Composite Signatures For Use In Internet PKI
draft-ounsworth-pq-composite-sigs-10
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| Last updated | 2023-10-23 (Latest revision 2023-05-29) | ||
| Replaced by | draft-ietf-lamps-pq-composite-sigs, draft-ietf-lamps-pq-composite-sigs, draft-ietf-lamps-pq-composite-sigs | ||
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draft-ounsworth-pq-composite-sigs-10
LAMPS M. Ounsworth
Internet-Draft J. Gray
Intended status: Standards Track Entrust
Expires: 25 April 2024 M. Pala
CableLabs
J. Klaussner
D-Trust GmbH
23 October 2023
Composite Signatures For Use In Internet PKI
draft-ounsworth-pq-composite-sigs-10
Abstract
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 cryptanalysis, 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
or signature such that they can be treated as a single atomic object
at the protocol level.
This document defines the structures CompositeSignaturePublicKey,
CompositeSignaturePrivateKey and CompositeSignatureValue, which are
sequences of the respective structure for each component algorithm.
Composite signature algorithm identifiers are specified in this
document which represent the explicit combinations of the underlying
component algorithms.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 25 April 2024.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Changes in version -10 . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
2.2. Composite Design Philosophy . . . . . . . . . . . . . . . 6
2.3. Composite Signatures . . . . . . . . . . . . . . . . . . 7
2.3.1. Composite KeyGen . . . . . . . . . . . . . . . . . . 7
2.3.2. Composite Sign . . . . . . . . . . . . . . . . . . . 7
2.3.3. Composite Verify . . . . . . . . . . . . . . . . . . 9
2.4. OID Concatenation . . . . . . . . . . . . . . . . . . . . 11
2.5. PreHashing the Message . . . . . . . . . . . . . . . . . 13
2.6. Algorithm Selection Criteria . . . . . . . . . . . . . . 13
3. Composite Signature Structures . . . . . . . . . . . . . . . 14
3.1. pk-CompositeSignature . . . . . . . . . . . . . . . . . . 14
3.2. CompositeSignaturePublicKey . . . . . . . . . . . . . . . 15
3.3. CompositeSignaturePrivateKey . . . . . . . . . . . . . . 15
3.4. Encoding Rules . . . . . . . . . . . . . . . . . . . . . 16
3.5. Key Usage Bits . . . . . . . . . . . . . . . . . . . . . 16
4. Composite Signature Structures . . . . . . . . . . . . . . . 17
4.1. sa-CompositeSignature . . . . . . . . . . . . . . . . . . 17
4.2. CompositeSignatureValue . . . . . . . . . . . . . . . . . 18
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5. Algorithm Identifiers . . . . . . . . . . . . . . . . . . . . 18
5.1. Notes on id-MLDSA44-RSA2048-PSS-SHA256 and
id-MLDSA65-RSA3072-PSS-SHA256 . . . . . . . . . . . . . . 21
6. ASN.1 Module . . . . . . . . . . . . . . . . . . . . . . . . 22
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29
7.1. Object Identifier Allocations . . . . . . . . . . . . . . 29
7.1.1. Module Registration - SMI Security for PKIX Module
Identifier . . . . . . . . . . . . . . . . . . . . . 29
7.1.2. Object Identifier Registrations - SMI Security for PKIX
Algorithms . . . . . . . . . . . . . . . . . . . . . 29
8. Security Considerations . . . . . . . . . . . . . . . . . . . 32
8.1. Policy for Deprecated and Acceptable Algorithms . . . . . 32
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 33
9.1. Normative References . . . . . . . . . . . . . . . . . . 33
9.2. Informative References . . . . . . . . . . . . . . . . . 34
Appendix A. Samples . . . . . . . . . . . . . . . . . . . . . . 37
A.1. Explicit Composite Signature Examples . . . . . . . . . . 37
A.1.1. MLDSA44-ECDSA-P256-SHA256 Public Key . . . . . . . . 37
A.1.2. MLDSA44-ECDSA-P256 Private Key . . . . . . . . . . . 37
A.1.3. MLDSA44-ECDSA-P256 Self-Signed X509 Certificate . . . 39
Appendix B. Implementation Considerations . . . . . . . . . . . 41
B.1. FIPS certification . . . . . . . . . . . . . . . . . . . 41
B.2. Backwards Compatibility . . . . . . . . . . . . . . . . . 42
B.2.1. Parallel PKIs . . . . . . . . . . . . . . . . . . . . 42
B.2.2. Hybrid Extensions (Keys and Signatures) . . . . . . . 43
Appendix C. Intellectual Property Considerations . . . . . . . . 43
Appendix D. Contributors and Acknowledgements . . . . . . . . . 43
D.1. Making contributions . . . . . . . . . . . . . . . . . . 44
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 44
1. Changes in version -10
Changes affecting interoperability:
* Changed all SEQUENCE OF SIZE (2..MAX) to SEQUENCE OF SIZE (2).
