]> Entrust Limited

2500 Solandt Road -- Suite 100 Ottawa, Ontario K2K 3G5 Canada mike.ounsworth@entrust.com

Entrust Limited

2500 Solandt Road -- Suite 100 Ottawa, Ontario K2K 3G5 Canada john.gray@entrust.com

OpenCA Labs

New York City, New York United States of America director@openca.org

Bundesdruckerei GmbH

Kommandantenstr. 18 Berlin 10969 Germany jan.klaussner@bdr.de

Cisco Systems

sfluhrer@cisco.com

Security LAMPS X.509 CMS Post-Quantum KEM This document introduces a set of Key Encapsulation Mechanism (KEM) schemes that use pairs of cryptographic elements such as public keys and cipher texts to combine their security properties. These schemes effectively mitigate risks associated with the adoption of post-quantum cryptography and are fully compatible with existing X.509, PKIX, and CMS data structures and protocols. This document defines eleven specific pairwise combinations, namely ML-KEM Composite Schemes, that blend ML-KEM with traditional algorithms such as RSA-OAEP, ECDH, X25519, and X448. For use within CMS, this document is intended to be coupled with the CMS KEMRecipientInfo mechanism in . These combinations are tailored to meet security best practices and regulatory requirements. About This Document The latest revision of this draft can be found at . Status information for this document may be found at . Discussion of this document takes place on the LAMPS Working Group mailing list (), which is archived at . Subscribe at . Source for this draft and an issue tracker can be found at .

Changes in version -04

• Specified the fixedInfo domain separators as the DER encoded object identifiers.
• Adjusted the combiner to be compliant with NIST SP800-56C as per https://mailarchive.ietf.org/arch/msg/spasm/nlyQF1i7ndp5A7zzcTsdYF_S9mI/ -- also aligns with X-Wing changes below.
• Removed reference to draft-ounsworth-cfrg-kem-combiners so that we don't end up in a downref situation.
• Changes inspired by X-Wing:
  • Combiner does not need ML-KEM ciphertext.
  • Combiner needs traditional ciphertext and public key.
  • KDF is now SHA3 and not KMAC.
• Since all combinations use ML-KEM; changed the document title to "Composite ML-KEM".
• In the "Use in CMS > Underlying Components" section, the MLKEM768 combinations were lifted from id-aes192-Wrap to id-aes256-Wrap because the latter is believed to have better general adoption.
• Added an appendix "Fixed Component Algorithm Identifiers" -- not finished, needs more work.
• Replaced RSA-KEM with RSA-OAEP.
• Added a section "Promotion of RSA-OAEP into a KEM".
• Removed references to I-D.ounsworth-lamps-cms-dhkem since we'll just inline a simplified version of RFC9180's DHKEM.

Still to do in a future version:

• [ ] We need PEM samples ... hackathon? OQS friends? David @ BC? The right format for samples is probably to follow the hackathon ... a Dilithium or ECDSA trust anchor certificate, a composite KEM end entity certificate, and a CMS EnvelopedData sample encrypted for that composite KEM certificate.
• [ ] Open question: do we need to include the ECDH, X25519, X448, and RSA public keys in the KDF? X-Wing does, but previous versions of this spec do not. In general existing ECC and RSA hardware decrypter implementations might not know their own public key.

Introduction The advent of quantum computing poses a significant threat to current cryptographic systems. Traditional cryptographic algorithms such as RSA-OAEP, ECDH and their elliptic curve variants are vulnerable to quantum attacks. During the transition to post-quantum cryptography (PQC), there is considerable uncertainty regarding the robustness of both existing and new cryptographic algorithms. While we can no longer fully trust traditional cryptography, we also cannot immediately place complete trust in post-quantum replacements until they have undergone extensive scrutiny and real-world testing to uncover and rectify potential implementation flaws. Unlike previous migrations between cryptographic algorithms, the decision of when to migrate and which algorithms to adopt is far from straightforward. Even after the migration period, it may be advantageous for an entity's cryptographic identity to incorporate multiple public-key algorithms to enhance security. Cautious implementers may opt to combine cryptographic algorithms in such a way that an attacker would need to break all of them simultaneously to compromise the protected data. These mechanisms are referred to as Post-Quantum/Traditional (PQ/T) Hybrids . Certain jurisdictions are already recommending or mandating that PQC lattice schemes be used exclusively within a PQ/T hybrid framework. The use of Composite scheme provides a straightforward implementation of hybrid solutions compatible with (and advocated by) some governments and cybersecurity agencies . In addition, specifically references this specification as a concrete example of hybrid X.509 certificates. A more recent example is , a document co-authored by French Cybersecurity Agency (ANSSI), Federal Office for Information Security (BSI), Netherlands National Communications Security Agency (NLNCSA), and Swedish National Communications Security Authority, Swedish Armed Forces which makes the following statement:

• "In light of the urgent need to stop relying only on quantum-vulnerable public-key cryptography for key establishment, the clear priority should therefore be the migration to post-quantum cryptography in hybrid solutions"

This specification represents the straightforward implementation of the hybrid solutions called for by European cyber security agencies. PQ/T Hybrid cryptography can, in general, provide solutions to two migration problems:

• Algorithm strength uncertainty: During the transition period, some post-quantum signature and encryption algorithms will not be fully trusted, while also the trust in legacy public key algorithms will start to erode. A relying party may learn some time after deployment that a public key algorithm has become untrustworthy, but in the interim, they may not know which algorithm an adversary has compromised.
• Ease-of-migration: During the transition period, systems will require mechanisms that allow for staged migrations from fully classical to fully post-quantum-aware cryptography.

This document defines a specific instantiation of the PQ/T Hybrid paradigm called "composite" where multiple cryptographic algorithms are combined to form a single key encapsulation mechanism (KEM) key and ciphertext such that they can be treated as a single atomic algorithm at the protocol level. Composite algorithms address algorithm strength uncertainty because the composite algorithm remains strong so long as one of its components remains strong. Concrete instantiations of composite KEM algorithms are provided based on ML-KEM, RSA-OAEP and ECDH. Backwards compatibility is not directly covered in this document, but is the subject of . This document is intended for general applicability anywhere that key establishment or enveloped content encryption is used within PKIX or CMS structures.

Terminology 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. This document is consistent with all terminology from . In addition, the following terms are used in this document: COMBINER: A combiner specifies how multiple shared secrets are combined into a single shared secret. DER: Distinguished Encoding Rules as defined in . KEM: A key encapsulation mechanism as defined in . PKI: Public Key Infrastructure, as defined in . SHARED SECRET: A value established between two communicating parties for use as cryptographic key material, but which cannot be learned by an active or passive adversary. This document is concerned with shared secrets established via public key cryptographic operations.

Composite Design Philosophy defines composites as:

• Composite Cryptographic Element: A cryptographic element that incorporates multiple component cryptographic elements of the same type in a multi-algorithm scheme.

