message, never a
   COSE_Untagged_Message.  If a nested EAT has more than one level of
   COSE, for example one that is both encrypted and signed, a
   COSE_Tagged_message must be used at every level.  Surrounding EAT is JSON format

   When a CWT is nested in a JWT, it must be as a 55799 tag in order to
   distinguish it from a nested JWT.

   When a nested EAT in a JWT is decoded, first remove the base64url
   encoding.  Next, check to see if it starts with the bytes 0xd9d9f7.

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   If so, then it is a CWT as a JWT will never start with these four
   bytes.  If not if it is a JWT.

   Other than the 55799 tag requirement, tag usage for CWT's nested in a
   JSON format token follow the same rules as for CWTs nested in CBOR-
   format tokens.  It may be a CWT CBOR tag or a CWT Protocol Message
   and COSE_Tagged_Message MUST be used at all COSE layers.  Unsecured JWTs and UCCS Tokens as Submodules

   To incorporate a UCCS token as a submodule, it MUST be as a non-token
   submodule.  This can be accomplished inserting the content of the
   UCCS Tag into the submodule map.  The content of a UCCS tag is
   exactly a map of claims as required for a non-token submodule.  If
   the UCCS is not a UCCS tag, then it can just be inserted into the
   submodule map directly.

   The definition of a nested EAT type of submodule is that it is one
   that is secured (signed) by an Attester.  Since UCCS tokens are
   unsecured, they do not fulfill this definition and must be non-token

   To incorporate an Unsecured JWT as a submodule, the null-security
   JOSE wrapping should be removed.  The resulting claims set should be
   inserted as a non-token submodule.

   To incorporate a UCCS token in a surrounding JSON token, the UCCS
   token claims should be translated from CBOR to JSON.  To incorporate
   an Unsecured JWT into a surrounding CBOR-format token, the null-
   security JOSE should be removed and the claims translated from JSON
   to CBOR.

3.16.2.  No Inheritance

   The subordinate modules do not inherit anything from the containing
   token.  The subordinate modules must explicitly include all of their
   claims.  This is the case even for claims like the nonce and age.

   This rule is in place for simplicity.  It avoids complex inheritance
   rules that might vary from one type of claim to another.

3.16.3.  Security Levels

   The security level of the non-token subordinate modules should always
   be less than or equal to that of the containing modules in the case
   of non-token submodules.  It makes no sense for a module of lesser
   security to be signing claims of a module of higher security.  An

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   example of this is a TEE signing claims made by the non-TEE parts
   (e.g. the high-level OS) of the device.

   The opposite may be true for the nested tokens.  They usually have
   their own more secure key material.  An example of this is an
   embedded secure element.

3.16.4.  Submodule Names

   The label or name for each submodule in the submods map is a text
   string naming the submodule.  No submodules may have the same name.

3.16.5.  submods CDDL

   {::include cddl/submods.cddl}

4.  Endorsements and Verification Keys

   TODO: fill this section in.  It will discuss key IDs, endorsement ID
   and such that are needed as input needed to by the Verifier to verify
   the signature.  This will NOT discuss the contents of an Endorsement,
   just and ID/locator.

5.  Encoding

   This makes use of the types defined in CDDL Appendix D, Standard

   Some of the CDDL included here is for claims that are defined in CWT
   [RFC8392] or JWT [RFC7519] or are in the IANA CWT or JWT registries.
   CDDL was not in use when these claims where defined.

5.1.  Common CDDL Types

   time-int is identical to the epoch-based time, but disallows
   floating-point representation.

   {::include cddl/common-types.cddl}

5.2.  CDDL for CWT-defined Claims

   This section provides CDDL for the claims defined in CWT.  It is non-
   normative as [RFC8392] is the authoritative definition of these

   {::include cddl/cwt.cddl}

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5.3.  JSON

5.3.1.  JSON Labels

   {::include cddl/json.cddl}

5.3.2.  JSON Interoperability

   JSON should be encoded per RFC 8610 Appendix E.  In addition, the
   following CDDL types are encoded in JSON as follows:

   o  bstr - must be base64url encoded

   o  time - must be encoded as NumericDate as described section 2 of

   o  string-or-uri - must be encoded as StringOrURI as described
      section 2 of [RFC7519].

