]> 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

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Cisco Systems

sfluhrer@cisco.com

Security LAMPS Internet-Draft This document introduces a set of signature schemes that use pairs of cryptographic elements such as public keys and signatures 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 thirteen specific pairwise combinations, namely ML-DSA Composite Schemes, that blend ML-DSA with traditional algorithms such as RSA, ECDSA, Ed25519, and Ed448. These combinations are tailored to meet security best practices and regulatory requirements.

Changes since the -01 version

• Added a "Use in CMS" section
• Removed a Falon reference from the ASN.1 document (which was a typo in reference to Falcon)
• Added SMIME-CAPS into the sa-CompositeSignature definition in the ASN.1 module
• Fixed nits and other typos
• Added PSS parameter Salt Lengths
• Changed the OID concatenation section to Domain Separators for clarity
• Accepted some edits by Jose Ignacio Escribano
• Expanded description for KeyGen algorithm
• Clarified the Subject Public Key Usage
• Various editorial changes

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 The advent of quantum computing poses a significant threat to current cryptographic systems. Traditional cryptographic algorithms such as RSA, Diffie-Hellman, DSA, and their elliptic curve variants are vulnerable to quantum attacks. During the transition to post-quantum cryptography (PQC), there is considerable uncertainty regarding the robustness of both existing and new cryptographic algorithms. While we can no longer fully trust traditional cryptography, we also cannot immediately place complete trust in post-quantum replacements until they have undergone extensive scrutiny and real-world testing to uncover and rectify potential implementation flaws. Unlike previous migrations between cryptographic algorithms, the decision of when to migrate and which algorithms to adopt is far from straightforward. Even after the migration period, it may be advantageous for an entity's cryptographic identity to incorporate multiple public-key algorithms to enhance security. Cautious implementers may opt to combine cryptographic algorithms in such a way that an attacker would need to break all of them simultaneously to compromise the protected data. These mechanisms are referred to as Post-Quantum/Traditional (PQ/T) Hybrids . Certain jurisdictions are already recommending or mandating that PQC lattice schemes be used exclusively within a PQ/T hybrid framework. The use of Composite scheme provides a straightforward implementation of hybrid solutions compatible with (and advocated by) some governments and cybersecurity agencies .

Conventions and 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 BCP14 when, and only when, they appear in all capitals, as shown here. These words may also appear in this document in lower case as plain English words, absent their normative meanings. This document is consistent with the terminology defined in . In addition, the following terminology is used throughout 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 Signatures Schemes The engineering principle behind the definition of Composite schemes is to define a new family of algorithms that combines the use of cryptographic operations from two different ones: ML-DSA one and a traditional one. The complexity of combining security properties from the selected two algorithms is handled at the cryptographic library or cryptographic module, thus minimal changes are expected at the application or protocol level. Composite schemes are fully compatible with the X.509 model: composite public keys, composite private keys, and ciphertexts can be carried in existing data structures and protocols such as PKCS#10 , CMP , X.509 , CMS , and the Trust Anchor Format [RFC5914]. Composite schemes are defined as cryptographic primitives 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 a 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 the security properties of the two underlying algorithms to be combined via standard signature operations such as generation and verify and can be used in all applications that use signatures without the need for changes in data structures or protocol messages.

Composite Schemes PreHashing Composite schemes' signature generation process and composite signature verification process are designed to provide security properties meant to address specific issues related to the use multiple algorithms and they require the use of pre-hasing. In Composite schemes, the value of the DER encoding of the selected signature scheme is concatenated with the calculated Hash over the original message. The output is then used as input for the Sign() and Verify() functions.

