LAMPS M. Ounsworth
Internet-Draft J. Gray
Intended status: Standards Track Entrust
Expires: 9 January 2025 M. Pala
OpenCA Labs
J. Klaussner
Bundesdruckerei GmbH
S. Fluhrer
Cisco Systems
8 July 2024
Composite ML-DSA for use in Internet PKI
draft-ietf-lamps-pq-composite-sigs-02
Abstract
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.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 9 January 2025.
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Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
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Table of Contents
1. Changes since the -01 version . . . . . . . . . . . . . . . . 3
1.1. Changes since adoption by the lamps working group . . . . 4
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Conventions and Terminology . . . . . . . . . . . . . . . 5
3. Composite Signatures Schemes . . . . . . . . . . . . . . . . 6
3.1. Composite Schemes PreHashing . . . . . . . . . . . . . . 7
4. Cryptographic Primitives . . . . . . . . . . . . . . . . . . 7
4.1. Key Generation . . . . . . . . . . . . . . . . . . . . . 7
4.2. Signature Generation . . . . . . . . . . . . . . . . . . 8
4.2.1. Signature Verify . . . . . . . . . . . . . . . . . . 11
5. Composite Key Structures . . . . . . . . . . . . . . . . . . 12
5.1. pk-CompositeSignature . . . . . . . . . . . . . . . . . . 12
5.2. CompositeSignaturePublicKey . . . . . . . . . . . . . . . 13
5.3. CompositeSignaturePrivateKey . . . . . . . . . . . . . . 14
5.4. Encoding Rules . . . . . . . . . . . . . . . . . . . . . 14
5.5. Key Usage Bits . . . . . . . . . . . . . . . . . . . . . 15
6. Composite Signature Structures . . . . . . . . . . . . . . . 15
6.1. sa-CompositeSignature . . . . . . . . . . . . . . . . . . 15
6.2. CompositeSignatureValue . . . . . . . . . . . . . . . . . 16
7. Algorithm Identifiers . . . . . . . . . . . . . . . . . . . . 17
7.1. Domain Separators . . . . . . . . . . . . . . . . . . . . 19
7.2. Notes on id-MLDSA44-RSA2048-PSS-SHA256 . . . . . . . . . 20
7.3. Notes on id-MLDSA65-RSA3072-PSS-SHA512 . . . . . . . . . 20
8. Use in CMS . . . . . . . . . . . . . . . . . . . . . . . . . 21
8.1. Underlying Components . . . . . . . . . . . . . . . . . . 21
8.2. SignedData Conventions . . . . . . . . . . . . . . . . . 22
8.3. Certificate Conventions . . . . . . . . . . . . . . . . . 23
8.4. SMIMECapabilities Attribute Conventions . . . . . . . . . 24
9. ASN.1 Module . . . . . . . . . . . . . . . . . . . . . . . . 24
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31
10.1. Object Identifier Allocations . . . . . . . . . . . . . 31
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10.1.1. Module Registration - SMI Security for PKIX Module
Identifier . . . . . . . . . . . . . . . . . . . . . 31
10.1.2. Object Identifier Registrations - SMI Security for
PKIX Algorithms . . . . . . . . . . . . . . . . . . . 31
11. Security Considerations . . . . . . . . . . . . . . . . . . . 33
11.1. Public Key Algorithm Selection Criteria . . . . . . . . 33
11.2. PreHashing Algorithm Selection Criteria . . . . . . . . 34
11.3. Policy for Deprecated and Acceptable Algorithms . . . . 35
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 36
12.1. Normative References . . . . . . . . . . . . . . . . . . 36
12.2. Informative References . . . . . . . . . . . . . . . . . 38
Appendix A. Component Algorithm Reference . . . . . . . . . . . 41
Appendix B. Samples . . . . . . . . . . . . . . . . . . . . . . 43
B.1. Explicit Composite Signature Examples . . . . . . . . . . 43
B.1.1. MLDSA44-ECDSA-P256-SHA256 Public Key . . . . . . . . 43
B.1.2. MLDSA44-ECDSA-P256 Private Key . . . . . . . . . . . 44
B.1.3. MLDSA44-ECDSA-P256 Self-Signed X509 Certificate . . . 46
Appendix C. Implementation Considerations . . . . . . . . . . . 48
C.1. FIPS certification . . . . . . . . . . . . . . . . . . . 48
C.2. Backwards Compatibility . . . . . . . . . . . . . . . . . 49
C.2.1. Hybrid Extensions (Keys and Signatures) . . . . . . . 49
Appendix D. Intellectual Property Considerations . . . . . . . . 49
Appendix E. Contributors and Acknowledgements . . . . . . . . . 50
E.1. Making contributions . . . . . . . . . . . . . . . . . . 50
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 50
1. 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
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* Various editorial changes
1.1. 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
2. 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
[I-D.driscoll-pqt-hybrid-terminology].
