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SEC None Internet-Draft This document specifies algorithm identifiers and ASN.1 encoding format for the United States National Institute of Standards and Technology's Post Quantum Cryptography Key Encapsulation Mechanism algorithms. The algorithms covered are Kyber 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 Kyber 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 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 . Subscribe at . Source for this draft and an issue tracker can be found at .

Introduction The US NIST PQC Project has selected the Kyber algorithm as winner of their PQC Project . This algorithm is a Key Encapsulation Mechanism(KEM). NIST has also defined object identifiers for these algorithms (TODO insert reference). This document specifies the use of the Kyber algorithm in X.509 public key certifiates, see . 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].

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 when, and only when, they appear in all capitals, as shown here.

Algorithm Identifiers Certificates conforming to 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: The fields in AlgorithmIdentifier have the following meanings:

• algorithm identifies the cryptographic algorithm with an object identifier. XXX such OIDs are defined in Sections .
• parameters, which are optional, are the associated parameters for the algorithm identifier in the algorithm field.

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.

Candidate TBD1 TODO insert object-identifiers for Kyber-768, Kyber-1024 etc.

Subject Public Key Fields In the X.509 certificate, the subjectPublicKeyInfo field has the SubjectPublicKeyInfo type, which has the following ASN.1 syntax: The fields in SubjectPublicKeyInfo have the following meanings:

• 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 Kyber TBD1 public key encoded using the textual encoding defined in .

Key Usage Bits The intended application for the key is indicated in the keyUsage certificate extension; see [RFC5280, section 4.2.1.3]. If the keyUsage extension is present in a certificate that indicates Kyber TBD1 in SubjectPublicKeyInfo, then the following MUST be present:

Private Key Format "Asymmetric Key Packages" 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. 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. The following is an example of a Kyber TBD private key encoded using the textual encoding defined in . The following example, in addition to encoding the Kyber TBD private key, has an attribute included as well as the public key. As with the prior example, the textual encoding defined in is used.

ASN.1 Module TODO ASN.1 Module

Security Considerations The Security Considerations section of applies to this specification as well. [EDNOTE: Discuss side-channels for Kyber TBD1.]

IANA Considerations This document will have some IANA actions.

References Normative References This memo profiles the X.509 v3 certificate and X.509 v2 certificate revocation list (CRL) for use in the Internet. An overview of this approach and model is provided as an introduction. The X.509 v3 certificate format is described in detail, with additional information regarding the format and semantics of Internet name forms. Standard certificate extensions are described and two Internet-specific extensions are defined. A set of required certificate extensions is specified. The X.509 v2 CRL format is described in detail along with standard and Internet-specific extensions. An algorithm for X.509 certification path validation is described. An ASN.1 module and examples are provided in the appendices. [STANDARDS-TRACK] In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. The Public Key Infrastructure using X.509 (PKIX) certificate format, and many associated formats, are expressed using ASN.1. The current ASN.1 modules conform to the 1988 version of ASN.1. This document updates those ASN.1 modules to conform to the 2002 version of ASN.1. There are no bits-on-the-wire changes to any of the formats; this is simply a change to the syntax. This document is not an Internet Standards Track specification; it is published for informational purposes. This document defines the syntax for private-key information and a content type for it. Private-key information includes a private key for a specified public-key algorithm and a set of attributes. The Cryptographic Message Syntax (CMS), as defined in RFC 5652, can be used to digitally sign, digest, authenticate, or encrypt the asymmetric key format content type. This document obsoletes RFC 5208. [STANDARDS-TRACK] Informative References National Institute of Standards and Technology This document describes and discusses the textual encodings of the Public-Key Infrastructure X.509 (PKIX), Public-Key Cryptography Standards (PKCS), and Cryptographic Message Syntax (CMS). The textual encodings are well-known, are implemented by several applications and libraries, and are widely deployed. This document articulates the de facto rules by which existing implementations operate and defines them so that future implementations can interoperate.

Acknowledgments TODO acknowledge.