* Removed CompositeSignatureParams since all params are now explicit
in the Object IDs
* Made RSA keys fixed-length at 3072
* Removee redundency of subject public key overhead since OID fully
specifies the keytype and parameters
* Re-worked wire format of the composite signature by prehashing and
concatenating the OID to each component signature. This is
believed to give the binding between the two component algorithms
a stronger non-separability property.
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Editorial changes:
* Made this document standalone by folding in the minimum necessary
content from composite-keys
* Added a paragraph describing how to reconstitute component Subject
Public Key Infos
* Added a section showing the HEX encoding of the String Algorithm
Names
* Added a section on pre-hashing
* Rename Dilithium to ML-DSA and Falcon to FN-DSA
* Added an Implementation Consideration about FIPS validation where
only one component algorithm is FIPS-approved.
* Added a section on Signature APIs (Keygen, Sign, Verify) in
introduction
* Added reference to draft-vaira-pquip-pqc-use-cases-00
* TODO Refactored to use MartinThomson github template
2. Introduction
During the transition to post-quantum cryptography, there will be
uncertainty as to the strength of cryptographic algorithms; we will
no longer fully trust traditional cryptography such as RSA, Diffie-
Hellman, DSA and their elliptic curve variants, but we will also not
fully trust their post-quantum replacements until they have had
sufficient scrutiny and time to discover and fix implementation bugs.
Unlike previous cryptographic algorithm migrations, the choice of
when to migrate and which algorithms to migrate to, is not so clear.
Even after the migration period, it may be advantageous for an
entity's cryptographic identity to be composed of multiple public-key
algorithms.
Cautious implementers may wish to combine cryptographic algorithms
such that an attacker would need to break all of them in order to
compromise the data being protected. Such mechanisms are referred to
as Post-Quantum / Traditional Hybrids
[I-D.driscoll-pqt-hybrid-terminology].
PQ/T Hybrid cryptography can, in general, provide solutions to two
migration problems:
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* Algorithm strength uncertainty: During the transition period, some
post-quantum signature and encryption algorithms will not be fully
trusted, while also the trust in legacy public key algorithms will
start to erode. A relying party may learn some time after
deployment that a public key algorithm has become untrustworthy,
but in the interim, they may not know which algorithm an adversary
has compromised.
* Ease-of-migration: During the transition period, systems will
require mechanisms that allow for staged migrations from fully
classical to fully post-quantum-aware cryptography.
* Safeguard against faulty algorithm implementations and compromised
keys: Even for long known algorithms there is a non-negligible
risk of severe implementation faults. Latest examples are the
ROCA attack and ECDSA psychic signatures. Using more than one
algorithms will mitigate these risks.
This document defines a specific instantiation of the PQ/T Hybrid
paradigm called "composite" where multiple cryptographic algorithms
are combined to form a single signature such that it can be treated
as a single atomic algorithm at the protocol level. Composite
algorithms address algorithm strength uncertainty because the
composite algorithm remains strong so long as one of its components
remains strong. Concrete instantiations of composite signature
algorithms are provided based on ML-DSA, Falcon, RSA and ECDSA.
Backwards compatibility is not directly covered in this document, but
is the subject of Appendix B.2.
This document is intended for general applicability anywhere that
digital signatures are used within PKIX and CMS structures. For a
more detailed use-case discussion for composite signatures, the
reader is encouraged to look at [I-D.vaira-pquip-pqc-use-cases]
2.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
The following terms are used in this document:
ALGORITHM: A standardized cryptographic primitive, as well as any
ASN.1 structures needed for encoding data and metadata needed to use
the algorithm. This document is primarily concerned with algorithms
for producing digital signatures.
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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 or more
component algorithms, as defined in Section 3.
DER: Distinguished Encoding Rules as defined in [X.690].
LEGACY: For the purposes of this document, a legacy algorithm is any
cryptographic algorithm currently is use which is not believe 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.
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.
2.2. Composite Design Philosophy
[I-D.driscoll-pqt-hybrid-terminology] defines composites as:
_Composite Cryptographic Element_: A cryptographic element that
incorporates multiple component cryptographic elements of the same
type in a multi-algorithm scheme.
Composite keys as defined here follow this definition and should be
regarded as a single key that performs a single cryptographic
operation such key generation, signing, verifying, encapsulating, or
decapsulating -- using its internal sequence of component keys as if
they form a single key. This generally means that the complexity of
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combining algorithms can and should be handled by the cryptographic
library or cryptographic module, and the single composite public key,
private key, and ciphertext can be carried in existing fields in
protocols such as PKCS#10 [RFC2986], CMP [RFC4210], X.509 [RFC5280],
CMS [RFC5652], and the Trust Anchor Format [RFC5914]. In this way,
composites achieve "protocol backwards-compatibility" in that they
will drop cleanly into any protocol that accepts KEM algorithms
without requiring any modification of the protocol to handle multiple
keys.
