]> 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. 15 Berlin 10969 Germany jan.klaussner@bdr.de

Cisco Systems

sfluhrer@cisco.com

Security LAMPS Internet-Draft This document defines Post-Quantum / Traditional composite Key Signaturem algorithms suitable for use within X.509, PKIX and CMS protocols. Composite algorithms are provided which combine ML-DSA with RSA, ECDSA, Ed25519, and Ed448. The provided set of composite algorithms should meet most X.509, PKIX, and CMS needs.

Changes since adoption by the lamps working group

• Added back in the version 13 changes which were dropped by mistake in the initial -00 adopted version
• Added Scott Fluher as an author due to his valuable contributions and participation in the draft writing process
• Removed the reference to Parallel PKI's in implementation considerations as it isn't adding value to the discussion
• Resolved comments from Kris Kwiatkowski regarding FIPS

Introduction During the transition to post-quantum cryptography, there will be uncertainty as to the strength of cryptographic algorithms; we will no longer fully trust traditional cryptography such as RSA, Diffie-Hellman, DSA and their elliptic curve variants, but we will also not fully trust their post-quantum replacements until they have had sufficient scrutiny and time to discover and fix implementation bugs. Unlike previous cryptographic algorithm migrations, the choice of when to migrate and which algorithms to migrate to, is not so clear. Even after the migration period, it may be advantageous for an entity's cryptographic identity to be composed of multiple public-key algorithms. Cautious implementers may wish to combine cryptographic algorithms such that an attacker would need to break all of them in order to compromise the data being protected. Such mechanisms are referred to as Post-Quantum / Traditional Hybrids . In particular, certain jurisdictions are recommending or requiring that PQC lattice schemes only be used within a PQ/T hybrid. As an example, we point to which includes the following recommendation: "Therefore, quantum computer-resistant methods should not be used alone - at least in a transitional period - but only in hybrid mode, i.e. in combination with a classical method. For this purpose, protocols must be modified or supplemented accordingly. In addition, public key infrastructures, for example, must also be adapted" 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.
• Safeguard against faulty algorithm implementations and compromised keys: Even for long known algorithms there is a non-negligible risk of severe implementation faults. Latest examples are the ROCA attack and ECDSA psychic signatures. Using more than one algorithms will mitigate these risks.

This document defines a specific instantiation of the PQ/T Hybrid paradigm called "composite" where multiple cryptographic algorithms are combined to form a single signature such that it 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 signature algorithms are provided based on ML-DSA, RSA and ECDSA. Backwards compatibility is not directly covered in this document, but is the subject of . This document is intended for general applicability anywhere that digital signatures are used within PKIX and CMS structures. For a more detailed use-case discussion for composite signatures, the reader is encouraged to look at This document attemps to bind the composite component keys together to achieve the weak non-separability property as defined in using a label as defined in .

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. The following terms are used in this document: ALGORITHM: A standardized cryptographic primitive, as well as any ASN.1 structures needed for encoding data and metadata needed to use the algorithm. This document is primarily concerned with algorithms for producing digital signatures. BER: Basic Encoding Rules (BER) as defined in . CLIENT: Any software that is making use of a cryptographic key. This includes a signer, verifier, encrypter, decrypter. COMPONENT ALGORITHM: A single basic algorithm which is contained within a composite algorithm. COMPOSITE ALGORITHM: An algorithm which is a sequence of two component algorithms, as defined in . DER: Distinguished Encoding Rules as defined in . LEGACY: For the purposes of this document, a legacy algorithm is any cryptographic algorithm currently in use which is not believed to be resistant to quantum cryptanalysis. PKI: Public Key Infrastructure, as defined in . POST-QUANTUM ALGORITHM: Any cryptographic algorithm which is believed to be resistant to classical and quantum cryptanalysis, such as the algorithms being considered for standardization by NIST. PUBLIC / PRIVATE KEY: The public and private portion of an asymmetric cryptographic key, making no assumptions about which algorithm. SIGNATURE: A digital cryptographic signature, making no assumptions about which algorithm. STRIPPING ATTACK: An attack in which the attacker is able to downgrade the cryptographic object to an attacker-chosen subset of original set of component algorithms in such a way that it is not detectable by the receiver. For example, substituting a composite public key or signature for a version with fewer components.

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 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 [RFC5914]. In this way, composites achieve "protocol backwards-compatibility" in that they will drop cleanly into any protocol that accepts signature algorithms without requiring any modification of the protocol to handle multiple keys.

Composite Signatures Here we define the signature mechanism in which a signature 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.
• Sign(sk, Message) -> (signature): A signing algorithm which takes as input a secret key sk and a Message, and outputs a signature
• Verify(pk, Message, signature) -> true or false: A verification algorithm which takes as input a public key, a Message and signature and outputs true if the signature verifies correctly. Thus it proves the Message was signed with the secret key associated with the public key and verifies the integrity of the Message. If the signature and public key cannot verify the Message, it returns false.

A composite signature allows two underlying signature algorithms to be combined into a single cryptographic signature operation and can be used for applications that require signatures.

Composite KeyGen The KeyGen() -> (pk, sk) of a composite signature algorithm will perform the KeyGen() of the respective component signature algorithms and it produces a composite public key pk as per and a composite secret key sk is per . The component keys MUST be uniquely generated for each component key of a Composite and MUST NOT be used in any other keys or as a standalone key.

Composite Sign Generation of a composite signature involves applying each component algorithm's signature process to the input message according to its specification, and then placing each component signature value into the CompositeSignatureValue structure defined in . The following process is used to generate composite signature values.

Composite Sign(sk, Message) (signature) Input: K1, K2 Signing private keys for each component. See note below on composite inputs. A1, A2 Component signature algorithms. See note below on composite inputs. Message The Message to be signed, an octet string HASH The Message Digest Algorithm used for pre-hashing. See section on pre-hashing below. OID The Composite Signature String Algorithm Name converted from ASCII to bytes. See section on OID concatenation below. Output: signature The composite signature, a CompositeSignatureValue Signature Generation Process: 1. Compute a Hash of the Message M' = HASH(Message) 2. Generate the n component signatures independently, according to their algorithm specifications. S1 := Sign( K1, A1, DER(OID) || M' ) S2 := Sign( K2, A2, DER(OID) || M' ) 3. Encode each component signature S1 and S2 into a BIT STRING according to its algorithm specification. signature ::= Sequence { S1, S2 } 4. Output signature ]]>

Note on composite inputs: the method of providing the list of component keys and algorithms is flexible and beyond the scope of this pseudo-code. When passed to the Composite Sign(sk, Message) API the sk is a CompositePrivateKey. It is possible to construct a CompositePrivateKey from component keys stored in separate software or hardware keystores. Variations in the process to accommodate particular private key storage mechanisms are considered to be conformant to this document so long as it produces the same output as the process sketched above. Since recursive composite public keys are disallowed, no component signature may itself be a composite; ie the signature generation process MUST fail if one of the private keys K1 or K2 is a composite. A composite signature MUST produce, and include in the output, a signature value for every component key in the corresponding CompositePublicKey, and they MUST be in the same order; ie in the output, S1 MUST correspond to K1, S2 to K2.

