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Versions: 00 01 02 03 04

HIP                                                         R. Moskowitz
Internet-Draft                                            HTT Consulting
Updates: 7401 (if approved)                                      S. Card
Intended status: Standards Track                         A. Wiethuechter
Expires: 26 July 2020                                      AX Enterprize
                                                         23 January 2020


                  New Cryptographic Algorithms for HIP
                   draft-moskowitz-hip-new-crypto-04

Abstract

   This document provides new cryptographic algorithms to be used with
   HIP.  The Edwards Elliptic Curve and the Keccak sponge functions are
   the main focus.  The HIP parameters and processing instructions
   impacted by these algorithms are defined.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 26 July 2020.

Copyright Notice

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

   This document is subject to BCP 78 and the IETF Trust's Legal
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   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Simplified BSD License.



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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terms and Definitions . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Requirements Terminology  . . . . . . . . . . . . . . . .   3
     2.2.  Definitions . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  HIP Parameter values for new Crytpo . . . . . . . . . . . . .   4
     3.1.  Elliptic Curves for Diffie-Hellman  . . . . . . . . . . .   4
       3.1.1.  DIFFIE_HELLMAN  . . . . . . . . . . . . . . . . . . .   4
     3.2.  Edward Digital Signature Algorithm  . . . . . . . . . . .   4
       3.2.1.  HOST_ID . . . . . . . . . . . . . . . . . . . . . . .   5
       3.2.2.  HIT_SUITE_LIST  . . . . . . . . . . . . . . . . . . .   5
     3.3.  Hashing with the Keccak Function  . . . . . . . . . . . .   6
       3.3.1.  The Keccak Permutation  . . . . . . . . . . . . . . .   6
       3.3.2.  RHASH . . . . . . . . . . . . . . . . . . . . . . . .   7
       3.3.3.  HIP_MAC and HIP_MAC2  . . . . . . . . . . . . . . . .   7
     3.4.  HIP Cipher  . . . . . . . . . . . . . . . . . . . . . . .   7
       3.4.1.  HIP_CIPHER  . . . . . . . . . . . . . . . . . . . . .   7
   4.  Generating a HIT from an HI . . . . . . . . . . . . . . . . .   8
   5.  HIP KEYMAT Generation . . . . . . . . . . . . . . . . . . . .   8
   6.  Using Keccak for a Pseudorandom Function  . . . . . . . . . .   8
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
     8.1.  Keymat vulnerabilities  . . . . . . . . . . . . . . . . .   9
     8.2.  KMAC Security as a KDF  . . . . . . . . . . . . . . . . .   9
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  10
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  10
     10.2.  Informative References . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   This document adds new cryptographic algorithms for HIPv2 [RFC7401].
   This includes:

   *  New elliptic curves for ECDH.

   *  The Edwards Elliptic Curve Digital Signature Algorithm (EdDSA)
      used in Host Identities (HI) and for Base Exchange (BEX)
      signatures.

   *  Hashes used in Host Identity Tag (HIT) generation, and wherever
      else hashes are needed.

   *  Keyed hashes used for KEYMAT generation and packet MACing
      operations.




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   *  AEAD and stream ciphers to use in HIP and HIP enabled secure
      communication protocols.

   The hashes and encryption are all built on the [Keccak] sponge
   function.

   These additions reflect selection of advances in the field of
   cryptography that would best benefit HIP, particularly in constrained
   devices and communications.

2.  Terms and Definitions

2.1.  Requirements Terminology

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

2.2.  Definitions

   Keccak (KECCAK Message Authentication Code):
      The family of all sponge functions with a KECCAK-f permutation as
      the underlying function and multi-rate padding as the padding
      rule.

   KMAC (KECCAK Message Authentication Code):
      A PRF and keyed hash function based on KECCAK.

   cSHAKE (The customizable SHAKE function):
      Extends the SHAKE scheme to allow users to customize their use of
      the function.

   SHAKE (Secure Hash Algorithm KECCAK):
      A secure hash that allows for an arbitrary output length.