2.3. Composite Signatures
Here we define the signature mechanism in which a signature is a
cryptographic primitive that consists of three algorithms:
* KeyGen() -> (pk, sk): A probabilistic key generation algorithm,
which generates a public key pk and a secret key sk.
* Sign(sk, Message) -> (signature): A signing algorithm which takes
as input a secret key sk and a Message, and outputs a signature
* Verify(pk, Message, signature) -> true or false: A verification
algorithm which takes as input a public key, a Message and
signature and outputs true if the signature and public key can be
used to verify the message. Thus it proves the Message was signed
with the secret key associated with the public key and verifies
the integrity of the Message. If the signature and public key
cannot verify the Message, it returns false.
A composite signature allows two or more underlying signature
algorithms to be combined into a single cryptographic signature
operation and can be used for applications that require signatures.
2.3.1. Composite KeyGen
The KeyGen() -> (pk, sk) of a composite signature algorithm will
perform the KeyGen() of the respective component signature algorithms
and it produces a composite public key pk as per Section 3.2 and a
composite secret key sk is per Section 3.3.
2.3.2. Composite Sign
Generation of a composite signature involves applying each component
algorithm's signature process to the input message according to its
specification, and then placing each component signature value into
the CompositeSignatureValue structure defined in Section 4.1.
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.
OID The Composite Signature String Algorithm Name converted
from ASCII to bytes. See section on OID concatenation
below.
Output:
signature The composite signature, a CompositeSignatureValue
Signature Generation Process:
1. Compute a Hash of the Message
M' = HASH(Message)
2. Generate the n component signatures independently,
according to their algorithm specifications.
S1 := Sign( K1, A1, OID || M' )
S2 := Sign( K2, A2, OID || M' )
3. Encode each component signature S1 and S2 into a BIT STRING
according to its algorithm specification.
signature ::= Sequence { S1, S2 }
4. Output signature
Figure 1: Composite Sign(sk, Message)
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Note on composite inputs: the method of providing the list of
component keys and algorithms is flexible and beyond the scope of
this pseudo-code. When passed to the Composite Sign(sk, Message) API
the sk is a CompositePrivateKey. It is possible to construct a
CompositePrivateKey from component keys stored in separate software
or hardware keystores. Variations in the process to accommodate
particular private key storage mechanisms are considered to be
conformant to this document so long as it produces the same output as
the process sketched above.
Since recursive composite public keys are disallowed, no component
signature may itself be a composite; ie the signature generation
process MUST fail if one of the private keys K1 or K2 is a composite.
A composite signature MUST produce, and include in the output, a
signature value for every component key in the corresponding
CompositePublicKey, and they MUST be in the same order; ie in the
output, S1 MUST correspond to K1, S2 to K2.
2.3.3. Composite Verify
Verification of a composite signature involves applying each
component algorithm's verification process according to its
specification.
In the absence of an application profile specifying otherwise,
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.
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OID The Composite Signature String Algorithm Name converted
from ASCII to bytes. See section on OID concatenation
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
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' = 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, OID || M', S1, A1 ) then
output "Invalid signature"
if not verify( P2, OID || M', S2, A2 ) then
output "Invalid signature"
if all succeeded, then
output "Valid signature"
Figure 2: Composite Verify(pk, Message, signature)
Note on composite inputs: the method of providing the list of
component keys and algorithms is flexible and beyond the scope of
this pseudo-code. When passed to the Composite Verify(pk, Message,
signature) API the pk is a CompositePublicKey. It is possible to
construct a CompositePublicKey from component keys stored in separate
software or hardware keystores. Variations in the process to
accommodate particular private key storage mechanisms are considered
to be conformant to this document so long as it produces the same
output as the process sketched above.
Since recursive composite public keys are disallowed, no component
signature may itself be a composite; ie the signature generation
process MUST fail if one of the private keys K1 or K2 is a composite.