Composite keys, as defined here, follow this definition and should be regarded as a single key that performs a single cryptographic operation such as key generation, signing, verifying, encapsulating, or decapsulating -- using its internal sequence of component keys as if they form a single key. This generally means that the complexity of combining algorithms can and should be handled by the cryptographic library or cryptographic module, and the single composite public key, private key, and ciphertext can be carried in existing fields in protocols such as PKCS#10 , CMP , X.509 , CMS , and the Trust Anchor Format . In this way, composites achieve "protocol backwards-compatibility" in that they will drop cleanly into any protocol that accepts KEM algorithms without requiring any modification of the protocol to handle multiple keys.

Composite Key Encapsulation Mechanisms (KEMs) We borrow here the definition of a key encapsulation mechanism (KEM) from , in which a KEM is a cryptographic primitive that consists of three algorithms:

• KeyGen() -> (pk, sk): A probabilistic key generation algorithm, which generates a public key pk and a secret key sk.
• Encaps(pk) -> (ct, ss): A probabilistic encapsulation algorithm, which takes as input a public key pk and outputs a ciphertext ct and shared secret ss.
• Decaps(sk, ct) -> ss: A decapsulation algorithm, which takes as input a secret key sk and ciphertext ct and outputs a shared secret ss, or in some cases a distinguished error value.

The KEM interface defined above differs from both traditional key transport mechanism (for example for use with KeyTransRecipientInfo defined in ), and key agreement (for example for use with KeyAgreeRecipientInfo defined in ). The KEM interface was chosen as the interface for a composite key establishment because it allows for arbitrary combinations of component algorithm types since both key transport and key agreement mechanisms can be promoted into KEMs. This specification uses the Post-Quantum KEM ML-KEM as specified in and . For Traditional KEMs, this document uses the RSA-OAEP algorithm defined in , the Elliptic Curve Diffie-Hellman key agreement schemes ECDH defined in section 5.7.1.2 of , and X25519 / X448 which are defined in . A combiner function is used to combine the two component shared secrets into a single shared secret.

Composite KeyGen The KeyGen() -> (pk, sk) of a composite KEM algorithm will perform the KeyGen() of the respective component KEM algorithms and it produces a composite public key pk as per and a composite secret key sk is per .

Promotion of RSA-OAEP into a KEM The RSA Optimal Asymmetric Encryption Padding (OAEP), more specifically the RSAES-OAEP key transport algorithm as specified in is a public key encryption algorithm used to transport key material from a sender to a receiver. It is promoted into a KEM by having the sender generate a random 256 bit secret and encrypt it. Decaps(sk, ct) -> ss is accomplished in the analogous way. The value of ss_len as well as the RSA-OAEP parameters used within this specification can be found in .

Promotion of ECDH into a KEM An elliptic curve Diffie-Hellman key agreement is promoted into a KEM Encaps(pk) -> (ct, ss) using a simplified version of the DHKEM definition from . Decaps(sk, ct) -> ss is accomplished in the analogous way. This construction applies for all variants of elliptic curve Diffie-Hellman used in this specification: ECDH, X25519, and X448. The simplifications from the DHKEM definition in is that since the ciphertext and receiver's public key are included explicitly in the composite KEM combiner, there is no need to construct the kem_context object, and since a domain separator is included explicitly in the composite KEM combiner there is no need to perform the labelled steps of ExtractAndExpand().

Composite Encaps The Encaps(pk) -> (ct, ss) of a composite KEM algorithm is defined as: where Combiner(tradSS, mlkemSS, tradCT, tradPK, domSep) is defined in general in with specific values for domSep per composite KEM algorithm in and CompositeCiphertextValue is defined in .

Composite Decaps The Decaps(sk, ct) -> ss of a composite KEM algorithm is defined as: where Combiner(tradSS, mlkemSS, tradCT, tradPK, domSep) is defined in general in with specific values for domSep per composite KEM algorithm in . CompositeCiphertextValue is defined in . Here the secret key values mlkemSK and tradSK may be interpreted as either literal secret key values, or as a handle to a cryptographic module which holds the secret key and is capable of performing the secret key operation.

Composite Key Structures

pk-CompositeKEM The following ASN.1 Information Object Class is a template to be used in defining all composite KEM public key types. As an example, the public key type pk-MLKEM512-ECDH-P256 is defined as: The full set of key types defined by this specification can be found in the ASN.1 Module in .

CompositeKEMPublicKey Composite public key data is represented by the following structure: A composite key MUST contain two component public keys. The order of the component keys is determined by the definition of the corresponding algorithm identifier as defined in section . Some applications may need to reconstruct the SubjectPublicKeyInfo objects corresponding to each component public key. in provides the necessary mapping between composite and their component algorithms for doing this reconstruction. This also motivates the design choice of SEQUENCE OF BIT STRING instead of SEQUENCE OF OCTET STRING; using BIT STRING allows for easier transcription between CompositeKEMPublicKey and SubjectPublicKeyInfo. When the CompositeKEMPublicKey must be provided in octet string or bit string format, the data structure is encoded as specified in .

CompositeKEMPrivateKey Use cases that require an inter-operable encoding for composite private keys, such as when private keys are carried in PKCS #12 , CMP or CRMF MUST use the following structure. Each element is a OneAsymmetricKey` object for a component private key. The parameters field MUST be absent. The order of the component keys is the same as the order defined in for the components of CompositeKEMPublicKey. When a CompositePrivateKey is conveyed inside a OneAsymmetricKey structure (version 1 of which is also known as PrivateKeyInfo) , the privateKeyAlgorithm field SHALL be set to the corresponding composite algorithm identifier defined according to , the privateKey field SHALL contain the CompositeKEMPrivateKey, and the publicKey field MUST NOT be present. Associated public key material MAY be present in the CompositeKEMPrivateKey. In some use-cases the private keys that comprise a composite key may not be represented in a single structure or even be contained in a single cryptographic module; for example if one component is within the FIPS boundary of a cryptographic module and the other is not; see for more discussion. The establishment of correspondence between public keys in a CompositeKEMPublicKey and private keys not represented in a single composite structure is beyond the scope of this document.

Encoding Rules Many protocol specifications will require that the composite public key and composite private key data structures be represented by an octet string or bit string. When an octet string is required, the DER encoding of the composite data structure SHALL be used directly. When a bit string is required, the octets of the DER encoded composite data structure SHALL be used as the bits of the bit string, with the most significant bit of the first octet becoming the first bit, and so on, ending with the least significant bit of the last octet becoming the last bit of the bit string.

Key Usage Bits For protocols such as X.509 that specify key usage along with the public key, then the composite public key associated with a composite KEM algorithm MUST contain only a keyEncipherment key usage, all other key usages MUST NOT be used. This is because the composite public key can only be used in situations that are appropriate for both component algorithms, so even if the classical component key supports both signing and encryption, the post-quantum algorithms do not.

Composite KEM Structures

kema-CompositeKEM The ASN.1 algorithm object for a composite KEM is:

CompositeCiphertextValue The compositeCipherTextValue is a concatenation of the ciphertexts of the underlying component algorithms. It is represented in ASN.1 as follows: The order of the component ciphertexts is the same as the order defined in .

