RATS Working Group                                           H. Birkholz
Internet-Draft                                                  M. Eckel
Intended status: Standards Track                          Fraunhofer SIT
Expires: 5 December 2021 27 January 2022                                     S. Bhandari
                                                             ThoughtSpot
                                                                 E. Voit
                                                               B. Sulzen
                                                                   Cisco
                                                                  L. Xia
                                                                  Huawei
                                                               T. Laffey
                                                                     HPE
                                                             G. Fedorkow
                                                                 Juniper
                                                             3 June
                                                            26 July 2021

   A YANG Data Model for Challenge-Response-based Remote Attestation
                         Procedures using TPMs
                   draft-ietf-rats-yang-tpm-charra-08
                   draft-ietf-rats-yang-tpm-charra-09

Abstract

   This document defines YANG RPCs and a small number of configuration
   nodes required to retrieve attestation evidence about integrity
   measurements from a device, following the operational context defined
   in TPM-based Network Device Remote Integrity Verification.
   Complementary measurement logs are also provided by the YANG RPCs,
   originating from one or more roots of trust for measurement (RTMs).
   The module defined requires at least one TPM 1.2 or TPM 2.0 as well
   as a corresponding TPM Software Stack (TSS), included in the device
   components of the composite device the YANG server is running on.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

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   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 5 December 2021. 27 January 2022.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
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   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements notation . . . . . . . . . . . . . . . . . .   3
   2.  The YANG Module for Basic Remote Attestation Procedures . . .   3
     2.1.  YANG Modules  . . . . . . . . . . . . . . . . . . . . . .   3
       2.1.1.  'ietf-tpm-remote-attestation' . . . . . . . . . . . .   3
       2.1.2.  'ietf-tcg-algs' . . . . . . . . . . . . . . . . . . .  32
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  47
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  47
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  48
   6.  Change Log  . . . . . . . . . . . . . . . . . . . . . . . . .  48
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  49
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  49
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  51
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  51

1.  Introduction

   This document is based on the general terminology defined in the
   [I-D.ietf-rats-architecture] and uses the operational context defined
   in [I-D.ietf-rats-tpm-based-network-device-attest] as well as the
   interaction model and information elements defined in
   [I-D.ietf-rats-reference-interaction-models].  The currently
   supported hardware security modules (HSMs) are the Trusted Platform
   Modules (TPMs) [TPM1.2] and [TPM2.0] as specified by the Trusted
   Computing Group (TCG).  One or more TPMs embedded in the components
   of a Composite Device are required in order to use the YANG module
   defined in this document.  A TPM is used as a root of trust for
   reporting (RTR) in order to retrieve attestation Evidence from a
   composite device (_TPM Quote_ primitive operation).  Additionally, it
   is used as a root of trust for storage (RTS) in order to retain
   shielded secrets and store system measurements using a folding hash
   function (_TPM PCR Extend_ primitive operation).

   Specific terms imported from [I-D.ietf-rats-architecture] and used in
   this document include: Attester, Composite Device, Evidence.

   Specific terms imported from [TPM2.0-Key] and used in this document
   include: Endorsement Key (EK), Initial Attestation Key (IAK), Local
   Attestation Key (LAK).

1.1.  Requirements notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  The YANG Module for Basic Remote Attestation Procedures

   One or more TPMs MUST be embedded in a Composite Device that provides
   attestation evidence via the YANG module defined in this document.
   The ietf-basic-remote-attestation YANG module enables a composite
   device to take on the role of an Attester, in accordance with the
   Remote Attestation Procedures (RATS) architecture
   [I-D.ietf-rats-architecture], and the corresponding challenge-
   response interaction model defined in the
   [I-D.ietf-rats-reference-interaction-models] document.  A fresh nonce
   with an appropriate amount of entropy MUST be supplied by the YANG
   client in order to enable a proof-of-freshness with respect to the
   attestation Evidence provided by the Attester running the YANG
   datastore.  Further, this nonce is used to prevent replay attacks.
   The functions of this YANG module are restricted to 0-1 TPMs per
   hardware component.

2.1.  YANG Modules

   In this section the several YANG modules are defined.

2.1.1.  'ietf-tpm-remote-attestation'

   This YANG module imports modules from [RFC6991], [RFC8348],
   [I-D.ietf-netconf-keystore], and "ietf-tcg-algs.yang"
   Section 2.1.2.3.

2.1.1.1.  Features

   This module supports the following features:

   *  'TPMs': Indicates that multiple TPMs on the device can support
      remote attestation.  This feature is applicable in cases where
      multiple line cards are present, each with its own TPM.

   *  'bios': Indicates that the device supports the retrieval of BIOS/
      UEFI event logs.

   *  'ima': Indicates that the device supports the retrieval of event
      logs from the Linux Integrity Measurement Architecture (IMA).

   *  'netequip_boot': Indicates that the device supports the retrieval
      of netequip boot event logs.

2.1.1.2.  Identities

   This module supports the following types of attestation event logs:
   'bios', 'ima', and 'netequip_boot'.

2.1.1.3.  Remote Procedure Calls (RPCs)

   In the following, RPCs for both TPM 1.2 and TPM 2.0 attestation
   procedures are defined.

2.1.1.3.1.  'tpm12-challenge-response-attestation'

   This RPC allows a Verifier to request signed TPM PCRs (_TPM Quote_
   operation) from a TPM 1.2 compliant cryptoprocessor.  Where the
   feature 'TPMs' is active, and one or more 'certificate-name' is not
   provided, all TPM 1.2 compliant cryptoprocessors will respond.  A
   YANG tree diagram of this RPC is as follows:

   +---x tpm12-challenge-response-attestation {taa:TPM12}?
      +---w input
      |  +---w tpm12-attestation-challenge
      |     +---w pcr-index*          pcr
      |     +---w nonce-value         binary
      |     +---w certificate-name*   certificate-name-ref {tpm:TPMs}?
      +--ro output
         +--ro tpm12-attestation-response* []
            +--ro certificate-name    certificate-name-ref
            +--ro up-time?            uint32
            +--ro TPM_QUOTE2?         binary

2.1.1.3.2.  'tpm20-challenge-response-attestation'

   This RPC allows a Verifier to request signed TPM PCRs (_TPM Quote_
   operation) from a TPM 2.0 compliant cryptoprocessor.  Where the
   feature 'TPMs' is active, and one or more 'certificate-name' is not
   provided, all TPM 2.0 compliant cryptoprocessors will respond.  A
   YANG tree diagram of this RPC is as follows:

   +---x tpm20-challenge-response-attestation {taa:TPM20}?
      +---w input
      |  +---w tpm20-attestation-challenge
      |     +---w nonce-value            binary
      |     +---w tpm20-pcr-selection* []
      |     |  +---w TPM20-hash-algo?   identityref
      |     |  +---w pcr-index*         tpm:pcr
      |     +---w certificate-name*      certificate-name-ref {tpm:TPMs}?
      +--ro output
         +--ro tpm20-attestation-response* []
            +--ro certificate-name       certificate-name-ref
            +--ro TPMS_QUOTE_INFO        binary
            +--ro quote-signature?       binary
            +--ro up-time?               uint32
            +--ro unsigned-pcr-values* []
               +--ro TPM20-hash-algo?   identityref
               +--ro pcr-values* [pcr-index]
                  +--ro pcr-index    pcr
                  +--ro pcr-value?   binary

   An example of an RPC challenge requesting PCRs 0-7 from a SHA-256
   bank could look like the following:

<rpc message-id="101" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <tpm20-challenge-response-attestation>
      xmlns="urn:ietf:params:xml:ns:yang:ietf-tpm-remote-attestation">
    <certificate-name>
      (identifier of a TPM signature key with which the Verifier is supposed
      to sign the attestation data)
    </certificate-name>
    <nonce>
      0xe041307208d9f78f5b1bbecd19e2d152ad49de2fc5a7d8dbf769f6b8ffdeab9d
    </nonce>
    <tpm20-pcr-selection>
      <tpm20-hash-algo
          xmlns:taa="urn:ietf:params:xml:ns:yang:ietf-tcg-algs">
        taa:TPM_ALG_SHA256
      </tpm20-hash-algo>
      <pcr-index>0</pcr-index>
      <pcr-index>1</pcr-index>
      <pcr-index>2</pcr-index>
      <pcr-index>3</pcr-index>
      <pcr-index>4</pcr-index>
      <pcr-index>5</pcr-index>
      <pcr-index>6</pcr-index>
      <pcr-index>7</pcr-index>
    </tpm20-pcr-selection>
  </tpm20-challenge-response-attestation>
</rpc>