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2.4. OID Concatenation
As mentioned above, the OID input value for the Composite Signature
Generation and verification process is the String representation of
the OID converted from ASCII to bytes. The following table shows the
HEX encoding of the ASCII String representation for each Signature
AlgorithmID
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+=============================+==================================================================================+
|Composite Signature |HEX Encoding to be prepended to each Message |
|AlgorithmID | |
+=============================+==================================================================================+
|id-MLDSA44-RSA2048-PSS-SHA256|69642D4D4C44534134342D525341323034382D5053532D534841323536 |
+-----------------------------+----------------------------------------------------------------------------------+
|id- |69642D4D4C44534134342D525341323034382D504B435331352D534841323536 |
|MLDSA44-RSA2048-PKCS15-SHA256| |
+-----------------------------+----------------------------------------------------------------------------------+
|id-MLDSA44-Ed25519-SHA512 |69642D4D4C44534134342D456432353531392D534841353132 |
+-----------------------------+----------------------------------------------------------------------------------+
|id-MLDSA44-ECDSA-P256-SHA256 |69642D4D4C44534134342D45434453412D503235362D534841323536 |
+-----------------------------+----------------------------------------------------------------------------------+
|id-MLDSA44-ECDSA- |69642D4D4C44534134342D45434453412D627261696E706F6F6C5032353672312D534841323536 |
|brainpoolP256r1-SHA256 | |
+-----------------------------+----------------------------------------------------------------------------------+
|id-MLDSA65-RSA3072-PSS-SHA256|69642D4D4C44534136352D525341333037322D5053532D534841323536 |
+-----------------------------+----------------------------------------------------------------------------------+
|id- |69642D4D4C44534136352D525341333037322D504B435331352D534841323536 |
|MLDSA65-RSA3072-PKCS15-SHA256| |
+-----------------------------+----------------------------------------------------------------------------------+
|id-MLDSA65-ECDSA-P256-SHA256 |69642D4D4C44534136352D45434453412D503235362D534841323536 |
+-----------------------------+----------------------------------------------------------------------------------+
|id-MLDSA65-ECDSA- |69642D4D4C44534136352D45434453412D627261696E706F6F6C5032353672312D534841323536 |
|brainpoolP256r1-SHA256 | |
+-----------------------------+----------------------------------------------------------------------------------+
|id-MLDSA65-Ed25519-SHA512 |69642D4D4C44534136352D456432353531392D534841353132 |
+-----------------------------+----------------------------------------------------------------------------------+
|id-MLDSA87-ECDSA-P384-SHA384 |69642D4D4C44534138372D45434453412D503338342D534841333834 |
+-----------------------------+----------------------------------------------------------------------------------+
|id-MLDSA87-ECDSA- |69642D4D4C44534138372D45434453412D627261696E706F6F6C5033383472312D534841333834 |
|brainpoolP384r1-SHA384 | |
+-----------------------------+----------------------------------------------------------------------------------+
|id-MLDSA87-Ed448-SHAKE256 |69642D4D4C44534138372D45643434382D5348414B45323536 |
+-----------------------------+----------------------------------------------------------------------------------+
|id-Falon512-ECDSA-P256-SHA256|69642D46616C6F6E3531322D45434453412D503235362D534841323536 |
+-----------------------------+----------------------------------------------------------------------------------+
|id-Falcon512-ECDSA- |69642D46616C636F6E3531322D45434453412D627261696E706F6F6C5032353672312D534841323536|
|brainpoolP256r1-SHA256 | |
+-----------------------------+----------------------------------------------------------------------------------+
|id-Falcon512-Ed25519-SHA512 |69642D46616C636F6E3531322D456432353531392D534841353132 |
+-----------------------------+----------------------------------------------------------------------------------+
Table 1: Composite Signature OID Concatenations
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2.5. PreHashing the Message
As noted in the composite signature generation process and composite
signature verification process, the Message should be pre-hashed into
M' with the digest algorithm specified in the composite signature
algorithm identifier. The choice of the digest algorithm was chosen
with the following criteria:
1. For composites paired with RSA or ECDSA, the hashing algorithm
SHA256 or SHA384 is used as part of the RSA or ECDSA signature
algorithm and is therefore also used as the composite prehashing
algorithm.
2. For Dilithium signing a digest of the message is allowed as long
as the hash function provides at least y bits of classical
security strength against both collision and second preimage
attacks. For MLDSA44 y is 128 bits, MLDSA65 y is 192 bits and
for MLDSA87 y is 256 bits. Therefore SHA256 paired with RSA and
SHA256 and SHA384 paired with ECDSA 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.
4. Ed448 [RFC8032] uses SHAKE256 internally, therefore SHA256 with
an output length of 512 bits is used to pre-hash the message when
Ed448 is a component algorithm. This is denoted in the table in
Section 5 as SHAKE256/512.
5. TODO: For Falcon signing it is expected prehashing digest
accomodations will be allowed.
2.6. 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.
3. Composite Signature Structures
In order for signatures to be composed of multiple algorithms, we
define encodings consisting of a sequence of signature primitives
(aka "component algorithms") such that these structures can be used
as a drop-in replacement for existing signature fields such as those
found in PKCS#10 [RFC2986], CMP [RFC4210], X.509 [RFC5280], CMS
[RFC5652].
3.1. pk-CompositeSignature
The following ASN.1 Information Object Class is a template to be used
in defining all composite Signature public key types.
pk-CompositeSignature {
OBJECT IDENTIFIER:id, FirstPublicKeyType,
SecondPublicKeyType} PUBLIC-KEY ::=
{
IDENTIFIER id
KEY SEQUENCE {
BIT STRING (CONTAINING FirstPublicKeyType)
BIT STRING (CONTAINING SecondPublicKeyType)
}
PARAMS ARE absent
CERT-KEY-USAGE { digitalSignature, nonRepudiation, keyCertSign, cRLSign }
}
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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 6.