5.4.  CBOR

5.4.1.  CBOR Interoperability

   Variations in the CBOR serializations supported in CBOR encoding and
   decoding are allowed and suggests that CBOR-based protocols specify
   how this variation is handled.  This section specifies what formats
   MUST be supported in order to achieve interoperability.

   The assumption is that the entity is likely to be a constrained
   device and relying party is likely to be a very capable server.  The
   approach taken is that the entity generating the token can use
   whatever encoding it wants, specifically encodings that are easier to
   implement such as indefinite lengths.  The relying party receiving
   the token must support decoding all encodings.

   These rules cover all types used in the claims in this document.
   They also are recommendations for additional claims.

   Canonical CBOR encoding, Preferred Serialization and
   Deterministically Encoded CBOR are explicitly NOT required as they
   would place an unnecessary burden on the entity implementation,
   particularly if the entity implementation is implemented in hardware.

   o  Integer Encoding (major type 0, 1) - The entity may use any
      integer encoding allowed by CBOR.  The server MUST accept all
      integer encodings allowed by CBOR.

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   o  String Encoding (major type 2 and 3) - The entity can use any
      string encoding allowed by CBOR including indefinite lengths.  It
      may also encode the lengths of strings in any way allowed by CBOR.
      The server must accept all string encodings.

   o  Major type 2, bstr, SHOULD have tag 21 to indicate conversion to
      base64url in case that conversion is performed.

   o  Map and Array Encoding (major type 4 and 5) - The entity can use
      any array or map encoding allowed by CBOR including indefinite
      lengths.  Sorting of map keys is not required.  Duplicate map keys
      are not allowed.  The server must accept all array and map
      encodings.  The server may reject maps with duplicate map keys.

   o  Date and Time - The entity should send dates as tag 1 encoded as
      64-bit or 32-bit integers.  The entity may not send floating-point
      dates.  The server must support tag 1 epoch-based dates encoded as
      64-bit or 32-bit integers.  The entity may send tag 0 dates,
      however tag 1 is preferred.  The server must support tag 0 UTC

   o  URIs - URIs should be encoded as text strings and marked with tag

   o  Floating Point - The entity may use any floating-point encoding.
      The relying party must support decoding of all types of floating-

   o  Other types - Other types like bignums, regular expressions and
      such, SHOULD NOT be used.  The server MAY support them but is not
      required to so interoperability is not guaranteed.

5.5.  Collected CDDL

   {::include cddl/eat-token.cddl}

6.  IANA Considerations

6.1.  Reuse of CBOR Web Token (CWT) Claims Registry

   Claims defined for EAT are compatible with those of CWT so the CWT
   Claims Registry is re used.  No new IANA registry is created.  All
   EAT claims should be registered in the CWT and JWT Claims Registries.

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6.2.  Claim Characteristics

   The following is design guidance for creating new EAT claims,
   particularly those to be registered with IANA.

   Much of this guidance is generic and could also be considered when
   designing new CWT or JWT claims.

6.2.1.  Interoperability and Relying Party Orientation

   It is a broad goal that EATs can be processed by relying parties in a
   general way regardless of the type, manufacturer or technology of the
   device from which they originate.  It is a goal that there be
   general-purpose verification implementations that can verify tokens
   for large numbers of use cases with special cases and configurations
   for different device types.  This is a goal of interoperability of
   the semantics of claims themselves, not just of the signing, encoding
   and serialization formats.

   This is a lofty goal and difficult to achieve broadly requiring
   careful definition of claims in a technology neutral way.  Sometimes
   it will be difficult to design a claim that can represent the
   semantics of data from very different device types.  However, the
   goal remains even when difficult.

6.2.2.  Operating System and Technology Neutral

   Claims should be defined such that they are not specific to an
   operating system.  They should be applicable to multiple large high-
   level operating systems from different vendors.  They should also be
   applicable to multiple small embedded operating systems from multiple
   vendors and everything in between.