Certain jurisdictions are already recommending or mandating that PQC
lattice schemes be used exclusively within a PQ/T hybrid framework.
The use of Composite scheme provides a straightforward implementation
of hybrid solutions compatible with (and advocated by) some
governments and cybersecurity agencies [BSI2021].
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2.1. 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 [RFC2119] [RFC8174] 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
[I-D.driscoll-pqt-hybrid-terminology]. 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 [X.690].
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 Section 5.
DER: Distinguished Encoding Rules as defined in [X.690].
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 [RFC5280].
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.
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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.
3. 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 [RFC2986], CMP [RFC4210],
X.509 [RFC5280], CMS [RFC5652], 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.
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3.1. 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.
4. Cryptographic Primitives
4.1. 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 Section 5.2, while
the corresponding composite secret key structure is defined in
Section 5.3.
The following process is used to generate composite keypair values:
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KeyGen() -> (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)
Figure 1: Composite KeyGen(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).
4.2. 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
[I-D.hale-pquip-hybrid-signature-spectrums] and the use of labels as
defined in [Bindel2017]
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Composite signature generation starts with pre-hashing the message
that is concatenated with the Domain separator Section 7.1. After
that, the signature process for each component algorithm is invoked
and the values are then placed in the CompositeSignatureValue
structure defined in Section 6.1.
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.
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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
Figure 2: Composite Sign(sk, Message)
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
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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.
4.2.1. 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)
Input:
P1, P2 Public verification keys. See note below on
composite inputs.
Message Message whose signature is to be verified,
an octet string.
signature CompositeSignatureValue containing the component
signature values (S1 and S2) to be verified.
A1, A2 Component signature algorithms. See note
below on composite inputs.
HASH The Message Digest Algorithm for pre-hashing. See
section on pre-hashing the message below.
Domain Domain separator value for binding the signature to the Composite OID.
See section on Domain Separators below.
Output:
Validity (bool) "Valid signature" (true) if the composite
signature is valid, "Invalid signature"
(false) otherwise.
Signature Verification Procedure::
1. Check keys, signatures, and algorithms lists for consistency.
If Error during Desequencing, or the sequences have
different numbers of elements, or any of the public keys
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P1 or P2 and the algorithm identifiers A1 or A2 are
composite then output "Invalid signature" and stop.
2. Compute a Hash of the Message
M' = Domain || HASH(Message)
3. Check each component signature individually, according to its
algorithm specification.
If any fail, then the entire signature validation fails.
if not verify( P1, M', S1, A1 ) then
output "Invalid signature"
if not verify( P2, M', S2, A2 ) then
output "Invalid signature"
if all succeeded, then
output "Valid signature"
Figure 3: 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.
5. 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 [RFC2986], CMP [RFC4210], X.509 [RFC5280], CMS
[RFC5652].
5.1. pk-CompositeSignature
The following ASN.1 Information Object Class is a template to be used
in defining all composite Signature public key types.
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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}
}
As an example, the public key type pk-MLDSA65-ECDSA-P256-SHA256 is
defined as:
pk-MLDSA65-ECDSA-P256-SHA256 PUBLIC-KEY ::=
pk-CompositeSignature{ id-MLDSA65-ECDSA-P256-SHA256,
OCTET STRING, ECPoint}
The full set of key types defined by this specification can be found
in the ASN.1 Module in Section 9.
5.2. CompositeSignaturePublicKey
Composite public key data is represented by the following structure:
CompositeSignaturePublicKey ::= SEQUENCE SIZE (2) OF BIT STRING
A composite key MUST contain two component public keys. The order of
the component keys is determined by the definition of the
corresponding algorithm identifier as defined in section Section 7.
Some applications may need to reconstruct the SubjectPublicKeyInfo
objects corresponding to each component public key. Table 2 in
Section 7 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
Section 5.4.
Component keys of a CompositeSignaturePublicKey MUST NOT be used in
any other type of key or as a standalone key.
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5.3. CompositeSignaturePrivateKey
Use cases that require an interoperable encoding for composite
private keys, such as when private keys are carried in PKCS #12
[RFC7292], CMP [RFC4210] or CRMF [RFC4211] MUST use the following
structure.
CompositeSignaturePrivateKey ::= SEQUENCE SIZE (2) OF OneAsymmetricKey
Each element is a OneAsymmetricKey` [RFC5958] object for a component
private key.
The parameters field MUST be absent.