   PRF (Pseudorandom Function):
      A function that can be used to generate output from a random seed
      such that the output is computationally indistinguishable from
      truly random output.

   capacity:
      In the sponge construction, the width of the underlying function
      minus the rate.

   rate:




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      In the sponge construction, the number of input bits processed per
      invocation of the underlying function.

   XOF (eXtendable-Output Function):
      A function on bit strings (also called messages) in which the
      output can be extended to any desired length.

3.  HIP Parameter values for new Crytpo

   HIP parameters carry information that is necessary for establishing
   and maintaining a HIP association.  For example, the device's public
   keys as well as the signaling for negotiating ciphers and payload
   handling are encapsulated in HIP parameters.  Additional information,
   meaningful for end hosts or middleboxes, may also be included in HIP
   parameters.  The specification of the HIP parameters and their
   mapping to HIP packets and packet types is flexible to allow HIP
   extensions to define new parameters and new protocol behavior.

3.1.  Elliptic Curves for Diffie-Hellman

   Elliptic curves Curve25519 and Curve448 [RFC7748] are specified here
   for use in the HIP Diffie-Hellman exchange.

   Curve25519 and Curve448 are already defined in Section 5.2.1 of
   [I-D.ietf-hip-dex], using the HIP-DEX CKDF.  Here they are defined
   for using the new KMAC [NIST.SP.800-185] derived KDF in Section 5.

3.1.1.  DIFFIE_HELLMAN

   The DIFFIE_HELLMAN parameter may be included in selected HIP packets
   based on the DH Group ID selected.  The DIFFIE_HELLMAN parameter is
   defined in Section 5.2.7 of [RFC7401].

   The following Elliptic Curves are defined here:

   Group                              KDF              Value

   Curve25519 [RFC7748]               KKDF             13
   Curve448   [RFC7748]               KKDF             14

   A new KDF for KEYMAT, Section 6.5 of [RFC7401] and Section 6.3 of
   [I-D.ietf-hip-dex] using Keccak is defined in Section 5.

3.2.  Edward Digital Signature Algorithm

   Edwards-Curve Digital Signature Algorithm (EdDSA) [RFC8032] are
   specified here for use as Host Identities (HIs).




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3.2.1.  HOST_ID

   The HOST_ID parameter specifies the public key algorithm, and for
   elliptic curves, a name.  The HOST_ID parameter is defined in
   Section 5.2.19 of [RFC7401].

        Algorithm
        profiles         Values

        EdDSA            13 [RFC8032]       (RECOMMENDED)

   For hosts that implement EdDSA as the algorithm, the following ECC
   curves are available:

        Algorithm    Curve            Values

        EdDSA        RESERVED         0
        EdDSA        EdDSA25519       1 [RFC8032]
        EdDSA        EdDSA25519ph     2 [RFC8032]
        EdDSA        EdDSA448         3 [RFC8032]
        EdDSA        EdDSA448ph       4 [RFC8032]

3.2.2.  HIT_SUITE_LIST

   The HIT_SUITE_LIST parameter contains a list of the supported HIT
   suite IDs of the Responder.  Based on the HIT_SUITE_LIST, the
   Initiator can determine which source HIT Suite IDs are supported by
   the Responder.  The HIT_SUITE_LIST parameter is defined in
   Section 5.2.10 of [RFC7401].

   The following HIT Suite ID is defined, and the relationship between
   the four-bit ID value used in the OGA ID field and the eight-bit
   encoding within the HIT_SUITE_LIST ID field is clarified:

        HIT Suite       Four-bit ID    Eight-bit encoding
        RESERVED            0             0x00
        EdDSA/SHAKE128      5             0x50           (RECOMMENDED)

   The following table provides more detail on the above HIT Suite
   combinations.  The input for each generation algorithm is the
   encoding of the HI as defined in Section 4.  The output is 96 bits
   long and is directly used in the ORCHID.