   Claims should not be defined such that they are specific to a SW
   environment or programming language.

   Claims should not be defined such that they are specific to a chip or
   particular hardware.  For example, they should not just be the
   contents of some HW status register as it is unlikely that the same
   HW status register with the same bits exists on a chip of a different

   The boot and debug state claims in this document are an example of a
   claim that has been defined in this neutral way.

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6.2.3.  Security Level Neutral

   Many use cases will have EATs generated by some of the most secure
   hardware and software that exists.  Secure Elements and smart cards
   are examples of this.  However, EAT is intended for use in low-
   security use cases the same as high-security use case.  For example,
   an app on a mobile device may generate EATs on its own.

   Claims should be defined and registered on the basis of whether they
   are useful and interoperable, not based on security level.  In
   particular, there should be no exclusion of claims because they are
   just used only in low-security environments.

6.2.4.  Reuse of Extant Data Formats

   Where possible, claims should use already standardized data items,
   identifiers and formats.  This takes advantage of the expertise put
   into creating those formats and improves interoperability.

   Often extant claims will not be defined in an encoding or
   serialization format used by EAT.  It is preferred to define a CBOR
   and JSON format for them so that EAT implementations do not require a
   plethora of encoders and decoders for serialization formats.

   In some cases, it may be better to use the encoding and serialization
   as is.  For example, signed X.509 certificates and CRLs can be
   carried as-is in a byte string.  This retains interoperability with
   the extensive infrastructure for creating and processing X.509
   certificates and CRLs.

6.2.5.  Proprietary Claims

   EAT allows the definition and use of proprietary claims.

   For example, a device manufacturer may generate a token with
   proprietary claims intended only for verification by a service
   offered by that device manufacturer.  This is a supported use case.

   In many cases proprietary claims will be the easiest and most obvious
   way to proceed, however for better interoperability, use of general
   standardized claims is preferred.

6.3.  Claims Registered by This Document

   o  Claim Name: UEID

   o  Claim Description: The Universal Entity ID

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   o  JWT Claim Name: N/A

   o  Claim Key: 8

   o  Claim Value Type(s): byte string

   o  Change Controller: IESG

   o  Specification Document(s): *this document*

   TODO: add the rest of the claims in here

7.  Privacy Considerations

   Certain EAT claims can be used to track the owner of an entity and
   therefore, implementations should consider providing privacy-
   preserving options dependent on the intended usage of the EAT.
   Examples would include suppression of location claims for EAT's
   provided to unauthenticated consumers.

7.1.  UEID Privacy Considerations

   A UEID is usually not privacy-preserving.  Any set of relying parties
   that receives tokens that happen to be from a single device will be
   able to know the tokens are all from the same device and be able to
   track the device.  Thus, in many usage situations ueid violates
   governmental privacy regulation.  In other usage situations UEID will
   not be allowed for certain products like browsers that give privacy
   for the end user.  It will often be the case that tokens will not
   have a UEID for these reasons.

   There are several strategies that can be used to still be able to put
   UEID's in tokens:

   o  The device obtains explicit permission from the user of the device
      to use the UEID.  This may be through a prompt.  It may also be
      through a license agreement.  For example, agreements for some
      online banking and brokerage services might already cover use of a

   o  The UEID is used only in a particular context or particular use
      case.  It is used only by one relying party.

   o  The device authenticates the relying party and generates a derived
      UEID just for that particular relying party.  For example, the
      relying party could prove their identity cryptographically to the
      device, then the device generates a UEID just for that relying

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      party by hashing a proofed relying party ID with the main device

   Note that some of these privacy preservation strategies result in
   multiple UEIDs per device.  Each UEID is used in a different context,
   use case or system on the device.  However, from the view of the
   relying party, there is just one UEID and it is still globally
   universal across manufacturers.

7.2.  Location Privacy Considerations

   Geographic location is most always considered personally identifiable
   information.  Implementers should consider laws and regulations
   governing the transmission of location data from end user devices to
   servers and services.  Implementers should consider using location
   management facilities offered by the operating system on the device
   generating the attestation.  For example, many mobile phones prompt
   the user for permission when before sending location data.

