Internet DRAFT - draft-ietf-lamps-kyber-certificates
draft-ietf-lamps-kyber-certificates
LAMPS S. Turner
Internet-Draft sn3rd
Intended status: Standards Track P. Kampanakis
Expires: 5 September 2024 J. Massimo
AWS
B. Westerbaan
Cloudflare
4 March 2024
Internet X.509 Public Key Infrastructure - Algorithm Identifiers for
Module-Lattice-Based Key-Encapsulation Mechanism (ML-KEM)
draft-ietf-lamps-kyber-certificates-03
Abstract
Module-Lattice-Based Key-Encapsulation Mechanism (ML-KEM), also known
as Kyber, is a key-encapsulation mechanism (KEM). This document
specifies algorithm identifiers and ASN.1 encoding format for ML-KEM
in public key certificates. The encoding for public and private keys
are also provided.
[EDNOTE: This document is not expected to be finalized before the
NIST PQC Project has standardized PQ algorithms. This specification
will use object identifiers for the new algorithms that are assigned
by NIST, and will use placeholders until these are released.]
About This Document
This note is to be removed before publishing as an RFC.
The latest revision of this draft can be found at https://lamps-
wg.github.io/kyber-certificates/#go.draft-ietf-lamps-kyber-
certificates.html. Status information for this document may be found
at https://datatracker.ietf.org/doc/draft-ietf-lamps-kyber-
certificates/.
Discussion of this document takes place on the Limited Additional
Mechanisms for PKIX and SMIME (lamps) Working Group mailing list
(mailto:spasm@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/browse/spasm/. Subscribe at
https://www.ietf.org/mailman/listinfo/spasm/.
Source for this draft and an issue tracker can be found at
https://github.com/lamps-wg/kyber-certificates.
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Status of This Memo
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This Internet-Draft will expire on 5 September 2024.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. ASN.1 and ML-KEM Identifiers . . . . . . . . . . . . . . 3
1.2. Applicability Statement . . . . . . . . . . . . . . . . . 3
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 3
3. Algorithm Identifiers . . . . . . . . . . . . . . . . . . . . 3
4. ML-KEM Public Key Identifiers . . . . . . . . . . . . . . . . 4
5. Subject Public Key Fields . . . . . . . . . . . . . . . . . . 5
6. Private Key Format . . . . . . . . . . . . . . . . . . . . . 6
7. ASN.1 Module . . . . . . . . . . . . . . . . . . . . . . . . 7
8. Security Considerations . . . . . . . . . . . . . . . . . . . 8
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
10.1. Normative References . . . . . . . . . . . . . . . . . . 8
10.2. Informative References . . . . . . . . . . . . . . . . . 9
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 9
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Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
| WARNING: This I-D includes examples. These examples were
| generated prior to NIST finalizing [DRAFTFIPS203].
Module-Lattice-Based Key-Encapsulation Mechanism (ML-KEM), also known
as Kyber, is a key-encapsulation mechanism (KEM) standardized by the
US NIST PQC Project [DRAFTFIPS203]. This document specifies the use
of the ML-KEM algorithm at three security levels: ML-KEM-512, ML-KEM-
768, and ML-KEM-1024, in X.509 public key certificates; see
[RFC5280]. Public and private key encodings are also specified.
1.1. ASN.1 and ML-KEM Identifiers
An ASN.1 module [X680] is included for reference purposes. Note that
as per [RFC5280], certificates use the Distinguished Encoding Rules;
see [X690]. Also note that NIST defined the object identifiers for
the ML-KEM algorithms in an ASN.1 modulle; see (TODO insert
reference).
1.2. Applicability Statement
ML-KEM certificates are used in protocols where the public key is
used to generate and encapsulate a shared secret used to derive a
symmetric key used to encrypt a payload; see [I-D.ietf-lamps-kyber].
To be used in TLS, ML-KEM certificates could only be used as end-
entity identity certificates and would require significant updates to
the protocol; see [I-D.celi-wiggers-tls-authkem].
2. Conventions and Definitions
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.
3. Algorithm Identifiers
Certificates conforming to [RFC5280] can convey a public key for any
public key algorithm. The certificate indicates the algorithm
through an algorithm identifier. An algorithm identifier consists of
an object identifier and optional parameters.
The AlgorithmIdentifier type, which is included herein for
convenience, is defined as follows:
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AlgorithmIdentifier{ALGORITHM-TYPE, ALGORITHM-TYPE:AlgorithmSet} ::=
SEQUENCE {
algorithm ALGORITHM-TYPE.&id({AlgorithmSet}),
parameters ALGORITHM-TYPE.
&Params({AlgorithmSet}{@algorithm}) OPTIONAL
}
| NOTE: The above syntax is from [RFC5912] and is compatible with
| the 2021 ASN.1 syntax [X680].