KEM Combiner TODO: as per https://www.enisa.europa.eu/publications/post-quantum-cryptography-integration-study section 4.2, might need to specify behaviour in light of KEMs with a non-zero failure probability. The KEM combiner construction is as follows:

Generic KEM combiner construction

where:

• KDF(message, outputBits) represents a hash function suitable to the chosen KEMs according to {tab-kem-combiners}.
• counter SHALL be the fixed 32-bit value 0x00000001 which is placed here solely for the purposes of compliance with .
• tradSS is the shared secret from the traditional component (elliptic curve or RSA).
• mlkemSS is the shared secret from the ML-KEM componont.
• tradCT is the ciphertext from the traditional component (elliptic curve or RSA).
• tradPK is the public key of the traditional component (elliptic curve or RSA).
• domSep SHALL be the DER encoded value of the object identifier of the composite KEM algorithm as listed in .
• || represents concatenation.

Each registered composite KEM algorithm must specify the choice of KDF, demSep, and outputBits to be used. Some of the design choices for the combiner, specifically to place tradSS first, and to allow tradCT || tradPK || domSep to be treated together as a FixedInfo block are made for the purposes of compliance with ; see for more discussion. See for further discussion of the security considerations of this KEM combiner.

FIPS Compliance This specification is compliant with which allows for multiple sources of shared secret material to be combined into a single shared secret and the combined shared secret to be considered FIPS compliant so long as the first input shared secret is the result of a FIPS compliant algorithm. In order to ease FIPS compliance issues during the transition period, this specification uses the traditional algorithm as the first input to the combiner so that the combiner is FIPS compliant so long as the traditional component is FIPS compliant. This construction is specifically designed to conform with Section 4.1 Option 1 (when KDF is SHA3) or Option 3 (when KDF is KMAC) in the following way: In both cases we match exactly the construction using the allowed "hybrid" shared secret of the form Z' = Z || T to yield the construction counter || Z || T || FixedInfo where:

• Z = tradSS is the algorithm assumed to always be FIPS-approved from a FIPS-certified implementation which is expected to be true during the period where organizations are migrating their existing deployments to add ML-KEM implementations which may not yet have received FIPS certification,
• T = mlkemSS, and
• FixedInfo = tradCT || tradPK || domSep.

In the case that KDF is KMAC, the message to be hashed MUST be post-pended with H_outputBits and the byte string 01001011 || 01000100 || 01000110, which represents the sequence of characters "K", "D," and "F" in 8-bit ASCII, as required by section 4.1 Option 3. salt is left empty since KMAC is only required to behave as a hash function and not as a keyed MAC.

Algorithm Identifiers This table summarizes the list of composite KEM algorithms and lists the OID, two component algorithms, and the combiner function. EDNOTE: The OID referenced are TBD and MUST be used only for prototyping and replaced with the final IANA-assigned OIDs. The following prefix is used for each: replace <CompKEM> with the String "2.16.840.1.114027.80.5.2". TODO: OIDs to be replaced by IANA. Therefore <CompKEM>.1 is equal to 2.16.840.1.114027.80.5.2.1 Composite KEM key types

Composite KEM	OID	First Algorithm	Second Algorithm	KDF
id-MLKEM512-ECDH-P256	<CompKEM>.1	MLKEM512	ECDH-P256	SHA3-256
id-MLKEM512-ECDH-brainpoolP256r1	<CompKEM>.2	MLKEM512	ECDH-brainpoolp256r1	SHA3-256
id-MLKEM512-X25519	<CompKEM>.3	MLKEM512	X25519	SHA3-256
id-MLKEM512-RSA2048	<CompKEM>.13	MLKEM512	RSA-OAEP 2048	SHA3-256
id-MLKEM512-RSA3072	<CompKEM>.4	MLKEM512	RSA-OAEP 3072	SHA3-256
id-MLKEM768-ECDH-P256	<CompKEM>.5	MLKEM768	ECDH-P256	SHA3-384
id-MLKEM768-ECDH-brainpoolP256r1	<CompKEM>.6	MLKEM768	ECDH-brainpoolp256r1	SHA3-384
id-MLKEM768-X25519	<CompKEM>.7	MLKEM768	X25519	SHA3-384
id-MLKEM1024-ECDH-P384	<CompKEM>.8	MLKEM1024	ECDH-P384	SHA3-512
id-MLKEM1024-ECDH-brainpoolP384r1	<CompKEM>.9	MLKEM1024	ECDH-brainpoolP384r1	SHA3-512
id-MLKEM1024-X448	<CompKEM>.10	MLKEM1024	X448	SHA3-512

Full specifications for the referenced algorithms can be found as follows:

• ECDH: There does not appear to be a single IETF definition of ECDH, so we refer to the following:
  • ECDH NIST: SHALL be Elliptic Curve Cryptography Cofactor Diffie-Hellman (ECC CDH) as defined in section 5.7.1.2 of .
  • ECDH BSI / brainpool: SHALL be Elliptic Curve Key Agreement algorithm (ECKA) as defined in section 4.3.1 of
• ML-KEM: and
• RSA-OAEP:
• X25519 / X448:

EDNOTE: I believe that and give equivalent and inter-operable algorithms, so maybe this is extraneous detail to include?

Domain Separators The KEM combiner defined in section requires a domain separator domSep input. The following table shows the HEX-encoded domain separator for each Composite KEM AlgorithmID; to use it, the value should be HEX-decoded and used in binary form. The domain separator is simply the DER encoding of the composite algorithm OID. EDNOTE: Should the domain separator values be the SHA-256 hash of the DER encoding of the corresponding composite algorithm OID? That way they would be fixed-length even if the OIDs are different lengths. See https://github.com/lamps-wg/draft-composite-sigs/issues/19 Composite KEM fixedInfo Domain Separators

Composite KEM AlgorithmID	Domain Separator (in Hex encoding)
id-MLKEM512-ECDH-P256	060B6086480186FA6B50050201
id-MLKEM512-ECDH-brainpoolP256r1	060B6086480186FA6B50050202
id-MLKEM512-X25519	060B6086480186FA6B50050203
id-MLKEM512-RSA2048	060B6086480186FA6B5005020D
id-MLKEM512-RSA3072	060B6086480186FA6B50050204
id-MLKEM768-ECDH-P256	060B6086480186FA6B50050205
id-MLKEM768-ECDH-brainpoolP256r1	060B6086480186FA6B50050206
id-MLKEM768-X25519	060B6086480186FA6B50050207
id-MLKEM1024-ECDH-P384	060B6086480186FA6B50050208
id-MLKEM1024-ECDH-brainpoolP384r1	060B6086480186FA6B50050209
id-MLKEM1024-X448	060B6086480186FA6B5005020A

EDNOTE: these domain separators are based on the prototyping OIDs assigned on the Entrust arc. We will need to ask for IANA early allocation of these OIDs so that we can re-compute the domain separators over the final OIDs.

