LAMPS M. Ounsworth Internet-Draft J. Gray Intended status: Standards Track Entrust Expires: 9 January 2025 M. Pala OpenCA Labs J. Klaussner Bundesdruckerei GmbH S. Fluhrer Cisco Systems 8 July 2024 Composite ML-KEM for Use in the Internet X.509 Public Key Infrastructure and CMS draft-ietf-lamps-pq-composite-kem-04 Abstract 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 [I-D.housley-lamps-cms-kemri]. These combinations are tailored to meet security best practices and regulatory requirements. 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/draft-composite-kem/draft-ietf-lamps-pq-composite- kem.html#name-asn1-module. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-ietf-lamps-pq- composite-kem/. Discussion of this document takes place on the LAMPS Working Group mailing list (mailto:spams@ietf.org), which is archived at https://datatracker.ietf.org/wg/lamps/about/. Subscribe at https://www.ietf.org/mailman/listinfo/spams/. Source for this draft and an issue tracker can be found at https://github.com/lamps-wg/draft-composite-kem. Ounsworth, et al. Expires 9 January 2025 [Page 1] Internet-Draft Composite ML-KEM July 2024 Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 9 January 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. Table of Contents 1. Changes in version -04 . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6 2.2. Composite Design Philosophy . . . . . . . . . . . . . . . 7 2.3. Composite Key Encapsulation Mechanisms (KEMs) . . . . . . 7 2.3.1. Composite KeyGen . . . . . . . . . . . . . . . . . . 8 2.3.2. Promotion of RSA-OAEP into a KEM . . . . . . . . . . 8 2.3.3. Promotion of ECDH into a KEM . . . . . . . . . . . . 9 2.3.4. Composite Encaps . . . . . . . . . . . . . . . . . . 9 2.3.5. Composite Decaps . . . . . . . . . . . . . . . . . . 10 3. Composite Key Structures . . . . . . . . . . . . . . . . . . 11 3.1. pk-CompositeKEM . . . . . . . . . . . . . . . . . . . . . 11 3.2. CompositeKEMPublicKey . . . . . . . . . . . . . . . . . . 11 3.3. CompositeKEMPrivateKey . . . . . . . . . . . . . . . . . 12 3.4. Encoding Rules . . . . . . . . . . . . . . . . . . . . . 13 Ounsworth, et al. Expires 9 January 2025 [Page 2] Internet-Draft Composite ML-KEM July 2024 3.5. Key Usage Bits . . . . . . . . . . . . . . . . . . . . . 13 4. Composite KEM Structures . . . . . . . . . . . . . . . . . . 13 4.1. kema-CompositeKEM . . . . . . . . . . . . . . . . . . . . 13 4.2. CompositeCiphertextValue . . . . . . . . . . . . . . . . 14 4.3. KEM Combiner . . . . . . . . . . . . . . . . . . . . . . 14 4.4. FIPS Compliance . . . . . . . . . . . . . . . . . . . . . 15 5. Algorithm Identifiers . . . . . . . . . . . . . . . . . . . . 16 5.1. Domain Separators . . . . . . . . . . . . . . . . . . . . 18 5.2. RSA-OAEP Parameters . . . . . . . . . . . . . . . . . . . 19 6. Use in CMS . . . . . . . . . . . . . . . . . . . . . . . . . 20 6.1. Underlying Components . . . . . . . . . . . . . . . . . . 21 6.2. RecipientInfo Conventions . . . . . . . . . . . . . . . . 22 6.3. Certificate Conventions . . . . . . . . . . . . . . . . . 23 6.4. SMIMECapabilities Attribute Conventions . . . . . . . . . 23 7. ASN.1 Module . . . . . . . . . . . . . . . . . . . . . . . . 23 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30 8.1. Object Identifier Allocations . . . . . . . . . . . . . . 30 8.1.1. Module Registration - SMI Security for PKIX Module Identifier . . . . . . . . . . . . . . . . . . . . . 30 8.1.2. Object Identifier Registrations - SMI Security for PKIX Algorithms . . . . . . . . . . . . . . . . . . . . . 30 9. Security Considerations . . . . . . . . . . . . . . . . . . . 32 9.1. Component Algorithm Selection Criteria . . . . . . . . . 32 9.2. Policy for Deprecated and Acceptable Algorithms . . . . . 33 9.3. KEM Combiner Security Analysis . . . . . . . . . . . . . 33 9.3.1. Ciphertext collision resistance . . . . . . . . . . . 34 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 34 10.1. Normative References . . . . . . . . . . . . . . . . . . 34 10.2. Informative References . . . . . . . . . . . . . . . . . 36 Appendix A. Samples . . . . . . . . . . . . . . . . . . . . . . 