Composite Verify Verification of a composite signature involves applying each component algorithm's verification process according to its specification. Compliant applications MUST output "Valid signature" (true) if and only if all component signatures were successfully validated, and "Invalid signature" (false) otherwise. The following process is used to perform this verification.

Composite Verify(pk, Message, signature)

Note on composite inputs: the method of providing the list of component keys and algorithms is flexible and beyond the scope of this pseudo-code. When passed to the Composite Verify(pk, Message, signature) API the pk is a CompositePublicKey. It is possible to construct a CompositePublicKey from component keys stored in separate software or hardware keystores. Variations in the process to accommodate particular private key storage mechanisms are considered to be conformant to this document so long as it produces the same output as the process sketched above. Since recursive composite public keys are disallowed, no component signature may itself be a composite; ie the signature generation process MUST fail if one of the private keys K1 or K2 is a composite.

OID Concatenation As mentioned above, the OID input value for the Composite Signature Generation and verification process is the DER encoding of the OID represented in Hexidecimal bytes. The following table shows the HEX encoding for each Signature AlgorithmID Composite Signature OID Concatenations

Composite Signature AlgorithmID	DER Encoding to be prepended to each Message
id-MLDSA44-RSA2048-PSS-SHA256	060B6086480186FA6B50080101
id-MLDSA44-RSA2048-PKCS15-SHA256	060B6086480186FA6B50080102
id-MLDSA44-Ed25519-SHA512	060B6086480186FA6B50080103
id-MLDSA44-ECDSA-P256-SHA256	060B6086480186FA6B50080104
id-MLDSA44-ECDSA-brainpoolP256r1-SHA256	060B6086480186FA6B50080105
id-MLDSA65-RSA3072-PSS-SHA512	060B6086480186FA6B50080106
id-MLDSA65-RSA3072-PKCS15-SHA512	060B6086480186FA6B50080107
id-MLDSA65-ECDSA-P256-SHA512	060B6086480186FA6B50080108
id-MLDSA65-ECDSA-brainpoolP256r1-SHA512	060B6086480186FA6B50080109
id-MLDSA65-Ed25519-SHA512	060B6086480186FA6B5008010A
id-MLDSA87-ECDSA-P384-SHA512	060B6086480186FA6B5008010B
id-MLDSA87-ECDSA-brainpoolP384r1-SHA512	060B6086480186FA6B5008010C
id-MLDSA87-Ed448-SHA512	060B6086480186FA6B5008010D

PreHashing the Message As noted in the composite signature generation process and composite signature verification process, the Message should be pre-hashed into M' with the digest algorithm specified in the composite signature algorithm identifier. The choice of the digest algorithm was chosen with the following criteria:

1. For composites paired with RSA or ECDSA, the hashing algorithm SHA256 or SHA512 is used as part of the RSA or ECDSA signature algorithm and is therefore also used as the composite prehashing algorithm.
2. For ML-DSA signing a digest of the message is allowed as long as the hash function provides at least y bits of classical security strength against both collision and second preimage attacks. For MLDSA44 y is 128 bits, MLDSA65 y is 192 bits and for MLDSA87 y is 256 bits. Therefore SHA256 is paired with RSA and ECDSA with MLDSA44 and SHA512 is paired with RSA and ECDSA with MLDSA65 and MLDSA87 to match the appropriate security strength.
3. Ed25519 uses SHA512 internally, therefore SHA512 is used to pre-hash the message when Ed25519 is a component algorithm.
4. Ed448 uses SHAKE256 internally, but to reduce the set of prehashing algorihtms, SHA512 was selected to pre-hash the message when Ed448 is a component algorithm.

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

1. A single RSA combination is provided at a key size of 3072 bits, matched with NIST PQC Level 3 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.

Composite Signature Structures In order for signatures to be composed of multiple algorithms, we define encodings consisting of a sequence of signature primitives (aka "component algorithms") such that these structures can be used as a drop-in replacement for existing signature fields such as those found in PKCS#10 , CMP , X.509 , CMS .

pk-CompositeSignature The following ASN.1 Information Object Class is a template to be used in defining all composite Signature public key types. As an example, the public key type pk-MLDSA65-ECDSA-P256-SHA256 is defined as: The full set of key types defined by this specification can be found in the ASN.1 Module in .

CompositeSignaturePublicKey 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 CompositeSignaturePublicKey and SubjectPublicKeyInfo. When the CompositeSignaturePublicKey must be provided in octet string or bit string format, the data structure is encoded as specified in . Component keys of a CompositeSignaturePublicKey MUST NOT be used in any other type of key or as a standalone key.

CompositeSignaturePrivateKey Usecases that require an interoperable 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 CompositeSignaturePublicKey. When a CompositeSignaturePrivateKey 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 CompositeSignaturePrivateKey, and the publicKey field MUST NOT be present. Associated public key material MAY be present in the CompositeSignaturePrivateKey. In some usecases 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 {sec-fips} for more discussion. The establishment of correspondence between public keys in a CompositeSignaturePublicKey and private keys not represented in a single composite structure is beyond the scope of this document. Component keys of a CompositeSignaturePrivateKey MUST NOT be used in any other type of key or as a standalone key.

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. In the interests of simplicity and avoiding compatibility issues, implementations that parse these structures MAY accept both BER and DER.