RSA-OAEP Parameters Use of RSA-OAEP within id-MLKEM512-RSA2048 and id-MLKEM512-RSA3072 requires additional specification. First, a quick note on the choice of RSA-OAEP as the supported RSA encryption primitive. RSA-KEM is more straightforward to work with, but it has fairly limited adoption and therefore is of limited backwards compatibility value. Also, while RSA-PKCS#1v1.5 is still everywhere, but hard to make secure and no longer FIPS-approved as of the end of 2023 , so it is of limited forwards value. This leaves RSA-OAEP as the remaining choice. The RSA component keys MUST be generated at the 2048-bit and 3072-bit security levels respectively. As with the other composite KEM algorithms, when id-MLKEM512-RSA2048 or id-MLKEM512-RSA3072 is used in an AlgorithmIdentifier, the parameters MUST be absent. The RSA-OAEP SHALL be instantiated with the following hard-coded parameters which are the same for both the 2048 and 3072 bit security levels. RSA-OAEP Parameters

RSA-OAEP Parameter	Value
hashFunc	id-sha2-256
maskGenFunc	mgf1SHA256Identifier
pSourceFunc	DEFAULT pSpecifiedEmptyIdentifier
ss_len	256 bits

where:

• id-sha256 is defined in .
• mgf1SHA256Identifier is defined in .
• pSpecifiedEmptyIdentifier is defined in

Use in CMS [EDNOTE: The convention in LAMPS is to specify algorithms and their CMS conventions in separate documents. Here we have presented them in the same document, but this section has been written so that it can easily be moved to a standalone document.] Composite KEM algorithms MAY be employed for one or more recipients in the CMS enveloped-data content type , the CMS authenticated-data content type , or the CMS authenticated-enveloped-data content type . In each case, the KEMRecipientInfo is used with the chosen composite KEM Algorithm to securely transfer the content-encryption key from the originator to the recipient.

Underlying Components A CMS implementation that supports a composite KEM algorithm MUST support at least the following underlying components: When a particular Composite KEM OID is supported, an implementation MUST support the corresponding KDF algorithm identifier in . When a particular Composite KEM OID is supported, an implementation MUST support the corresponding key-encryption algorithm identifier in . The following table lists the REQUIRED KDF and key-encryption algorithms to preserve security and performance characteristics of each composite algorithm. REQUIRED pairings for CMS KDF and WRAP

Composite KEM OID	KDF	Key Encryption Alg
id-MLKEM512-ECDH-P256	SHA3-256	id-aes128-Wrap
id-MLKEM512-ECDH-brainpoolP256r1	SHA3-256	id-aes128-Wrap
id-MLKEM512-X25519	SHA3-256	id-aes128-Wrap
id-MLKEM512-RSA2048	SHA3-256	id-aes128-Wrap
id-MLKEM512-RSA3072	SHA3-256	id-aes128-Wrap
id-MLKEM768-ECDH-P256	SHA3-384	id-aes256-Wrap
id-MLKEM768-ECDH-brainpoolP256r1	SHA3-384	id-aes256-Wrap
id-MLKEM768-X25519	SHA3-384	id-aes256-Wrap
id-MLKEM1024-ECDH-P384	SHA3-512	id-aes256-Wrap
id-MLKEM1024-ECDH-brainpoolP384r1	SHA3-512	id-aes256-Wrap
id-MLKEM1024-X448	SHA3-512	id-aes256-Wrap

Note: id-aes256-Wrap is stronger than necessary for the MLKEM768 combinations at the NIST level 3 192 bit security level, however id-aes256-Wrap was chosen because it has better general adoption than id-aes192-Wrap. where:

• SHA3-* KDF instantiations are defined in .
• id-aes*-Wrap are defined in .

RecipientInfo Conventions When a composite KEM Algorithm is employed for a recipient, the RecipientInfo alternative for that recipient MUST be OtherRecipientInfo using the KEMRecipientInfo structure . The fields of the KEMRecipientInfo MUST have the following values: version is the syntax version number; it MUST be 0. rid identifies the recipient's certificate or public key. kem identifies the KEM algorithm; it MUST contain one of the OIDs listed in . kemct is the ciphertext produced for this recipient; it contains the ct output from Encaps(pk) of the KEM algorithm identified in the kem parameter. kdf identifies the key-derivation function (KDF). Note that the KDF used for CMS RecipientInfo process MAY be different than the KDF used within the composite KEM Algorithm, which MAY be different than the KDFs (if any) used within the component KEMs of the composite KEM Algorithm. kekLength is the size of the key-encryption key in octets. ukm is an optional random input to the key-derivation function. wrap identifies a key-encryption algorithm used to encrypt the keying material. encryptedKey is the result of encrypting the keying material with the key-encryption key. When used with the CMS enveloped-data content type , the keying material is a content-encryption key. When used with the CMS authenticated-data content type , the keying material is a message-authentication key. When used with the CMS authenticated-enveloped-data content type , the keying material is a content-authenticated-encryption key.

Certificate Conventions The conventions specified in this section augment RFC 5280 . The willingness to accept a composite KEM Algorithm MAY be signaled by the use of the SMIMECapabilities Attribute as specified in Section 2.5.2. of or the SMIMECapabilities certificate extension as specified in . The intended application for the public key MAY be indicated in the key usage certificate extension as specified in Section 4.2.1.3 of . If the keyUsage extension is present in a certificate that conveys a composite KEM public key, then the key usage extension MUST contain only the following value: keyEncipherment The digitalSignature and dataEncipherment values MUST NOT be present. That is, a public key intended to be employed only with a composite KEM algorithm MUST NOT also be employed for data encryption or for digital signatures. This requirement does not carry any particular security consideration; only the convention that KEM keys be identified with the keyEncipherment key usage.

SMIMECapabilities Attribute Conventions Section 2.5.2 of defines the SMIMECapabilities attribute to announce a partial list of algorithms that an S/MIME implementation can support. When constructing a CMS signed-data content type , a compliant implementation MAY include the SMIMECapabilities attribute that announces support for the RSA-OAEP Algorithm. The SMIMECapability SEQUENCE representing a composite KEM Algorithm MUST include the appropriate object identifier as per in the capabilityID field.