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   +-------+----------+---------+------------------+-------------------+
   | Index | Hash     | HMAC    | Signature        | Description       |
   |       | function |         | algorithm        |                   |
   |       |          |         | family           |                   |
   +=======+==========+=========+==================+===================+
   |     5 | SHAKE128 | KMAC128 | EdDSA            | EdDSA HI hashed   |
   |       |          |         |                  | with cSHAKE128,   |
   |       |          |         |                  | output is 96 bits |
   +-------+----------+---------+------------------+-------------------+

                            Table 1: HIT Suites

3.3.  Hashing with the Keccak Function

   The [Keccak] sponge function is the basis for the new SHA-3, standard
   [NIST.FIPS.202], and the customized XOF functions in
   [NIST.SP.800-185].  These are used here as an alternative to all the
   hashing functions in HIP.

   Hardware implementation of Keccak in VHDL is available from [Keccak].

3.3.1.  The Keccak Permutation

   Keccak is described as a sponge function.  The analogy to a sponge is
   that an arbitrary number of input bits are "absorbed" into the state
   of the function, after which an arbitrary number of output bits are
   "squeezed" out of its state.

      The Keccak function is defined to have a width of b bits.  Where b
      is the capacity (c) + rate (r).

      The rate is the number of bits "fed" into the sponge at a time.

      The capacity is twice the desired hash "strength" and part of the
      sponge width.

   b is one of the set {25, 50, 100, 200, 400, 800, 1600}.  In FIPS 202,
   b=1600.  Thus a hash strength of 128 bits can be delivered with c=256
   and r=1344, or 168 byte segment input to the sponge.

   Keccak can also provide a hash strength of 128 bit with b=800 (r=544
   or 68 bytes) and b=400 (r=144 or 18 bytes).  256 bit strength can
   only be provided with b=1600 or 800.

   FIPS 202 does not specify use of these smaller values for b which may
   be preferred in memory constrained devices, processing relatively
   short input strings.  Future work will determine if the smaller




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   values for b result in a significant performance/memory improvement
   to warrant their use.

3.3.2.  RHASH

   The RHASH is the general term used throughout [RFC7401] to refer to
   the hash used for a specific HIT suite.  For this addendum SHAKE128
   is used, even for HIs of EdDSA448.

   Unless otherwise specified, L of SHAKE128 is 256, resulting in a
   similar output to SHA256.  Any truncation used for, older, fixed
   output hashes is still used.  This is to simplify code integration.
   One exception to this is in Section 4.

3.3.3.  HIP_MAC and HIP_MAC2

   The HIP_MAC and HIP_MAC2 parameters in [RFC7401] use HMAC [RFC2104].
   This performs two hashes on a string with a key for a keyed hash the
   length of the underlying hash.

   Here, KMAC from NIST SP 800-185 [NIST.SP.800-185] is used.  This is a
   single pass using the underlying cSHAKE function.  The function call
   is:

        KMAC128(Key, Input String, 256, "")

3.4.  HIP Cipher

   HIP encrypted parameters use the HIP_CIPHER, Section 5.2.8 of
   [RFC7401].  The Keccak Keyak cipher, [Keyak_Cipher], is recommended.
   Keyak is a candidate in the NIST Lightweight Cryptography competition
   and is consistent with the overall approach in this addendum to use
   Keccak functions for simplicity in design and implementation.

3.4.1.  HIP_CIPHER

   The HIP_CIPHER parameter values for Keyak are:

   hip_cipher
        Suite ID           Value

        RIVER KEYAK        6     (Keyak)
        LAKE KEYAK         7     (Keyak)

   For use as the HIP Cipher, the TAG generated in Keyak is length 0.
   The Keyak SUV is the key plus IV specified for the encrypted
   parameter.  River Keyak MAY be used for [Keyak_Cipher], in place of
   AES-CTR.



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   Lake Keyak can provide 256 bits of security by following the
   recommendations for the Keyak cipher.

4.  Generating a HIT from an HI

   The EdDSA/cSHAKE based HITs vary slightly the ORCHID generation
   method described in section 3.2 of [RFC7401].  The XOF functionality
   of cSHAKE produces an output of L bits.  This replaces the Encode_96
   function in the ORCHID generation.