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 signature MUST have a signing-type key usage. 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. If the keyUsage extension is present in a Certification Authority (CA) certificate that indicates a composite key, then any combination of the following values MAY be present and any other values MUST NOT be present: If the keyUsage extension is present in an End Entity (EE) certificate that indicates a composite key, then any combination of the following values MAY be present and any other values MUST NOT be present:

Composite Signature Structures

sa-CompositeSignature The ASN.1 algorithm object for a composite signature is: The following is an explanation how SIGNATURE-ALGORITHM elements are used to create Composite Signatures:

SIGNATURE-ALGORITHM element	Definition
IDENTIFIER	The Object ID used to identify the composite Signature Algorithm
VALUE	The Sequence of BIT STRINGS for each component signature value
PARAMS	Parameters are absent
PUBLIC-KEYS	The composite key required to produce the composite signature

CompositeSignatureValue The output of the composite signature algorithm is the DER encoding of the following structure: Where each BIT STRING within the SEQUENCE is a signature value produced by one of the component keys. It MUST contain one signature value produced by each component algorithm, and in the same order as specified in the object identifier. The choice of SEQUENCE SIZE (2) OF BIT STRING, rather than for example a single BIT STRING containing the concatenated signature values, is to gracefully handle variable-length signature values by taking advantage of ASN.1's built-in length fields.

Algorithm Identifiers This section defines the algorithm identifiers for explicit combinations. For simplicity and prototyping purposes, the signature algorithm object identifiers specified in this document are the same as the composite key object Identifiers. A proper implementation should not presume that the object ID of a composite key will be the same as its composite signature algorithm. This section is not intended to be exhaustive and other authors may define other composite signature algorithms so long as they are compatible with the structures and processes defined in this and companion public and private key documents. Some use-cases desire the flexibility for clients to use any combination of supported algorithms, while others desire the rigidity of explicitly-specified combinations of algorithms. The following table summarizes the details for each explicit composite signature algorithms: The OID referenced are TBD for prototyping only, and the following prefix is used for each: replace <CompSig> with the String "2.16.840.1.114027.80.8.1" Therefore <CompSig>.1 is equal to 2.16.840.1.114027.80.8.1.1 Signature public key types: Composite Signature Algorithms

Composite Signature AlgorithmID	OID	First Algorithm	Second Algorithm	Pre-Hash
id-MLDSA44-RSA2048-PSS-SHA256	<CompSig>.1	MLDSA44	SHA256WithRSAPSS	SHA256
id-MLDSA44-RSA2048-PKCS15-SHA256	<CompSig>.2	MLDSA44	SHA256WithRSAEncryption	SHA256
id-MLDSA44-Ed25519-SHA512	<CompSig>.3	MLDSA44	Ed25519	SHA512
id-MLDSA44-ECDSA-P256-SHA256	<CompSig>.4	MLDSA44	SHA256withECDSA	SHA256
id-MLDSA44-ECDSA-brainpoolP256r1-SHA256	<CompSig>.5	MLDSA44	SHA256withECDSA	SHA256
id-MLDSA65-RSA3072-PSS-SHA512	<CompSig>.6	MLDSA65	SHA512WithRSAPSS	SHA512
id-MLDSA65-RSA3072-PKCS15-SHA512	<CompSig>.7	MLDSA65	SHA512WithRSAEncryption	SHA512
id-MLDSA65-ECDSA-P256-SHA512	<CompSig>.8	MLDSA65	SHA512withECDSA	SHA512
id-MLDSA65-ECDSA-brainpoolP256r1-SHA512	<CompSig>.9	MLDSA65	SHA512withECDSA	SHA512
id-MLDSA65-Ed25519-SHA512	<CompSig>.10	MLDSA65	Ed25519	SHA512
id-MLDSA87-ECDSA-P384-SHA512	<CompSig>.11	MLDSA87	SHA512withECDSA	SHA512
id-MLDSA87-ECDSA-brainpoolP384r1-SHA512	<CompSig>.12	MLDSA87	SHA512withECDSA	SHA512
id-MLDSA87-Ed448-SHA512	<CompSig>.13	MLDSA87	Ed448	SHA512

The table above contains everything needed to implement the listed explicit composite algorithms. See the ASN.1 module in section for the explicit definitions of the above Composite signature algorithms. Full specifications for the referenced algorithms can be found as follows:

• MLDSA: and [FIPS.204-ipd]
• ECDSA:
• Ed25519 / Ed448:
• RSAES-PKCS-v1_5:
• RSASSA-PSS:

Notes on id-MLDSA44-RSA2048-PSS-SHA256 Use of RSA-PSS deserves a special explanation. The RSA component keys MUST be generated at the 2048-bit security level in order to match with ML-DSA-44 As with the other composite signature algorithms, when id-MLDSA44-RSA2048-PSS-SHA256 is used in an AlgorithmIdentifier, the parameters MUST be absent. id-MLDSA44-RSA2048-PSS-SHA256 SHALL instantiate RSA-PSS with the following parameters: RSA-PSS 2048 Parameters

RSA-PSS Parameter	Value
Mask Generation Function	mgf1
Mask Generation params	SHA-256
Message Digest Algorithm	SHA-256

where:

• Mask Generation Function (mgf1) is defined in
• SHA-256 is defined in .

Notes on id-MLDSA65-RSA3072-PSS-SHA512 The RSA component keys MUST be generated at the 3072-bit security level in order to match with ML-DSA-65. As with the other composite signature algorithms, when id-MLDSA65-RSA3072-PSS-SHA512 is used in an AlgorithmIdentifier, the parameters MUST be absent. id-MLDSA65-RSA3072-PSS-SHA512 SHALL instantiate RSA-PSS with the following parameters: RSA-PSS 3072 Parameters

RSA-PSS Parameter	Value
Mask Generation Function	mgf1
Mask Generation params	SHA-512
Message Digest Algorithm	SHA-512

where:

• Mask Generation Function (mgf1) is defined in
• SHA-512 is defined in .