The order of the component keys is the same as the order defined in
Section 5.2 for the components of CompositeSignaturePublicKey.
When a CompositeSignaturePrivateKey is conveyed inside a
OneAsymmetricKey structure (version 1 of which is also known as
PrivateKeyInfo) [RFC5958], the privateKeyAlgorithm field SHALL be set
to the corresponding composite algorithm identifier defined according
to Section 7, 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.
5.4. Encoding Rules
Many protocol specifications will require that the composite public
key and composite private key data structures be represented by an
octet string or bit string.
When an octet string is required, the DER encoding of the composite
data structure SHALL be used directly.
CompositeSignaturePublicKeyOs ::= OCTET STRING (CONTAINING CompositeSignaturePublicKey ENCODED BY der)
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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.
CompositeSignaturePublicKeyBs ::= BIT STRING (CONTAINING CompositeSignaturePublicKey ENCODED BY der)
In the interests of simplicity and avoiding compatibility issues,
implementations that parse these structures MAY accept both BER and
DER.
5.5. Key Usage Bits
For protocols such as X.509 [RFC5280] that specify key usage along
with the public key, then the composite public key associated with a
composite 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:
digitalSignature;
nonRepudiation;
keyCertSign; and
cRLSign.
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:
digitalSignature; and
nonRepudiation;
6. Composite Signature Structures
6.1. sa-CompositeSignature
The ASN.1 algorithm object for a composite signature is:
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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 }
}
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 |
+-----------------------------+-----------------------------------+
Table 1
6.2. CompositeSignatureValue
The output of the composite signature algorithm is the DER encoding
of the following structure:
CompositeSignatureValue ::= SEQUENCE SIZE (2) OF BIT STRING
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.
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7. 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:
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+=============================+============+===========+=======================+======+
|Composite Signature |OID |First |Second AlgorithmID |Pre- |
|AlgorithmID | |AlgorithmID| |Hash |
+=============================+============+===========+=======================+======+
|id-MLDSA44-RSA2048-PSS-SHA256|<CompSig>.1 |id-ML- |id-RSASA-PSS with id- |id- |
| | |DSA-44 |sha256 |sha256|
+-----------------------------+------------+-----------+-----------------------+------+
|id- |<CompSig>.2 |id-ML- |sha256WithRSAEncryption|id- |
|MLDSA44-RSA2048-PKCS15-SHA256| |DSA-44 | |sha256|
+-----------------------------+------------+-----------+-----------------------+------+
|id-MLDSA44-Ed25519-SHA512 |<CompSig>.3 |id-ML- |id-Ed25519 |id- |
| | |DSA-44 | |sha512|
+-----------------------------+------------+-----------+-----------------------+------+
|id-MLDSA44-ECDSA-P256-SHA256 |<CompSig>.4 |id-ML- |ecdsa-with-SHA256 with |id- |
| | |DSA-44 |secp256r1 |sha256|
+-----------------------------+------------+-----------+-----------------------+------+
|id-MLDSA44-ECDSA- |<CompSig>.5 |id-ML- |ecdsa-with-SHA256 with |id- |
|brainpoolP256r1-SHA256 | |DSA-44 |brainpoolP256r1 |sha256|
+-----------------------------+------------+-----------+-----------------------+------+
|id-MLDSA65-RSA3072-PSS-SHA512|<CompSig>.6 |id-ML- |id-RSASA-PSS with id- |id- |
| | |DSA-65 |sha512 |sha512|
+-----------------------------+------------+-----------+-----------------------+------+
|id- |<CompSig>.7 |id-ML- |sha512WithRSAEncryption|id- |
|MLDSA65-RSA3072-PKCS15-SHA512| |DSA-65 | |sha512|
+-----------------------------+------------+-----------+-----------------------+------+
|id-MLDSA65-ECDSA-P256-SHA512 |<CompSig>.8 |id-ML- |ecdsa-with-SHA512 with |id- |
| | |DSA-65 |secp256r1 |sha512|
+-----------------------------+------------+-----------+-----------------------+------+
|id-MLDSA65-ECDSA- |<CompSig>.9 |id-ML- |ecdsa-with-SHA512 with |id- |
|brainpoolP256r1-SHA512 | |DSA-65 |brainpoolP256r1 |sha512|
+-----------------------------+------------+-----------+-----------------------+------+
|id-MLDSA65-Ed25519-SHA512 |<CompSig>.10|id-ML- |id-Ed25519 |id- |
| | |DSA-65 | |sha512|
+-----------------------------+------------+-----------+-----------------------+------+
|id-MLDSA87-ECDSA-P384-SHA512 |<CompSig>.11|id-ML- |ecdsa-with-SHA512 with |id- |
| | |DSA-87 |secp384r1 |sha512|
+-----------------------------+------------+-----------+-----------------------+------+
|id-MLDSA87-ECDSA- |<CompSig>.12|id-ML- |ecdsa-with-SHA512 with |id- |
|brainpoolP384r1-SHA512 | |DSA-87 |brainpoolP384r1 |sha512|
+-----------------------------+------------+-----------+-----------------------+------+
|id-MLDSA87-Ed448-SHA512 |<CompSig>.13|id-ML- |id-Ed448 |id- |
| | |DSA-87 | |sha512|
+-----------------------------+------------+-----------+-----------------------+------+
Table 2: Composite Signature Algorithms
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The table above contains everything needed to implement the listed
explicit composite algorithms. See the ASN.1 module in section
Section 9 for the explicit definitions of the above Composite
signature algorithms.