3.2. 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 5.
Some applications may need to reconstruct the SubjectPublicKeyInfo
objects corresponding to each component public key. Table 3 in
Section 5 provides the necessary mapping between composite and their
component algorithms for doing this reconstruction. This also
motivates the design choice of SEQUENCE OF BIT STRING instead of
SEQUENCE OF OCTET STRING; using BIT STRING allows for easier
transcription between 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 3.4.
3.3. CompositeSignaturePrivateKey
Usecases 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 3.2 for the components of CompositeSignaturePublicKey.
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When a CompositePrivateKey is conveyed inside a OneAsymmetricKey
structure (version 1 of which is also known as PrivateKeyInfo)
[RFC5958], the privateKeyAlgorithm field SHALL be set to the
corresponding composite algorithm identifier defined according to
Section 5, the privateKey field SHALL contain the
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.
3.4. Encoding Rules
Many protocol specifications will require that the composite public
key and composite private key data structures be represented by an
octet string or bit string.
When an octet string is required, the DER encoding of the composite
data structure SHALL be used directly.
CompositeSignaturePublicKeyOs ::= OCTET STRING (CONTAINING CompositeSignaturePublicKey ENCODED BY der)
When a bit string is required, the octets of the DER encoded
composite data structure SHALL be used as the bits of the bit string,
with the most significant bit of the first octet becoming the first
bit, and so on, ending with the least significant bit of the last
octet becoming the last bit of the bit string.
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.
3.5. Key Usage Bits
For protocols such as X.509 [RFC5280] that specify key usage along
with the public key, then the composite public key associated with a
composite signature MUST have a signing-type key usage.
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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:
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:
digitalSignature; and
nonRepudiation;
4. Composite Signature Structures
4.1. sa-CompositeSignature
The ASN.1 algorithm object for a composite signature is:
sa-CompositeSignature {
OBJECT IDENTIFIER:id,
PUBLIC-KEY:publicKeyType }
SIGNATURE-ALGORITHM ::= {
IDENTIFIER id
VALUE CompositeSignatureValue
PARAMS ARE absent
PUBLIC-KEYS { publicKeyType }
}
The following is an explanation how SIGNATURE-ALGORITHM elements are
used to create Composite Signatures:
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+=============================+===================================+
| 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 2
4.2. 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.
5. 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 others composite signature algorithms so long as they are
compatible with the structures and processes defined in this and
companion public and private key documents.
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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 "2.16.840.1.114027.80.7.1"
Therefore <CompSig>.1 is equal to 2.16.840.1.114027.80.7.1.1
Signature public key types:
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+=============================+============+=========+=======================+============+
|Composite Signature |OID |First |Second Algorithm |Pre-Hash |
|AlgorithmID | |Algorithm| | |
+=============================+============+=========+=======================+============+
|id-MLDSA44-RSA2048-PSS-SHA256|<CompSig>.1 |MLDSA44 |SHA256WithRSAEncryption|SHA256 |
+-----------------------------+------------+---------+-----------------------+------------+
|id- |<CompSig>.2 |MLDSA44 |SHA256WithRSAEncryption|SHA256 |
|MLDSA44-RSA2048-PKCS15-SHA256| | | | |