ASN.1 Module Composite-KEM-2023 {iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-composite-kems(TBDMOD) } DEFINITIONS IMPLICIT TAGS ::= BEGIN EXPORTS ALL; IMPORTS PUBLIC-KEY, AlgorithmIdentifier{} FROM AlgorithmInformation-2009 -- RFC 5912 [X509ASN1] { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-algorithmInformation-02(58) } KEM-ALGORITHM, KEMAlgSet FROM KEMAlgorithmInformation-2023 { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-kemAlgorithmInformation-2023(99) } SubjectPublicKeyInfo FROM PKIX1Explicit-2009 { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-pkix1-explicit-02(51) } OneAsymmetricKey FROM AsymmetricKeyPackageModuleV1 { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) modules(0) id-mod-asymmetricKeyPkgV1(50) } RSAPublicKey, ECPoint FROM PKIXAlgs-2009 { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-pkix1-algorithms2008-02(56) } ; -- -- Object Identifiers -- -- Defined in ITU-T X.690 der OBJECT IDENTIFIER ::= {joint-iso-itu-t asn1(1) ber-derived(2) distinguished-encoding(1)} -- -- Composite KEM basic structures -- CompositeKEMPublicKey ::= SEQUENCE SIZE (2) OF BIT STRING CompositeKEMPublicKeyOs ::= OCTET STRING (CONTAINING CompositeKEMPublicKey ENCODED BY der) CompositeKEMPublicKeyBs ::= BIT STRING (CONTAINING CompositeKEMPublicKey ENCODED BY der) CompositeKEMPrivateKey ::= SEQUENCE SIZE (2) OF OneAsymmetricKey CompositeCiphertextValue ::= SEQUENCE SIZE (2) OF OCTET STRING -- -- Information Object Classes -- pk-CompositeKEM { OBJECT IDENTIFIER:id, FirstPublicKeyType, SecondPublicKeyType} PUBLIC-KEY ::= { IDENTIFIER id KEY SEQUENCE { BIT STRING (CONTAINING FirstPublicKeyType) BIT STRING (CONTAINING SecondPublicKeyType) } PARAMS ARE absent CERT-KEY-USAGE { keyEncipherment } } kema-CompositeKEM { OBJECT IDENTIFIER:id, PUBLIC-KEY:publicKeyType } KEM-ALGORITHM ::= { IDENTIFIER id VALUE CompositeCiphertextValue PARAMS ARE absent PUBLIC-KEYS { publicKeyType } SMIME-CAPS { IDENTIFIED BY id } } -- -- Composite KEM Algorithms -- -- TODO: OID to be replaced by IANA id-MLKEM512-ECDH-P256 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) explicitcomposite(5) kem(2) 1 } pk-MLKEM512-ECDH-P256 PUBLIC-KEY ::= pk-CompositeKEM { id-MLKEM512-ECDH-P256, OCTET STRING, ECPoint } kema-MLKEM512-ECDH-P256 KEM-ALGORITHM ::= kema-CompositeKEM{ id-MLKEM512-ECDH-P256, pk-MLKEM512-ECDH-P256 } -- TODO: OID to be replaced by IANA id-MLKEM512-ECDH-brainpoolP256r1 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) explicitcomposite(5) kem(2) 2 } pk-MLKEM512-ECDH-brainpoolP256r1 PUBLIC-KEY ::= pk-CompositeKEM { id-MLKEM512-ECDH-brainpoolP256r1, OCTET STRING, ECPoint } kema-MLKEM512-ECDH-brainpoolP256r1 KEM-ALGORITHM ::= kema-CompositeKEM{ id-MLKEM512-ECDH-brainpoolP256r1, pk-MLKEM512-ECDH-brainpoolP256r1 } -- TODO: OID to be replaced by IANA id-MLKEM512-X25519 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) explicitcomposite(5) kem(2) 3 } pk-MLKEM512-X25519 PUBLIC-KEY ::= pk-CompositeKEM { id-MLKEM512-X25519, OCTET STRING, OCTET STRING } kema-MLKEM512-X25519 KEM-ALGORITHM ::= kema-CompositeKEM{ id-MLKEM512-X25519, pk-MLKEM512-X25519 } -- TODO: OID to be replaced by IANA id-MLKEM512-RSA2048 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) explicitcomposite(5) kem(2) 13 } pk-MLKEM512-RSA2048 PUBLIC-KEY ::= pk-CompositeKEM { id-MLKEM512-RSA2048, OCTET STRING, RSAPublicKey } kema-MLKEM512-RSA2048 KEM-ALGORITHM ::= kema-CompositeKEM{ id-MLKEM512-RSA2048, pk-MLKEM512-RSA2048 } -- TODO: OID to be replaced by IANA id-MLKEM512-RSA3072 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) explicitcomposite(5) kem(2) 4 } pk-MLKEM512-RSA3072 PUBLIC-KEY ::= pk-CompositeKEM { id-MLKEM512-RSA3072, OCTET STRING, RSAPublicKey } kema-MLKEM512-RSA3072 KEM-ALGORITHM ::= kema-CompositeKEM{ id-MLKEM512-RSA3072, pk-MLKEM512-RSA3072 } -- TODO: OID to be replaced by IANA id-MLKEM768-ECDH-P256 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) explicitcomposite(5) kem(2) 5 } pk-MLKEM768-ECDH-P256 PUBLIC-KEY ::= pk-CompositeKEM { id-MLKEM768-ECDH-P256, OCTET STRING, ECPoint } kema-MLKEM768-ECDH-P256 KEM-ALGORITHM ::= kema-CompositeKEM{ id-MLKEM768-ECDH-P256, pk-MLKEM768-ECDH-P256 } -- TODO: OID to be replaced by IANA id-MLKEM768-ECDH-brainpoolP256r1 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) explicitcomposite(5) kem(2) 6 } pk-MLKEM768-ECDH-brainpoolP256r1 PUBLIC-KEY ::= pk-CompositeKEM { id-MLKEM768-ECDH-brainpoolP256r1, OCTET STRING, ECPoint } kema-MLKEM768-ECDH-brainpoolP256r1 KEM-ALGORITHM ::= kema-CompositeKEM{ id-MLKEM768-ECDH-brainpoolP256r1, pk-MLKEM768-ECDH-brainpoolP256r1 } -- TODO: OID to be replaced by IANA id-MLKEM768-X25519 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) explicitcomposite(5) kem(2) 7 } pk-MLKEM768-X25519 PUBLIC-KEY ::= pk-CompositeKEM { id-MLKEM768-X25519, OCTET STRING, OCTET STRING } kema-MLKEM768-X25519 KEM-ALGORITHM ::= kema-CompositeKEM{ id-MLKEM768-X25519, pk-MLKEM768-X25519 } -- TODO: OID to be replaced by IANA id-MLKEM1024-ECDH-P384 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) explicitcomposite(5) kem(2) 8 } pk-MLKEM1024-ECDH-P384 PUBLIC-KEY ::= pk-CompositeKEM { id-MLKEM1024-ECDH-P384, OCTET STRING, ECPoint } kema-MLKEM1024-ECDH-P384 KEM-ALGORITHM ::= kema-CompositeKEM{ id-MLKEM1024-ECDH-P384, pk-MLKEM1024-ECDH-P384 } -- TODO: OID to be replaced by IANA id-MLKEM1024-ECDH-brainpoolP384r1 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) explicitcomposite(5) kem(2) 9 } pk-MLKEM1024-ECDH-brainpoolP384r1 PUBLIC-KEY ::= pk-CompositeKEM{ id-MLKEM1024-ECDH-brainpoolP384r1, OCTET STRING, ECPoint } kema-MLKEM1024-ECDH-brainpoolP384r1 KEM-ALGORITHM ::= kema-CompositeKEM{ id-MLKEM1024-ECDH-brainpoolP384r1, pk-MLKEM1024-ECDH-brainpoolP384r1 } -- TODO: OID to be replaced by IANA id-MLKEM1024-X448 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) explicitcomposite(5) kem(2) 10 } pk-MLKEM1024-X448 PUBLIC-KEY ::= pk-CompositeKEM { id-MLKEM1024-X448, OCTET STRING, OCTET STRING } kema-MLKEM1024-X448 KEM-ALGORITHM ::= kema-CompositeKEM{ id-MLKEM1024-X448, pk-MLKEM1024-X448 } -- -- Expand the S/MIME capabilities set used by CMS [RFC5911] -- SMimeCaps SMIME-CAPS ::= { kema-MLKEM512-ECDH-P256-KMAC128.&smimeCaps | kema-MLKEM512-ECDH-brainpoolP256r1-KMAC128.&smimeCaps | kema-MLKEM512-X25519-KMAC128.&smimeCaps | kema-MLKEM512-RSA2048-KMAC128.&smimeCaps | kema-MLKEM512-RSA3072-KMAC128.&smimeCaps | kema-MLKEM768-ECDH-P256-KMAC256.&smimeCaps | kema-MLKEM768-ECDH-brainpoolP256r1-KMAC256.&smimeCaps | kema-MLKEM768-X25519-KMAC256.&smimeCaps | kema-MLKEM1024-ECDH-P384-KMAC256.&smimeCaps | kema-MLKEM1024-ECDH-brainpoolP384r1-KMAC256.&smimeCaps | kema-MLKEM1024-X448-KMAC256.&smimeCaps, ... } END ]]>