Full specifications for the referenced algorithms can be found in
Appendix A.
7.1. 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 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|
+---------------------------------------+--------------------------+
Table 3: Composite Signature Domain Separators
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7.2. Notes on id-MLDSA44-RSA2048-PSS-SHA256
Use of RSA-PSS [RFC8017] 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 Parameter | Value |
+==========================+=========+
| Mask Generation Function | mgf1 |
+--------------------------+---------+
| Mask Generation params | SHA-256 |
+--------------------------+---------+
| Message Digest Algorithm | SHA-256 |
+--------------------------+---------+
| Salt Length in bits | 256 |
+--------------------------+---------+
Table 4: RSA-PSS 2048 Parameters
where:
* Mask Generation Function (mgf1) is defined in [RFC8017]
* SHA-256 is defined in [RFC6234].
7.3. 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:
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+==========================+=========+
| RSA-PSS Parameter | Value |
+==========================+=========+
| Mask Generation Function | mgf1 |
+--------------------------+---------+
| Mask Generation params | SHA-512 |
+--------------------------+---------+
| Message Digest Algorithm | SHA-512 |
+--------------------------+---------+
| Salt Length in bits | 512 |
+--------------------------+---------+
Table 5: RSA-PSS 3072 Parameters
where:
* Mask Generation Function (mgf1) is defined in [RFC8017]
* SHA-512 is defined in [RFC6234].
8. 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 [RFC5652].
8.1. Underlying Components
When a particular Composite Signature OID is supported in CMS, an
implementation SHOULD support the corresponding Secure Hash algorithm
identifier in Table 6 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.
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+=========================================+=============+
| 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 |
+-----------------------------------------+-------------+
Table 6: Composite Signature SHA Algorithms
where:
* SHA2 instantiations are defined in [FIPS180].
8.2. SignedData Conventions
As specified in CMS [RFC5652], 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
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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:
IF (signed attributes are absent)
THEN Composite_Sign(content)
ELSE message-digest attribute = Hash(content);
Composite_Sign(DER(SignedAttributes))
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 Table 6
signature: The signature field contains the signature value resulting
from the composite signing operation of the specified
signatureAlgorithm.
8.3. Certificate Conventions
The conventions specified in this section augment RFC 5280 [RFC5280].
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 [RFC8551] or the SMIMECapabilities certificate
extension as specified in [RFC4262].
The intended application for the public key MAY be indicated in the
key usage certificate extension as specified in Section 4.2.1.3 of
[RFC5280]. If the keyUsage extension is present in a certificate
that conveys a composite Signature public key, then the key usage
extension MUST contain only the following value:
digitalSignature
nonRepudiation
keyCertSign
cRLSign
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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.
8.4. SMIMECapabilities Attribute Conventions
Section 2.5.2 of [RFC8551] defines the SMIMECapabilities attribute to
announce a partial list of algorithms that an S/MIME implementation
can support. When constructing a CMS signed-data content type
[RFC5652], a compliant implementation MAY include the
SMIMECapabilities attribute that announces support for the RSA-KEM
Algorithm.
The SMIMECapability SEQUENCE representing a composite signature
Algorithm MUST include the appropriate object identifier as per
Table 6 in the capabilityID field.
9. ASN.1 Module
<CODE STARTS>
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
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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
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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 ::=
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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 ::=
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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 }
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-- 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)
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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
<CODE ENDS>
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10. IANA Considerations
IANA is requested to allocate a value from the "SMI Security for PKIX
Module Identifier" registry [RFC7299] for the included ASN.1 module,
and allocate values from "SMI Security for PKIX Algorithms" to
identify the fourteen Algorithms defined within.
10.1. Object Identifier Allocations
EDNOTE to IANA: OIDs will need to be replaced in both the ASN.1
module and in Table 2.