+-----------------------------+------------+---------+-----------------------+------------+
|id-MLDSA44-Ed25519-SHA512 |<CompSig>.3 |MLDSA44 |Ed25519 |SHA512 |
+-----------------------------+------------+---------+-----------------------+------------+
|id-MLDSA44-ECDSA-P256-SHA256 |<CompSig>.4 |MLDSA44 |SHA256withECDSA |SHA256 |
+-----------------------------+------------+---------+-----------------------+------------+
|id-MLDSA44-ECDSA- |<CompSig>.5 |MLDSA44 |SHA256withECDSA |SHA256 |
|brainpoolP256r1-SHA256 | | | | |
+-----------------------------+------------+---------+-----------------------+------------+
|id-MLDSA65-RSA3072-PSS-SHA256|<CompSig>.6 |MLDSA65 |SHA256WithRSAPSS |SHA256 |
+-----------------------------+------------+---------+-----------------------+------------+
|id- |<CompSig>.7 |MLDSA65 |SHA256WithRSAEncryption|SHA256 |
|MLDSA65-RSA3072-PKCS15-SHA256| | | | |
+-----------------------------+------------+---------+-----------------------+------------+
|id-MLDSA65-ECDSA-P256-SHA256 |<CompSig>.8 |MLDSA65 |SHA256withECDSA |SHA256 |
+-----------------------------+------------+---------+-----------------------+------------+
|id-MLDSA65-ECDSA- |<CompSig>.9 |MLDSA65 |SHA256withECDSA |SHA256 |
|brainpoolP256r1-SHA256 | | | | |
+-----------------------------+------------+---------+-----------------------+------------+
|id-MLDSA65-Ed25519-SHA512 |<CompSig>.10|MLDSA65 |Ed25519 |SHA512 |
+-----------------------------+------------+---------+-----------------------+------------+
|id-MLDSA87-ECDSA-P384-SHA384 |<CompSig>.11|MLDSA87 |SHA384withECDSA |SHA384 |
+-----------------------------+------------+---------+-----------------------+------------+
|id-MLDSA87-ECDSA- |<CompSig>.12|MLDSA87 |SHA384withECDSA |SHA384 |
|brainpoolP384r1-SHA384 | | | | |
+-----------------------------+------------+---------+-----------------------+------------+
|id-MLDSA87-Ed448-SHAKE256 |<CompSig>.13|MLDSA87 |Ed448 |SHAKE256/512|
+-----------------------------+------------+---------+-----------------------+------------+
|id-Falon512-ECDSA-P256-SHA256|<CompSig>.14|Falcon512|SHA256withECDSA |SHA256 |
+-----------------------------+------------+---------+-----------------------+------------+
|id-Falcon512-ECDSA- |<CompSig>.15|Falcon512|SHA256withECDSA |SHA256 |
|brainpoolP256r1-SHA256 | | | | |
+-----------------------------+------------+---------+-----------------------+------------+
|id-Falcon512-Ed25519-SHA512 |<CompSig>.16|Falcon512|Ed25519 |SHA512 |
+-----------------------------+------------+---------+-----------------------+------------+
Table 3: 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 6 for the explicit definitions of the above Composite
signature algorithms.
Full specifications for the referenced algorithms can be found as
follows:
* _MLDSA_: [I-D.ietf-lamps-dilithium-certificates] and
[FIPS.204-ipd]
* _ECDSA_: [RFC5480]
* _Ed25519 / Ed448_: [RFC8410]
* _Falcon_: TBD
* _RSAES-PKCS-v1_5_: [RFC8017]
* _RSASSA-PSS_: [RFC8017]
5.1. Notes on id-MLDSA44-RSA2048-PSS-SHA256 and id-MLDSA65-RSA3072-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 security level with ML-DSA-44 or at 3072-bits
to match ML-DSA-65.
As with the other composite signature algorithms, when id-
MLDSA44-RSA2048-PSS-SHA256 or id-MLDSA65-RSA3072-PSS-SHA256 is used
in an AlgorithmIdentifier, the parameters MUST be absent. id-
MLDSA44-RSA2048-PSS-SHA256 and id-MLDSA65-RSA3072-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 |
+--------------------------+---------+
Table 4: RSA-PSS 2048 and 3072
Parameters
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where:
* Mask Generation Function (mgf1) is defined in [RFC8017]
* SHA-256 is defined in [RFC6234].
6. 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
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)}
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;
--
-- 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 OCTET 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}
--
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-- Information Object Classes
--