39 Appendix B. Fixed Component Algorithm Identifiers . . . . . . . 39 Appendix C. Implementation Considerations . . . . . . . . . . . 39 C.1. FIPS certification . . . . . . . . . . . . . . . . . . . 39 C.2. Backwards Compatibility . . . . . . . . . . . . . . . . . 40 C.2.1. Parallel PKIs . . . . . . . . . . . . . . . . . . . . 40 Appendix D. Intellectual Property Considerations . . . . . . . . 41 Appendix E. Contributors and Acknowledgments . . . . . . . . . . 41 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 41 1. 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. Ounsworth, et al. Expires 9 January 2025 [Page 3] Internet-Draft Composite ML-KEM July 2024 * 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 [RFC5990] 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. Ounsworth, et al. Expires 9 January 2025 [Page 4] Internet-Draft Composite ML-KEM July 2024 2. 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 [I-D.driscoll-pqt-hybrid-terminology]. 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 [BSI2021]. In addition, [BSI2021] specifically references this specification as a concrete example of hybrid X.509 certificates. A more recent example is [ANSSI2024], 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. Ounsworth, et al. Expires 9 January 2025 [Page 5] Internet-Draft Composite ML-KEM July 2024 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 Appendix C.2. This document is intended for general applicability anywhere that key establishment or enveloped content encryption is used within PKIX or CMS structures. 2.1. 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 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. This document is consistent with all terminology from [I-D.driscoll-pqt-hybrid-terminology]. 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 [X.690]. Ounsworth, et al. Expires 9 January 2025 [Page 6] Internet-Draft Composite ML-KEM July 2024 *KEM:* A key encapsulation mechanism as defined in Section 2.3. *PKI:* Public Key Infrastructure, as defined in [RFC5280]. *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. 2.2. Composite Design Philosophy [I-D.driscoll-pqt-hybrid-terminology] 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 [RFC2986], CMP [RFC4210], X.509 [RFC5280], CMS [RFC5652], and the Trust Anchor Format [RFC5914]. 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. 2.3. Composite Key Encapsulation Mechanisms (KEMs) We borrow here the definition of a key encapsulation mechanism (KEM) from [I-D.ietf-tls-hybrid-design], 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. Ounsworth, et al. Expires 9 January 2025 [Page 7] Internet-Draft Composite ML-KEM July 2024 * 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 [RFC5652]), and key agreement (for example for use with KeyAgreeRecipientInfo defined in [RFC5652]). 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 [I-D.ietf-lamps-kyber-certificates] and [FIPS.203-ipd]. For Traditional KEMs, this document uses the RSA-OAEP algorithm defined in [RFC3560], the Elliptic Curve Diffie-Hellman key agreement schemes ECDH defined in section 5.7.1.2 of [SP.800-56Ar3], and X25519 / X448 which are defined in [RFC8410]. A combiner function is used to combine the two component shared secrets into a single shared secret. 2.3.1. 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 Section 3.2 and a composite secret key sk is per Section 3.3. CompositeKEM.KeyGen(): (compositePK[0], compositeSK[0]) = MLKEM.KeyGen() (compositePK[1], compositeSK[1]) = TradKEM.KeyGen() return (compositePK, compositeSK) 2.3.2. 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 [RFC3560] 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. DHKEM.Encaps(pkR): shared_secret = SecureRandom(ss_len) enc = RSA-OAEP.Encrypt(pkR, shared_secret) return enc, shared_secret Ounsworth, et al. Expires 9 January 2025 [Page 8] Internet-Draft Composite ML-KEM July 2024 Decaps(sk, ct) -> ss is accomplished in the analogous way. DHKEM.Decap(skR, enc): shared_secret = RSA-OAEP.Decrypt(skR, enc) return shared_secret The value of ss_len as well as the RSA-OAEP parameters used within this specification can be found in Section 5.2. 2.3.3. 