   For identities that are EdDSA public keys, ORCHIDs will be generated
   per the process defined in Using cSHAKE in ORCHIDs
   [I-D.moskowitz-orchid-cshake]

5.  HIP KEYMAT Generation

   The KMAC function provides a new, more efficient, key derivation
   function over HKDF [RFC5869].  This will be referred to as KKDF.

   The choice of KMAC128 or KMAC256 is based on the strength of the
   output key material.  For 256 bits of strength equivalent to HMAC-
   SHA256, use KMAC256.  Per [NIST.SP.800-56Cr1], Section 4.1, Option 3:

        OKM = KMAC[128|256](salt | info, IKM, L, S)

   L is the derived key bit length.  Since 4 HIP keys are "drawn" from
   this output, the length is 4 * HIP_key_size.  Per ASIACRYPT 2017, pp.
   606-637 [ASIACRYPT-2017] each of these derived keys will have the
   same strength as the Diffie-Hellman shared secret.

   S is the byte string 01001011 || 01000100 || 01000110, which
   represents the sequence of characters "K", "D", and "F" in 8-bit
   ASCII.

   Salt and info are derived as defined in [RFC7401] or
   [I-D.ietf-hip-dex].  There are special security considerations for
   IKM per [RFC7748].  The two HIs MUST be used in constructing IKM as
   follows:

        IKM = Diffie-Hellman secret | HI-R |  HI-I

   These are separately DER encoded.

6.  Using Keccak for a Pseudorandom Function

   Appendix B of NIST SP 800-185 [NIST.SP.800-185] defines how to use
   SHAKE, cSHAKE, or KMAC as a PRF.




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7.  IANA Considerations

   IANA will need to make the following changes to the "Host Identity
   Protocol (HIP) Parameters" registries:

   Diffie Hellman:
      This document defines the new Curve25519 and Curve448 for the
      Diffie-Hellman exchange (see Section 3.1.1).

   Host ID:
      This document defines the new EdDSA Host ID (see Section 3.2.1).

   HIT Suite ID:
      This document defines the new HIT Suite of EdDSA/cSHAKE (see
      Section 3.2.2).

   HIP Cipher:
      This document defines the new Keyak ciphers for HIP encrypted
      parameters (see Section 3.4.1).

8.  Security Considerations

8.1.  Keymat vulnerabilities

   [RFC7748] warns about using Curve25519 and Curve448 in Diffie-Hellman
   for key derivation:

   Designers using these curves should be aware that for each public
   key, there are several publicly computable public keys that are
   equivalent to it, i.e., they produce the same shared secrets.  Thus
   using a public key as an identifier and knowledge of a shared secret
   as proof of ownership (without including the public keys in the key
   derivation) might lead to subtle vulnerabilities.

   This applies to [I-D.ietf-hip-dex], but may have broader
   consequences.  Thus the two Host IDs are included with the Diffie-
   Hellman secret.

8.2.  KMAC Security as a KDF

   Section 4.1 of NIST SP 800-185 [NIST.SP.800-185] states:

   "The KECCAK Message Authentication Code (KMAC) algorithm is a PRF and
   keyed hash function based on KECCAK . It provides variable-length
   output"

   That is, the output of KMAC is indistinguishable from a random
   string, regardless of the length of the output.  As such, the output



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   of KMAC can be divided into multiple substrings, each with the
   strength of the function (KMAC128 or KMAC256) and provided that a
   long enough key is used, as discussed in Sec. 8.4.1 of SP 800-185.

   For example KMAC128(K, X, 512, S), where K is at least 128 bits, can
   produce 4 128 bit keys each with a strength of 128 bits.  That is a
   single sponge operation is replacing perhaps 5 HMAC-SHA256 operations
   (each 2 SHA256 operations) in HKDF.

9.  Acknowledgments

   Quynh Dang of NIST gave considerable guidance on using Keccak and the
   NIST supporting documents.  Joan Deamen of the Keccak team was
   especially helpful in many aspects of using Keccak, particularly with
   the KEYMAT section and the strength of the derived keys.