The fields in AlgorithmIdentifier have the following meanings:
* algorithm identifies the cryptographic algorithm with an object
identifier.
* parameters, which are optional, are the associated parameters for
the algorithm identifier in the algorithm field.
Section 4 includes object identifiers for ML-KEM-512, ML-KEM-768, and
ML-KEM-1024. For all of these OIDs, the parameters MUST be absent.
| NOTE: It is possible to find systems that require the
| parameters to be present. This can be due to either a defect
| in the original 1997 syntax or a programming error where
| developers never got input where this was not true. The
| optimal solution is to fix these systems; where this is not
| possible, the problem needs to be restricted to that subsystem
| and not propagated to the Internet.
4. ML-KEM Public Key Identifiers
The AlgorithmIdentifier for a ML-KEM public key MUST use one of the
id-alg-ml-kem object identifiers listed below, based on the security
level. The parameters field of the AlgorithmIdentifier for the ML-
KEM public key MUST be absent.
When any of the ML-KEM AlgorithmIdentifier appears in the
SubjectPublicKeyInfo field of an X.509 certificate, the key usage
certificate extension MUST only contain keyEncipherment
Section 4.2.1.3 of [RFC5280].
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pk-ml-kem-512 PUBLIC-KEY ::= {
IDENTIFIER id-alg-ml-kem-512
-- KEY no ASN.1 wrapping --
PARAMS ARE absent
CERT-KEY-USAGE
{ keyEncipherment }
--- PRIVATE-KEY no ASN.1 wrapping --
}
pk-ml-kem-768 PUBLIC-KEY ::= {
IDENTIFIER id-alg-ml-kem-768
-- KEY no ASN.1 wrapping --
PARAMS ARE absent
CERT-KEY-USAGE
{ keyEncipherment }
--- PRIVATE-KEY no ASN.1 wrapping --
}
pk-ml-kem-1024 PUBLIC-KEY ::= {
IDENTIFIER id-alg-ml-kem-1024
-- KEY no ASN.1 wrapping --
PARAMS ARE absent
CERT-KEY-USAGE
{ keyEncipherment }
--- PRIVATE-KEY no ASN.1 wrapping --
}
| NOTE: As noted in Section 3, the values for these object
| identifers will be assigned by NIST. Once assigned, they will
| be added to a future revision of this document.
5. Subject Public Key Fields
In the X.509 certificate, the subjectPublicKeyInfo field has the
SubjectPublicKeyInfo type, which has the following ASN.1 syntax:
SubjectPublicKeyInfo {PUBLIC-KEY: IOSet} ::= SEQUENCE {
algorithm AlgorithmIdentifier {PUBLIC-KEY, {IOSet}},
subjectPublicKey BIT STRING
}
| NOTE: The above syntax is from [RFC5912] and is compatible with
| the 2021 ASN.1 syntax [X680].
The fields in SubjectPublicKeyInfo have the following meaning:
* algorithm is the algorithm identifier and parameters for the
public key (see above).
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* subjectPublicKey contains the byte stream of the public key. The
algorithms defined in this document always encode the public key
as TODO pick format e.g., exact multiple of 8 bits?.
The following is an example of a ML-KEM-512 public key encoded using
the textual encoding defined in [RFC7468]:
| WARNING: This example was generated prior to NIST finalizing
| [DRAFTFIPS203].
-----BEGIN PUBLIC KEY-----
TODO insert example public key
-----END PUBLIC KEY-------
6. Private Key Format
"Asymmetric Key Packages" [RFC5958] describes how to encode a private
key in a structure that both identifies what algorithm the private
key is for and allows for the public key and additional attributes
about the key to be included as well. For illustration, the ASN.1
structure OneAsymmetricKey is replicated below. The algorithm-
specific details of how a private key is encoded are left for the
document describing the algorithm itself.
OneAsymmetricKey ::= SEQUENCE {
version Version,
privateKeyAlgorithm SEQUENCE {
algorithm PUBLIC-KEY.&id({PublicKeySet}),
parameters PUBLIC-KEY.&Params({PublicKeySet}
{@privateKeyAlgorithm.algorithm})
OPTIONAL}
privateKey OCTET STRING (CONTAINING
PUBLIC-KEY.&PrivateKey({PublicKeySet}
{@privateKeyAlgorithm.algorithm})),
attributes [0] Attributes OPTIONAL,
...,
[[2: publicKey [1] BIT STRING (CONTAINING
PUBLIC-KEY.&Params({PublicKeySet}
{@privateKeyAlgorithm.algorithm})
OPTIONAL,
...