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 [RFC9180]. DHKEM.Encaps(pkR): skE, pkE = GenerateKeyPair() shared_secret = DH(skE, pkR) enc = SerializePublicKey(pkE) return enc, shared_secret Decaps(sk, ct) -> ss is accomplished in the analogous way. DHKEM.Decap(skR, enc): pkE = DeserializePublicKey(enc) shared_secret = DH(skR, pkE) return shared_secret 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 [RFC9180] 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(). 2.3.4. Composite Encaps The Encaps(pk) -> (ct, ss) of a composite KEM algorithm is defined as: Ounsworth, et al. Expires 9 January 2025 [Page 9] Internet-Draft Composite ML-KEM July 2024 CompositeKEM.Encaps(pk): # Split the component public keys mlkemPK = pk[0] tradPK = pk[1] # Perform the respective component Encaps operations (mlkemCT, mlkemSS) = MLKEM.Encaps(mlkemPK) (tradCT, tradSS) = TradKEM.Encaps(tradPK) # Combine # note that the order of the traditional and ML-KEM components # is flipped here in order to satisfy NIST SP800-56Cr2. ct = CompositeCiphertextValue(ct1, ct2) ss = Combiner(tradSS, mlkemSS, tradCT, tradPK, domSep) return (ct, ss) where Combiner(tradSS, mlkemSS, tradCT, tradPK, domSep) is defined in general in Section 4.3 with specific values for domSep per composite KEM algorithm in Section 5 and CompositeCiphertextValue is defined in Section 4.2. 2.3.5. Composite Decaps The Decaps(sk, ct) -> ss of a composite KEM algorithm is defined as: CompositeKEM.Decaps(ct, mlkemSK, tradSK): # split the component ciphertexts mlkemCT = ct[0] tradCT = ct[1] # Perform the respective component Decaps operations mlkemSS = MLKEM.Decaps(mlkemSK, mlkemCT) tradSS = TradKEM.Decaps(tradSK, tradCT) # Combine # note that the order of the traditional and ML-KEM components # is flipped here in order to satisfy NIST SP800-56Cr2. ss = Combiner(tradSS, mlkemSS, tradCT, tradPK, domSep) return ss where Combiner(tradSS, mlkemSS, tradCT, tradPK, domSep) is defined in general in Section 4.3 with specific values for domSep per composite KEM algorithm in Section 5. CompositeCiphertextValue is defined in Section 4.2. Ounsworth, et al. Expires 9 January 2025 [Page 10] Internet-Draft Composite ML-KEM July 2024 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. 3. Composite Key Structures 3.1. pk-CompositeKEM The following ASN.1 Information Object Class is a template to be used in defining all composite KEM public key types. 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 } } As an example, the public key type pk-MLKEM512-ECDH-P256 is defined as: pk-MLKEM512-ECDH-P256 PUBLIC-KEY ::= pk-CompositeKEM { id-MLKEM512-ECDH-P256, OCTET STRING, ECPoint } The full set of key types defined by this specification can be found in the ASN.1 Module in Section 7. 3.2. CompositeKEMPublicKey Composite public key data is represented by the following structure: CompositeKEMPublicKey ::= SEQUENCE SIZE (2) OF BIT STRING 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 Section 5. Ounsworth, et al. Expires 9 January 2025 [Page 11] Internet-Draft Composite ML-KEM July 2024 Some applications may need to reconstruct the SubjectPublicKeyInfo objects corresponding to each component public key. Table 1 in Section 5 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 Section 3.4. 3.3. CompositeKEMPrivateKey Use cases that require an inter-operable encoding for composite private keys, such as when private keys are carried in PKCS #12 [RFC7292], CMP [RFC4210] or CRMF [RFC4211] MUST use the following structure. CompositeKEMPrivateKey ::= SEQUENCE SIZE (2) OF OneAsymmetricKey Each element is a OneAsymmetricKey` [RFC5958] 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 Section 3.2 for the components of CompositeKEMPublicKey. When a CompositePrivateKey is conveyed inside a OneAsymmetricKey structure (version 1 of which is also known as PrivateKeyInfo) [RFC5958], the privateKeyAlgorithm field SHALL be set to the corresponding composite algorithm identifier defined according to Section 5, 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 Appendix C.1 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. Ounsworth, et al. Expires 9 January 2025 [Page 12] Internet-Draft Composite ML-KEM July 2024 3.4. 