Cryptographic Primitives

Key Generation To generate a new keypair for Composite schemes, the KeyGen() -> (pk, sk) function is used. The KeyGen() function calls the two key generation functions of the component algorithms for the Composite keypair in no particular order. Multi-process or multi-threaded applications might choose to execute the key generation functions in parallel for better key generation performance. The generated public key structure is described in , while the corresponding composite secret key structure is defined in . The following process is used to generate composite keypair values:

Composite KeyGen(pk, sk) (pk, sk) Input: sk_1, sk_2 Private keys for each component. pk_1, pk_2 Public keys for each component. A1, A2 Component signature algorithms. Output: (pk, sk) The composite keypair. Function KeyGen(): (pk_1, sk_1) <- A1.KeyGen() (pk_2, sk_2) <- A2.KeyGen() if NOT (pk_1, sk_1) or NOT (pk_2, sk_2): // Component key generation failure return NULL (pk, sk) <- encode[(pk_1, sk_1), (pk_2, sk_2)] if NOT (pk, sk): // Encoding failure return False // Success return (pk, sk) ]]>

The key generation functions MUST be executed for both algorithms. Compliant parties MUST NOT use or import component keys that are used in other contexts, combinations, or by themselves (i.e., not only in X.509 certificates).

Signature Generation Composite schemes' signatures provide important properties for multi-key environments such as non-separability and key-binding. For more information on the additional security properties and their applicability to multi-key or hybrid environments, please refer to and the use of labels as defined in Composite signature generation starts with pre-hashing the message that is concatenated with the Domain separator . After that, the signature process for each component algorithm is invoked and the values are then placed in the CompositeSignatureValue structure defined in . A composite signature's value MUST include two signature components and MUST be in the same order as the components from the corresponding signing key. 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. Domain Domain separator value for binding the signature to the Composite OID. See section on Domain Separators below. Output: signature The composite signature, a CompositeSignatureValue Signature Generation Process: 1. Compute the new Message M' by concatenating the Domain identifier (i.e., the DER encoding of the Composite signature algorithm identifier) with the Hash of the Message M' := Domain || HASH(Message) 2. Generate the 2 component signatures independently, by calculating the signature over M' according to their algorithm specifications that might involve the use of the hash-n-sign paradigm. S1 := Sign( K1, A1, M' ) S2 := Sign( K2, A2, M' ) 3. Encode each component signature S1 and S2 into a BIT STRING according to its algorithm specification. signature := NULL IF (S1 != NULL) and (S2 != NULL): signature := Sequence { S1, S2 } 4. Output signature return signature ]]>

It is possible to construct CompositePrivateKey(s) to generate signatures 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.

Signature Verify Verification of a composite signature involves reconstructing the M' message first by concatenating the Domain separator (i.e., the DER encoding of the used Composite scheme's OID) with the Hash of the original message and then applying each component algorithm's verification process to the new message M'. 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)

It is possible to construct CompositePublicKey(s) to verify signatures 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.

Composite Key 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 Use cases 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 AlgorithmID	Second AlgorithmID	Pre-Hash
id-MLDSA44-RSA2048-PSS-SHA256	<CompSig>.1	id-ML-DSA-44	id-RSASA-PSS with id-sha256	id-sha256
id-MLDSA44-RSA2048-PKCS15-SHA256	<CompSig>.2	id-ML-DSA-44	sha256WithRSAEncryption	id-sha256
id-MLDSA44-Ed25519-SHA512	<CompSig>.3	id-ML-DSA-44	id-Ed25519	id-sha512
id-MLDSA44-ECDSA-P256-SHA256	<CompSig>.4	id-ML-DSA-44	ecdsa-with-SHA256 with secp256r1	id-sha256
id-MLDSA44-ECDSA-brainpoolP256r1-SHA256	<CompSig>.5	id-ML-DSA-44	ecdsa-with-SHA256 with brainpoolP256r1	id-sha256
id-MLDSA65-RSA3072-PSS-SHA512	<CompSig>.6	id-ML-DSA-65	id-RSASA-PSS with id-sha512	id-sha512
id-MLDSA65-RSA3072-PKCS15-SHA512	<CompSig>.7	id-ML-DSA-65	sha512WithRSAEncryption	id-sha512
id-MLDSA65-ECDSA-P256-SHA512	<CompSig>.8	id-ML-DSA-65	ecdsa-with-SHA512 with secp256r1	id-sha512
id-MLDSA65-ECDSA-brainpoolP256r1-SHA512	<CompSig>.9	id-ML-DSA-65	ecdsa-with-SHA512 with brainpoolP256r1	id-sha512
id-MLDSA65-Ed25519-SHA512	<CompSig>.10	id-ML-DSA-65	id-Ed25519	id-sha512
id-MLDSA87-ECDSA-P384-SHA512	<CompSig>.11	id-ML-DSA-87	ecdsa-with-SHA512 with secp384r1	id-sha512
id-MLDSA87-ECDSA-brainpoolP384r1-SHA512	<CompSig>.12	id-ML-DSA-87	ecdsa-with-SHA512 with brainpoolP384r1	id-sha512
id-MLDSA87-Ed448-SHA512	<CompSig>.13	id-ML-DSA-87	id-Ed448	id-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 in .