10.1.1. Module Registration - SMI Security for PKIX Module Identifier
* Decimal: IANA Assigned - *Replace TBDMOD*
* Description: Composite-Signatures-2023 - id-mod-composite-
signatures
* References: This Document
10.1.2. 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
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* 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
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* 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
11. Security Considerations
11.1. 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.
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2. Elliptic curve algorithms are provided with combinations on each
of the NIST [RFC6090], Brainpool [RFC5639], and Edwards [RFC7748]
curves. NIST PQC Levels 1 - 3 algorithms are matched with
256-bit curves, while NIST levels 4 - 5 are matched with 384-bit
elliptic curves. This provides a balance between matching
classical security levels of post-quantum and traditional
algorithms, and also selecting elliptic curves which already have
wide adoption.
3. NIST level 1 candidates are provided, matched with 256-bit
elliptic curves, intended for constrained use cases.
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.
11.2. 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 [RFC8032] uses SHA512 internally, therefore SHA512 is
used to pre-hash the message when Ed25519 is a component
algorithm.
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4. Ed448 [RFC8032] 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.
11.3. 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.
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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 [RFC5280]), 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.
12. References
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2986] Nystrom, M. and B. Kaliski, "PKCS #10: Certification
Request Syntax Specification Version 1.7", RFC 2986,
DOI 10.17487/RFC2986, November 2000,
<https://www.rfc-editor.org/info/rfc2986>.
[RFC4210] Adams, C., Farrell, S., Kause, T., and T. Mononen,
"Internet X.509 Public Key Infrastructure Certificate
Management Protocol (CMP)", RFC 4210,
DOI 10.17487/RFC4210, September 2005,
<https://www.rfc-editor.org/info/rfc4210>.
[RFC4211] Schaad, J., "Internet X.509 Public Key Infrastructure
Certificate Request Message Format (CRMF)", RFC 4211,
DOI 10.17487/RFC4211, September 2005,
<https://www.rfc-editor.org/info/rfc4211>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>.
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[RFC5480] Turner, S., Brown, D., Yiu, K., Housley, R., and T. Polk,
"Elliptic Curve Cryptography Subject Public Key
Information", RFC 5480, DOI 10.17487/RFC5480, March 2009,
<https://www.rfc-editor.org/info/rfc5480>.
[RFC5639] Lochter, M. and J. Merkle, "Elliptic Curve Cryptography
(ECC) Brainpool Standard Curves and Curve Generation",
RFC 5639, DOI 10.17487/RFC5639, March 2010,
<https://www.rfc-editor.org/info/rfc5639>.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC5652, September 2009,
<https://www.rfc-editor.org/info/rfc5652>.
[RFC5758] Dang, Q., Santesson, S., Moriarty, K., Brown, D., and T.
Polk, "Internet X.509 Public Key Infrastructure:
Additional Algorithms and Identifiers for DSA and ECDSA",
RFC 5758, DOI 10.17487/RFC5758, January 2010,
<https://www.rfc-editor.org/info/rfc5758>.
[RFC5958] Turner, S., "Asymmetric Key Packages", RFC 5958,
DOI 10.17487/RFC5958, August 2010,
<https://www.rfc-editor.org/info/rfc5958>.
[RFC6090] McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic
Curve Cryptography Algorithms", RFC 6090,
DOI 10.17487/RFC6090, February 2011,
<https://www.rfc-editor.org/info/rfc6090>.
[RFC6234] Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms
(SHA and SHA-based HMAC and HKDF)", RFC 6234,
DOI 10.17487/RFC6234, May 2011,
<https://www.rfc-editor.org/info/rfc6234>.
[RFC7748] Langley, A., Hamburg, M., and S. Turner, "Elliptic Curves
for Security", RFC 7748, DOI 10.17487/RFC7748, January
2016, <https://www.rfc-editor.org/info/rfc7748>.
[RFC8032] Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital
Signature Algorithm (EdDSA)", RFC 8032,
DOI 10.17487/RFC8032, January 2017,
<https://www.rfc-editor.org/info/rfc8032>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
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[RFC8410] Josefsson, S. and J. Schaad, "Algorithm Identifiers for
Ed25519, Ed448, X25519, and X448 for Use in the Internet
X.509 Public Key Infrastructure", RFC 8410,
DOI 10.17487/RFC8410, August 2018,
<https://www.rfc-editor.org/info/rfc8410>.
[RFC8411] Schaad, J. and R. Andrews, "IANA Registration for the
Cryptographic Algorithm Object Identifier Range",
RFC 8411, DOI 10.17487/RFC8411, August 2018,
<https://www.rfc-editor.org/info/rfc8411>.
