Internet-Draft PQC KEM for Certificates March 2022
Turner, et al. Expires 8 September 2022 [Page]
Intended Status:
Standards Track
S. Turner
P. Kampanakis
J. Massimo
B. Westerbaan

Algorithm Identifiers for NIST's PQC Algorithms for Use in the Internet X.509 Public Key Infrastructure


This document specifies algorithm identifiers and ASN.1 encoding format for the US NIST's PQC KEM (United States National Institute of Standards and Technology's Post Quantum Cryptography Key Encapsulation Mechanism) algorithms. The algorithms covered are Candidate TBD1. The encoding for public key and private key is also provided.

[EDNOTE: This draft is not expected to be finalized before the NIST PQC Project has standardized PQ algorithms. After NIST has standardized its first algorithms, this document will replace TBD, with the appropriate algorithms and parameters before proceeding to ratification. The algorithm Candidate TBD1 has been added as an example in this draft, to provide a more detailed illustration of the content - it by no means indicates its inclusion in the final version. 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.

Status information for this document may be found at

Discussion of this document takes place on the Limited Additional Mechanisms for PKIX and SMIME (lamps) Working Group mailing list (, which is archived at

Source for this draft and an issue tracker can be found at seanturner/draft-turner-lamps-nist-pqc-kem-certificates.

Status of This Memo

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This Internet-Draft will expire on 8 September 2022.

Table of Contents

1. Introduction

The US NIST PQC Project has selected the Candidate TBD1 algorithms as winners of their PQC Project [PQCProj]. These algorithms are KEM algorithms. NIST has also defined object identifiers for these algorithms (TODO insert reference).

This document specifies the use of the Candidate TBD1 algorithms in X.509 public key certifiates, see [RFC5280]. It also specifies private key encoding. An ASN.1 module is included for reference purposes.

These certificates could be used as Issuers in CMS where the public key is used to encapsulate a shared secret used to derive a symmetric key used to encrypt content in CMS [EDNOTE: Add reference draft-perret-prat-lamps-cms-pq-kem]. To be used in TLS, these certificates could only be used as end-entity identity certificates and would require significant updates to the protocol [EDNOTE: Add reference draft-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:

   AlgorithmIdentifier  ::=  SEQUENCE  {
       algorithm   OBJECT IDENTIFIER,
       parameters  ANY DEFINED BY algorithm OPTIONAL

The fields in AlgorithmIdentifier have the following meanings:

In this document, TODO (specify number) new OIDs for identifying the different algorithm and parameter pairs. For all of the object identifiers, the parameters MUST be absent.

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. Candidate TBD1

TODO insert object-identifiers

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  ::=  SEQUENCE  {
      algorithm         AlgorithmIdentifier,
      subjectPublicKey  BIT STRING

The fields in SubjectPublicKeyInfo have the following meanings:

The following is an example of a TBD public key encoded using the textual encoding defined in [RFC7468].

  -----BEGIN PUBLIC KEY-----
  TODO insert example public key
  -----END PUBLIC KEY-------

6. Key Usage Bits

The intended application for the key is indicated in the keyUsage certificate extension; see Section of [RFC5280].

If the keyUsage extension is present in a certificate that indicates Candidate TBD1 in SubjectPublicKeyInfo, then the following MUST be present:


7. 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      PrivateKeyAlgorithmIdentifier,
      privateKey               PrivateKey,
      attributes           [0] IMPLICIT Attributes OPTIONAL,
      [[2: publicKey       [1] IMPLICIT PublicKey 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 TBD private key encoded using the textual encoding defined in [RFC7468].

  TODO iser example private key
  -----END PRIVATE KEY-------

The following example, in addition to encoding the TBD 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.

  TODO insert example private key with attribute
  -----END PRIVATE KEY-------

8. ASN.1 Module

TODO ASN.1 Module

9. Security Considerations

The Security Considerations section of [RFC5280] applies to this specification as well.

[EDNOTE: Discuss side-channels for Candidate TBD1.]

10. IANA Considerations

This document will have some IANA actions.

11. References

11.1. Normative References

Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <>.
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, , <>.
Hoffman, P. and J. Schaad, "New ASN.1 Modules for the Public Key Infrastructure Using X.509 (PKIX)", RFC 5912, DOI 10.17487/RFC5912, , <>.
Turner, S., "Asymmetric Key Packages", RFC 5958, DOI 10.17487/RFC5958, , <>.
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <>.

11.2. Informative References

National Insititue of Standards and Technology, "Post-Quantum Cryptography Project", , <>.
Josefsson, S. and S. Leonard, "Textual Encodings of PKIX, PKCS, and CMS Structures", RFC 7468, DOI 10.17487/RFC7468, , <>.


TODO acknowledge.

Authors' Addresses

Sean Turner
Panos Kampanakis
Jake Massimo
Bas Westerbaan