   A successful response could be formatted as follows:

   <rpc-reply message-id="101"
     xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <tpm20-attestation-response
       xmlns="urn:ietf:params:xml:ns:yang:ietf-tpm-remote-attestation">
       <certificate-name
           xmlns:ks=urn:ietf:params:xml:ns:yang:ietf-keystore>
          ks:(instance of Certificate name in the Keystore)
       </certificate-name>
       <attestation-data>
          (raw attestation data, i.e. the TPM quote; this includes
          a composite digest of requested PCRs, the nonce,
          and TPM 2.0 time information.)
       </attestation-data>
       <quote-signature>
           (signature over attestation-data using the TPM key
           identified by sig-key-id)
       </quote-signature>
     </tpm20-attestation-response>
   </rpc-reply>

2.1.1.4.  'log-retrieval'

   This RPC allows a Verifier to acquire the evidence which was extended
   into specific TPM PCRs.  A YANG tree diagram of this RPC is as
   follows:

       +---x log-retrieval
          +---w input
          |  +---w log-selector* []
          |  |  +---w name*                      string
          |  |  +---w (index-type)?
          |  |  |  +--:(last-entry)
          |  |  |  |  +---w last-entry-value?    binary
          |  |  |  +--:(index)
          |  |  |  |  +---w last-index-number?   uint64
          |  |  |  +--:(timestamp)
          |  |  |     +---w timestamp?           yang:date-and-time
          |  |  +---w log-entry-quantity?        uint16
          |  +---w log-type        identityref
          +--ro output
             +--ro system-event-logs
                +--ro node-data* []
                   +--ro name?         string
                   +--ro up-time?      uint32
                   +--ro log-result
                      +--ro (attested_event_log_type)
                         +--:(bios) {bios}?
                         |  +--ro bios-event-logs
                         |     +--ro bios-event-entry* [event-number]
                         |        +--ro event-number    uint32
                         |        +--ro event-type?     uint32
                         |        +--ro pcr-index?      pcr
                         |        +--ro digest-list* []
                         |        |  +--ro hash-algo?   identityref
                         |        |  +--ro digest*      binary
                         |        +--ro event-size?     uint32
                         |        +--ro event-data*     uint8
                         +--:(ima) {ima}?
                         |  +--ro ima-event-logs
                         |     +--ro ima-event-entry* [event-number]
                         |        +--ro event-number               uint64
                         |        +--ro ima-template?              string
                         |        +--ro filename-hint?             string
                         |        +--ro filedata-hash?             binary
                         |        +--ro filedata-hash-algorithm?   string
                         |        +--ro template-hash-algorithm?   string
                         |        +--ro template-hash?             binary
                         |        +--ro pcr-index?                 pcr
                         |        +--ro signature?                 binary
                         +--:(netequip_boot) {netequip_boot}?
                            +--ro boot-event-logs
                               +--ro boot-event-entry* [event-number]
                                  +--ro event-number               uint64
                                  +--ro ima-template?              string
                                  +--ro filename-hint?             string
                                  +--ro filedata-hash?             binary
                                  +--ro filedata-hash-algorithm?   string
                                  +--ro template-hash-algorithm?   string
                                  +--ro template-hash?             binary
                                  +--ro pcr-index?                 pcr
                                  +--ro signature?                 binary

2.1.1.5.  Data Nodes

   This section provides a high level description of the data nodes
   containing the configuration and operational objects with the YANG
   model.  For more details, please see the YANG model itself in
   Figure 1.

   Container 'rats-support-structures':  This houses the set of
      information relating to a device's TPM(s).

   Container 'tpms':  Provides configuration and operational details for
      each supported TPM, including the tpm-firmware-version, PCRs which
      may be quoted, certificates which are associated with that TPM,
      and the current operational status.  Of note are the certificates
      which are associated with that TPM.  As a certificate is
      associated with a particular TPM attestation key, knowledge of the
      certificate allows a specific TPM to be identified.

   +--rw tpms
      +--rw tpm* [name]
         +--rw name                string
         +--ro hardware-based?     boolean
         +--ro physical-index?     int32 {ietfhw:entity-mib}?
         +--ro path?               string
         +--ro compute-node        compute-node-ref {tpm:tpms}?
         +--ro manufacturer?       string
         +--rw firmware-version    identityref
         +--rw tpm12-hash-algo?    identityref
         +--rw tpm12-pcrs*         pcr
         +--rw tpm20-pcr-bank* [tpm20-hash-algo]
         |  +--rw tpm20-hash-algo    identityref
         |  +--rw pcr-index*         tpm:pcr
         +--ro status              enumeration
         +--rw certificates
            +--rw certificate* [name]
               +--rw name            string
               +--rw keystore-ref?   leafref
               +--rw type?           enumeration

   container 'attester-supported-algos' - Identifies which TCG hash
   algorithms are available for use on the Attesting platform.  This
   allows an operator to limit algorithms available for use by RPCs to
   just a desired set from the universe of all allowed hash algorithms
   by the TCG.

        +--rw attester-supported-algos
           +--rw tpm12-asymmetric-signing*   identityref
           +--rw tpm12-hash*                 identityref
           +--rw tpm20-asymmetric-signing*   identityref
           +--rw tpm20-hash*                 identityref

   container 'compute-nodes' - When there is more than one TPM
   supported, this container maintains the set of information related to
   the compute node associated with a specific TPM.  This allows each
   specific TPM to identify to which 'compute-node' it belongs.

   +--rw compute-nodes {tpm:TPMs}?
      +--ro compute-node* [node-id]
         +--ro node-id                string
         +--ro node-physical-index?   int32 {ietfhw:entity-mib}?
         +--ro node-name?             string
         +--ro node-location?         string

2.1.1.6.  YANG Module
   <CODE BEGINS> file "ietf-tpm-remote-attestation@2021-05-11.yang"
   module ietf-tpm-remote-attestation {
     namespace "urn:ietf:params:xml:ns:yang:ietf-tpm-remote-attestation";
     prefix tpm;

     import ietf-yang-types {
       prefix yang;
     }
     import ietf-hardware {
       prefix ietfhw;
     }
     import ietf-keystore {
       prefix ks;
     }
     import ietf-tcg-algs {
       prefix taa;
     }

     organization
       "IETF RATS (Remote ATtestation procedureS) Working Group";
     contact
       "WG Web  : <http://datatracker.ietf.org/wg/rats/>
        WG List : <mailto:rats@ietf.org>
        Author  : Eric Voit <evoit@cisco.com>
        Author  : Henk Birkholz <henk.birkholz@sit.fraunhofer.de>
        Author  : Michael Eckel <michael.eckel@sit.fraunhofer.de>
        Author  : Shwetha Bhandari <shwetha.bhandari@thoughtspot.com>
        Author  : Bill Sulzen <bsulzen@cisco.com>
        Author  : Liang Xia (Frank) <frank.xialiang@huawei.com>
        Author  : Tom Laffey <tom.laffey@hpe.com>
        Author  : Guy Fedorkow <gfedorkow@juniper.net>";
     description
       "A YANG module to enable a TPM 1.2 and TPM 2.0 based
        remote attestation procedure using a challenge-response
        interaction model and the TPM 1.2 and TPM 2.0 Quote
        primitive operations.
        Copyright (c) 2021 IETF Trust and the persons identified
        as authors of the code. All rights reserved.
        Redistribution and use in source and binary forms, with
        or without modification, is permitted pursuant to, and
        subject to the license terms contained in, the Simplified
        BSD License set forth in Section 4.c of the IETF Trust's
        Legal Provisions Relating to IETF Documents
        (https://trustee.ietf.org/license-info).
        This version of this YANG module is part of RFC XXXX
        (https://www.rfc-editor.org/info/rfcXXXX); see the RFC
        itself for full legal notices.