}
PrivateKey ::= OCTET STRING
PublicKey ::= BIT STRING
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| NOTE: The above syntax is from [RFC5958] and is compatible with
| the 2021 ASN.1 syntax [X680].
For the keys defined in this document, the private key is always an
opaque byte sequence. The ASN.1 type PqckemPrivateKey is defined in
this document to hold the byte sequence. Thus, when encoding a
OneAsymmetricKey object, the private key is wrapped in a
PqckemPrivateKey object and wrapped by the OCTET STRING of the
"privateKey" field.
PqckemPrivateKey ::= OCTET STRING
The following is an example of a ML-KEM-512 private key encoded using
the textual encoding defined in [RFC7468]:
| WARNING: This example was generated prior to NIST finalizing
| [DRAFTFIPS203].
-----BEGIN PRIVATE KEY-----
TODO iser example private key
-----END PRIVATE KEY-------
The following example, in addition to encoding the ML-KEM-512 private
key, has an attribute included as well as the public key. As with
the prior example, the textual encoding defined in [RFC7468] is used:
| WARNING: This example was generated prior to NIST finalizing
| [DRAFTFIPS203].
-----BEGIN PRIVATE KEY-----
TODO insert example private key with attribute
-----END PRIVATE KEY-------
| NOTE: There exist some private key import functions that have
| not implemented the new ASN.1 structure OneAsymmetricKey that
| is defined in [RFC5958]. This means that they will not accept
| a private key structure that contains the public key field.
| This means a balancing act needs to be done between being able
| to do a consistency check on the key pair and widest ability to
| import the key.
7. ASN.1 Module
TODO ASN.1 Module
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8. Security Considerations
The Security Considerations section of [RFC5280] applies to this
specification as well.
| To Do: Discuss side-channels for Kyber TBD1.
9. IANA Considerations
This document will have some IANA actions.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/rfc/rfc5280>.
[RFC5912] Hoffman, P. and J. Schaad, "New ASN.1 Modules for the
Public Key Infrastructure Using X.509 (PKIX)", RFC 5912,
DOI 10.17487/RFC5912, June 2010,
<https://www.rfc-editor.org/rfc/rfc5912>.
[RFC5958] Turner, S., "Asymmetric Key Packages", RFC 5958,
DOI 10.17487/RFC5958, August 2010,
<https://www.rfc-editor.org/rfc/rfc5958>.
[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/rfc/rfc8174>.
[X680] ITU-T, "Information technology - Abstract Syntax Notation
One (ASN.1): Specification of basic notation", ITU-T
Recommendation X.680, ISO/IEC 8824-1:2021, February 2021,
<https://www.itu.int/rec/T-REC-X.680>.
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[X690] ITU-T, "Information technology - Abstract Syntax Notation
One (ASN.1): ASN.1 encoding rules: Specification of Basic
Encoding Rules (BER), Canonical Encoding Rules (CER) and
Distinguished Encoding Rules (DER)", ITU-T
Recommendation X.690, ISO/IEC 8825-1:2021, February 2021,
<https://www.itu.int/rec/T-REC-X.690>.
10.2. Informative References
[DRAFTFIPS203]
National Institute of Standards and Technology (NIST),
"DRAFT Module-Lattice-based Key-Encapsulation Mechanism
Standard", FIPS PUB 203, August 2023,
<https://csrc.nist.gov/projects/post-quantum-
cryptography>.
[I-D.celi-wiggers-tls-authkem]
Wiggers, T., Celi, S., Schwabe, P., Stebila, D., and N.
Sullivan, "KEM-based Authentication for TLS 1.3", Work in
Progress, Internet-Draft, draft-celi-wiggers-tls-authkem-
02, 18 August 2023,
<https://datatracker.ietf.org/doc/html/draft-celi-wiggers-
tls-authkem-02>.
[I-D.ietf-lamps-kyber]
Prat, J. and M. Ounsworth, "Use of KYBER in the
Cryptographic Message Syntax (CMS)", Work in Progress,
Internet-Draft, draft-ietf-lamps-kyber-00, 10 November
2022, <https://datatracker.ietf.org/doc/html/draft-ietf-
lamps-kyber-00>.
[RFC7468] Josefsson, S. and S. Leonard, "Textual Encodings of PKIX,
PKCS, and CMS Structures", RFC 7468, DOI 10.17487/RFC7468,
April 2015, <https://www.rfc-editor.org/rfc/rfc7468>.
Acknowledgments
TODO acknowledge.
Authors' Addresses
Sean Turner
sn3rd
Email: sean@sn3rd.com
Panos Kampanakis
AWS
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Email: kpanos@amazon.com
Jake Massimo
AWS
Email: jakemas@amazon.com
Bas Westerbaan
Cloudflare
Email: bas@westerbaan.name
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