8.  Security Considerations

   The security considerations provided in Section 8 of [RFC8392] and
   Section 11 of [RFC7519] apply to EAT in its CWT and JWT form,
   respectively.  In addition, implementors should consider the

8.1.  Key Provisioning

   Private key material can be used to sign and/or encrypt the EAT, or
   can be used to derive the keys used for signing and/or encryption.
   In some instances, the manufacturer of the entity may create the key
   material separately and provision the key material in the entity
   itself.  The manfuacturer of any entity that is capable of producing
   an EAT should take care to ensure that any private key material be
   suitably protected prior to provisioning the key material in the
   entity itself.  This can require creation of key material in an
   enclave (see [RFC4949] for definition of "enclave"), secure
   transmission of the key material from the enclave to the entity using
   an appropriate protocol, and persistence of the private key material
   in some form of secure storage to which (preferably) only the entity
   has access.

8.1.1.  Transmission of Key Material

   Regarding transmission of key material from the enclave to the
   entity, the key material may pass through one or more intermediaries.
   Therefore some form of protection ("key wrapping") may be necessary.
   The transmission itself may be performed electronically, but can also

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   be done by human courier.  In the latter case, there should be
   minimal to no exposure of the key material to the human (e.g.
   encrypted portable memory).  Moreover, the human should transport the
   key material directly from the secure enclave where it was created to
   a destination secure enclave where it can be provisioned.

8.2.  Transport Security

   As stated in Section 8 of [RFC8392], "The security of the CWT relies
   upon on the protections offered by COSE".  Similar considerations
   apply to EAT when sent as a CWT.  However, EAT introduces the concept
   of a nonce to protect against replay.  Since an EAT may be created by
   an entity that may not support the same type of transport security as
   the consumer of the EAT, intermediaries may be required to bridge
   communications between the entity and consumer.  As a result, it is
   RECOMMENDED that both the consumer create a nonce, and the entity
   leverage the nonce along with COSE mechanisms for encryption and/or
   signing to create the EAT.

   Similar considerations apply to the use of EAT as a JWT.  Although
   the security of a JWT leverages the JSON Web Encryption (JWE) and
   JSON Web Signature (JWS) specifications, it is still recommended to
   make use of the EAT nonce.

8.3.  Multiple EAT Consumers

   In many cases, more than one EAT consumer may be required to fully
   verify the entity attestation.  Examples include individual consumers
   for nested EATs, or consumers for individual claims with an EAT.
   When multiple consumers are required for verification of an EAT, it
   is important to minimize information exposure to each consumer.  In
   addition, the communication between multiple consumers should be

   For instance, consider the example of an encrypted and signed EAT
   with multiple claims.  A consumer may receive the EAT (denoted as the
   "receiving consumer"), decrypt its payload, verify its signature, but
   then pass specific subsets of claims to other consumers for
   evaluation ("downstream consumers").  Since any COSE encryption will
   be removed by the receiving consumer, the communication of claim
   subsets to any downstream consumer should leverage a secure protocol
   (e.g.one that uses transport-layer security, i.e. TLS),

   However, assume the EAT of the previous example is hierarchical and
   each claim subset for a downstream consumer is created in the form of
   a nested EAT.  Then transport security between the receiving and
   downstream consumers is not strictly required.  Nevertheless,

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   downstream consumers of a nested EAT should provide a nonce unique to
   the EAT they are consuming.

9.  References

9.1.  Normative References

   [CoSWID]   "Concise Software Identification Tags", November 2020,

   [EAN-13]   GS1, "International Article Number - EAN/UPC barcodes",
              2019, <https://www.gs1.org/standards/barcodes/ean-upc>.

              The FIDO Alliance, "FIDO Authenticator Allowed Restricted
              Operating Environments List", November 2019,

              IANA, "CBOR Web Token (CWT) Claims",

              IANA, "JSON Web Token (JWT) Claims",

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC7049]  Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
              October 2013, <https://www.rfc-editor.org/info/rfc7049>.