        The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
        'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',
        'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document
        are to be interpreted as described in BCP 14 (RFC 2119)
        (RFC 8174) when, and only when, they appear in all
        capitals, as shown here.";

     revision 2021-05-11 {
       description
         "Initial version";
       reference
         "draft-ietf-rats-yang-tpm-charra";
     }

     /*****************/
     /*   Features    */
     /*****************/

     feature tpms {
       description
         "The device supports the remote attestation of multiple
          TPM based cryptoprocessors.";
     }

     feature bios {
       description
         "The device supports the bios logs.";
       reference
         "https://trustedcomputinggroup.org/wp-content/uploads/
          PC-ClientSpecific_Platform_Profile_for_TPM_2p0_Systems_v51.pdf
          Section 9.4.5.2";
     }

     feature ima {
       description
         "The device supports Integrity Measurement Architecture logs.";
       reference
         "https://www.trustedcomputinggroup.org/wp-content/uploads/
          TCG_IWG_CEL_v1_r0p30_13feb2021.pdf  Section 4.3";
     }

     feature netequip_boot {
       description
         "The device supports the netequip_boot logs.";
     }

     /*****************/
     /*   Typedefs    */
     /*****************/

     typedef pcr {
       type uint8 {
         range "0..31";
       }
       description
         "Valid index number for a PCR.  At this point 0-31 is viable.";
     }

     typedef compute-node-ref {
       type leafref {
         path "/tpm:rats-support-structures/tpm:compute-nodes"
            + "/tpm:compute-node/tpm:node-name";
       }
       description
         "This type is used to reference a hardware node.  It is quite
          possible this leafref will eventually point to another YANG
          module's node.";
     }

     typedef certificate-name-ref {
       type leafref {
         path "/tpm:rats-support-structures/tpm:tpms/tpm:tpm"
            + "/tpm:certificates/tpm:certificate/tpm:name";
       }
       description
         "A type which allows identification of a TPM based certificate.";
     }

     /******************/
     /*   Identities   */
     /******************/

     identity attested_event_log_type {
       description
         "Base identity allowing categorization of the reasons why and
          attested measurement has been taken on an Attester.";
     }

     identity ima {
       base attested_event_log_type;
       description
         "An event type recorded in IMA.";
     }

     identity bios {
       base attested_event_log_type;
       description
         "An event type associated with BIOS/UEFI.";
     }

     identity netequip_boot {
       base attested_event_log_type;
       description
         "An event type associated with Network Equipment Boot.";
     }

     /*****************/
     /*   Groupings   */
     /*****************/

     grouping tpm20-hash-algo {
       description
         "The cryptographic algorithm used to hash the TPM2 PCRs.  This
          must be from the list of platform supported options.";
       leaf tpm20-hash-algo {
         type identityref {
           base taa:hash;
         }
         must '/tpm:rats-support-structures/tpm:attester-supported-algos'
            + '/tpm:tpm20-hash' {
           error-message "This platform does not support tpm20-hash-algo";
         }
         default "taa:TPM_ALG_SHA256";
         description
           "The hash scheme that is used to hash a TPM1.2 PCR. This
            must be one of those supported by a platform.";
       }
     }

     grouping tpm12-hash-algo {
       description
         "The cryptographic algorithm used to hash the TPM1.2 PCRs.";
       leaf tpm12-hash-algo {
         type identityref {
           base taa:hash;
         }
         must '/tpm:rats-support-structures/tpm:attester-supported-algos'
            + '/tpm:tpm12-hash' {
           error-message "This platform does not support tpm12-hash-algo";
         }
         default "taa:TPM_ALG_SHA1";
         description
           "The hash scheme that is used to hash a TPM1.2 PCR. This
            MUST be one of those supported by a platform.  This assumes
            that an algorithm other than SHA1 can be supported on some
            TPM1.2 cryptoprocessor variant.";
       }
     }

     grouping nonce {
       description
         "A random number intended to be used once to show freshness
          and to allow the detection of replay attacks.";
       leaf nonce-value {
         type binary;
         mandatory true;
         description
           "A cryptographically generated random number which should
            not be predictable prior to its issuance from a random
            number generation function. The random number MUST be
            derived from an entropy source external to the Attester.";
       }
     }

     grouping tpm12-pcr-selection {
       description
         "A Verifier can request one or more PCR values using its
          individually created Attestation Key Certificate (AC).
          The corresponding selection filter is represented in this
          grouping.
          Requesting a PCR value that is not in scope of the AC used,
          detailed exposure via error msg should be avoided.";
       leaf-list pcr-index {
         type pcr;
         must '/tpm:rats-support-structures/tpm:tpms'
            + '/tpm:tpm[name = current()] and '
            + '/tpm:rats-support-structures/tpm:tpms'
            + '/tpm:tpm[tpm12-pcrs = current()]' {
           error-message "Acquiring this PCR index is not supported";
         }
         description
           "The numbers/indexes of the PCRs. At the moment this is limited
            to 32.";
       }
     }

     grouping tpm20-pcr-selection {
       description
         "A Verifier can acquire one or more PCR values, which are hashed
          together in a TPM2B_DIGEST coming from the TPM2.  The selection
          list of desired PCRs and the Hash Algorithm is represented in
          this grouping.";

       list tpm20-pcr-selection {
         unique "tpm20-hash-algo";
         description
           "Specifies the list of PCRs and Hash Algorithms that can be
            returned within a TPM2B_DIGEST.";
         reference
           "https://www.trustedcomputinggroup.org/wp-content/uploads/
            TPM-Rev-2.0-Part-2-Structures-01.38.pdf  Section 10.9.7";
         uses tpm20-hash-algo;
         leaf-list pcr-index {
           type pcr;
           must '/tpm:rats-support-structures/tpm:tpms'
              + '/tpm:tpm[name = current()] and '
              + '/tpm:rats-support-structures/tpm:tpms/tpm:tpm'
              + '/tpm:tpm20-pcr-bank[pcr-index = current()]' {
             error-message "Acquiring this PCR index is not supported";
           }
           description
             "The numbers of the PCRs that which are being tracked
              with a hash based on the tpm20-hash-algo.";
         }
       }
     }

     grouping certificate-name-ref {
       description
         "Identifies a certificate in a keystore.";
       leaf certificate-name {
         type certificate-name-ref;
         mandatory true;
         description
           "Identifies a certificate in a keystore.";
       }
     }

     grouping tpm-name {
       description
         "A unique TPM on a device.";
       leaf name {
         type string;
         description
           "Unique system generated name for a TPM on a device.";
       }
     }

     grouping tpm-name-selector {
       description
         "One or more TPM on a device.";

       leaf-list name {
         type string;
         config false;
         description
           "Name of one or more unique TPMs on a device.  If this object
            exists, a selection should pull only the objects related to
            these TPM(s).  If it does not exist, all qualifying TPMs that
            are 'hardware-based' equals true on the device are selected.";
       }
     }

     grouping node-uptime {
       description
         "Uptime in seconds of the node.";
       leaf up-time {
         type uint32;
         description
           "Uptime in seconds of this node reporting its data";
       }
     }

     grouping tpm12-attestation {
       description
         "Contains an instance of TPM1.2 style signed cryptoprocessor
          measurements.  It is supplemented by unsigned Attester
          information.";
       uses node-uptime;
       leaf TPM_QUOTE2 {
         type binary;
         description
           "Result of a TPM1.2 Quote2 operation. This includes PCRs,
            signatures, locality, the provided nonce and other data which
            can be further parsed to appraise the Attester.";
         reference
           "TPM1.2 commands rev116 July 2007, Section 16.5";
       }
     }

     grouping tpm20-attestation {
       description
         "Contains an instance of TPM2 style signed cryptoprocessor
          measurements.  It is supplemented by unsigned Attester
          information.";
       leaf TPMS_QUOTE_INFO {
         type binary;
         mandatory true;
         description
           "A hash of the latest PCR values (and the hash algorithm used)
            which have been returned from a Verifier for the selected PCRs
            and Hash Algorithms.";
         reference
           "https://www.trustedcomputinggroup.org/wp-content/uploads/
            TPM-Rev-2.0-Part-2-Structures-01.38.pdf  Section 10.12.1";
       }
       leaf quote-signature {
         type binary;
         description
           "Quote signature returned by TPM Quote.  The signature was
            generated using the key associated with the
            certificate 'name'.";
         reference
           "https://www.trustedcomputinggroup.org/wp-content/uploads/
            TPM-Rev-2.0-Part-2-Structures-01.38.pdf  Section 11.2.1";
       }
       uses node-uptime;
       list unsigned-pcr-values {
         description
           "PCR values in each PCR bank. This might appear redundant with
            the TPM2B_DIGEST, but that digest is calculated across multiple
            PCRs.  Having to verify across multiple PCRs does not
            necessarily make it easy for a Verifier to appraise just the
            minimum set of PCR information which has changed since the last
            received TPM2B_DIGEST.  Put another way, why should a Verifier
            reconstruct the proper value of all PCR Quotes when only a
            single PCR has changed?
            To help this happen, if the Attester does know specific PCR
            values, the Attester can provide these individual values via
            'unsigned-pcr-values'.   By comparing this information to the
            what has previously been validated, it is possible for a
            Verifier to confirm the Attester's signature while eliminating
            significant processing.";
         uses tpm20-hash-algo;
         list pcr-values {
           key "pcr-index";
           description
             "List of one PCR bank.";
           leaf pcr-index {
             type pcr;
             description
               "PCR index number.";
           }
           leaf pcr-value {
             type binary;
             description
               "PCR value.";
             reference
               "https://www.trustedcomputinggroup.org/wp-content/uploads/
                TPM-Rev-2.0-Part-2-Structures-01.38.pdf  Section 10.9.7";
           }
         }
       }
     }

     grouping log-identifier {
       description
         "Identifier for type of log to be retrieved.";
       leaf log-type {
         type identityref {
           base attested_event_log_type;
         }
         mandatory true;
         description
           "The corresponding measurement log type identity.";
       }
     }
     grouping boot-event-log {
       description
         "Defines an event log corresponding to the event that extended
          the PCR";
       leaf event-number {
         type uint32;
         description
           "Unique event number of this event";
       }
       leaf event-type {
           type uint32;
           description
             "log event type";
       }
       leaf pcr-index {
         type pcr;
         description
           "Defines the PCR index that this event extended";
       }
       list digest-list {
         description
           "Hash of event data";
         leaf hash-algo {
           type identityref {
             base taa:hash;
           }
           description
             "The hash scheme that is used to compress the event data in
              each of the leaf-list digest items.";

