Internet-Draft | ML-KEM in Certificates | September 2024 |
Turner, et al. | Expires 24 March 2025 | [Page] |
- Workgroup:
- LAMPS
- Internet-Draft:
- draft-ietf-lamps-kyber-certificates-04
- Published:
- Intended Status:
- Standards Track
- Expires:
Internet X.509 Public Key Infrastructure - Algorithm Identifiers for Module-Lattice-Based Key-Encapsulation Mechanism (ML-KEM)
Abstract
Module-Lattice-Based Key-Encapsulation Mechanism (ML-KEM) is a quantum-resistant 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.¶
Status of This Memo
This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.¶
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This Internet-Draft will expire on 24 March 2025.¶
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the document authors. All rights reserved.¶
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶
1. Introduction
Module-Lattice-Based Key-Encapsulation Mechanism (ML-KEM), previously known as known as Kyber, is a quantum-resistant key-encapsulation mechanism (KEM) standardized by the US NIST PQC Project [NIST-PQC] in [DRAFTFIPS203]. This document specifies the use of ML-KEM in Public Key Infrastructure X.509 (PKIX) certificates [RFC5280] at three security levels: ML-KEM-512, ML-KEM-768, and ML-KEM-1024, using object identifiers assigned by NIST.¶
This specification includes conventions for the subjectPublicKeyInfo field within Internet X.509 certificates [RFC5280], like [RFC3279] did for classic cryptography and [RFC5480] did for elliptic curve cryptography. The private key format is also specified.¶
1.1. ASN.1 Module 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 module; 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. 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:¶
AlgorithmIdentifier{ALGORITHM-TYPE, ALGORITHM-TYPE:AlgorithmSet} ::= SEQUENCE { algorithm ALGORITHM-TYPE.&id({AlgorithmSet}), parameters ALGORITHM-TYPE. &Params({AlgorithmSet}{@algorithm}) OPTIONAL }¶
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.¶
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].¶
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 -- }¶
4. 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 }¶
The fields in SubjectPublicKeyInfo have the following meaning:¶
-
algorithm is the algorithm identifier and parameters for the public key (see above).¶
-
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]:¶
-----BEGIN PUBLIC KEY----- TODO insert example public key -----END PUBLIC KEY-------¶
5. 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¶
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]:¶
-----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:¶
-----BEGIN PRIVATE KEY----- TODO insert example private key with attribute -----END PRIVATE KEY-------¶
6. ASN.1 Module
TODO ASN.1 Module¶
7. Security Considerations
The Security Considerations section of [RFC5280] applies to this specification as well.¶
8. IANA Considerations
This document will have some IANA actions.¶
9. References
9.1. Normative References
- [DRAFTFIPS203]
- National Institute of Standards and Technology (NIST), "DRAFT Module-Lattice-based Key-Encapsulation Mechanism Standard", FIPS PUB 203, , <https://csrc.nist.gov/projects/post-quantum-cryptography>.
- [RFC2119]
- Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <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, , <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, , <https://www.rfc-editor.org/rfc/rfc5912>.
- [RFC5958]
- Turner, S., "Asymmetric Key Packages", RFC 5958, DOI 10.17487/RFC5958, , <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, , <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, , <https://www.itu.int/rec/T-REC-X.680>.
- [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, , <https://www.itu.int/rec/T-REC-X.690>.
9.2. Informative References
- [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-03, , <https://datatracker.ietf.org/doc/html/draft-celi-wiggers-tls-authkem-03>.
- [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, , <https://datatracker.ietf.org/doc/html/draft-ietf-lamps-kyber-00>.
- [NIST-PQC]
- National Institute of Standards and Technology (NIST), "Post-Quantum Cryptography Project", , <https://csrc.nist.gov/projects/post-quantum-cryptography>.
- [RFC3279]
- Bassham, L., Polk, W., and R. Housley, "Algorithms and Identifiers for the Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 3279, DOI 10.17487/RFC3279, , <https://www.rfc-editor.org/rfc/rfc3279>.
- [RFC5480]
- Turner, S., Brown, D., Yiu, K., Housley, R., and T. Polk, "Elliptic Curve Cryptography Subject Public Key Information", RFC 5480, DOI 10.17487/RFC5480, , <https://www.rfc-editor.org/rfc/rfc5480>.
- [RFC7468]
- Josefsson, S. and S. Leonard, "Textual Encodings of PKIX, PKCS, and CMS Structures", RFC 7468, DOI 10.17487/RFC7468, , <https://www.rfc-editor.org/rfc/rfc7468>.
Acknowledgments
TODO acknowledge.¶