ASN.1 Module Composite-Signatures-2023 { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) id-composite-signatures-2023 (TBDMOD) } DEFINITIONS IMPLICIT TAGS ::= BEGIN EXPORTS ALL; IMPORTS PUBLIC-KEY, SIGNATURE-ALGORITHM, 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) } 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) } sa-rsaSSA-PSS FROM PKIX1-PSS-OAEP-Algorithms-2009 {iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-pkix1-rsa-pkalgs-02(54)} ; -- -- Object Identifiers -- -- Defined in ITU-T X.690 der OBJECT IDENTIFIER ::= {joint-iso-itu-t asn1(1) ber-derived(2) distinguished-encoding(1)} -- -- Signature Algorithm -- -- -- Composite Signature basic structures -- CompositeSignaturePublicKey ::= SEQUENCE SIZE (2) OF BIT STRING CompositeSignaturePublicKeyOs ::= OCTET STRING (CONTAINING CompositeSignaturePublicKey ENCODED BY der) CompositeSignaturePublicKeyBs ::= BIT STRING (CONTAINING CompositeSignaturePublicKey ENCODED BY der) CompositeSignaturePrivateKey ::= SEQUENCE SIZE (2) OF OneAsymmetricKey CompositeSignatureValue ::= SEQUENCE SIZE (2) OF BIT STRING -- Composite Signature Value is just a sequence of OCTET STRINGS -- CompositeSignaturePair{FirstSignatureValue, SecondSignatureValue} ::= -- SEQUENCE { -- signaturevalue1 FirstSignatureValue, -- signaturevalue2 SecondSignatureValue } -- An Explicit Compsite Signature is a set of Signatures which -- are composed of OCTET STRINGS -- ExplicitCompositeSignatureValue ::= CompositeSignaturePair { -- OCTET STRING,OCTET STRING} -- -- Information Object Classes -- pk-CompositeSignature {OBJECT IDENTIFIER:id, FirstPublicKeyType,SecondPublicKeyType} PUBLIC-KEY ::= { IDENTIFIER id KEY SEQUENCE { firstPublicKey BIT STRING (CONTAINING FirstPublicKeyType), secondPublicKey BIT STRING (CONTAINING SecondPublicKeyType) } PARAMS ARE absent CERT-KEY-USAGE { digitalSignature, nonRepudiation, keyCertSign, cRLSign} } sa-CompositeSignature{OBJECT IDENTIFIER:id, PUBLIC-KEY:publicKeyType } SIGNATURE-ALGORITHM ::= { IDENTIFIER id VALUE CompositeSignatureValue PARAMS ARE absent PUBLIC-KEYS {publicKeyType} } -- TODO: OID to be replaced by IANA id-MLDSA44-RSA2048-PSS-SHA256 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) composite(8) signature(1) 1 } pk-MLDSA44-RSA2048-PSS-SHA256 PUBLIC-KEY ::= pk-CompositeSignature{ id-MLDSA44-RSA2048-PSS-SHA256, OCTET STRING, RSAPublicKey} sa-MLDSA44-RSA2048-PSS-SHA256 SIGNATURE-ALGORITHM ::= sa-CompositeSignature{ id-MLDSA44-RSA2048-PSS-SHA256, pk-MLDSA44-RSA2048-PSS-SHA256 } -- TODO: OID to be replaced by IANA id-MLDSA44-RSA2048-PKCS15-SHA256 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) composite(8) signature(1) 2 } pk-MLDSA44-RSA2048-PKCS15-SHA256 PUBLIC-KEY ::= pk-CompositeSignature{ id-MLDSA44-RSA2048-PKCS15-SHA256, OCTET STRING, RSAPublicKey} sa-MLDSA44-RSA2048-PKCS15-SHA256 SIGNATURE-ALGORITHM ::= sa-CompositeSignature{ id-MLDSA44-RSA2048-PKCS15-SHA256, pk-MLDSA44-RSA2048-PKCS15-SHA256 } -- TODO: OID to be replaced by IANA id-MLDSA44-Ed25519-SHA512 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) composite(8) signature(1) 3 } pk-MLDSA44-Ed25519-SHA512 PUBLIC-KEY ::= pk-CompositeSignature{ id-MLDSA44-Ed25519-SHA512, OCTET STRING, ECPoint} sa-MLDSA44-Ed25519-SHA512 SIGNATURE-ALGORITHM ::= sa-CompositeSignature{ id-MLDSA44-Ed25519-SHA512, pk-MLDSA44-Ed25519-SHA512 } -- TODO: OID to be replaced by IANA id-MLDSA44-ECDSA-P256-SHA256 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) composite(8) signature(1) 4 } pk-MLDSA44-ECDSA-P256-SHA256 PUBLIC-KEY ::= pk-CompositeSignature{ id-MLDSA44-ECDSA-P256-SHA256, OCTET STRING, ECPoint} sa-MLDSA44-ECDSA-P256-SHA256 SIGNATURE-ALGORITHM ::= sa-CompositeSignature{ id-MLDSA44-ECDSA-P256-SHA256, pk-MLDSA44-ECDSA-P256-SHA256 } -- TODO: OID to be replaced by IANA id-MLDSA44-ECDSA-brainpoolP256r1-SHA256 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) composite(8) signature(1) 5 } pk-MLDSA44-ECDSA-brainpoolP256r1-SHA256 PUBLIC-KEY ::= pk-CompositeSignature{ id-MLDSA44-ECDSA-brainpoolP256r1-SHA256, OCTET STRING, ECPoint} sa-MLDSA44-ECDSA-brainpoolP256r1-SHA256 SIGNATURE-ALGORITHM ::= sa-CompositeSignature{ id-MLDSA44-ECDSA-brainpoolP256r1-SHA256, pk-MLDSA44-ECDSA-brainpoolP256r1-SHA256 } -- TODO: OID to be replaced by IANA id-MLDSA65-RSA3072-PSS-SHA512 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) composite(8) signature(1) 6 } pk-MLDSA65-RSA3072-PSS-SHA512 PUBLIC-KEY ::= pk-CompositeSignature{ id-MLDSA65-RSA3072-PSS-SHA512, OCTET STRING, RSAPublicKey} sa-MLDSA65-RSA3072-PSS-SHA512 SIGNATURE-ALGORITHM ::= sa-CompositeSignature{ id-MLDSA65-RSA3072-PSS-SHA512, pk-MLDSA65-RSA3072-PSS-SHA512 } -- TODO: OID to be replaced by IANA id-MLDSA65-RSA3072-PKCS15-SHA512 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) composite(8) signature(1) 7 } pk-MLDSA65-RSA3072-PKCS15-SHA512 PUBLIC-KEY ::= pk-CompositeSignature{ id-MLDSA65-RSA3072-PKCS15-SHA512, OCTET STRING, RSAPublicKey} sa-MLDSA65-RSA3072-PKCS15-SHA512 SIGNATURE-ALGORITHM ::= sa-CompositeSignature{ id-MLDSA65-RSA3072-PKCS15-SHA512, pk-MLDSA65-RSA3072-PKCS15-SHA512 } -- TODO: OID to be replaced by IANA id-MLDSA65-ECDSA-P256-SHA512 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) composite(8) signature(1) 8 } pk-MLDSA65-ECDSA-P256-SHA512 PUBLIC-KEY ::= pk-CompositeSignature{ id-MLDSA65-ECDSA-P256-SHA512, OCTET STRING, ECPoint} sa-MLDSA65-ECDSA-P256-SHA512 SIGNATURE-ALGORITHM ::= sa-CompositeSignature{ id-MLDSA65-ECDSA-P256-SHA512, pk-MLDSA65-ECDSA-P256-SHA512 } -- TODO: OID to be replaced by IANA id-MLDSA65-ECDSA-brainpoolP256r1-SHA512 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) composite(8) signature(1) 9 } pk-id-MLDSA65-ECDSA-brainpoolP256r1-SHA512 PUBLIC-KEY ::= pk-CompositeSignature{ id-MLDSA65-ECDSA-brainpoolP256r1-SHA512, OCTET STRING, ECPoint} sa-id-MLDSA65-ECDSA-brainpoolP256r1-SHA512 SIGNATURE-ALGORITHM ::= sa-CompositeSignature{ id-MLDSA65-ECDSA-brainpoolP256r1-SHA512, pk-id-MLDSA65-ECDSA-brainpoolP256r1-SHA512 } -- TODO: OID to be replaced by IANA id-MLDSA65-Ed25519-SHA512 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) composite(8) signature(1) 10 } pk-MLDSA65-Ed25519-SHA512 PUBLIC-KEY ::= pk-CompositeSignature{ id-MLDSA65-Ed25519-SHA512, OCTET STRING, ECPoint} sa-MLDSA65-Ed25519-SHA512 SIGNATURE-ALGORITHM ::= sa-CompositeSignature{ id-MLDSA65-Ed25519-SHA512, pk-MLDSA65-Ed25519-SHA512 } -- TODO: OID to be replaced by IANA id-MLDSA87-ECDSA-P384-SHA512 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) composite(8) signature(1) 11 } pk-MLDSA87-ECDSA-P384-SHA512 PUBLIC-KEY ::= pk-CompositeSignature{ id-MLDSA87-ECDSA-P384-SHA512, OCTET STRING, ECPoint} sa-MLDSA87-ECDSA-P384-SHA512 SIGNATURE-ALGORITHM ::= sa-CompositeSignature{ id-MLDSA87-ECDSA-P384-SHA512, pk-MLDSA87-ECDSA-P384-SHA512 } -- TODO: OID to be replaced by IANA id-MLDSA87-ECDSA-brainpoolP384r1-SHA512 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) composite(8) signature(1) 12 } pk-MLDSA87-ECDSA-brainpoolP384r1-SHA512 PUBLIC-KEY ::= pk-CompositeSignature{ id-MLDSA87-ECDSA-brainpoolP384r1-SHA512, OCTET STRING, ECPoint} sa-MLDSA87-ECDSA-brainpoolP384r1-SHA512 SIGNATURE-ALGORITHM ::= sa-CompositeSignature{ id-MLDSA87-ECDSA-brainpoolP384r1-SHA512, pk-MLDSA87-ECDSA-brainpoolP384r1-SHA512 } -- TODO: OID to be replaced by IANA id-MLDSA87-Ed448-SHA512 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) composite(8) signature(1) 13 } pk-MLDSA87-Ed448-SHA512 PUBLIC-KEY ::= pk-CompositeSignature{ id-MLDSA87-Ed448-SHA512, OCTET STRING, ECPoint} sa-MLDSA87-Ed448-SHA512 SIGNATURE-ALGORITHM ::= sa-CompositeSignature{ id-MLDSA87-Ed448-SHA512, pk-MLDSA87-Ed448-SHA512 } -- TODO: OID to be replaced by IANA id-Falon512-ECDSA-P256-SHA256 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) algorithm(80) composite(8) signature(1) 14 } pk-Falon512-ECDSA-P256-SHA256 PUBLIC-KEY ::= pk-CompositeSignature{ id-Falon512-ECDSA-P256-SHA256, OCTET STRING, ECPoint} sa-Falon512-ECDSA-P256-SHA256 SIGNATURE-ALGORITHM ::= sa-CompositeSignature{ id-Falon512-ECDSA-P256-SHA256, pk-Falon512-ECDSA-P256-SHA256 } END ]]>

