title: > Internet X.509 Public Key Infrastructure - Algorithm Identifiers for Module-Lattice-Based Key-Encapsulation Mechanism (ML-KEM) abbrev: ML-KEM in Certificates category: std
docname: draft-ietf-lamps-kyber-certificates-latest submissiontype: IETF number: date: consensus: true v: 3 area: SEC workgroup: LAMPS keyword: ML-KEM Kyber KEM Certificate X.509 PKIX venue: group: "Limited Additional Mechanisms for PKIX and SMIME (lamps)" type: "Working Group" mail: "spasm@ietf.org" arch: "https://mailarchive.ietf.org/arch/browse/spasm/" github: "lamps-wg/kyber-certificates" latest: "https://lamps-wg.github.io/kyber-certificates/#go.draft-ietf-lamps-kyber-certificates.html"
name: Sean Turner
organization: sn3rd
email: sean@sn3rd.com
- ins: P. Kampanakis name: Panos Kampanakis org: AWS email: kpanos@amazon.com
- ins: J. Massimo name: Jake Massimo organization: AWS email: jakemas@amazon.com
- ins: B. Westerbaan name: Bas Westerbaan organization: Cloudflare email: bas@westerbaan.name
normative: X680: target: https://www.itu.int/rec/T-REC-X.680 title: > Information technology - Abstract Syntax Notation One (ASN.1): Specification of basic notation date: 2021-02 author: - org: ITU-T seriesinfo: ITU-T Recommendation: X.680 ISO/IEC: 8824-1:2021 X690: target: https://www.itu.int/rec/T-REC-X.690 title: > 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) date: 2021-02 author: - org: ITU-T seriesinfo: ITU-T Recommendation: X.690 ISO/IEC: 8825-1:2021 DRAFTFIPS203: target: https://csrc.nist.gov/projects/post-quantum-cryptography title: > DRAFT Module-Lattice-based Key-Encapsulation Mechanism Standard author: - org: National Institute of Standards and Technology (NIST) date: 2023-08 seriesinfo: "FIPS PUB": "203"
informative: NIST-PQC: target: https://csrc.nist.gov/projects/post-quantum-cryptography title: > Post-Quantum Cryptography Project author: - org: National Institute of Standards and Technology (NIST) date: 2016-12-20
--- 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.]
--- middle
WARNING: This I-D includes examples. These examples were generated prior to NIST finalizing [DRAFTFIPS203].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.
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).
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}}.
{::boilerplate bcp14-tagged}
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 --
}
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}}:
WARNING: This example was generated prior to NIST finalizing [DRAFTFIPS203]. -----BEGIN PUBLIC KEY-----
TODO insert example public key
-----END PUBLIC KEY-------
"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}}:
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-------
TODO ASN.1 Module
The Security Considerations section of {{RFC5280}} applies to this specification as well.
To Do: Discuss side-channels for Kyber TBD1.This document will have some IANA actions.
--- back
{:numbered="false"}
TODO acknowledge.