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. CompositeKEMPublicKeyOs ::= OCTET STRING (CONTAINING CompositeKEMPublicKey ENCODED BY der) 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. CompositeKEMPublicKeyBs ::= BIT STRING (CONTAINING CompositeKEMPublicKey ENCODED BY der) 3.5. Key Usage Bits For protocols such as X.509 [RFC5280] 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. 4. Composite KEM Structures 4.1. kema-CompositeKEM The ASN.1 algorithm object for a composite KEM is: kema-CompositeKEM { OBJECT IDENTIFIER:id, PUBLIC-KEY:publicKeyType } KEM-ALGORITHM ::= { IDENTIFIER id VALUE CompositeCiphertextValue PARAMS ARE absent PUBLIC-KEYS { publicKeyType } } Ounsworth, et al. Expires 9 January 2025 [Page 13] Internet-Draft Composite ML-KEM July 2024 4.2. CompositeCiphertextValue The compositeCipherTextValue is a concatenation of the ciphertexts of the underlying component algorithms. It is represented in ASN.1 as follows: CompositeCiphertextValue ::= SEQUENCE SIZE (2) OF OCTET STRING The order of the component ciphertexts is the same as the order defined in Section 3.2. 4.3. 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: KEK <- Combiner(tradSS, mlkemSS, tradCT, tradPK, domSep) = KDF(counter || tradSS || mlkemSS || tradCT || tradPK || domSep, outputBits) Figure 1: 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 [SP.800-56Cr2]. * 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 Section 5.1. * || represents concatenation. Ounsworth, et al. Expires 9 January 2025 [Page 14] Internet-Draft Composite ML-KEM July 2024 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 [SP.800-56Cr2]; see Section 4.4 for more discussion. See Section 9.3 for further discussion of the security considerations of this KEM combiner. 4.4. FIPS Compliance This specification is compliant with [SP.800-56Cr2] 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 Ounsworth, et al. Expires 9 January 2025 [Page 15] Internet-Draft Composite ML-KEM July 2024 "F" in 8-bit ASCII, as required by [SP.800-56Cr2] 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. 5. 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 with the String "2.16.840.1.114027.80.5.2". TODO: OIDs to be replaced by IANA. Therefore .1 is equal to 2.16.840.1.114027.80.5.2.1 Ounsworth, et al. Expires 9 January 2025 [Page 16] Internet-Draft Composite ML-KEM July 2024 +===================+============+=========+===============+========+ | Composite KEM |OID |First |Second |KDF | | | |Algorithm|Algorithm | | +===================+============+=========+===============+========+ | id-MLKEM512-ECDH |.1 |MLKEM512 |ECDH-P256 |SHA3-256| | -P256 | | | | | +-------------------+------------+---------+---------------+--------+ | id-MLKEM512- |.2 |MLKEM512 |ECDH- |SHA3-256| | ECDH- | | |brainpoolp256r1| | | brainpoolP256r1 | | | | | +-------------------+------------+---------+---------------+--------+ | id- |.3 |MLKEM512 |X25519 |SHA3-256| | MLKEM512-X25519 | | | | | +-------------------+------------+---------+---------------+--------+ | id- |.13|MLKEM512 |RSA-OAEP 2048 |SHA3-256| | MLKEM512-RSA2048 | | | | | +-------------------+------------+---------+---------------+--------+ | id- |.4 |MLKEM512 |RSA-OAEP 3072 |SHA3-256| | MLKEM512-RSA3072 | | | | | +-------------------+------------+---------+---------------+--------+ | id-MLKEM768-ECDH |.5 |MLKEM768 |ECDH-P256 |SHA3-384| | -P256 | | | | | +-------------------+------------+---------+---------------+--------+ | id-MLKEM768- |.6 |MLKEM768 |ECDH- |SHA3-384| | ECDH- | | |brainpoolp256r1| | | brainpoolP256r1 | | | | | +-------------------+------------+---------+---------------+--------+ | id- |.7 |MLKEM768 |X25519 |SHA3-384| | MLKEM768-X25519 | | | | | +-------------------+------------+---------+---------------+--------+ | id-MLKEM1024-ECD |.8 |MLKEM1024|ECDH-P384 |SHA3-512| | H-P384 | | | | | +-------------------+------------+---------+---------------+--------+ | id-MLKEM1024- |.9 |MLKEM1024|ECDH- |SHA3-512| | ECDH- | | |brainpoolP384r1| | | brainpoolP384r1 | | | | | +-------------------+------------+---------+---------------+--------+ | id- |.10|MLKEM1024|X448 |SHA3-512| | MLKEM1024-X448 | | | | | +-------------------+------------+---------+---------------+--------+ Table 1: Composite KEM key types 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: Ounsworth, et al. Expires 9 January 2025 [Page 17] Internet-Draft Composite ML-KEM July 2024 - _ECDH NIST_: SHALL be Elliptic Curve Cryptography Cofactor Diffie-Hellman (ECC CDH) as defined in section 5.7.1.2 of [SP.800-56Ar3]. - _ECDH BSI / brainpool_: SHALL be Elliptic Curve Key Agreement algorithm (ECKA) as defined in section 4.3.1 of [BSI-ECC] * _ML-KEM_: [I-D.ietf-lamps-kyber-certificates] and [FIPS.203-ipd] * _RSA-OAEP_: [RFC3560] * _X25519 / X448_: [RFC8410] EDNOTE: I believe that [SP.800-56Ar3] and [BSI-ECC] give equivalent and inter-operable algorithms, so maybe this is extraneous detail to include? 5.1. Domain Separators The KEM combiner defined in section Section 4.3 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 Ounsworth, et al. Expires 9 January 2025 [Page 18] Internet-Draft Composite ML-KEM July 2024 +===================================+============================+ | 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 | +-----------------------------------+----------------------------+ Table 2: Composite KEM fixedInfo Domain Separators 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. 5.2. RSA-OAEP Parameters Use of RSA-OAEP [RFC3560] 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 [RFC5990] 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 [RFC8017] is still everywhere, but hard to make secure and no longer FIPS-approved as of the end of 2023 [SP800-131Ar2], so it is of limited forwards value. This leaves RSA-OAEP [RFC3560] as the remaining choice. Ounsworth, et al. Expires 9 January 2025 [Page 19] Internet-Draft Composite ML-KEM July 2024 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 Parameter | Value | +====================+===================================+ | hashFunc | id-sha2-256 | +--------------------+-----------------------------------+ | maskGenFunc | mgf1SHA256Identifier | +--------------------+-----------------------------------+ | pSourceFunc | DEFAULT pSpecifiedEmptyIdentifier | +--------------------+-----------------------------------+ | ss_len | 256 bits | +--------------------+-----------------------------------+ Table 3: RSA-OAEP Parameters where: * id-sha256 is defined in [RFC8017]. * mgf1SHA256Identifier is defined in [RFC4055]. * pSpecifiedEmptyIdentifier is defined in [RFC3560] 6. 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 [RFC5652], the CMS authenticated-data content type [RFC5652], or the CMS authenticated- enveloped-data content type [RFC5083]. In each case, the KEMRecipientInfo [I-D.ietf-lamps-cms-kemri] is used with the chosen composite KEM Algorithm to securely transfer the content-encryption key from the originator to the recipient. Ounsworth, et al. Expires 9 January 2025 [Page 20] Internet-Draft Composite ML-KEM July 2024 6.1. 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 Table 4. When a particular Composite KEM OID is supported, an implementation MUST support the corresponding key-encryption algorithm identifier in Table 4. The following table lists the REQUIRED KDF and key-encryption algorithms to preserve security and performance characteristics of each composite algorithm. +===================================+==========+====================+ | 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 | +-----------------------------------+----------+--------------------+ Table 4: REQUIRED pairings for CMS KDF and WRAP Ounsworth, et al. Expires 9 January 2025 [Page 21] Internet-Draft Composite ML-KEM July 2024 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 [I-D.ietf-lamps-cms-sha3-hash]. * id-aes*-Wrap are defined in [RFC3394]. 6.2. 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 [I-D.ietf-lamps-cms-kemri]. 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 Table 1. 