[X.690] ITU-T, "Information technology - ASN.1 encoding Rules:
Specification of Basic Encoding Rules (BER), Canonical
Encoding Rules (CER) and Distinguished Encoding Rules
(DER)", ISO/IEC 8825-1:2015, November 2015.
12.2. Informative References
[ANSSI2024]
French Cybersecurity Agency (ANSSI), Federal Office for
Information Security (BSI), Netherlands National
Communications Security Agency (NLNCSA), and Swedish
National Communications Security Authority, Swedish Armed
Forces, "Position Paper on Quantum Key Distribution",
n.d., <https://cyber.gouv.fr/sites/default/files/document/
Quantum_Key_Distribution_Position_Paper.pdf>.
[Bindel2017]
Bindel, N., Herath, U., McKague, M., and D. Stebila,
"Transitioning to a quantum-resistant public key
infrastructure", 2017, <https://link.springer.com/
chapter/10.1007/978-3-319-59879-6_22>.
[BSI2021] Federal Office for Information Security (BSI), "Quantum-
safe cryptography - fundamentals, current developments and
recommendations", October 2021,
<https://www.bsi.bund.de/SharedDocs/Downloads/EN/BSI/
Publications/Brochure/quantum-safe-cryptography.pdf>.
[I-D.becker-guthrie-noncomposite-hybrid-auth]
Becker, A., Guthrie, R., and M. J. Jenkins, "Non-Composite
Hybrid Authentication in PKIX and Applications to Internet
Protocols", Work in Progress, Internet-Draft, draft-
becker-guthrie-noncomposite-hybrid-auth-00, 22 March 2022,
<https://datatracker.ietf.org/doc/html/draft-becker-
guthrie-noncomposite-hybrid-auth-00>.
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[I-D.driscoll-pqt-hybrid-terminology]
D, F., "Terminology for Post-Quantum Traditional Hybrid
Schemes", Work in Progress, Internet-Draft, draft-
driscoll-pqt-hybrid-terminology-01, 20 October 2022,
<https://datatracker.ietf.org/doc/html/draft-driscoll-pqt-
hybrid-terminology-01>.
[I-D.guthrie-ipsecme-ikev2-hybrid-auth]
Guthrie, R., "Hybrid Non-Composite Authentication in
IKEv2", Work in Progress, Internet-Draft, draft-guthrie-
ipsecme-ikev2-hybrid-auth-00, 25 March 2022,
<https://datatracker.ietf.org/doc/html/draft-guthrie-
ipsecme-ikev2-hybrid-auth-00>.
[I-D.hale-pquip-hybrid-signature-spectrums]
Bindel, N., Hale, B., Connolly, D., and F. D, "Hybrid
signature spectrums", Work in Progress, Internet-Draft,
draft-hale-pquip-hybrid-signature-spectrums-01, 6 November
2023, <https://datatracker.ietf.org/doc/html/draft-hale-
pquip-hybrid-signature-spectrums-01>.
[I-D.ietf-lamps-dilithium-certificates]
Massimo, J., Kampanakis, P., Turner, S., and B.
Westerbaan, "Internet X.509 Public Key Infrastructure:
Algorithm Identifiers for Dilithium", Work in Progress,
Internet-Draft, draft-ietf-lamps-dilithium-certificates-
01, 6 February 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-lamps-
dilithium-certificates-01>.
[I-D.massimo-lamps-pq-sig-certificates]
Massimo, J., Kampanakis, P., Turner, S., and B.
Westerbaan, "Algorithms and Identifiers for Post-Quantum
Algorithms", Work in Progress, Internet-Draft, draft-
massimo-lamps-pq-sig-certificates-00, 8 July 2022,
<https://datatracker.ietf.org/doc/html/draft-massimo-
lamps-pq-sig-certificates-00>.
[I-D.ounsworth-pq-composite-kem]
Ounsworth, M. and J. Gray, "Composite KEM For Use In
Internet PKI", Work in Progress, Internet-Draft, draft-
ounsworth-pq-composite-kem-01, 13 March 2023,
<https://datatracker.ietf.org/doc/html/draft-ounsworth-pq-
composite-kem-01>.
[I-D.pala-klaussner-composite-kofn]
Pala, M. and J. Klaußner, "K-threshold Composite
Signatures for the Internet PKI", Work in Progress,
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Internet-Draft, draft-pala-klaussner-composite-kofn-00, 15
November 2022, <https://datatracker.ietf.org/doc/html/
draft-pala-klaussner-composite-kofn-00>.
[I-D.vaira-pquip-pqc-use-cases]
Vaira, A., Brockhaus, H., Railean, A., Gray, J., and M.