IANA Considerations IANA is requested to allocate a value from the "SMI Security for PKIX Module Identifier" registry for the included ASN.1 module, and allocate values from "SMI Security for PKIX Algorithms" to identify the fourteen Algorithms defined within.

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-Signatures-2023 - id-mod-composite-signatures
• References: This Document

Object Identifier Registrations - SMI Security for PKIX Algorithms

• id-MLDSA44-RSA2048-PSS-SHA256
• Decimal: IANA Assigned
• Description: id-MLDSA44-RSA2048-PSS-SHA256
• References: This Document
• id-MLDSA44-RSA2048-PKCS15-SHA256
• Decimal: IANA Assigned
• Description: id-MLDSA44-RSA2048-PKCS15-SHA256
• References: This Document
• id-MLDSA44-Ed25519-SHA512
• Decimal: IANA Assigned
• Description: id-MLDSA44-Ed25519-SHA512
• References: This Document
• id-MLDSA44-ECDSA-P256-SHA256
• Decimal: IANA Assigned
• Description: id-MLDSA44-ECDSA-P256-SHA256
• References: This Document
• id-MLDSA44-ECDSA-brainpoolP256r1-SHA256
• Decimal: IANA Assigned
• Description: id-MLDSA44-ECDSA-brainpoolP256r1-SHA256
• References: This Document
• id-MLDSA65-RSA3072-PSS-SHA512
• Decimal: IANA Assigned
• Description: id-MLDSA65-RSA3072-PSS-SHA512
• References: This Document
• id-MLDSA65-RSA3072-PKCS15-SHA512
• Decimal: IANA Assigned
• Description: id-MLDSA65-RSA3072-PKCS15-SHA512
• References: This Document
• id-MLDSA65-ECDSA-P256-SHA512
• Decimal: IANA Assigned
• Description: id-MLDSA65-ECDSA-P256-SHA512
• References: This Document
• id-MLDSA65-ECDSA-brainpoolP256r1-SHA512
• Decimal: IANA Assigned
• Description: id-MLDSA65-ECDSA-brainpoolP256r1-SHA512
• References: This Document
• id-MLDSA65-Ed25519-SHA512
• Decimal: IANA Assigned
• Description: id-MLDSA65-Ed25519-SHA512
• References: This Document
• id-MLDSA87-ECDSA-P384-SHA512
• Decimal: IANA Assigned
• Description: id-MLDSA87-ECDSA-P384-SHA512
• References: This Document
• id-MLDSA87-ECDSA-brainpoolP384r1-SHA512
• Decimal: IANA Assigned
• Description: id-MLDSA87-ECDSA-brainpoolP384r1-SHA512
• References: This Document
• id-MLDSA87-Ed448-SHA512
• Decimal: IANA Assigned
• Description: id-MLDSA87-Ed448-SHA512
• References: This Document