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 [RFC5652], the keying material is a content-encryption key. When used with the CMS authenticated-data content type [RFC5652], the Ounsworth, et al. Expires 9 January 2025 [Page 22] Internet-Draft Composite ML-KEM July 2024 keying material is a message-authentication key. When used with the CMS authenticated-enveloped-data content type [RFC5083], the keying material is a content-authenticated-encryption key. 6.3. Certificate Conventions The conventions specified in this section augment RFC 5280 [RFC5280]. 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 [RFC8551] or the SMIMECapabilities certificate extension as specified in [RFC4262]. 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 [RFC5280]. 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. 6.4. SMIMECapabilities Attribute Conventions Section 2.5.2 of [RFC8551] 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 [RFC5652], 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 Table 1 in the capabilityID field. 7. ASN.1 Module Ounsworth, et al. Expires 9 January 2025 [Page 23] Internet-Draft Composite ML-KEM July 2024 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 Ounsworth, et al. Expires 9 January 2025 [Page 24] Internet-Draft Composite ML-KEM July 2024 -- -- 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 Ounsworth, et al. Expires 9 January 2025 [Page 25] Internet-Draft Composite ML-KEM July 2024 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) Ounsworth, et al. Expires 9 January 2025 [Page 26] Internet-Draft Composite ML-KEM July 2024 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 Ounsworth, et al. Expires 9 January 2025 [Page 27] Internet-Draft Composite ML-KEM July 2024 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 } Ounsworth, et al. Expires 9 January 2025 [Page 28] Internet-Draft Composite ML-KEM July 2024 -- 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 } Ounsworth, et al. Expires 9 January 2025 [Page 29] Internet-Draft Composite ML-KEM July 2024 -- -- 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 8. IANA Considerations 8.1. Object Identifier Allocations EDNOTE to IANA: OIDs will need to be replaced in both the ASN.1 module and in Table 1. 8.1.1. Module Registration - SMI Security for PKIX Module Identifier * Decimal: IANA Assigned - *Replace TBDMOD* * Description: Composite-KEM-2023 - id-mod-composite-kems * References: This Document 8.1.2. Object Identifier Registrations - SMI Security for PKIX Algorithms * id-MLKEM512-ECDH-P256 - Decimal: IANA Assigned - Description: id-MLKEM512-ECDH-P256 - References: This Document Ounsworth, et al. Expires 9 January 2025 [Page 30] Internet-Draft Composite ML-KEM July 2024 * 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 Ounsworth, et al. Expires 9 January 2025 [Page 31] Internet-Draft Composite ML-KEM July 2024 * 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 9. Security Considerations 9.1. 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 [RFC6090], Brainpool [RFC5639], and Edwards [RFC7748] 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. Ounsworth, et al. Expires 9 January 2025 [Page 32] Internet-Draft Composite ML-KEM July 2024 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. 9.2. 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 Section 4.3 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. 9.3. 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 [X-Wing]. Ounsworth, et al. Expires 9 January 2025 [Page 33] Internet-Draft Composite ML-KEM July 2024 9.3.1. Ciphertext collision resistance The notion of a ciphertext collision resistant KEM is defined in [X-Wing] 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 [X-Wing] 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. 10. References 10.1. Normative References [BSI-ECC] Federal Office for Information Security (BSI), "Technical Guideline BSI TR-03111: Elliptic Curve Cryptography. Version 2.10", 1 June 2018. [FIPS.203-ipd] National Institute of Standards and Technology (NIST), "Module-Lattice-based Key-Encapsulation Mechanism Standard", August 2023, . [I-D.ietf-lamps-cms-kemri] Housley, R., Gray, J., and T. Okubo, "Using Key Encapsulation Mechanism (KEM) Algorithms in the Cryptographic Message Syntax (CMS)", Work in Progress, Internet-Draft, draft-ietf-lamps-cms-kemri-08, 6 February 2024, . [I-D.ietf-lamps-cms-sha3-hash] Housley, R., "Use of the SHA3 