Ounsworth, "Post-quantum cryptography use cases", Work in
Progress, Internet-Draft, draft-vaira-pquip-pqc-use-cases-
00, 23 October 2023,
<https://datatracker.ietf.org/doc/html/draft-vaira-pquip-
pqc-use-cases-00>.
[RFC3279] Bassham, L., Polk, W., and R. Housley, "Algorithms and
Identifiers for the Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 3279, DOI 10.17487/RFC3279, April
2002, <https://www.rfc-editor.org/info/rfc3279>.
[RFC7292] Moriarty, K., Ed., Nystrom, M., Parkinson, S., Rusch, A.,
and M. Scott, "PKCS #12: Personal Information Exchange
Syntax v1.1", RFC 7292, DOI 10.17487/RFC7292, July 2014,
<https://www.rfc-editor.org/info/rfc7292>.
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
2014, <https://www.rfc-editor.org/info/rfc7296>.
[RFC7299] Housley, R., "Object Identifier Registry for the PKIX
Working Group", RFC 7299, DOI 10.17487/RFC7299, July 2014,
<https://www.rfc-editor.org/info/rfc7299>.
[RFC8017] Moriarty, K., Ed., Kaliski, B., Jonsson, J., and A. Rusch,
"PKCS #1: RSA Cryptography Specifications Version 2.2",
RFC 8017, DOI 10.17487/RFC8017, November 2016,
<https://www.rfc-editor.org/info/rfc8017>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
[RFC8551] Schaad, J., Ramsdell, B., and S. Turner, "Secure/
Multipurpose Internet Mail Extensions (S/MIME) Version 4.0
Message Specification", RFC 8551, DOI 10.17487/RFC8551,
April 2019, <https://www.rfc-editor.org/info/rfc8551>.
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Appendix A. Component Algorithm Reference
This section provides references to the full specification of the
algorithms used in the composite constructions.
+=======================+========================+=======================================+
|Component Signature |OID |Specification |
|Algorithm ID | | |
+=======================+========================+=======================================+
|id-ML-DSA-44 |1.3.6.1.4.1.2.267.12.4.4|_ML-DSA_: |
| | |[I-D.ietf-lamps-dilithium-certificates]|
| | |and [FIPS.204-ipd] |
+-----------------------+------------------------+---------------------------------------+
|id-ML-DSA-65 |1.3.6.1.4.1.2.267.12.6.5|_ML-DSA_: |
| | |[I-D.ietf-lamps-dilithium-certificates]|
| | |and [FIPS.204-ipd] |
+-----------------------+------------------------+---------------------------------------+
|id-ML-DSA-87 |1.3.6.1.4.1.2.267.12.8.7|_ML-DSA_: |
| | |[I-D.ietf-lamps-dilithium-certificates]|
| | |and [FIPS.204-ipd] |
+-----------------------+------------------------+---------------------------------------+
|id-Ed25519 |iso(1) identified- |_Ed25519 / Ed448_: [RFC8410] |
| |organization(3) | |
| |thawte(101) 112 | |
+-----------------------+------------------------+---------------------------------------+
|id-Ed448 |iso(1) identified- |_Ed25519 / Ed448_: [RFC8410] |
| |organization(3) | |
| |thawte(101) id- | |
| |Ed448(113) | |
+-----------------------+------------------------+---------------------------------------+
|ecdsa-with-SHA256 |iso(1) member-body(2) |_ECDSA_: [RFC5758] |
| |us(840) ansi- | |
| |X9-62(10045) | |
| |signatures(4) ecdsa- | |
| |with-SHA2(3) 2 | |
+-----------------------+------------------------+---------------------------------------+
|ecdsa-with-SHA512 |iso(1) member-body(2) |_ECDSA_: [RFC5758] |
| |us(840) ansi- | |
| |X9-62(10045) | |
| |signatures(4) ecdsa- | |
| |with-SHA2(3) 4 | |
+-----------------------+------------------------+---------------------------------------+
|sha256WithRSAEncryption|iso(1) member-body(2) |_RSAES-PKCS-v1_5_: [RFC8017] |
| |us(840) rsadsi(113549) | |
| |pkcs(1) pkcs-1(1) 11 | |
+-----------------------+------------------------+---------------------------------------+
|sha512WithRSAEncryption|iso(1) member-body(2) |_RSAES-PKCS-v1_5_: [RFC8017] |
| |us(840) rsadsi(113549) | |
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| |pkcs(1) pkcs-1(1) 13 | |
+-----------------------+------------------------+---------------------------------------+
|id-RSASA-PSS |iso(1) member-body(2) |_RSASSA-PSS_: [RFC8017] |
| |us(840) rsadsi(113549) | |
| |pkcs(1) pkcs-1(1) 10 | |
+-----------------------+------------------------+---------------------------------------+
Table 7: Component Signature Algorithms used in Composite
Constructions
+=================+=================================+===============+
| Elliptic | OID | Specification |
| CurveID | | |
+=================+=================================+===============+
| secp256r1 | iso(1) member-body(2) | [RFC6090] |
| | us(840) ansi-x962(10045) | |