Domain Separators As mentioned above, the OID input value is used as a domain separator for the Composite Signature Generation and verification process and is the DER encoding of the OID. The following table shows the HEX encoding for each Signature AlgorithmID. Composite Signature Domain Separators

Composite Signature AlgorithmID	Domain Separator (in Hex encoding)
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

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
Salt Length in bits	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
Salt Length in bits	512

where:

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

Use in CMS [EDNOTE: The convention in LAMPS is to specify algorithms and their CMS conventions in separate documents. Here we have presented them in the same document, but this section has been written so that it can easily be moved to a standalone document.] Composite Signature algorithms MAY be employed for one or more recipients in the CMS signed-data content type .

Underlying Components When a particular Composite Signature OID is supported in CMS, an implementation SHOULD support the corresponding Secure Hash algorithm identifier in that was used as the pre-hash. The following table lists the MANDATORY HASH algorithms to preserve security and performance characteristics of each composite algorithm. Composite Signature SHA Algorithms

Composite Signature AlgorithmID	Secure Hash
id-MLDSA44-RSA2048-PSS-SHA256	SHA256
id-MLDSA44-RSA2048-PKCS15-SHA256	SHA256
id-MLDSA44-Ed25519-SHA512	SHA512
id-MLDSA44-ECDSA-P256-SHA256	SHA256
id-MLDSA44-ECDSA-brainpoolP256r1-SHA256	SHA256
id-MLDSA65-RSA3072-PSS-SHA512	SHA512
id-MLDSA65-RSA3072-PKCS15-SHA512	SHA512
id-MLDSA65-ECDSA-P256-SHA512	SHA512
id-MLDSA65-ECDSA-brainpoolP256r1-SHA512	SHA512
id-MLDSA65-Ed25519-SHA512	SHA512
id-MLDSA87-ECDSA-P384-SHA512	SHA512
id-MLDSA87-ECDSA-brainpoolP384r1-SHA512	SHA512
id-MLDSA87-Ed448-SHA512	SHA512

where:

• SHA2 instantiations are defined in [FIPS180].

SignedData Conventions As specified in CMS , the digital signature is produced from the message digest and the signer's private key. The signature is computed over different values depending on whether signed attributes are absent or present. When signed attributes are absent, the composite signature is computed over the content. When signed attributes are present, a hash is computed over the content using the same hash function that is used in the composite pre-hash, and then a message-digest attribute is constructed to contain the resulting hash value, and then the result of DER encoding the set of signed attributes, which MUST include a content-type attribute and a message-digest attribute, and then the composite signature is computed over the DER-encoded output. In summary: When using Composite Signatures, the fields in the SignerInfo are used as follows: digestAlgorithm: The digestAlgorithm contains the one-way hash function used by the CMS signer. signatureAlgorithm: The signatureAlgorithm MUST contain one of the the Composite Signature algorithm identifiers as specified in signature: The signature field contains the signature value resulting from the composite signing operation of the specified signatureAlgorithm.

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

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

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} SMIME-CAPS { IDENTIFIED BY id } } -- 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 } 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

Public Key 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.