One-way Hash Functions in the Cryptographic Message Syntax (CMS)", Work in Progress, Internet-Draft, draft-ietf-lamps-cms-sha3-hash-04, 16 May 2024, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . Ounsworth, et al. Expires 9 January 2025 [Page 34] Internet-Draft Composite ML-KEM July 2024 [RFC3394] Schaad, J. and R. Housley, "Advanced Encryption Standard (AES) Key Wrap Algorithm", RFC 3394, DOI 10.17487/RFC3394, September 2002, . [RFC3560] Housley, R., "Use of the RSAES-OAEP Key Transport Algorithm in Cryptographic Message Syntax (CMS)", RFC 3560, DOI 10.17487/RFC3560, July 2003, . [RFC4055] Schaad, J., Kaliski, B., and R. Housley, "Additional Algorithms and Identifiers for RSA Cryptography for use in the Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 4055, DOI 10.17487/RFC4055, June 2005, . [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, May 2008, . [RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70, RFC 5652, DOI 10.17487/RFC5652, September 2009, . [RFC5958] Turner, S., "Asymmetric Key Packages", RFC 5958, DOI 10.17487/RFC5958, August 2010, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8410] Josefsson, S. and J. Schaad, "Algorithm Identifiers for Ed25519, Ed448, X25519, and X448 for Use in the Internet X.509 Public Key Infrastructure", RFC 8410, DOI 10.17487/RFC8410, August 2018, . [RFC8411] Schaad, J. and R. Andrews, "IANA Registration for the Cryptographic Algorithm Object Identifier Range", RFC 8411, DOI 10.17487/RFC8411, August 2018, . [SP.800-56Ar3] National Institute of Standards and Technology (NIST), "Recommendation for Pair-Wise Key-Establishment Schemes Ounsworth, et al. Expires 9 January 2025 [Page 35] Internet-Draft Composite ML-KEM July 2024 Using Discrete Logarithm Cryptography", April 2018, . [SP.800-56Cr2] National Institute of Standards and Technology (NIST), "Recommendation for Key-Derivation Methods in Key- Establishment Schemes", August 2020, . [X.690] ITU-T, "Information technology - ASN.1 encoding Rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER)", ISO/IEC 8825-1:2015, November 2015. 10.2. Informative References [ANSSI2024] 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, "Position Paper on Quantum Key Distribution", n.d., . [BSI2021] Federal Office for Information Security (BSI), "Quantum- safe cryptography - fundamentals, current developments and recommendations", October 2021, . [I-D.driscoll-pqt-hybrid-terminology] D, F., "Terminology for Post-Quantum Traditional Hybrid Schemes", Work in Progress, Internet-Draft, draft- driscoll-pqt-hybrid-terminology-01, 20 October 2022, . [I-D.housley-lamps-cms-kemri] Housley, R., Gray, J., and T. Okubo, "Using Key Encapsulation Mechanism (KEM) Algorithms in the Cryptographic Message Syntax (CMS)", Work in Progress, Internet-Draft, draft-housley-lamps-cms-kemri-02, 20 February 2023, . Ounsworth, et al. Expires 9 January 2025 [Page 36] Internet-Draft Composite ML-KEM July 2024 [I-D.ietf-lamps-kyber-certificates] Turner, S., Kampanakis, P., Massimo, J., and B. Westerbaan, "Internet X.509 Public Key Infrastructure - Algorithm Identifiers for Kyber", Work in Progress, Internet-Draft, draft-ietf-lamps-kyber-certificates-01, 28 March 2023, . [I-D.ietf-tls-hybrid-design] Stebila, D., Fluhrer, S., and S. Gueron, "Hybrid key exchange in TLS 1.3", Work in Progress, Internet-Draft, draft-ietf-tls-hybrid-design-04, 11 January 2022, . [RFC2986] Nystrom, M. and B. Kaliski, "PKCS #10: Certification Request Syntax Specification Version 1.7", RFC 2986, DOI 10.17487/RFC2986, November 2000, . [RFC4210] Adams, C., Farrell, S., Kause, T., and T. Mononen, "Internet X.509 Public Key Infrastructure Certificate Management Protocol (CMP)", RFC 4210, DOI 10.17487/RFC4210, September 2005, . [RFC4211] Schaad, J., "Internet X.509 Public Key Infrastructure Certificate Request Message Format (CRMF)", RFC 4211, DOI 10.17487/RFC4211, September 2005, . [RFC4262] Santesson, S., "X.509 Certificate Extension for Secure/ Multipurpose Internet Mail Extensions (S/MIME) Capabilities", RFC 4262, DOI 10.17487/RFC4262, December 2005, . [RFC5083] Housley, R., "Cryptographic Message Syntax (CMS) Authenticated-Enveloped-Data Content Type", RFC 5083, DOI 