Security Considerations

Policy for Deprecated and Acceptable Algorithms Traditionally, a public key, certificate, or signature contains a single cryptographic algorithm. If and when an algorithm becomes deprecated (for example, RSA-512, or SHA1), then clients performing signatures or verifications should be updated to adhere to appropriate policies. 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 indpendently from that of their component algorithms. For example a cryptographic policy might continue to allow id-MLDSA65-ECDSA-P256-SHA512 even after ECDSA-P256 is deprecated. When considering stripping attacks, one need consider the case where an attacker has fully compromised one of the component algorithms to the point that they can produce forged signatures that appear valid under one of the component public keys, and thus fool a victim verifier into accepting a forged signature. The protection against this attack relies on the victim verifier trusting the pair of public keys as a single composite key, and not trusting the individual component keys by themselves. Specifically, in order to achieve this non-separability property, this specification makes two assumptions about how the verifier will establish trust in a composite public key:

1. This specification assumes that all of the component keys within a composite key are freshly generated for the composite; ie a given public key MUST NOT appear as a component within a composite key and also within single-algorithm constructions.
2. This specification assumes that composite public keys will be bound in a structure that contains a signature over the public key (for example, an X.509 Certificate ), which is chained back to a trust anchor, and where that signature algorithm is at least as strong as the composite public key that it is protecting.

There are mechanisms within Internet PKI where trusted public keys do not appear within signed structures -- such as the Trust Anchor format defined in [RFC5914]. In such cases, it is the responsibility of implementers to ensure that trusted composite keys are distributed in a way that is tamper-resistant and does not allow the component keys to be trusted independently.

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 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 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 specifies the syntax and semantics for the Subject Public Key Information field in certificates that support Elliptic Curve Cryptography. This document updates Sections 2.3.5 and 5, and the ASN.1 module of "Algorithms and Identifiers for the Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 3279. [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 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] 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. Federal Information Processing Standard, FIPS 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 describes elliptic curve signature scheme Edwards-curve Digital Signature Algorithm (EdDSA). The algorithm is instantiated with recommended parameters for the edwards25519 and edwards448 curves. An example implementation and test vectors are provided. 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. ITU-T Informative References This document specifies algorithm identifiers and ASN.1 encoding formats for digital signatures and subject public keys used in the Internet X.509 Public Key Infrastructure (PKI). Digital signatures are used to sign certificates and certificate revocation list (CRLs). Certificates include the public key of the named subject. [STANDARDS-TRACK] 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. When the Public-Key Infrastructure using X.509 (PKIX) Working Group was chartered, an object identifier arc was allocated by IANA for use by that working group. This document describes the object identifiers that were assigned in that arc, returns control of that arc to IANA, and establishes IANA allocation policies for any future assignments within that arc. 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 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. SandboxAQ Naval Postgraduate School SandboxAQ UK National Cyber Security Centre This document describes classification of design goals and security considerations for hybrid digital signature schemes, including proof composability, non-separability of the ingredient signatures given a hybrid signature, backwards/forwards compatiblity, hybrid generality, and simultaneous verification. Discussion of this work is encouraged to happen on the IETF PQUIP mailing list pqc@ietf.org or on the GitHub repository which contains the draft: https://github.com/dconnolly/draft-hale-pquip-hybrid- signature-spectrums Entrust Limited Entrust Limited The migration to post-quantum cryptography is unique in the history of modern digital cryptography in that neither the old outgoing nor the new incoming algorithms are fully trusted to protect data for the required data lifetimes. The outgoing algorithms, such as RSA and elliptic curve, may fall to quantum cryptalanysis, while the incoming post-quantum algorithms face uncertainty about both the underlying mathematics as well as hardware and software implementations that have not had sufficient maturing time to rule out classical cryptanalytic attacks and implementation bugs. Cautious implementers may wish to layer cryptographic algorithms such that an attacker would need to break all of them in order to compromise the data being protected using either a Post-Quantum / Traditional Hybrid, Post-Quantum / Post-Quantum Hybrid, or combinations thereof. This document, and its companions, defines a specific instantiation of hybrid paradigm called "composite" where multiple cryptographic algorithms are combined to form a single key, signature, or key encapsulation mechanism (KEM) such that they can be treated as a single atomic object at the protocol level. This document defines the structure CompositeCiphertextValue which is a sequence of the respective ciphertexts for each component algorithm. Explicit pairings of algorithms are defined which should meet most Internet needs. The generic composite key type is also defined which allows arbitrary combinations of key types to be placed in the CompositePublicKey and CompositePrivateKey structures without needing the combination to be pre-registered or pre-agreed. For the purpose of combining KEMs, the combiner function from [I-D.ounsworth-cfrg-kem-combiners] is used. This document is intended to be coupled with the composite keys structure define in [I-D.ounsworth-pq-composite-keys] and the CMS KEMRecipientInfo mechanism in [I-D.housley-lamps-cms-kemri]. National Security Agency National Security Agency National Security Agency The advent of cryptographically relevant quantum computers (CRQC) will threaten the public key cryptography that is currently in use in today's secure internet protocol infrastructure. To address this, organizations such as the National Institute of Standards and Technology (NIST) will standardize new post-quantum cryptography (PQC) that is resistant to attacks by both classical and quantum computers. After PQC algorithms are standardized, the widespread implementation of this cryptography will be contingent upon adapting current protocols to accommodate PQC. Hybrid solutions are one way to facilitate the transition between traditional and PQ algorithms: they use both a traditional and a PQ algorithm in order to perform encryption or authentication, with the guarantee that the given security property will still hold in the case that one algorithm fails. Hybrid solutions can be constructed in many ways, and the cryptographic community has already begun to explore this space. This document introduces non-composite hybrid authentication, which requires updates at the protocol level and limits impact to the certificate-issuing infrastructure. National Security Agency This document describes how to extend the Internet Key Exchange Protocol Version 2 (IKEv2) to allow hybrid non-composite authentication. The intended purpose for this extension is to enable the use of a Post-Quantum (PQ) digital signature and X.509 certificate in addition to the use of a traditional authentication method. This document enables peers to signify support for hybrid non-composite authentication, and send additional CERTREQ, AUTH, and CERT payloads to perform multiple authentications. CableLabs Inc. D-Trust GmbH With the need to evolve the cryptography used in today applications, devices, and networks, there might be many scenarios where the use of a single-key certificate is not sufficient. For example, there might be the need for migrating between two existing algorithms (e.g., from classic to post-quantum) or there might be the need to test the capabilities of devices via test drivers and/or non-standard algorithms. Differently from the situation where algorithms are not yet (or no more) trusted to be used by themselves, this document addresses the use of multiple keys and signatures that can be individually trusted to implement a generic 1-threshold and K-threshold signature validation procedures. This document provides the definition of a new type of multi- algorithm public key and relies on the definition of CompositePrivateKey, and CompositeSignature which are sequences of the respective structure for each component algorithm as defined in [I-D.ounsworth-pq-composite-sigs] and [I-D.ounsworth-pq-composite-sigs]. 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. Siemens Siemens Siemens Entrust Entrust This document focuses on the critical challenge of migrating long- term security assertions with security requirements spanning over a decade, encompassing X.509 certificates, including those that serve as manufacturer issued certificates (IDevID), signed firmware/ software, and other electronic artifacts. We investigate a range of migration strategies, specifically hybrid cryptography and the feasibility of stateful Hash-Based Signatures (HBS) schemes, including its pros and cons. To offer a comprehensive context, we present a list of use cases centered around long-lived security assertions, categorize them, and evaluate them against the various migration strategies identified. We also aim at listing pros and cons associated with each method. AWS AWS sn3rd Cloudflare Digital signatures are used within X.509 certificates, Certificate Revocation Lists (CRLs), and to sign messages. This document describes the conventions for using Dilithium quantum-resistant signatures in Internet X.509 certificates and certifiate revocation lists. The conventions for the associated post-quantum signatures, subject public keys, and private key are also described. AWS AWS sn3rd Cloudflare Digital signatures are used within X.509 certificates, Certificate Revocation Lists (CRLs), and to sign messages. This document describes the conventions for using Dilithium quantum-resistant signatures in Internet X.509 certificates and certificate revocation lists. The conventions for the associated post-quantum signatures, subject public keys, and private key are also described. 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.