   [RFC7517]  Jones, M., "JSON Web Key (JWK)", RFC 7517,
              DOI 10.17487/RFC7517, May 2015,

   [RFC7519]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
              (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,

   [RFC7800]  Jones, M., Bradley, J., and H. Tschofenig, "Proof-of-
              Possession Key Semantics for JSON Web Tokens (JWTs)",
              RFC 7800, DOI 10.17487/RFC7800, April 2016,

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   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,

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

   [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>.

   [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>.

   [RFC8610]  Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
              Definition Language (CDDL): A Notational Convention to
              Express Concise Binary Object Representation (CBOR) and
              JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
              June 2019, <https://www.rfc-editor.org/info/rfc8610>.

   [RFC8747]  Jones, M., Seitz, L., Selander, G., Erdtman, S., and H.
              Tschofenig, "Proof-of-Possession Key Semantics for CBOR
              Web Tokens (CWTs)", RFC 8747, DOI 10.17487/RFC8747, March
              2020, <https://www.rfc-editor.org/info/rfc8747>.

              3GPP, "3rd Generation Partnership Project; Technical
              Specification Group Core Network and Terminals; Numbering,
              addressing and identification", 2019,

   [TIME_T]   The Open Group Base Specifications, "Vol. 1: Base
              Definitions, Issue 7", Section 4.15 'Seconds Since the
              Epoch', IEEE Std 1003.1, 2013 Edition, 2013,

              Birkholz, H., "A CBOR Tag for Unprotected CWT Claims
              Sets", 2020,

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   [WGS84]    National Imagery and Mapping Agency, "National Imagery and
              Mapping Agency Technical Report 8350.2, Third Edition",
              2000, <http://earth-

9.2.  Informative References

   [ASN.1]    International Telecommunication Union, "Information
              Technology -- ASN.1 encoding rules: Specification of Basic
              Encoding Rules (BER), Canonical Encoding Rules (CER) and
              Distinguished Encoding Rules (DER)", ITU-T Recommendation
              X.690, 1994.

              "Birthday attack",

              "Common Criteria for Information Technology Security
              Evaluation", April 2017,

              "Ecma International, "ECMAScript Language Specification,
              5.1 Edition", ECMA Standard 262", June 2011,

              The FIDO Alliance, "FIDO Registry of Predefined Values",
              December 2019, <https://fidoalliance.org/specs/common-

              National Institue of Standards, "Security Requirements for
              Cryptographic Modules", May 2001,

   [IDevID]   "IEEE Standard, "IEEE 802.1AR Secure Device Identifier"",
              December 2009, <http://standards.ieee.org/findstds/

              "IEEE Standard For Local And Metropolitan Area Networks
              Overview And Architecture", 2007,

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   [IEEE.RA]  "IEEE Registration Authority",

              "Guidelines for Use of Extended Unique Identifier (EUI),
              Organizationally Unique Identifier (OUI), and Company ID
              (CID)", August 2017,

              "IEEE Registration Authority Assignments",

   [RFC4122]  Leach, P., Mealling, M., and R. Salz, "A Universally
              Unique IDentifier (UUID) URN Namespace", RFC 4122,
              DOI 10.17487/RFC4122, July 2005,

   [RFC4949]  Shirey, R., "Internet Security Glossary, Version 2",
              FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,

              Worldwide Web Consortium, "Geolocation API Specification
              2nd Edition", January 2018, <https://www.w3.org/TR/

              Worldwide Web Consortium, "Web Authentication: A Web API
              for accessing scoped credentials", 2016.

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Appendix A.  Examples

A.1.  Very Simple EAT

   This is shown in CBOR diagnostic form.  Only the payload signed by
   COSE is shown.

   {::include cddl/examples/simple.diag}

A.2.  Example with Submodules, Nesting and Security Levels

   {::include cddl/examples/submods.diag}

Appendix B.  UEID Design Rationale

B.1.  Collision Probability

   This calculation is to determine the probability of a collision of
   UEIDs given the total possible entity population and the number of
   entities in a particular entity management database.