IANA Considerations

Object Identifier Allocations EDNOTE to IANA: OIDs will need to be replaced in both the ASN.1 module and in .

Module Registration - SMI Security for PKIX Module Identifier

• Decimal: IANA Assigned - Replace TBDMOD
• Description: Composite-KEM-2023 - id-mod-composite-kems
• References: This Document

Object Identifier Registrations - SMI Security for PKIX Algorithms

• id-MLKEM512-ECDH-P256
  • Decimal: IANA Assigned
  • Description: id-MLKEM512-ECDH-P256
  • References: This Document
• id-MLKEM512-ECDH-brainpoolP256r1
  • Decimal: IANA Assigned
  • Description: id-MLKEM512-ECDH-brainpoolP256r1
  • References: This Document
• id-MLKEM512-X25519
  • Decimal: IANA Assigned
  • Description: id-MLKEM512-X25519
  • References: This Document
• id-MLKEM768-RSA3072
  • Decimal: IANA Assigned
  • Description: id-MLKEM768-3072
  • References: This Document
• id-MLKEM768-ECDH-P256
  • Decimal: IANA Assigned
  • Description: id-MLKEM768-ECDH-P256
  • References: This Document
• id-MLKEM768-ECDH-brainpoolP256r1
  • Decimal: IANA Assigned
  • Description: id-MLKEM768-ECDH-brainpoolP256r1
  • References: This Document
• id-MLKEM768-X25519
  • Decimal: IANA Assigned
  • Description: id-MLKEM768-X25519
  • References: This Document
• id-MLKEM1024-ECDH-P384
  • Decimal: IANA Assigned
  • Description: id-MLKEM1024-ECDH-P384
  • References: This Document
• id-MLKEM1024-ECDH-brainpoolP384r1
  • Decimal: IANA Assigned
  • Description: id-MLKEM1024-ECDH-brainpoolP384r1
  • References: This Document
• id-MLKEM1024-X448
  • Decimal: IANA Assigned
  • Description: id-MLKEM1024-X448
  • References: This Document

Security Considerations

Component Algorithm Selection Criteria The composite algorithm combinations defined in this document were chosen according to the following guidelines:

1. RSA combinations are provided at key sizes of 2048 and 3072 bits. Since RSA 2048 and 3072 are considered to have 112 and 128 bits of classical security respectively, they are both matched with NIST PQC Level 1 algorithms and 128-bit symmetric algorithms.
2. Elliptic curve algorithms are provided with combinations on each of the NIST , Brainpool , and Edwards curves. NIST PQC Levels 1 - 3 algorithms are matched with 256-bit curves, while NIST levels 4 - 5 are matched with 384-bit elliptic curves. This provides a balance between matching classical security levels of post-quantum and traditional algorithms, and also selecting elliptic curves which already have wide adoption.
3. NIST level 1 candidates are provided, matched with 256-bit elliptic curves, intended for constrained use cases.

If other combinations are needed, a separate specification should be submitted to the IETF LAMPS working group. To ease implementation, these specifications are encouraged to follow the construction pattern of the algorithms specified in this document. The composite structures defined in this specification allow only for pairs of algorithms. This also does not preclude future specification from extending these structures to define combinations with three or more components.

Policy for Deprecated and Acceptable Algorithms Traditionally, a public key or certificate contains a single cryptographic algorithm. If and when an algorithm becomes deprecated (for example, RSA-512, or SHA1), it is obvious that the public keys or certificates using that algorithm are to be considered revoked. In the composite model this is less obvious since implementers may decide that certain cryptographic algorithms have complementary security properties and are acceptable in combination even though one or both algorithms are deprecated for individual use. As such, a single composite public key or certificate may contain a mixture of deprecated and non-deprecated algorithms. Since composite algorithms are registered independently of their component algorithms, their deprecation can be handled independently from that of their component algorithms. For example a cryptographic policy might continue to allow id-MLKEM512-ECDH-P256 even after ECDH-P256 is deprecated. The composite KEM design specified in this document, and especially that of the KEM combiner specified in means that the overall composite KEM algorithm should be considered to have the security strength of the strongest of its component algorithms; ie as long as one component algorithm remains strong, then the overall composite algorithm remains strong.

KEM Combiner Security Analysis TODO EDNOTE: the exact text to put here depends on the outcome of the CFRG KEM Combiners and X-Wing discussion. If CFRG doesn't move fast enough for us, then we may need to leverage this security consideration directly on top of the X-Wing paper .

Ciphertext collision resistance The notion of a ciphertext collision resistant KEM is defined in being the property that it is computationally difficult to find two different ciphertexts that will decapsulate to the same shared secret under the same public key. In it is proven that ML-KEM has this property and therefore the ML-KEM ciphertext can safely be omitted from the KEM combiner. Ciphertext collision resistance is not guaranteed for either RSA-OAEP or ECDH, therefore these ciphertexts are bound to the key derivation.