Samples

Explicit Composite Signature Examples

MLDSA44-ECDSA-P256-SHA256 Public Key -----BEGIN PUBLIC KEY----- MIIFgTANBgtghkgBhvprUAgBBAOCBW4AMIIFaQOCBSEAJaSzbEOXCT27FgXshv87 2HLTgePmYCJCH2OVUi/PB9YTyBXXnw+smoXT4w0pcq3WPs7qQXz6GKj7R0mFfTjp Rd6uH3hgdS5cbg+PwMWsRKigE6mWFpMwrliS8CfR2yYgjhRav7wGa4ja7RdmZoLz T8UBN2Yg6P/KceWA1gX6rdVUalrUvmcfR64ry06IfotXXNFwQc3vI6s7khHSUZX5 Rsw55RK3E0ElNpZxfFHv17d2xwFkGRAYqJao+qo37WtfG6Ynx4cqQyLJzlRn++5R G6K1nCwqhErpk4vDR2uHIwAPiW0StX9ZbBjO2smRTIuWS2WhmhZwJkDqSHmCiRI2 tPsxCtLpM8t2IhTVy/ObAdQGPDngTNIPH8kuoRrBhWGIiWJMlo8LkImCRt5m/8Di aL8C2BQNL+BWBBcak/JZrLkKZOZM7pFwWruHVEd0608XerfiVO3ypqAxImJ2xcdD kLys4jDlEMsC3oz4RQGXahj2Pr8Jxu8i0TIDDdV5MZw9wId/m+0/vSD8BOAu09Wu V6ppUWkDZLHlzf12zx3ZzBF/CMqZNsxMdTFNbu2qQ2/CZMlEvZ9f0gxn6qNf8NHC UqdeRr7p9z8PuGHErLHqCvQMrzia71cD4URV//SR8EUQkoo9imtw3XT2uKGUIjT/ dDyqWl8BlAZ64dUp9EWmHwG1cyKBcu2dtD0d4BMol1g4TOF7u/3hHcgOoiR+ON/3 7MoxkX9mHt6tP7hkVWy0Mb3Sjej12DG75D9z8gAzHyQhOs3suNliCzCUmUVYm5Mv WdySiuShm6yu+9Ah+GqvESuNr/h6s1gZGbdCe9llGdFPniilhL5J9oDgYMp+wi2I EeOugOFoaY1e2OI1OPjBpg1071ko9B3CGD+0PkPvKYmMGs0HTnzFWCLPj5dG2kg7 PEltarKvLVTIxrbjw03l3SXmqpNPU8SqFJ7hB3OpFJgjqL95IRTa68UM8aaUKLMa Qjjx08+e13P3wwY3niCR5U751fus4ArGLN2JgfPB7bPSdz043PIvxsCYZxUQXSW3 xWhWQqaHJLml19obvnf/tEXQZLheAr7hOEb/UTNUIBj/A6LfB0Gs012B1aXfne4W 9K/OFXc9p0C7aWIfjfMrA/idOrd1Eoo2NGLid+wp8aXyDZkCf5OUretEFHqQcQ2J znh8R4mh2Tf7hT8+Gj5Su6bZggHi9iIJZ1G7i0j4Wm3g6DJAXF6KbChMayKRunDp k6Nm5iOeTmT+Vi4OJncuI6HezZMzO2s+2iY33uDL7tFR8fVn7dQiF78c1aNhWjfm fIsLNQdZxt6orvnwSrZpdVhOtAu+vYVaEAShdHgfzvPSDHIjgyxs6mGdk0uDsGpP f5d3e9KV40rXir2OXaYMOq2KTkLb6KHHxZayLG0D9/qSBOnSE/aXNhh1cHtKeYAe jjXmfzsmgNELPNxFRrx8pEHG1Se0GJNJVZE9u6B2r9f09TgTxgPX/6XpBNUrlz21 fsIvNpRL48cwLHOCgYP/SAgE3gzRC6G5NEE19wQZHsFNGeUeGvrvUQgTyT1YwLx+ Abvp57bVjgLWli185/K1a8BmJ204RHfDhSFe7sVAIoI2pUcz7ydb178DCAvupP20 CxUIkgOk3C+cgUzTwsFU4iiix282ZBa8/nTUnH9r3IDJQJwdWtMCnByCc43UeVSh WV3isRF+ANl6lSevNj0uzGE07a5gPahctBWMmevh6qFcv5XucwNRe7en96o7CgK+ 5QNCAAReie6V/SXhsV0+AAEPt/7UjJqzbrZU1ZHKBLCDbX1cv1Zkpy+SabE2Pfpd K7SzfBpZw0txE+bjIUT4j3zjgIDa -----END PUBLIC KEY-----