pk-CompositeSignature {
OBJECT IDENTIFIER:id, FirstPublicKeyType,
SecondPublicKeyType} PUBLIC-KEY ::=
{
IDENTIFIER id
KEY SEQUENCE {
BIT STRING (CONTAINING FirstPublicKeyType)
BIT STRING (CONTAINING SecondPublicKeyType)
}
PARAMS ARE absent
CERT-KEY-USAGE { digitalSignature, nonRepudiation, keyCertSign, cRLSign }
}
sa-CompositeSignature{OBJECT IDENTIFIER:id,
PUBLIC-KEY:publicKeyType }
SIGNATURE-ALGORITHM ::= {
IDENTIFIER id
VALUE CompositeSignatureValue
PARAMS ARE absent
PUBLIC-KEYS {publicKeyType}
}
-- TODO: OID to be replaced by IANA
id-MLDSA44-RSA2048-PSS-SHA256 OBJECT IDENTIFIER ::= {
joint-iso-itu-t(2) country(16) us(840) organization(1)
entrust(114027) algorithm(80) composite(7) 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(7) signature(1) 2 }
pk-MLDSA44-RSA2048-PKCS15-SHA256 PUBLIC-KEY ::=
pk-CompositeSignature{ id-MLDSA44-RSA2048-PKCS15-SHA256,
OCTET STRING, RSAPublicKey}
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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(7) 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(7) 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(7) 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,
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pk-MLDSA44-ECDSA-brainpoolP256r1-SHA256 }
-- TODO: OID to be replaced by IANA
id-MLDSA65-RSA3072-PSS-SHA256 OBJECT IDENTIFIER ::= {
joint-iso-itu-t(2) country(16) us(840) organization(1)
entrust(114027) algorithm(80) composite(7) signature(1) 6 }
pk-MLDSA65-RSA3072-PSS-SHA256 PUBLIC-KEY ::=
pk-CompositeSignature{ id-MLDSA65-RSA3072-PSS-SHA256,
OCTET STRING, RSAPublicKey}
sa-MLDSA65-RSA3072-PSS-SHA256 SIGNATURE-ALGORITHM ::=
sa-CompositeSignature{
id-MLDSA65-RSA3072-PSS-SHA256,
pk-MLDSA65-RSA3072-PSS-SHA256 }
-- TODO: OID to be replaced by IANA
id-MLDSA65-RSA3072-PKCS15-SHA256 OBJECT IDENTIFIER ::= {
joint-iso-itu-t(2) country(16) us(840) organization(1)
entrust(114027) algorithm(80) composite(7) signature(1) 7 }
pk-MLDSA65-RSA3072-PKCS15-SHA256 PUBLIC-KEY ::=
pk-CompositeSignature{ id-MLDSA65-RSA3072-PKCS15-SHA256,
OCTET STRING, RSAPublicKey}
sa-MLDSA65-RSA3072-PKCS15-SHA256 SIGNATURE-ALGORITHM ::=
sa-CompositeSignature{
id-MLDSA65-RSA3072-PKCS15-SHA256,
pk-MLDSA65-RSA3072-PKCS15-SHA256 }
-- TODO: OID to be replaced by IANA
id-MLDSA65-ECDSA-P256-SHA256 OBJECT IDENTIFIER ::= {
joint-iso-itu-t(2) country(16) us(840) organization(1)
entrust(114027) algorithm(80) composite(7) signature(1) 8 }
pk-MLDSA65-ECDSA-P256-SHA256 PUBLIC-KEY ::=
pk-CompositeSignature{ id-MLDSA65-ECDSA-P256-SHA256,
OCTET STRING, ECPoint}
sa-MLDSA65-ECDSA-P256-SHA256 SIGNATURE-ALGORITHM ::=
sa-CompositeSignature{
id-MLDSA65-ECDSA-P256-SHA256,
pk-MLDSA65-ECDSA-P256-SHA256 }
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-- TODO: OID to be replaced by IANA
id-id-MLDSA65-ECDSA-brainpoolP256r1-SHA256 OBJECT IDENTIFIER ::= {
joint-iso-itu-t(2) country(16) us(840) organization(1)
entrust(114027) algorithm(80) composite(7) signature(1) 9 }
pk-id-MLDSA65-ECDSA-brainpoolP256r1-SHA256 PUBLIC-KEY ::=
pk-CompositeSignature{ id-MLDSA65-ECDSA-brainpoolP256r1-SHA256,
OCTET STRING, ECPoint}
sa-id-MLDSA65-ECDSA-brainpoolP256r1-SHA256 SIGNATURE-ALGORITHM ::=
sa-CompositeSignature{
id-id-MLDSA65-ECDSA-brainpoolP256r1-SHA256,
pk-id-MLDSA65-ECDSA-brainpoolP256r1-SHA256 }
-- 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(7) 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-SHA384 OBJECT IDENTIFIER ::= {
joint-iso-itu-t(2) country(16) us(840) organization(1)
entrust(114027) algorithm(80) composite(7) signature(1) 11 }
pk-MLDSA87-ECDSA-P384-SHA384 PUBLIC-KEY ::=
pk-CompositeSignature{ id-MLDSA87-ECDSA-P384-SHA384,
OCTET STRING, ECPoint}
sa-MLDSA87-ECDSA-P384-SHA384 SIGNATURE-ALGORITHM ::=
sa-CompositeSignature{
id-MLDSA87-ECDSA-P384-SHA384,
pk-MLDSA87-ECDSA-P384-SHA384 }
-- TODO: OID to be replaced by IANA
id-MLDSA87-ECDSA-brainpoolP384r1-SHA384 OBJECT IDENTIFIER ::= {
joint-iso-itu-t(2) country(16) us(840) organization(1)
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entrust(114027) algorithm(80) composite(7) signature(1) 12 }