PreHashing Algorithm Selection Criteria 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 selection 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 ML-DSA-44 y is 128 bits, for ML-DSA-65 y is 192 bits and for ML-DSA-87 y is 256 bits. Therefore SHA256 is paired with RSA and ECDSA with ML-DSA-44 and SHA512 is paired with RSA and ECDSA with ML-DSA-65 and ML-DSA-87 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.

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 independently 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 updates RFC 3279 to specify algorithm identifiers and ASN.1 encoding rules for the Digital Signature Algorithm (DSA) and Elliptic Curve Digital Signature Algorithm (ECDSA) digital signatures when using SHA-224, SHA-256, SHA-384, or SHA-512 as the hashing algorithm. This specification applies to the Internet X.509 Public Key infrastructure (PKI) when digital signatures are used to sign certificates and certificate revocation lists (CRLs). This document also identifies all four SHA2 hash algorithms for use in the Internet X.509 PKI. [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.

Component Algorithm Reference This section provides references to the full specification of the algorithms used in the composite constructions. Component Signature Algorithms used in Composite Constructions

Component Signature Algorithm ID	OID	Specification
id-ML-DSA-44	1.3.6.1.4.1.2.267.12.4.4	ML-DSA: and [FIPS.204-ipd]
id-ML-DSA-65	1.3.6.1.4.1.2.267.12.6.5	ML-DSA: and [FIPS.204-ipd]
id-ML-DSA-87	1.3.6.1.4.1.2.267.12.8.7	ML-DSA: and [FIPS.204-ipd]
id-Ed25519	iso(1) identified-organization(3) thawte(101) 112	Ed25519 / Ed448:
id-Ed448	iso(1) identified-organization(3) thawte(101) id-Ed448(113)	Ed25519 / Ed448:
ecdsa-with-SHA256	iso(1) member-body(2) us(840) ansi-X9-62(10045) signatures(4) ecdsa-with-SHA2(3) 2	ECDSA:
ecdsa-with-SHA512	iso(1) member-body(2) us(840) ansi-X9-62(10045) signatures(4) ecdsa-with-SHA2(3) 4	ECDSA:
sha256WithRSAEncryption	iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-1(1) 11	RSAES-PKCS-v1_5:
sha512WithRSAEncryption	iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-1(1) 13	RSAES-PKCS-v1_5:
id-RSASA-PSS	iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-1(1) 10	RSASSA-PSS:

Elliptic Curves used in Composite Constructions

Elliptic CurveID	OID	Specification
secp256r1	iso(1) member-body(2) us(840) ansi-x962(10045) curves(3) prime(1) 7
secp384r1	iso(1) identified-organization(3) certicom(132) curve(0) 34
brainpoolP256r1	iso(1) identified-organization(3) teletrust(36) algorithm(3) signatureAlgorithm(3) ecSign(2) ecStdCurvesAndGeneration(8) ellipticCurve(1) versionOne(1) 7
brainpoolP384r1	iso(1) identified-organization(3) teletrust(36) algorithm(3) signatureAlgorithm(3) ecSign(2) ecStdCurvesAndGeneration(8) ellipticCurve(1) versionOne(1) 11

Hash algorithms used in Composite Constructions

HashID	OID	Specification
id-sha256	joint-iso-itu-t(2) country(16) us(840) organization(1) gov(101) csor(3) nistAlgorithms(4) hashAlgs(2) 1
id-sha512	joint-iso-itu-t(2) country(16) us(840) organization(1) gov(101) csor(3) nistAlgorithms(4) hashAlgs(2) 3

Samples

Explicit Composite Signature Examples

MLDSA44-ECDSA-P256-SHA256 Public Key

MLDSA44-ECDSA-P256 Private Key

MLDSA44-ECDSA-P256 Self-Signed X509 Certificate

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 algorithm 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 (CryptoNext), Britta Hale, Tim Hollebeek (Digicert), Panos Kampanakis (Cisco Systems), Richard Kisley (IBM), Serge Mister (Entrust), Francois Rousseau, Falko Strenzke, Felipe Ventura (Entrust), Alexander Ralien (Siemens), Jose Ignacio Escribano and Jan Oupicky 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