         }
         leaf-list digest {
           type binary;
           description
             "The hash of the event data using the algorithm of the
              'hash-algo' against 'event data'.";
         }
       }
       leaf event-size {
         type uint32;
         description
           "Size of the event data";
       }
       leaf-list event-data {
         type uint8;
         description
           "The event data size determined by event-size";
       }
     }
     grouping bios-event-log {
       description
         "Measurement log created by the BIOS/UEFI.";
       list bios-event-entry {
         key event-number;
           description
             "Ordered list of TCG described event log
              that extended the PCRs in the order they
              were logged";
         uses boot-event-log;
       }
     }
     grouping ima-event {
       description
         "Defines an hash log extend event for IMA measurements";
       reference
         "https://www.trustedcomputinggroup.org/wp-content/uploads/
          TCG_IWG_CEL_v1_r0p30_13feb2021.pdf  Section 4.3";
       leaf event-number {
         type uint64;
         description
           "Unique number for this event for sequencing";
       }
       leaf ima-template {
         type string;
         description
           "Name of the template used for event logs
            for e.g. ima, ima-ng, ima-sig";
       }
       leaf filename-hint {
         type string;
         description
           "File that was measured";
       }
       leaf filedata-hash {
         type binary;
         description
           "Hash of filedata";
       }
       leaf filedata-hash-algorithm {
         type string;
         description
           "Algorithm used for filedata-hash";
       }
       leaf template-hash-algorithm {
         type string;
         description
           "Algorithm used for template-hash";
       }
       leaf template-hash {
         type binary;
         description
           "hash(filedata-hash, filename-hint)";
       }
       leaf pcr-index {
         type pcr;
         description
           "Defines the PCR index that this event extended";
       }
       leaf signature {
         type binary;
         description
           "The file signature";
       }
     }
     grouping ima-event-log {
       description
         "Measurement log created by IMA.";
       list ima-event-entry {
         key event-number;
         description
         "Ordered list of ima event logs by event-number";
          uses ima-event;
       }
     }

     grouping network-equipment-boot-event-log {
       description
         "Measurement log created by Network Equipment Boot. The Network
          Equipment Boot format is identical to the IMA format. In
          contrast to the IMA log, the Network Equipment Boot log
          includes every measurable event from an Attester, including
          the boot stages of BIOS, Bootloader, etc. In essence, the scope
          of events represented in this format combines the scope of BIOS
          events and IMA events.";
       list boot-event-entry {
         key event-number;
         description
           "Ordered list of Network Equipment Boot event logs
            by event-number, using the IMA event format.";
         uses ima-event;
       }
     }
     grouping event-logs {
       description
         "A selector for the log and its type.";
       choice attested_event_log_type {
         mandatory true;
         description
           "Event log type determines the event logs content.";
         case bios {
           if-feature "bios";
           description
             "BIOS/UEFI event logs";
           container bios-event-logs {
             description
               "BIOS/UEFI event logs";
             uses bios-event-log;
           }
         }
         case ima {
           if-feature "ima";
           description
             "IMA event logs.";
           container ima-event-logs {
             description
               "IMA event logs.";
             uses ima-event-log;
           }
         }
         case netequip_boot {
           if-feature "netequip_boot";
           description
             "Network Equipment Boot event logs";
           container boot-event-logs {
             description
               "Network equipment boot event logs.";
             uses network-equipment-boot-event-log;
           }
         }
       }
     }

     /**********************/
     /*   RPC operations   */
     /**********************/

     rpc tpm12-challenge-response-attestation {
       if-feature "taa:tpm12";
       description
         "This RPC accepts the input for TSS TPM 1.2 commands made to the
          attesting device.";
       input {
         container tpm12-attestation-challenge {
           description
             "This container includes every information element defined
              in the reference challenge-response interaction model for
              remote attestation. Corresponding values are based on
              TPM 1.2 structure definitions";
           uses tpm12-pcr-selection;
           uses nonce;
           leaf-list certificate-name {
             if-feature "tpm:tpms";
             type certificate-name-ref;
             must "/tpm:rats-support-structures/tpm:tpms"
                + "/tpm:tpm[tpm:firmware-version='taa:tpm12']"
                + "/tpm:certificates/"
                + "/tpm:certificate[name=current()]" {
               error-message "Not an available TPM1.2 AIK certificate.";
             }
             description
               "When populated, the RPC will only get a Quote for the
                TPMs associated with these certificate(s).";
           }
         }
       }
       output {
         list tpm12-attestation-response {
           unique "certificate-name";
           description
             "The binary output of TPM 1.2 TPM_Quote/TPM_Quote2, including
              the PCR selection and other associated attestation evidence
              metadata";

           uses certificate-name-ref {
             description
               "Certificate associated with this tpm12-attestation.";
           }
           uses tpm12-attestation;
         }
       }
     }

     rpc tpm20-challenge-response-attestation {
       if-feature "taa:tpm20";
       description
         "This RPC accepts the input for TSS TPM 2.0 commands of the
          managed device. ComponentIndex from the hardware manager YANG
          module to refer to dedicated TPM in composite devices,
          e.g. smart NICs, is still a TODO.";
       input {
         container tpm20-attestation-challenge {
           description
             "This container includes every information element defined
              in the reference challenge-response interaction model for
              remote attestation. Corresponding values are based on
              TPM 2.0 structure definitions";
           uses nonce;
           uses tpm20-pcr-selection;
           leaf-list certificate-name {
             if-feature "tpm:tpms";
             type certificate-name-ref;
             must "/tpm:rats-support-structures/tpm:tpms"
                + "/tpm:tpm[tpm:firmware-version='taa:tpm20']"
                + "/tpm:certificates/"
                + "/tpm:certificate[name=current()]" {
               error-message "Not an available TPM2.0 AIK certificate.";
             }
             description
               "When populated, the RPC will only get a Quote for the
                TPMs associated with the certificates.";
           }
         }
       }
       output {
         list tpm20-attestation-response {
           unique "certificate-name";
           description
             "The binary output of TPM2b_Quote in one TPM chip of the
              node which identified by node-id. An TPMS_ATTEST structure
              including a length, encapsulated in a signature";
           uses certificate-name-ref {
             description
               "Certificate associated with this tpm20-attestation.";
           }
           uses tpm20-attestation;
         }
       }
     }

     rpc log-retrieval {
       description
         "Logs Entries are either identified via indices or via providing
          the last line received. The number of lines returned can be
          limited. The type of log is a choice that can be augmented.";
       input {
         list log-selector {
           description
             "Selection of log entries to be reported.";
           uses tpm-name-selector;
           choice index-type {
             description
               "Last log entry received, log index number, or timestamp.";
             case last-entry {
               description
                 "The last entry of the log already retrieved.";
               leaf last-entry-value {
                 type binary;
                 description
                   "Content of an log event which matches 1:1 with a
                    unique event record contained within the log.  Log
                    entries subsequent to this will be passed to the
                    requester.  Note: if log entry values are not unique,
                    this MUST return an error.";
               }
             }
             case index {
               description
                 "Numeric index of the last log entry retrieved, or
                  zero.";
               leaf last-index-number {
                 type uint64;
                 description
                   "The last numeric index number of a log entry.
                    Zero means to start at the beginning of the log.
                    Entries subsequent to this will be passed to the
                    requester.";
               }
             }
             case timestamp {
               leaf timestamp {
                 type yang:date-and-time;
                 description
                   "Timestamp from which to start the extraction.  The
                    next log entry subsequent to this timestamp is to
                    be sent.";
               }
               description
                 "Timestamp from which to start the extraction.";
             }
           }
           leaf log-entry-quantity {
             type uint16;
             description
               "The number of log entries to be returned. If omitted, it
                means all of them.";
           }
         }
         uses log-identifier;
       }
       output {
         container system-event-logs {
           description
             "The requested data of the measurement event logs";
           list node-data {
             unique "name";
             description
               "Event logs of a node in a distributed system
                identified by the node name";
             uses tpm-name;
             uses node-uptime;
             container log-result {
               description
                 "The requested entries of the corresponding log.";
               uses event-logs;
             }
           }
         }
       }
     }