   Three different sized databases are considered.  The number of
   devices per person roughly models non-personal devices such as
   traffic lights, devices in stores they shop in, facilities they work
   in and so on, even considering individual light bulbs.  A device may
   have individually attested subsystems, for example parts of a car or
   a mobile phone.  It is assumed that the largest database will have at
   most 10% of the world's population of devices.  Note that databases
   that handle more than a trillion records exist today.

   The trillion-record database size models an easy-to-imagine reality
   over the next decades.  The quadrillion-record database is roughly at
   the limit of what is imaginable and should probably be accommodated.
   The 100 quadrillion datadbase is highly speculative perhaps involving
   nanorobots for every person, livestock animal and domesticated bird.
   It is included to round out the analysis.

   Note that the items counted here certainly do not have IP address and
   are not individually connected to the network.  They may be connected
   to internal buses, via serial links, Bluetooth and so on.  This is
   not the same problem as sizing IP addresses.

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   | People  | Devices /  | Subsystems / | Database   | Database Size  |
   |         | Person     | Device       | Portion    |                |
   | 10      | 100        | 10           | 10%        | trillion       |
   | billion |            |              |            | (10^12)        |
   | 10      | 100,000    | 10           | 10%        | quadrillion    |
   | billion |            |              |            | (10^15)        |
   | 100     | 1,000,000  | 10           | 10%        | 100            |
   | billion |            |              |            | quadrillion    |
   |         |            |              |            | (10^17)        |

   This is conceptually similar to the Birthday Problem where m is the
   number of possible birthdays, always 365, and k is the number of
   people.  It is also conceptually similar to the Birthday Attack where
   collisions of the output of hash functions are considered.

   The proper formula for the collision calculation is

      p = 1 - e^{-k^2/(2n)}

      p   Collision Probability
      n   Total possible population
      k   Actual population

   However, for the very large values involved here, this formula
   requires floating point precision higher than commonly available in
   calculators and SW so this simple approximation is used.  See

       p = k^2 / 2n

   For this calculation:

       p  Collision Probability
       n  Total population based on number of bits in UEID
       k  Population in a database

   | Database Size        | 128-bit UEID | 192-bit UEID | 256-bit UEID |
   | trillion (10^12)     | 2 * 10^-15   | 8 * 10^-35   | 5 * 10^-55   |
   | quadrillion (10^15)  | 2 * 10^-09   | 8 * 10^-29   | 5 * 10^-49   |
   | 100 quadrillion      | 2 * 10^-05   | 8 * 10^-25   | 5 * 10^-45   |
   | (10^17)              |              |              |              |

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   Next, to calculate the probability of a collision occurring in one
   year's operation of a database, it is assumed that the database size
   is in a steady state and that 10% of the database changes per year.
   For example, a trillion record database would have 100 billion states
   per year.  Each of those states has the above calculated probability
   of a collision.

   This assumption is a worst-case since it assumes that each state of
   the database is completely independent from the previous state.  In
   reality this is unlikely as state changes will be the addition or
   deletion of a few records.

   The following tables gives the time interval until there is a
   probability of a collision based on there being one tenth the number
   of states per year as the number of records in the database.

     t = 1 / ((k / 10) * p)

     t  Time until a collision
     p  Collision probability for UEID size
     k  Database size

   | Database Size       | 128-bit UEID  | 192-bit UEID | 256-bit UEID |
   | trillion (10^12)    | 60,000 years  | 10^24 years  | 10^44 years  |
   | quadrillion (10^15) | 8 seconds     | 10^14 years  | 10^34 years  |
   | 100 quadrillion     | 8             | 10^11 years  | 10^31 years  |
   | (10^17)             | microseconds  |              |              |

   Clearly, 128 bits is enough for the near future thus the requirement
   that UEIDs be a minimum of 128 bits.

   There is no requirement for 256 bits today as quadrillion-record
   databases are not expected in the near future and because this time-
   to-collision calculation is a very worst case.  A future update of
   the standard may increase the requirement to 256 bits, so there is a
   requirement that implementations be able to receive 256-bit UEIDs.