| | curves(3) prime(1) 7 | |
+-----------------+---------------------------------+---------------+
| secp384r1 | iso(1) identified- | [RFC6090] |
| | organization(3) | |
| | certicom(132) curve(0) 34 | |
+-----------------+---------------------------------+---------------+
| brainpoolP256r1 | iso(1) identified- | [RFC5639] |
| | organization(3) | |
| | teletrust(36) algorithm(3) | |
| | signatureAlgorithm(3) | |
| | ecSign(2) | |
| | ecStdCurvesAndGeneration(8) | |
| | ellipticCurve(1) | |
| | versionOne(1) 7 | |
+-----------------+---------------------------------+---------------+
| brainpoolP384r1 | iso(1) identified- | [RFC5639] |
| | organization(3) | |
| | teletrust(36) algorithm(3) | |
| | signatureAlgorithm(3) | |
| | ecSign(2) | |
| | ecStdCurvesAndGeneration(8) | |
| | ellipticCurve(1) | |
| | versionOne(1) 11 | |
+-----------------+---------------------------------+---------------+
Table 8: Elliptic Curves used in Composite Constructions
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+===========+=================================+===============+
| HashID | OID | Specification |
+===========+=================================+===============+
| id-sha256 | joint-iso-itu-t(2) country(16) | [RFC6234] |
| | us(840) organization(1) | |
| | gov(101) csor(3) | |
| | nistAlgorithms(4) hashAlgs(2) 1 | |
+-----------+---------------------------------+---------------+
| id-sha512 | joint-iso-itu-t(2) country(16) | [RFC6234] |
| | us(840) organization(1) | |
| | gov(101) csor(3) | |
| | nistAlgorithms(4) hashAlgs(2) 3 | |
+-----------+---------------------------------+---------------+
Table 9: Hash algorithms used in Composite Constructions
Appendix B. Samples
B.1. Explicit Composite Signature Examples
B.1.1. MLDSA44-ECDSA-P256-SHA256 Public Key
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Internet-Draft PQ Composite ML-DSA July 2024
-----BEGIN PUBLIC KEY-----
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-----END PUBLIC KEY-----
B.1.2. MLDSA44-ECDSA-P256 Private Key
-----BEGIN PRIVATE KEY-----
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Ounsworth, et al. Expires 9 January 2025 [Page 44]
Internet-Draft PQ Composite ML-DSA July 2024
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Ounsworth, et al. Expires 9 January 2025 [Page 45]
Internet-Draft PQ Composite ML-DSA July 2024
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-----END PRIVATE KEY-----
B.1.3. MLDSA44-ECDSA-P256 Self-Signed X509 Certificate
-----BEGIN CERTIFICATE-----
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Ounsworth, et al. Expires 9 January 2025 [Page 46]
Internet-Draft PQ Composite ML-DSA July 2024
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-----END CERTIFICATE-----
Appendix C. Implementation Considerations
C.1. FIPS certification
One of the primary design goals of this specification is for the
overall composite algorithm to be able to be considered FIPS-approved
even when one of the component algorithms is not.
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.
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C.2. 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 [RFC8446] and IKEv2
[RFC7296], to non-negotiated asynchronous protocols such as S/MIME
signed email [RFC8551], 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
[RFC5652] signed structures. Composite simplifies the protocol
design work because it can be implemented as a signature algorithm
that fits into existing systems.
C.2.1. 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.
Appendix D. Intellectual Property Considerations
The following IPR Disclosure relates to this draft:
https://datatracker.ietf.org/ipr/3588/
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Appendix E. 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" -
[RFC8411].
E.1. 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
Authors' Addresses
Mike Ounsworth
Entrust Limited
2500 Solandt Road -- Suite 100
Ottawa, Ontario K2K 3G5
Canada
Email: mike.ounsworth@entrust.com
John Gray
Entrust Limited
2500 Solandt Road -- Suite 100
Ottawa, Ontario K2K 3G5
Canada
Email: john.gray@entrust.com
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Massimiliano Pala
OpenCA Labs
New York City, New York,
United States of America
Email: director@openca.org
Jan Klaussner
Bundesdruckerei GmbH
Kommandantenstr. 18
10969 Berlin
Germany
Email: jan.klaussner@bdr.de
Scott Fluhrer
Cisco Systems
Email: sfluhrer@cisco.com
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