     /**************************************/
     /*   Config & Oper accessible nodes   */
     /**************************************/

     container rats-support-structures {
       description
         "The datastore definition enabling verifiers or relying
          parties to discover the information necessary to use the
          remote attestation RPCs appropriately.";
       container compute-nodes {
         if-feature "tpm:tpms";
         description
           "Holds the set device subsystems/components in this composite
            device that support TPM operations.";
         list compute-node {
           key "node-id";
           config false;
           min-elements 2;
           description
             "A component within this composite device which
              supports TPM operations.";
           leaf node-id {
             type string;
             description
               "ID of the compute node, such as Board Serial Number.";
           }
           leaf node-physical-index {
             if-feature "ietfhw:entity-mib";
             type int32 {
               range "1..2147483647";
             }
             config false;
             description
               "The entPhysicalIndex for the compute node.";
             reference
               "RFC 6933: Entity MIB (Version 4) - entPhysicalIndex";
           }
           leaf node-name {
             type string;
             description
               "Name of the compute node.";
           }
           leaf node-location {
             type string;
             description
               "Location of the compute node, such as slot number.";
           }
         }
       }
       container tpms {
         description
           "Holds the set of TPMs within an Attester.";
         list tpm {
           key "name";
           unique "path";
           description
             "A list of TPMs in this composite device that RATS
              can be conducted with.";
           uses tpm-name;
           leaf hardware-based {
             type boolean;
             config false;
             description
               "Answers the question: is this TPM is a hardware based
                TPM?";
           }
           leaf physical-index {
             if-feature "ietfhw:entity-mib";
             type int32 {
               range "1..2147483647";
             }
             config false;
             description
               "The entPhysicalIndex for the TPM.";
             reference
               "RFC 6933: Entity MIB (Version 4) - entPhysicalIndex";
           }
           leaf path {
             type string;
             config false;
             description
               "Path to a unique TPM on a device.  This can change across
                reboots.";
           }
           leaf compute-node {
             if-feature "tpm:tpms";
             type compute-node-ref;
             config false;
             mandatory true;
             description
               "Indicates the compute node measured by this TPM.";
           }
           leaf manufacturer {
             type string;
             config false;
             description
               "TPM manufacturer name.";
           }
           leaf firmware-version {
             type identityref {
               base taa:cryptoprocessor;
             }
             mandatory true;
             description
               "Identifies the cryptoprocessor API set supported.  This
                is automatically configured by the device and should not
                be changed.";
           }
           uses tpm12-hash-algo {
             when "firmware-version = 'taa:tpm12'";
             refine "tpm12-hash-algo" {
               description
                 "The hash algorithm overwrites the default used for PCRs
                  on this TPM1.2 compliant cryptoprocessor.";
             }
           }
           leaf-list tpm12-pcrs {
             when "../firmware-version = 'taa:tpm12'";
             type pcr;
             description
               "The PCRs which may be extracted from this TPM1.2
                compliant cryptoprocessor.";
           }
           list tpm20-pcr-bank {
             when "../firmware-version = 'taa:tpm20'";
             key "tpm20-hash-algo";
             description
               "Specifies the list of PCRs that may be extracted for
                a specific Hash Algorithm on this TPM2 compliant
                cryptoprocessor.  A bank is a set of PCRs which are
                extended using a particular hash algorithm.";
             reference
               "https://www.trustedcomputinggroup.org/wp-content/uploads/
                TPM-Rev-2.0-Part-2-Structures-01.38.pdf  Section 10.9.7";
             leaf tpm20-hash-algo {
               type identityref {
                 base taa:hash;
               }
               must '/tpm:rats-support-structures'
                  + '/tpm:attester-supported-algos'
                  + '/tpm:tpm20-hash' {
                 error-message
                    "This platform does not support tpm20-hash-algo";
               }
               description
                 "The hash scheme actively being used to hash a
                  one or more TPM2.0 PCRs.";
             }
             leaf-list pcr-index {
               type tpm:pcr;
               description
                 "Defines what TPM2 PCRs are available to be extracted.";
             }
           }
           leaf status {
             type enumeration {
               enum operational {
                 value 0;
                 description
                   "The TPM currently is currently running normally and
                    is ready to accept and process TPM quotes.";
                 reference
                   "TPM-Rev-2.0-Part-1-Architecture-01.07-2014-03-13.pdf
                    Section 12";
               }
               enum non-operational {
                 value 1;
                 description
                   "TPM is in a state such as startup or shutdown which
                    precludes the processing of TPM quotes.";
               }
             }
             config false;
             mandatory true;
             description
               "TPM chip self-test status.";
           }
           container certificates {
             description
               "The TPM's certificates, including EK certificates
                and AK certificates.";
             list certificate {
               key "name";
               description
                 "Three types of certificates can be accessed via
                  this statement, including Initial Attestation
                  Key Certificate, Local Attestation Key Certificate or
                  Endorsement Key Certificate.";
               leaf name {
                 type string;
                 description
                   "An arbitrary name uniquely identifying a certificate
                    associated within key within a TPM.";
               }
               leaf keystore-ref {
                 type leafref {
                   path "/ks:keystore/ks:asymmetric-keys/ks:asymmetric-key"
                      + "/ks:certificates/ks:certificate/ks:name";
                 }
                 description
                   "A reference to a specific certificate of an
                    asymmetric key in the Keystore.";
               }
               leaf type {
                 type enumeration {
                   enum endorsement-certificate {
                     value 0;
                     description
                       "Endorsement Key (EK) Certificate type.";
                     reference
                       "https://trustedcomputinggroup.org/wp-content/
                        uploads/TCG_IWG_DevID_v1r2_02dec2020.pdf
                        Section 3.11";
                   }
                   enum initial-attestation-certificate {
                     value 1;
                     description
                       "Initial Attestation key (IAK) Certificate type.";
                     reference
                       "https://trustedcomputinggroup.org/wp-content/
                        uploads/TCG_IWG_DevID_v1r2_02dec2020.pdf
                        Section 3.2";
                   }
                   enum local-attestation-certificate {
                     value 2;
                     description
                       "Local Attestation Key (LAK) Certificate type.";
                     reference
                       "https://trustedcomputinggroup.org/wp-content/
                        uploads/TCG_IWG_DevID_v1r2_02dec2020.pdf
                        Section 3.2";
                   }
                 }
                 description
                   "Function supported by this certificate from within the
                    TPM.";
               }
             }
           }
         }
       }
       container attester-supported-algos {
         description
           "Identifies which TPM algorithms are available for use on an
            attesting platform.";
         leaf-list tpm12-asymmetric-signing {
           when "../../tpm:tpms"
              + "/tpm:tpm[tpm:firmware-version='taa:tpm12']";
           type identityref {
             base taa:asymmetric;
           }
           description
             "Platform Supported TPM12 asymmetric algorithms.";
         }
         leaf-list tpm12-hash {
           when "../../tpm:tpms"
              + "/tpm:tpm[tpm:firmware-version='taa:tpm12']";
           type identityref {
             base taa:hash;
           }
           description
             "Platform supported TPM12 hash algorithms.";
         }
         leaf-list tpm20-asymmetric-signing {
           when "../../tpm:tpms"
              + "/tpm:tpm[tpm:firmware-version='taa:tpm20']";
           type identityref {
             base taa:asymmetric;
           }
           description
             "Platform Supported TPM20 asymmetric algorithms.";
         }
         leaf-list tpm20-hash {
           when "../../tpm:tpms"
              + "/tpm:tpm[tpm:firmware-version='taa:tpm20']";
           type identityref {
             base taa:hash;
           }
           description
             "Platform supported TPM20 hash algorithms.";
         }
       }
     }
   }
   <CODE ENDS>

                                  Figure 1

2.1.2.  'ietf-tcg-algs'

   Cryptographic algorithm types were initially included within -v14
   NETCONF's iana-crypto-types.yang.  Unfortunately, all this content
   including the algorithms needed here failed to make the -v15 used
   WGLC.  As a result, this document has encoded the TCG Algorithm
   definitions of [TCG-Algos], revision 1.32.  By including this full
   table as a separate YANG file within this document, it is possible
   for other YANG models to leverage the contents of this model.