References Normative References 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. This document describes the conventions for using the RSAES-OAEP key transport algorithm with the Cryptographic Message Syntax (CMS). The CMS specifies the enveloped-data content type, which consists of an encrypted content and encrypted content-encryption keys for one or more recipients. The RSAES-OAEP key transport algorithm can be used to encrypt content-encryption keys for intended recipients. [STANDARDS-TRACK] This document supplements RFC 3279. It describes the conventions for using the RSA Probabilistic Signature Scheme (RSASSA-PSS) signature algorithm, the RSA Encryption Scheme - Optimal Asymmetric Encryption Padding (RSAES-OAEP) key transport algorithm and additional one-way hash functions with the Public-Key Cryptography Standards (PKCS) #1 version 1.5 signature algorithm in the Internet X.509 Public Key Infrastructure (PKI). Encoding formats, algorithm identifiers, and parameter formats are specified. [STANDARDS-TRACK] 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] This document describes the Cryptographic Message Syntax (CMS). This syntax is used to digitally sign, digest, authenticate, or encrypt arbitrary message content. [STANDARDS-TRACK] 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] 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. This document specifies algorithm identifiers and ASN.1 encoding formats for elliptic curve constructs using the curve25519 and curve448 curves. The signature algorithms covered are Ed25519 and Ed448. The key agreement algorithms covered are X25519 and X448. The encoding for public key, private key, and Edwards-curve Digital Signature Algorithm (EdDSA) structures is provided. When the Curdle Security Working Group was chartered, a range of object identifiers was donated by DigiCert, Inc. for the purpose of registering the Edwards Elliptic Curve key agreement and signature algorithms. This donated set of OIDs allowed for shorter values than would be possible using the existing S/MIME or PKIX arcs. This document describes the donated range and the identifiers that were assigned from that range, transfers control of that range to IANA, and establishes IANA allocation policies for any future assignments within that range. Vigil Security, LLC Entrust DigiCert, Inc. The Cryptographic Message Syntax (CMS) supports key transport and key agreement algorithms. In recent years, cryptographers have been specifying Key Encapsulation Mechanism (KEM) algorithms, including quantum-secure KEM algorithms. This document defines conventions for the use of KEM algorithms by the originator and recipients to encrypt and decrypt CMS content. This document updates RFC 5652. Vigil Security, LLC This document describes the conventions for using the one-way hash functions in the SHA3 family with the Cryptographic Message Syntax (CMS). The SHA3 family can be used as a message digest algorithm, as part of a signature algorithm, as part of a message authentication code, or part of a key derivation function. ITU-T Federal Office for Information Security (BSI) National Institute of Standards and Technology (NIST) National Institute of Standards and Technology (NIST) National Institute of Standards and Technology (NIST) Informative References This memo represents a republication of PKCS #10 v1.7 from RSA Laboratories' Public-Key Cryptography Standards (PKCS) series, and change control is retained within the PKCS process. The body of this document, except for the security considerations section, is taken directly from the PKCS #9 v2.0 or the PKCS #10 v1.7 document. This memo provides information for the Internet community. This document describes the Internet X.509 Public Key Infrastructure (PKI) Certificate Management Protocol (CMP). Protocol messages are defined for X.509v3 certificate creation and management. CMP provides on-line interactions between PKI components, including an exchange between a Certification Authority (CA) and a client system. [STANDARDS-TRACK] This document describes the Certificate Request Message Format (CRMF) syntax and semantics. This syntax is used to convey a request for a certificate to a Certification Authority (CA), possibly via a Registration Authority (RA), for the purposes of X.509 certificate production. The request will typically include a public key and the associated registration information. This document does not define a certificate request protocol. [STANDARDS-TRACK] This document defines a certificate extension for inclusion of Secure/Multipurpose Internet Mail Extensions (S/MIME) Capabilities in X.509 public key certificates, as defined by RFC 3280. This certificate extension provides an optional method to indicate the cryptographic capabilities of an entity as a complement to the S/MIME Capabilities signed attribute in S/MIME messages according to RFC 3851. [STANDARDS-TRACK] This document describes an additional content type for the Cryptographic Message Syntax (CMS). The authenticated-enveloped-data content type is intended for use with authenticated encryption modes. All of the various key management techniques that are supported in the CMS enveloped-data content type are also supported by the CMS authenticated-enveloped-data content type. [STANDARDS-TRACK] This memo proposes several elliptic curve domain parameters over finite prime fields for use in cryptographic applications. The domain parameters are consistent with the relevant international standards, and can be used in X.509 certificates and certificate revocation lists (CRLs), for Internet Key Exchange (IKE), Transport Layer Security (TLS), XML signatures, and all applications or protocols based on the cryptographic message syntax (CMS). This document is not an Internet Standards Track specification; it is published for informational purposes. This document describes a structure for representing trust anchor information. A trust anchor is an authoritative entity represented by a public key and associated data. The public key is used to verify digital signatures, and the associated data is used to constrain the types of information or actions for which the trust anchor is authoritative. The structures defined in this document are intended to satisfy the format-related requirements defined in Trust Anchor Management Requirements. [STANDARDS-TRACK] The RSA-KEM Key Transport Algorithm is a one-pass (store-and-forward) mechanism for transporting keying data to a recipient using the recipient's RSA public key. ("KEM" stands for "key encapsulation mechanism".) This document specifies the conventions for using the RSA-KEM Key Transport Algorithm with the Cryptographic Message Syntax (CMS). The ASN.1 syntax is aligned with an expected forthcoming change to American National Standard (ANS) X9.44. This note describes the fundamental algorithms of Elliptic Curve Cryptography (ECC) as they were defined in some seminal references from 1994 and earlier. These descriptions may be useful for implementing the fundamental algorithms without using any of the specialized methods that were developed in following years. Only elliptic curves defined over fields of characteristic greater than three are in scope; these curves are those used in Suite B. This document is not an Internet Standards Track specification; it is published for informational purposes. PKCS #12 v1.1 describes a transfer syntax for personal identity information, including private keys, certificates, miscellaneous secrets, and extensions. Machines, applications, browsers, Internet kiosks, and so on, that support this standard will allow a user to import, export, and exercise a single set of personal identity information. This standard supports direct transfer of personal information under several privacy and integrity modes. This document represents a republication of PKCS #12 v1.1 from RSA Laboratories' Public Key Cryptography Standard (PKCS) series. By publishing this RFC, change control is transferred to the IETF. This document describes version 2 of the Internet Key Exchange (IKE) protocol. IKE is a component of IPsec used for performing mutual authentication and establishing and maintaining Security Associations (SAs). This document obsoletes RFC 5996, and includes all of the errata for it. It advances IKEv2 to be an Internet Standard. This memo specifies two elliptic curves over prime fields that offer a high level of practical security in cryptographic applications, including Transport Layer Security (TLS). These curves are intended to operate at the ~128-bit and ~224-bit security level, respectively, and are generated deterministically based on a list of required properties. This document provides recommendations for the implementation of public-key cryptography based on the RSA algorithm, covering cryptographic primitives, encryption schemes, signature schemes with appendix, and ASN.1 syntax for representing keys and for identifying the schemes. This document represents a republication of PKCS #1 v2.2 from RSA Laboratories' Public-Key Cryptography Standards (PKCS) series. By publishing this RFC, change control is transferred to the IETF. This document also obsoletes RFC 3447. This document specifies version 1.3 of the Transport Layer Security (TLS) protocol. TLS allows client/server applications to communicate over the Internet in a way that is designed to prevent eavesdropping, tampering, and message forgery. This document updates RFCs 5705 and 6066, and obsoletes RFCs 5077, 5246, and 6961. This document also specifies new requirements for TLS 1.2 implementations. This document defines Secure/Multipurpose Internet Mail Extensions (S/MIME) version 4.0. S/MIME provides a consistent way to send and receive secure MIME data. Digital signatures provide authentication, message integrity, and non-repudiation with proof of origin. Encryption provides data confidentiality. Compression can be used to reduce data size. This document obsoletes RFC 5751. This document describes a scheme for hybrid public key encryption (HPKE). This scheme provides a variant of public key encryption of arbitrary-sized plaintexts for a recipient public key. It also includes three authenticated variants, including one that authenticates possession of a pre-shared key and two optional ones that authenticate possession of a key encapsulation mechanism (KEM) private key. HPKE works for any combination of an asymmetric KEM, key derivation function (KDF), and authenticated encryption with additional data (AEAD) encryption function. Some authenticated variants may not be supported by all KEMs. We provide instantiations of the scheme using widely used and efficient primitives, such as Elliptic Curve Diffie-Hellman (ECDH) key agreement, HMAC-based key derivation function (HKDF), and SHA2. This document is a product of the Crypto Forum Research Group (CFRG) in the IRTF. University of Waterloo Cisco Systems University of Haifa and Amazon Web Services Hybrid key exchange refers to using multiple key exchange algorithms simultaneously and combining the result with the goal of providing security even if all but one of the component algorithms is broken. It is motivated by transition to post-quantum cryptography. This document provides a construction for hybrid key exchange in the Transport Layer Security (TLS) protocol version 1.3. Discussion of this work is encouraged to happen on the TLS IETF mailing list tls@ietf.org or on the GitHub repository which contains the draft: https://github.com/dstebila/draft-ietf-tls-hybrid-design. UK National Cyber Security Centre One aspect of the transition to post-quantum algorithms in cryptographic protocols is the development of hybrid schemes that incorporate both post-quantum and traditional asymmetric algorithms. This document defines terminology for such schemes. It is intended to ensure consistency and clarity across different protocols, standards, and organisations. sn3rd AWS AWS Cloudflare Kyber is a key-encapsulation mechanism (KEM). This document specifies algorithm identifiers and ASN.1 encoding format for Kyber 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.] Vigil Security, LLC Entrust DigiCert, Inc. The Cryptographic Message Syntax (CMS) supports key transport and key agreement algorithms. In recent years, cryptographers have been specifying Key Encapsulation Mechanism (KEM) algorithms, including quantum-secure KEM algorithms. This document defines conventions for the use of KEM algorithms by the originator and recipients to encrypt CMS content. Federal Office for Information Security (BSI) French Cybersecurity Agency (ANSSI) Federal Office for Information Security (BSI) Netherlands National Communications Security Agency (NLNCSA) Swedish National Communications Security Authority, Swedish Armed Forces n.d. n.d.