B.2.  No Use of UUID

   A UEID is not a UUID [RFC4122] by conscious choice for the following

   UUIDs are limited to 128 bits which may not be enough for some future
   use cases.

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   Today, cryptographic-quality random numbers are available from common
   CPUs and hardware.  This hardware was introduced between 2010 and
   2015.  Operating systems and cryptographic libraries give access to
   this hardware.  Consequently, there is little need for
   implementations to construct such random values from multiple sources
   on their own.

   Version 4 UUIDs do allow for use of such cryptographic-quality random
   numbers, but do so by mapping into the overall UUID structure of time
   and clock values.  This structure is of no value here yet adds
   complexity.  It also slightly reduces the number of actual bits with

   UUIDs seem to have been designed for scenarios where the implementor
   does not have full control over the environment and uniqueness has to
   be constructed from identifiers at hand.  UEID takes the view that
   hardware, software and/or manufacturing process directly implement
   UEID in a simple and direct way.  It takes the view that
   cryptographic quality random number generators are readily available
   as they are implemented in commonly used CPU hardware.

Appendix C.  Changes from Previous Drafts

   The following is a list of known changes from the previous drafts.
   This list is non-authoritative.  It is meant to help reviewers see
   the significant differences.

C.1.  From draft-rats-eat-01

   o  Added UEID design rationale appendix

C.2.  From draft-mandyam-rats-eat-00

   This is a fairly large change in the orientation of the document, but
   no new claims have been added.

   o  Separate information and data model using CDDL.

   o  Say an EAT is a CWT or JWT

   o  Use a map to structure the boot_state and location claims

C.3.  From draft-ietf-rats-eat-01

   o  Clarifications and corrections for OEMID claim

   o  Minor spelling and other fixes

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   o  Add the nonce claim, clarify jti claim

C.4.  From draft-ietf-rats-eat-02

   o  Roll all EUIs back into one UEID type

   o  UEIDs can be one of three lengths, 128, 192 and 256.

   o  Added appendix justifying UEID design and size.

   o  Submods part now includes nested eat tokens so they can be named
      and there can be more tha one of them

   o  Lots of fixes to the CDDL

   o  Added security considerations

C.5.  From draft-ietf-rats-eat-03

   o  Split boot_state into secure-boot and debug-disable claims

   o  Debug disable is an enumerated type rather than Booleans

C.6.  From draft-ietf-rats-eat-04

   o  Change IMEI-based UEIDs to be encoded as a 14-byte string

   o  CDDL cleaned up some more

   o  CDDL allows for JWTs and UCCSs

   o  CWT format submodules are byte string wrapped

   o  Allows for JWT nested in CWT and vice versa

   o  Allows UCCS (unsigned CWTs) and JWT unsecured tokens

   o  Clarify tag usage when nesting tokens

   o  Add section on key inclusion

   o  Add hardware version claims

   o  Collected CDDL is now filled in.  Other CDDL corrections.

   o  Rename debug-disable to debug-status; clarify that it is not

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   o  Security level claim is not extensible

   o  Improve specification of location claim and added a location
      privacy section

   o  Add intended use claim

Authors' Addresses

   Giridhar Mandyam
   Qualcomm Technologies Inc.
   5775 Morehouse Drive
   San Diego, California

   Phone: +1 858 651 7200
   EMail: mandyam@qti.qualcomm.com

   Laurence Lundblade
   Security Theory LLC

   EMail: lgl@island-resort.com

   Miguel Ballesteros
   Qualcomm Technologies Inc.
   5775 Morehouse Drive
   San Diego, California

   Phone: +1 858 651 4299
   EMail: mballest@qti.qualcomm.com

   Jeremy O'Donoghue
   Qualcomm Technologies Inc.
   279 Farnborough Road
   Farnborough  GU14 7LS
   United Kingdom

   Phone: +44 1252 363189
   EMail: jodonogh@qti.qualcomm.com

Mandyam, et al.           Expires June 4, 2021                 [Page 41]

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