2.1.2.1.  Features

   There are two types of features supported: 'TPM12' and 'TPM20'.
   Support for either of these features indicates that a cryptoprocessor
   supporting the corresponding type of TCG TPM API is present on an
   Attester.  Most commonly, only one type of cryptoprocessor will be
   available on an Attester.

2.1.2.2.  Identities

   There are three types of identities in this model:

   1.  *Cryptographic functions* supported by a TPM algorithm; these
       include: 'asymmetric', 'symmetric', 'hash', 'signing',
       'anonymous_signing', 'encryption_mode', 'method', and
       'object_type'.  The definitions of each of these are in Table 2
       of [TCG-Algos].

   2.  *API specifications* for TPMs: 'tpm12' and 'tpm20'

   3.  *Specific algorithm types*: Each algorithm type defines what
       cryptographic functions may be supported, and on which type of
       API specification.  It is not required that an implementation of
       a specific TPM will support all algorithm types.  The contents of
       each specific algorithm mirrors what is in Table 3 of
       [TCG-Algos].

2.1.2.3.  YANG Module

   <CODE BEGINS> file "ietf-tcg-algs@2021-05-11.yang"
   module ietf-tcg-algs {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-tcg-algs";
     prefix taa;

     organization
       "IETF RATS Working Group";

     contact
       "WG Web:   <http://datatracker.ietf.org/wg/rats/>
        WG List:  <mailto:rats@ietf.org>
        Author:   Eric Voit <mailto:evoit@cisco.com>";

     description
       "This module defines a identities for asymmetric algorithms.

        Copyright (c) 2021 IETF Trust and the persons identified
        as authors of the code. All rights reserved.
        Redistribution and use in source and binary forms, with
        or without modification, is permitted pursuant to, and
        subject to the license terms contained in, the Simplified
        BSD License set forth in Section 4.c of the IETF Trust's
        Legal Provisions Relating to IETF Documents
        (https://trustee.ietf.org/license-info).
        This version of this YANG module is part of RFC XXXX
        (https://www.rfc-editor.org/info/rfcXXXX); see the RFC
        itself for full legal notices.
        The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
        'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',
        'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document
        are to be interpreted as described in BCP 14 (RFC 2119)
        (RFC 8174) when, and only when, they appear in all
        capitals, as shown here.";

     revision 2021-05-11 {
       description
         "Initial version";
       reference
         "RFC XXXX: tbd";
     }

     /*****************/
     /*   Features    */
     /*****************/

     feature tpm12 {
       description
         "This feature indicates algorithm support for the TPM 1.2 API
          as per TPM-main-1.2-Rev94-part-2, Section 4.8.";
     }

     feature tpm20 {
       description
         "This feature indicates algorithm support for the TPM 2.0 API
          as per TPM-Rev-2.0-Part-1-Architecture-01.38 Section 11.4.";
     }
     /*****************/
     /*  Identities   */
     /*****************/

     /*  There needs to be collasping/verification of some of the identity
         types between the various algorithm types listed below */

     identity asymmetric {
       description
         "A TCG recognized asymmetric algorithm with a public and
          private key.";
       reference
         "http://trustedcomputinggroup.org/resource/tcg-algorithm-registry/
          TCG_Algorithm_Registry_r1p32_pub Table 2";
     }

     identity symmetric {
       description
         "A TCG recognized symmetric algorithm with only a private key.";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 2";
     }

     identity hash {
       description
         "A TCG recognized hash algorithm that compresses input data to
          a digest value or indicates a method that uses a hash.";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 2";
     }

     identity signing {
       description
         "A TCG recognized signing algorithm";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 2";
     }

     identity anonymous_signing {
       description
         "A TCG recognized anonymous signing algorithm.";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 2";
     }

     identity encryption_mode {
       description
         "A TCG recognized encryption mode.";

       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 2";
     }

     identity method {
       description
         "A TCG recognized method such as a mask generation function.";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 2";
     }

     identity object_type {
       description
         "A TCG recognized object type.";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 2";
     }

     identity cryptoprocessor {
       description
         "Base identity identifying a crytoprocessor.";
     }

     identity tpm12 {
       if-feature "tpm12";
       base cryptoprocessor;
       description
         "Supportable by a TPM1.2.";
       reference
         "TPM-Main-Part-2-TPM-Structures_v1.2_rev116_01032011.pdf
          TPM_ALGORITHM_ID values, page 18";
     }

     identity tpm20 {
       if-feature "tpm12";
       base cryptoprocessor;
       description
         "Supportable by a TPM2.";
       reference
         "TPM-Rev-2.0-Part-2-Structures-01.38.pdf
          The TCG Algorithm Registry. Table 9";
     }

     identity TPM_ALG_RSA {
       if-feature "tpm12 or tpm20";
       base tpm12;
       base tpm20;
       base asymmetric;
       base object_type;
       description
         "RSA algorithm";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          RFC 8017. ALG_ID: 0x0001";
     }

     identity TPM_ALG_TDES {
       if-feature "tpm12";
       base tpm12;
       base symmetric;
       description
         "Block cipher with various key sizes (Triple Data Encryption
          Algorithm, commonly called Triple Data Encryption Standard)
          Note: was banned in TPM1.2 v94";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          ISO/IEC 18033-3. ALG_ID: 0x0003";
     }

     identity TPM_ALG_SHA1 {
       if-feature "tpm12 or tpm20";
       base hash;
       base tpm12;
       base tpm20;
       description
         "SHA1 algorithm - Deprecated due to insufficient cryptographic
          protection.  However it is still useful for hash algorithms
          where protection is not required.";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          ISO/IEC 10118-3. ALG_ID: 0x0004";
     }

     identity TPM_ALG_HMAC  {
       if-feature "tpm12 or tpm20";
       base tpm12;
       base tpm20;
       base hash;
       base signing;
       description
         "Hash Message Authentication Code (HMAC) algorithm";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3,
          ISO/IEC 9797-2 and RFC2014. ALG_ID: 0x0005";
     }
     identity TPM_ALG_AES  {
       if-feature "tpm12";
       base tpm12;
       base symmetric;
       description
         "The AES algorithm with various key sizes";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          ISO/IEC 18033-3. ALG_ID: 0x0006";
     }

     identity TPM_ALG_MGF1 {
       if-feature "tpm20";
       base tpm20;
       base hash;
       base method;
       description
         "hash-based mask-generation function";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3,
          IEEE Std 1363-2000 and IEEE Std 1363a -2004.
          ALG_ID: 0x0007";
     }

     identity TPM_ALG_KEYEDHASH {
       if-feature "tpm20";
       base tpm20;
       base hash;
       base object_type;
       description
         "An encryption or signing algorithm using a keyed hash.  These
          may use XOR for encryption or an HMAC for signing and may
          also refer to a data object that is neither signing nor
          encrypting.";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          TCG TPM 2.0 library specification. . ALG_ID: 0x0008";
       }

     identity TPM_ALG_XOR {
       if-feature "tpm12 or tpm20";
       base tpm12;
       base tpm20;
       base hash;
       base symmetric;
       description
         "The XOR encryption algorithm.";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          TCG TPM 2.0 library specification. ALG_ID: 0x000A";
     }

     identity TPM_ALG_SHA256 {
       if-feature "tpm20";
       base tpm20;
       base hash;
       description
         "The SHA 256 algorithm";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          ISO/IEC 10118-3. ALG_ID: 0x000B";
     }

     identity TPM_ALG_SHA384  {
       if-feature "tpm20";
       base tpm20;
       base hash;
       description
         "The SHA 384 algorithm";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          ISO/IEC 10118-3. ALG_ID: 0x000C";
     }

     identity TPM_ALG_SHA512  {
       if-feature "tpm20";
       base tpm20;
       base hash;
       description
         "The SHA 512 algorithm";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          ISO/IEC 10118-3. ALG_ID: 0x000D";
     }

     identity TPM_ALG_NULL {
       if-feature "tpm20";
       base tpm20;
       description
         "NULL algorithm";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          TCG TPM 2.0 library specification. ALG_ID: 0x0010";
     }

     identity TPM_ALG_SM3_256 {
       if-feature "tpm20";
       base tpm20;
       base hash;
       description
         "The SM3 hash algorithm.";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          GM/T 0004-2012 - SM3_256. ALG_ID: 0x0012";
     }

     identity TPM_ALG_SM4 {
       if-feature "tpm20";
       base tpm20;
       base symmetric;
       description
         "SM4 symmetric block cipher";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          GB/T 32907-2016. ALG_ID: 0x0013";
     }