10.  References

10.1.  Normative References

   [NIST.FIPS.202]
              Dworkin, M., "SHA-3 Standard: Permutation-Based Hash and
              Extendable-Output Functions", National Institute of
              Standards and Technology report,
              DOI 10.6028/nist.fips.202, July 2015,
              <https://doi.org/10.6028/nist.fips.202>.

   [NIST.SP.800-185]
              Kelsey, J., Change, S., and R. Perlner, "SHA-3 derived
              functions: cSHAKE, KMAC, TupleHash and ParallelHash",
              National Institute of Standards and Technology report,
              DOI 10.6028/nist.sp.800-185, December 2016,
              <https://doi.org/10.6028/nist.sp.800-185>.

   [NIST.SP.800-56Cr1]
              Barker, E., Chen, L., and R. Davis, "Recommendation for
              key-derivation methods in key-establishment schemes",
              National Institute of Standards and Technology report,
              DOI 10.6028/nist.sp.800-56cr1, April 2018,
              <https://doi.org/10.6028/nist.sp.800-56cr1>.

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

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC




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              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

10.2.  Informative References

   [ASIACRYPT-2017]
              Daemen, J., Mennink, B., and G. Van Assche, "Full-State
              Keyed Duplex with Built-In Multi-user Support",
              DOI 10.1007/978-3-319-70697-9_21, Advances in Cryptology -
              ASIACRYPT 2017 pp. 606-637, 2017,
              <https://doi.org/10.1007/978-3-319-70697-9_21>.

   [I-D.ietf-hip-dex]
              Moskowitz, R., Hummen, R., and M. Komu, "HIP Diet EXchange
              (DEX)", Work in Progress, Internet-Draft, draft-ietf-hip-
              dex-11, 31 October 2019,
              <https://tools.ietf.org/html/draft-ietf-hip-dex-11>.

   [I-D.moskowitz-orchid-cshake]
              Moskowitz, R., Card, S., and A. Wiethuechter, "Using
              cSHAKE in ORCHIDs", Work in Progress, Internet-Draft,
              draft-moskowitz-orchid-cshake-00, 11 December 2019,
              <https://tools.ietf.org/html/draft-moskowitz-orchid-
              cshake-00>.

   [Keccak]   Bertoni, G., Daemen, J., Peeters, M., Van Assche, G., and
              R. Van Keer, "The Keccak Function",
              <https://keccak.team/index.html>.

   [Keyak_Cipher]
              Bertoni, G., Daemen, J., Peeters, M., Van Assche, G., and
              R. Van Keer, "The Keyak Cipher",
              <https://keccak.team/keyak.html>.

   [RFC2104]  Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
              Hashing for Message Authentication", RFC 2104,
              DOI 10.17487/RFC2104, February 1997,
              <https://www.rfc-editor.org/info/rfc2104>.

   [RFC5869]  Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-Expand
              Key Derivation Function (HKDF)", RFC 5869,
              DOI 10.17487/RFC5869, May 2010,
              <https://www.rfc-editor.org/info/rfc5869>.

   [RFC7401]  Moskowitz, R., Ed., Heer, T., Jokela, P., and T.
              Henderson, "Host Identity Protocol Version 2 (HIPv2)",
              RFC 7401, DOI 10.17487/RFC7401, April 2015,
              <https://www.rfc-editor.org/info/rfc7401>.



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   [RFC7748]  Langley, A., Hamburg, M., and S. Turner, "Elliptic Curves
              for Security", RFC 7748, DOI 10.17487/RFC7748, January
              2016, <https://www.rfc-editor.org/info/rfc7748>.

   [RFC8032]  Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital
              Signature Algorithm (EdDSA)", RFC 8032,
              DOI 10.17487/RFC8032, January 2017,
              <https://www.rfc-editor.org/info/rfc8032>.

Authors' Addresses

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

   Email: rgm@labs.htt-consult.com


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

   Email: stu.card@axenterprize.com


   Adam Wiethuechter
   AX Enterprize
   4947 Commercial Drive
   Yorkville, NY 13495
   United States of America

   Email: adam.wiethuechter@axenterprize.com
















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