Samples TBD

Fixed Component Algorithm Identifiers The following table lists explicitly the DER encoded AlgorithmID that MUST be used when reconstructing SubjectPublicKeyInfo objects for each component public key, which may be required for example if cryptographic library requires the public key in this form in order to process each component algorithm. The public key BIT STRING should be taken directly from the respective component of the CompositeKEMPublicKey.

Composite KEM	First AlgorithmID	Second AlgorithmID
TODO	TODO	TODO

TODO: see https://github.com/lamps-wg/draft-composite-kem/issues/20

Implementation Considerations

FIPS certification One of the primary design goals of this specification is for the overall composite algorithm to be able to be considered FIPS-approved even when one of the component algorithms is not. The combiner presented in was chosen to align with for this reason. Implementers seeking FIPS certification of a composite KEM algorithm where only one of the component algorithms has been FIPS-validated or FIPS-approved should credit the FIPS-validated component algorithm with full security strength, the non-FIPS-validated component algorithm with zero security, and the overall composite should be considered full strength and thus FIPS-approved. The authors wish to note that this gives composite algorithms great future utility both for future cryptographic migrations as well as bridging across jurisdictions; for example defining composite algorithms which combine FIPS cryptography with cryptography from a different national standards body.

Backwards Compatibility As noted in the introduction, the post-quantum cryptographic migration will face challenges in both ensuring cryptographic strength against adversaries of unknown capabilities, as well as providing ease of migration. The composite mechanisms defined in this document primarily address cryptographic strength, however this section contains notes on how backwards compatibility may be obtained. The term "ease of migration" is used here to mean that existing systems can be gracefully transitioned to the new technology without requiring large service disruptions or expensive upgrades. The term "backwards compatibility" is used here to mean something more specific; that existing systems as they are deployed today can inter-operate with the upgraded systems of the future. These migration and interoperability concerns need to be thought about in the context of various types of protocols that make use of X.509 and PKIX with relation to key establishment and content encryption, from online negotiated protocols such as TLS 1.3 and IKEv2 , to non-negotiated asynchronous protocols such as S/MIME signed email , as well as myriad other standardized and proprietary protocols and applications that leverage CMS encrypted structures.

Parallel PKIs EDNOTE: remove this section? We present the term "Parallel PKI" to refer to the setup where a PKI end entity possesses two or more distinct public keys or certificates for the same identity (name), but containing keys for different cryptographic algorithms. One could imagine a set of parallel PKIs where an existing PKI using legacy algorithms (RSA, ECC) is left operational during the post-quantum migration but is shadowed by one or more parallel PKIs using pure post quantum algorithms or composite algorithms (legacy and post-quantum). Equipped with a set of parallel public keys in this way, a client would have the flexibility to choose which public key(s) or certificate(s) to use in a given signature operation. For negotiated protocols, the client could choose which public key(s) or certificate(s) to use based on the negotiated algorithms. For non-negotiated protocols, the details for obtaining backwards compatibility will vary by protocol, but for example in CMS . EDNOTE: I copied and pruned this text from I-D.ounsworth-pq-composite-sigs. It probably needs to be fleshed out more as we better understand the implementation concerns around composite encryption.

Intellectual Property Considerations The following IPR Disclosure relates to this draft: https://datatracker.ietf.org/ipr/3588/ EDNOTE TODO: Check with Max Pala whether this IPR actually applies to this draft.

Contributors and Acknowledgments This document incorporates contributions and comments from a large group of experts. The Editors would especially like to acknowledge the expertise and tireless dedication of the following people, who attended many long meetings and generated millions of bytes of electronic mail and VOIP traffic over the past year in pursuit of this document: Serge Mister (Entrust), Ali Noman (Entrust), and Douglas Stebila (University of Waterloo). We are grateful to all, including any contributors who may have been inadvertently omitted from this list. This document borrows text from similar documents, including those referenced below. Thanks go to the authors of those documents. "Copying always makes things easier and less error prone" - .