     identity TPM_ALG_RSASSA {
       if-feature "tpm20";
       base tpm20;
       base asymmetric;
       base signing;
       description
         "Signature algorithm defined in section 8.2 (RSASSAPKCS1-v1_5)";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and RFC 8017.
          ALG_ID: 0x0014";
     }

     identity TPM_ALG_RSAES {
       if-feature "tpm20";
       base tpm20;
       base asymmetric;
       base encryption_mode;
       description
         "Signature algorithm defined in section 7.2 (RSAES-PKCS1-v1_5)";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and RFC 8017
          ALG_ID: 0x0015";
     }

     identity TPM_ALG_RSAPSS {
       if-feature "tpm20";
       base tpm20;
       base asymmetric;
       base signing;
       description
         "Padding algorithm defined in section 8.1 (RSASSA PSS)";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and RFC 8017.
          ALG_ID: 0x0016";
     }

     identity TPM_ALG_OAEP {
       if-feature "tpm20";
       base tpm20;
       base asymmetric;
       base encryption_mode;
       description
         "Padding algorithm defined in section 7.1 (RSASSA OAEP)";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and RFC 8017.
          ALG_ID: 0x0017";
     }

     identity TPM_ALG_ECDSA {
       if-feature "tpm20";
       base tpm20;
       base asymmetric;
       base signing;
       description
         "Signature algorithm using elliptic curve cryptography (ECC)";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          ISO/IEC 14888-3. ALG_ID: 0x0018";
     }

     identity TPM_ALG_ECDH {
       if-feature "tpm20";
       base tpm20;
       base asymmetric;
       base method;
       description
         "Secret sharing using ECC";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          NIST SP800-56A and RFC 7748. ALG_ID: 0x0019";
     }

     identity TPM_ALG_ECDAA {
       if-feature "tpm20";
       base tpm20;
       base asymmetric;
       base signing;
       base anonymous_signing;
       description
         "Elliptic-curve based anonymous signing scheme";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          TCG TPM 2.0 library specification. ALG_ID: 0x001A";
     }

     identity TPM_ALG_SM2 {
       if-feature "tpm20";
       base tpm20;
       base asymmetric;
       base signing;
       base encryption_mode;
       base method;
       description
         "SM2 - depending on context, either an elliptic-curve based,
          signature algorithm, an encryption scheme, or a key exchange
          protocol";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          A GM/T 0003.1-2012, GM/T 0003.2-2012, GM/T 0003.3-2012,
          GM/T 0003.5-2012 SM2. ALG_ID: 0x001B";
     }

     identity TPM_ALG_ECSCHNORR {
       if-feature "tpm20";
       base tpm20;
       base asymmetric;
       base signing;
       description
         "Elliptic-curve based Schnorr signature";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          TCG TPM 2.0 library specification. ALG_ID: 0x001C";
     }

     identity TPM_ALG_ECMQV {
       if-feature "tpm20";
       base tpm20;
       base asymmetric;
       base method;
       description
         "Two-phase elliptic-curve key";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          NIST SP800-56A. ALG_ID: 0x001D";
     }

     identity TPM_ALG_KDF1_SP800_56A {
       if-feature "tpm20";
       base tpm20;
       base hash;
       base method;
       description
         "Concatenation key derivation function";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          NIST SP800-56A  (approved alternative1) section 5.8.1.
          ALG_ID: 0x0020";
     }

     identity TPM_ALG_KDF2  {
       if-feature "tpm20";
       base tpm20;
       base hash;
       base method;
       description
         "Key derivation function";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          IEEE 1363a-2004 KDF2 section 13.2. ALG_ID: 0x0021";
     }

     identity TPM_ALG_KDF1_SP800_108 {
       base TPM_ALG_KDF2;
       description
         "A key derivation method";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          NIST SP800-108 - Section 5.1 KDF. ALG_ID: 0x0022";
     }

     identity TPM_ALG_ECC {
       if-feature "tpm20";
       base tpm20;
       base asymmetric;
       base object_type;
       description
         "Prime field ECC";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          ISO/IEC 15946-1. ALG_ID: 0x0023";
     }
     identity TPM_ALG_SYMCIPHER {
       if-feature "tpm20";
       base tpm20;
       description
         "Object type for a symmetric block cipher";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          TCG TPM 2.0 library specification. ALG_ID: 0x0025";
     }

     identity TPM_ALG_CAMELLIA {
       if-feature "tpm20";
       base tpm20;
       base symmetric;
       description
         "The Camellia algorithm";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          ISO/IEC 18033-3. ALG_ID: 0x0026";
     }

     identity TPM_ALG_SHA3_256  {
       if-feature "tpm20";
       base tpm20;
       base hash;
       description
         "ISO/IEC 10118-3 - the SHA 256 algorithm";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          NIST PUB FIPS 202. ALG_ID: 0x0027";
     }

     identity TPM_ALG_SHA3_384 {
       if-feature "tpm20";
       base tpm20;
       base hash;
       description
         "The SHA 384 algorithm";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          NIST PUB FIPS 202. ALG_ID: 0x0028";
     }

     identity TPM_ALG_SHA3_512 {
       if-feature "tpm20";
       base tpm20;
       base hash;
       description
         "The SHA 512 algorithm";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          NIST PUB FIPS 202. ALG_ID: 0x0029";
     }

     identity TPM_ALG_CMAC {
       if-feature "tpm20";
       base tpm20;
       base symmetric;
       base signing;
       description
         "block Cipher-based Message Authentication Code (CMAC)";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          ISO/IEC 9797-1:2011 Algorithm 5. ALG_ID: 0x003F";
     }

     identity TPM_ALG_CTR {
       if-feature "tpm20";
       base tpm20;
       base symmetric;
       base encryption_mode;
       description
         "Counter mode";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          ISO/IEC 10116. ALG_ID: 0x0040";
     }

     identity TPM_ALG_OFB {
       base tpm20;
       base symmetric;
       base encryption_mode;
       description
         "Output Feedback mode";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          ISO/IEC 10116. ALG_ID: 0x0041";
     }

     identity TPM_ALG_CBC {
       if-feature "tpm20";
       base tpm20;
       base symmetric;
       base encryption_mode;
       description
         "Cipher Block Chaining mode";

       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          ISO/IEC 10116. ALG_ID: 0x0042";
     }

     identity TPM_ALG_CFB {
       if-feature "tpm20";
       base tpm20;
       base symmetric;
       base encryption_mode;
       description
         "Cipher Feedback mode";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          ISO/IEC 10116. ALG_ID: 0x0043";
     }

     identity TPM_ALG_ECB  {
       if-feature "tpm20";
       base tpm20;
       base symmetric;
       base encryption_mode;
       description
         "Electronic Codebook mode";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          ISO/IEC 10116. ALG_ID: 0x0044";
     }

     identity TPM_ALG_CCM  {
       if-feature "tpm20";
       base tpm20;
       base symmetric;
       base signing;
       base encryption_mode;
       description
         "Counter with Cipher Block Chaining-Message Authentication
         Code (CCM)";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          NIST SP800-38C. ALG_ID: 0x0050";
     }

     identity TPM_ALG_GCM {
       if-feature "tpm20";
       base tpm20;
       base symmetric;
       base signing;
       base encryption_mode;
       description
         "Galois/Counter Mode (GCM)";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          NIST SP800-38D. ALG_ID: 0x0051";
     }

     identity TPM_ALG_KW {
       if-feature "tpm20";
       base tpm20;
       base symmetric;
       base signing;
       base encryption_mode;
       description
         "AES Key Wrap (KW)";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          NIST SP800-38F. ALG_ID: 0x0052";
     }

     identity TPM_ALG_KWP {
       if-feature "tpm20";
       base tpm20;
       base symmetric;
       base signing;
       base encryption_mode;
       description
         "AES Key Wrap with Padding (KWP)";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          NIST SP800-38F. ALG_ID: 0x0053";
     }

     identity TPM_ALG_EAX  {
       if-feature "tpm20";
       base tpm20;
       base symmetric;
       base signing;
       base encryption_mode;
       description
         "Authenticated-Encryption Mode";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          NIST SP800-38F. ALG_ID: 0x0054";
     }

     identity TPM_ALG_EDDSA {
       if-feature "tpm20";
       base tpm20;
       base asymmetric;
       base signing;
       description
         "Edwards-curve Digital Signature Algorithm (PureEdDSA)";
       reference
         "TCG_Algorithm_Registry_r1p32_pub Table 3 and
          RFC 8032. ALG_ID: 0x0060";
     }
   }
   <CODE ENDS>

   Note that not all cryptographic functions are required for use by
   "ietf-tpm-remote-attestation.yang".  However the full definition of
   Table 3 of [TCG-Algos] will allow use by additional YANG
   specifications.