MLDSA44-ECDSA-P256 Private Key -----BEGIN PRIVATE KEY----- MIIP6gIBADANBgtghkgBhvprUAgBBASCD9Qwgg/QMIIPNgIBADANBgsrBgEEAQKC CwwEBASCDyAlpLNsQ5cJPbsWBeyG/zvYctOB4+ZgIkIfY5VSL88H1oyY3xD+KvF2 4bnFPT7nM4+8rPjsCuuk2PyUr7vzEHf++3ovDEFUsHo88ez4zfzBeW+Aho6yC4Gf H8BFsgVYv0HmRUPUEmVhrJUKt8VwHbOVyak7a4JWl6MWpwxnRYqso1rCcWKWZKQC bZIQQhGIKaIyZQSVRSI4bdBAShuBaQPGkBwUDgM3QQgGbhHDSBqzLQk4MooWSUk0 Zhk4JCAgUhg0ZVkkECOYTYBIMRQGjFICSaMiIYAAShMTJVAwbaFCakg0QcFCZolC CmBEUQm5cQESASEQDCSgRGAyhMQGDWOAKRkZZESiAOI0KWAWbaIkbBoUJWOiiQk5 hhBCadqGhZEYglhIQACkMJo4kmEwSIDGBYtELcCoAVuGJMPAhCOFDRE1RCSGLAq0 AAA1Cgk3CgjAZYEUKovCaBs5hti2CZO0DePECBvHZASnMdmmURsxRFA4YRxGUOSy EeEyUIA2isM0LRwJAgEAjGHGLRySJYjAgROBYQO1UUSCSRjACdg0ZAGgABQHjAkm juOUQBpEgNy0jOPGIAzETdyIhZMIMVRCZgyyRUAgLQQwcchIbFIWRswgIQHAJQMV RJgQJFqERFuiJQqjBIsChVpEMEsCKFqwCFgkciRHIcwCICKUAEgWScTESdgiYWQy MtCgIISkARMZRAg3ieMGKlBITMM2iosCgiQ2MIKiKeI2TFhGaQKWAckEJmE4hhII bSEyjQuECMlASBTBJFlIahIHaRhAAeQoMRQSDhQCcsiwYYg4BiETCAwiMRwwEcyU 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MLDSA44-ECDSA-P256 Self-Signed X509 Certificate -----BEGIN CERTIFICATE----- MIIP+TCCBhqgAwIBAgIUEsa5EwG0Ligbb3NMHEmsqr0IoKMwDQYLYIZIAYb6a1AI AQQwEjEQMA4GA1UEAwwHb3FzdGVzdDAeFw0yNDAzMDEyMzE5MzFaFw0yNTAzMDEy MzE5MzFaMBIxEDAOBgNVBAMMB29xc3Rlc3QwggWBMA0GC2CGSAGG+mtQCAEEA4IF bgAwggVpA4IFIQAlpLNsQ5cJPbsWBeyG/zvYctOB4+ZgIkIfY5VSL88H1hPIFdef D6yahdPjDSlyrdY+zupBfPoYqPtHSYV9OOlF3q4feGB1LlxuD4/AxaxEqKATqZYW kzCuWJLwJ9HbJiCOFFq/vAZriNrtF2ZmgvNPxQE3ZiDo/8px5YDWBfqt1VRqWtS+ Zx9HrivLToh+i1dc0XBBze8jqzuSEdJRlflGzDnlErcTQSU2lnF8Ue/Xt3bHAWQZ EBiolqj6qjfta18bpifHhypDIsnOVGf77lEborWcLCqESumTi8NHa4cjAA+JbRK1 f1lsGM7ayZFMi5ZLZaGaFnAmQOpIeYKJEja0+zEK0ukzy3YiFNXL85sB1AY8OeBM 0g8fyS6hGsGFYYiJYkyWjwuQiYJG3mb/wOJovwLYFA0v4FYEFxqT8lmsuQpk5kzu kXBau4dUR3TrTxd6t+JU7fKmoDEiYnbFx0OQvKziMOUQywLejPhFAZdqGPY+vwnG 7yLRMgMN1XkxnD3Ah3+b7T+9IPwE4C7T1a5XqmlRaQNkseXN/XbPHdnMEX8Iypk2 zEx1MU1u7apDb8JkyUS9n1/SDGfqo1/w0cJSp15Gvun3Pw+4YcSsseoK9AyvOJrv VwPhRFX/9JHwRRCSij2Ka3DddPa4oZQiNP90PKpaXwGUBnrh1Sn0RaYfAbVzIoFy 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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. Implementors seeking FIPS certification of a composite Signature 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 algorith with zero security, and the overall composite should be considered at least as strong 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 The term "backwards compatibility" is used here to mean something more specific; that existing systems as they are deployed today can interoperate with the upgraded systems of the future. This draft explicitly does not provide backwards compatibility, only upgraded systems will understand the OIDs defined in this document. If backwards compatibility is required, then additional mechanisms will be needed. 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 digital signature objects, from online negotiated protocols such as TLS 1.3 and IKEv2 , to non-negotiated asynchronous protocols such as S/MIME signed email , document signing such as in the context of the European eIDAS regulations [eIDAS2014], and publicly trusted code signing [codeSigningBRsv2.8], as well as myriad other standardized and proprietary protocols and applications that leverage CMS signed structures. Composite simplifies the protocol design work because it can be implemented as a signature algorithm that fits into existing systems.

Hybrid Extensions (Keys and Signatures) The use of Composite Crypto provides the possibility to process multiple algorithms without changing the logic of applications, but updating the cryptographic libraries: one-time change across the whole system. However, when it is not possible to upgrade the crypto engines/libraries, it is possible to leverage X.509 extensions to encode the additional keys and signatures. When the custom extensions are not marked critical, although this approach provides the most backward-compatible approach where clients can simply ignore the post-quantum (or extra) keys and signatures, it also requires all applications to be updated for correctly processing multiple algorithms together.

Intellectual Property Considerations The following IPR Disclosure relates to this draft: https://datatracker.ietf.org/ipr/3588/

Contributors and Acknowledgements 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 few years in pursuit of this document: Daniel Van Geest (ISARA), Britta Hale, Tim Hollebeek (Digicert), Panos Kampanakis (Cisco Systems), Richard Kisley (IBM), Serge Mister (Entrust), Francois Rousseau, Falko Strenzke, Felipe Ventura (Entrust) and Alexander Ralien (Siemens) 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" - .

Making contributions Additional contributions to this draft are welcome. Please see the working copy of this draft at, as well as open issues at: https://github.com/lamps-wg/draft-composite-sigs