10.17487/RFC5083, November 2007, . [RFC5639] Lochter, M. and J. Merkle, "Elliptic Curve Cryptography (ECC) Brainpool Standard Curves and Curve Generation", RFC 5639, DOI 10.17487/RFC5639, March 2010, . Ounsworth, et al. Expires 9 January 2025 [Page 37] Internet-Draft Composite ML-KEM July 2024 [RFC5914] Housley, R., Ashmore, S., and C. Wallace, "Trust Anchor Format", RFC 5914, DOI 10.17487/RFC5914, June 2010, . [RFC5990] Randall, J., Kaliski, B., Brainard, J., and S. Turner, "Use of the RSA-KEM Key Transport Algorithm in the Cryptographic Message Syntax (CMS)", RFC 5990, DOI 10.17487/RFC5990, September 2010, . [RFC6090] McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic Curve Cryptography Algorithms", RFC 6090, DOI 10.17487/RFC6090, February 2011, . [RFC7292] Moriarty, K., Ed., Nystrom, M., Parkinson, S., Rusch, A., and M. Scott, "PKCS #12: Personal Information Exchange Syntax v1.1", RFC 7292, DOI 10.17487/RFC7292, July 2014, . [RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T. Kivinen, "Internet Key Exchange Protocol Version 2 (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October 2014, . [RFC7748] Langley, A., Hamburg, M., and S. Turner, "Elliptic Curves for Security", RFC 7748, DOI 10.17487/RFC7748, January 2016, . [RFC8017] Moriarty, K., Ed., Kaliski, B., Jonsson, J., and A. Rusch, "PKCS #1: RSA Cryptography Specifications Version 2.2", RFC 8017, DOI 10.17487/RFC8017, November 2016, . [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, . [RFC8551] Schaad, J., Ramsdell, B., and S. Turner, "Secure/ Multipurpose Internet Mail Extensions (S/MIME) Version 4.0 Message Specification", RFC 8551, DOI 10.17487/RFC8551, April 2019, . [RFC9180] Barnes, R., Bhargavan, K., Lipp, B., and C. Wood, "Hybrid Public Key Encryption", RFC 9180, DOI 10.17487/RFC9180, February 2022, . Ounsworth, et al. Expires 9 January 2025 [Page 38] Internet-Draft Composite ML-KEM July 2024 [SP800-131Ar2] Barker, E. and A. Roginksy, "Transitioning the Use of Cryptographic Algorithms and Key Lengths", n.d., . [X-Wing] Barbosa, M., Connolly, D., Duarte, J., Kaiser, A., Schwabe, P., Varner, K., and B. Westerbaan, "X-Wing The Hybrid KEM You've Been Looking For", 9 January 2024, . Appendix A. Samples TBD Appendix B. 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 | +---------------+-------------------+--------------------+ Table 5 TODO: see https://github.com/lamps-wg/draft-composite-kem/issues/20 Appendix C. Implementation Considerations C.1. 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 Section 4.3 was chosen to align with [SP.800-56Cr2] 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 Ounsworth, et al. Expires 9 January 2025 [Page 39] Internet-Draft Composite ML-KEM July 2024 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. C.2. 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 [RFC8446] and IKEv2 [RFC7296], to non-negotiated asynchronous protocols such as S/MIME signed email [RFC8551], as well as myriad other standardized and proprietary protocols and applications that leverage CMS [RFC5652] encrypted structures. C.2.1. 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). Ounsworth, et al. Expires 9 January 2025 [Page 40] Internet-Draft Composite ML-KEM July 2024 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 [RFC5652]. 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. Appendix D. 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. Appendix E. 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" - [RFC8411]. Authors' Addresses Ounsworth, et al. Expires 9 January 2025 [Page 41] Internet-Draft Composite ML-KEM July 2024 Mike Ounsworth Entrust Limited 2500 Solandt Road -- Suite 100 Ottawa, Ontario K2K 3G5 Canada Email: mike.ounsworth@entrust.com John Gray Entrust Limited 2500 Solandt Road -- Suite 100 Ottawa, Ontario K2K 3G5 Canada Email: john.gray@entrust.com Massimiliano Pala OpenCA Labs New York City, New York, United States of America Email: director@openca.org Jan Klaussner Bundesdruckerei GmbH Kommandantenstr. 18 10969 Berlin Germany Email: jan.klaussner@bdr.de Scott Fluhrer Cisco Systems Email: sfluhrer@cisco.com Ounsworth, et al. Expires 9 January 2025 [Page 42]