3.  IANA Considerations

   This document will include requests to IANA:

   To be defined yet.  But keeping up with changes to "ietf-tcg-
   algs.yang" will be necessary.

4.  Security Considerations

   The YANG module specified in this document defines a schema for data
   that is designed to be accessed via network management protocols such
   as NETCONF [RFC6241] or RESTCONF [RFC8040].  The lowest NETCONF layer
   is the secure transport layer, and the mandatory-to-implement secure
   transport is Secure Shell (SSH) [RFC6242].  The lowest RESTCONF layer
   is HTTPS, and the mandatory-to-implement secure transport is TLS
   [RFC8446].

   There are a number of data nodes defined in this YANG module that are
   writable/creatable/deletable (i.e., _config true_, which is the
   default).  These data nodes may be considered sensitive or vulnerable
   in some network environments.  Write operations (e.g., _edit-config_)
   to these data nodes without proper protection can have a negative
   effect on network operations.  These are the subtrees and data nodes
   as well as their sensitivity/vulnerability:

   Container '/rats-support-structures/attester-supported-algos':  'tpm1
      2-asymmetric-signing', 'tpm12-hash', 'tpm20-asymmetric-signing',
      and 'tpm20-hash'.  All could be populated with algorithms that are
      not supported by the underlying physical TPM installed by the
      equipment vendor.

   Container: '/rats-support-structures/tpms':  'name': Although shown
      as 'rw', it is system generated.  Therefore it should not be
      possible for an operator to add or remove a TPM from the
      configuration.

      'tpm20-pcr-bank': It is possible to configure PCRs for extraction
      which are not being extended by system software.  This could
      unnecessarily use TPM resources.

      'certificates': It is possible to provision a certificate which
      does not correspond to an Attestation Identity Key (AIK) within
      the TPM 1.2, or an Attestation Key (AK) within the TPM 2.0
      respectively.

   RPC 'tpm12-challenge-response-attestation':  It must be verified that
      the certificate is for an active AIK, i. e. the certificate
      provided is able to support Attestation on the targeted TPM 1.2.

   RPC 'tpm20-challenge-response-attestation':  It must be verified that
      the certificate is for an active AK, i. e. the certificate
      provided is able to support Attestation on the targeted TPM 2.0.

   RPC 'log-retrieval':  Pulling lots of logs can chew up system
      resources.

5.  Acknowledgements

   Not yet.

6.  Change Log

   Changes from version 05 to version 06:

   *  More YANG Dr comments covered

   Changes from version 04 to version 05:

   *  YANG Dr comments covered

   Changes from version 03 to version 04:

   *  TPM1.2 Quote1 eliminated

   *  YANG model simplifications so redundant info isn't exposed

   Changes from version 02 to version 03:

   *  moved to tcg-algs
   *  cleaned up model to eliminate sources of errors

   *  removed key establishment RPC

   *  added lots of XPATH which must all be scrubbed still

   *  Descriptive text added on model contents.

   Changes from version 01 to version 02:

   *  Extracted Crypto-types into a separate YANG file

   *  Mades the algorithms explicit, not strings

   *  Hash Algo as key the selected TPM2 PCRs

   *  PCR numbers are their own type

   *  Eliminated nested keys for node-id plus tpm-name

   *  Eliminated TPM-Name of "ALL"

   *  Added TPM-Path

   Changes from version 00 to version 01:

   *  Addressed author's comments

   *  Extended complementary details about attestation-certificates

   *  Relabeled chunk-size to log-entry-quantity

   *  Relabeled location with compute-node or tpm-name where appropriate

   *  Added a valid entity-mib physical-index to compute-node and tpm-
      name to map it back to hardware inventory

   *  Relabeled name to tpm_name

   *  Removed event-string in last-entry

7.  References

7.1.  Normative References

   [I-D.ietf-netconf-keystore]
              Watsen, K., "A YANG Data Model for a Keystore", Work in
              Progress, Internet-Draft, draft-ietf-netconf-keystore-22,
              18 May 2021, <https://www.ietf.org/archive/id/draft-ietf-
              netconf-keystore-22.txt>.

   [I-D.ietf-rats-architecture]
              Birkholz, H., Thaler, D., Richardson, M., Smith, N., and
              W. Pan, "Remote Attestation Procedures Architecture", Work
              in Progress, Internet-Draft, draft-ietf-rats-architecture-
              12, 23 April 2021, <https://www.ietf.org/archive/id/draft-
              ietf-rats-architecture-12.txt>.

   [I-D.ietf-rats-reference-interaction-models]
              Birkholz, H., Eckel, M., Pan, W., and E. Voit, "Reference
              Interaction Models for Remote Attestation Procedures",
              Work in Progress, Internet-Draft, draft-ietf-rats-
              reference-interaction-models-02, 25 April 2021,
              <https://www.ietf.org/archive/id/draft-ietf-rats-
              reference-interaction-models-02.txt>.

   [I-D.ietf-rats-tpm-based-network-device-attest]
              Fedorkow, G., Voit, E., and J. Fitzgerald-McKay, "TPM-
              based Network Device Remote Integrity Verification", Work
              in Progress, Internet-Draft, draft-ietf-rats-tpm-based-
              network-device-attest-06, 7 December 2020,
              network-device-attest-07, 10 June 2021,
              <https://www.ietf.org/archive/id/draft-ietf-rats-tpm-
              based-network-device-attest-06.txt>.
              based-network-device-attest-07.txt>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC6991]  Schoenwaelder, J., Ed., "Common YANG Data Types",
              RFC 6991, DOI 10.17487/RFC6991, July 2013,
              <https://www.rfc-editor.org/info/rfc6991>.

   [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>.

   [RFC8348]  Bierman, A., Bjorklund, M., Dong, J., and D. Romascanu, "A
              YANG Data Model for Hardware Management", RFC 8348,
              DOI 10.17487/RFC8348, March 2018,
              <https://www.rfc-editor.org/info/rfc8348>.

   [TCG-Algos]
              "TCG_Algorithm_Registry_r1p32_pub", n.d.,
              <https://trustedcomputinggroup.org/resource/tcg-algorithm-
              registry/>.

   [TPM1.2]   TCG, ., "TPM 1.2 Main Specification", 2 October 2003,
              <https://trustedcomputinggroup.org/resource/tpm-main-
              specification/>.

   [TPM2.0]   TCG, ., "TPM 2.0 Library Specification", 15 March 2013,
              <https://trustedcomputinggroup.org/resource/tpm-library-
              specification/>.

   [TPM2.0-Key]
              TCG, ., "TPM 2.0 Keys for Device Identity and Attestation,
              Rev10", 14 April 2021, <https://trustedcomputinggroup.org/
              wp-content/uploads/TCG_IWG_DevID_v1r2_02dec2020.pdf>.

7.2.  Informative References

   [I-D.ietf-rats-reference-interaction-models]
              Birkholz, H., Eckel, M., Pan, W., and E. Voit, "Reference
              Interaction Models for Remote Attestation Procedures",
              Work in Progress, Internet-Draft, draft-ietf-rats-
              reference-interaction-models-03, 12 July 2021,
              <https://www.ietf.org/archive/id/draft-ietf-rats-
              reference-interaction-models-03.txt>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
              <https://www.rfc-editor.org/info/rfc6242>.

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/info/rfc8040>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

Authors' Addresses

   Henk Birkholz
   Fraunhofer SIT
   Rheinstrasse 75
   64295 Darmstadt
   Germany

   Email: henk.birkholz@sit.fraunhofer.de
   Michael Eckel
   Fraunhofer SIT
   Rheinstrasse 75
   64295 Darmstadt
   Germany

   Email: michael.eckel@sit.fraunhofer.de

   Shwetha Bhandari
   ThoughtSpot

   Email: shwetha.bhandari@thoughtspot.com

   Eric Voit
   Cisco Systems

   Email: evoit@cisco.com

   Bill Sulzen
   Cisco Systems

   Email: bsulzen@cisco.com

   Liang Xia (Frank)
   Huawei Technologies
   101 Software Avenue, Yuhuatai District
   Nanjing
   Jiangsu, 210012
   China

   Email: Frank.Xialiang@huawei.com

   Tom Laffey
   Hewlett Packard Enterprise

   Email: tom.laffey@hpe.com

   Guy C. Fedorkow
   Juniper Networks
   10 Technology Park Drive
   Westford
   Email: gfedorkow@juniper.net