pk-MLDSA87-ECDSA-brainpoolP384r1-SHA384 PUBLIC-KEY ::=
pk-CompositeSignature{ id-MLDSA87-ECDSA-brainpoolP384r1-SHA384,
OCTET STRING, ECPoint}
sa-MLDSA87-ECDSA-brainpoolP384r1-SHA384 SIGNATURE-ALGORITHM ::=
sa-CompositeSignature{
id-MLDSA87-ECDSA-brainpoolP384r1-SHA384,
pk-MLDSA87-ECDSA-brainpoolP384r1-SHA384 }
-- TODO: OID to be replaced by IANA
id-MLDSA87-Ed448-SHAKE256 OBJECT IDENTIFIER ::= {
joint-iso-itu-t(2) country(16) us(840) organization(1)
entrust(114027) algorithm(80) composite(7) signature(1) 13 }
pk-MLDSA87-Ed448-SHAKE256 PUBLIC-KEY ::=
pk-CompositeSignature{ id-MLDSA87-Ed448-SHAKE256,
OCTET STRING, ECPoint}
sa-MLDSA87-Ed448-SHAKE256 SIGNATURE-ALGORITHM ::=
sa-CompositeSignature{
id-MLDSA87-Ed448-SHAKE256,
pk-MLDSA87-Ed448-SHAKE256 }
-- TODO: OID to be replaced by IANA
id-Falon512-ECDSA-P256-SHA256 OBJECT IDENTIFIER ::= {
joint-iso-itu-t(2) country(16) us(840) organization(1)
entrust(114027) algorithm(80) composite(7) signature(1) 14 }
pk-Falon512-ECDSA-P256-SHA256 PUBLIC-KEY ::=
pk-CompositeSignature{ id-MLDSA87-Ed448-SHAKE256,
OCTET STRING, ECPoint}
sa-Falon512-ECDSA-P256-SHA256 SIGNATURE-ALGORITHM ::=
sa-CompositeSignature{
id-Falon512-ECDSA-P256-SHA256,
pk-Falon512-ECDSA-P256-SHA256 }
-- TODO: OID to be replaced by IANA
id-Falcon512-ECDSA-brainpoolP256r1-SHA256 OBJECT IDENTIFIER ::= {
joint-iso-itu-t(2) country(16) us(840) organization(1)
entrust(114027) algorithm(80) composite(7) signature(1) 15 }
pk-Falcon512-ECDSA-brainpoolP256r1-SHA256 PUBLIC-KEY ::=
pk-CompositeSignature{ id-Falcon512-ECDSA-brainpoolP256r1-SHA256,
OCTET STRING, ECPoint}
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sa-Falcon512-ECDSA-brainpoolP256r1-SHA256 SIGNATURE-ALGORITHM ::=
sa-CompositeSignature{
id-Falcon512-ECDSA-brainpoolP256r1-SHA256,
pk-Falcon512-ECDSA-brainpoolP256r1-SHA256 }
-- TODO: OID to be replaced by IANA
id-Falcon512-Ed25519-SHA512 OBJECT IDENTIFIER ::= {
joint-iso-itu-t(2) country(16) us(840) organization(1)
entrust(114027) algorithm(80) composite(7) signature(1) 16 }
pk-Falcon512-Ed25519-SHA512 PUBLIC-KEY ::=
pk-CompositeSignature{ id-Falcon512-Ed25519-SHA512,
OCTET STRING, ECPoint}
sa-Falcon512-Ed25519-SHA512 SIGNATURE-ALGORITHM ::=
sa-CompositeSignature{
id-Falcon512-Ed25519-SHA512,
pk-Falcon512-Ed25519-SHA512 }
END
<CODE ENDS>
7. IANA Considerations
7.1. Object Identifier Allocations
EDNOTE to IANA: OIDs will need to be replaced in both the ASN.1
module and in Table 3.
7.1.1. Module Registration - SMI Security for PKIX Module Identifier
* Decimal: IANA Assigned - *Replace TBDMOD*
* Description: Composite-Signatures-2023 - id-mod-composite-
signatures
* References: This Document
7.1.2. Object Identifier Registrations - SMI Security for PKIX
Algorithms
* id-MLDSA44-RSA2048-PSS-SHA256
* Decimal: IANA Assigned
* Description: id-MLDSA44-RSA2048-PSS-SHA256
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* 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-SHA256
* Decimal: IANA Assigned
* Description: id-MLDSA65-RSA3072-PSS-SHA256
* References: This Document
* id-MLDSA65-RSA3072-PKCS15-SHA256
* Decimal: IANA Assigned
* Description: id-MLDSA65-RSA3072-PKCS15-SHA256
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* References: This Document
* id-MLDSA65-ECDSA-P256-SHA256
* Decimal: IANA Assigned
* Description: id-MLDSA65-ECDSA-P256-SHA256
* References: This Document
* id-MLDSA65-ECDSA-brainpoolP256r1-SHA256
* Decimal: IANA Assigned
* Description: id-MLDSA65-ECDSA-brainpoolP256r1-SHA256
* References: This Document
* id-MLDSA65-Ed25519-SHA512
* Decimal: IANA Assigned
* Description: id-MLDSA65-Ed25519-SHA512
* References: This Document
* id-MLDSA87-ECDSA-P384-SHA384
* Decimal: IANA Assigned
* Description: id-MLDSA87-ECDSA-P384-SHA384
* References: This Document
* id-MLDSA87-ECDSA-brainpoolP384r1-SHA384
* Decimal: IANA Assigned
* Description: id-MLDSA87-ECDSA-brainpoolP384r1-SHA384
* References: This Document
* id-MLDSA87-Ed448-SHAKE256
* Decimal: IANA Assigned
* Description: id-MLDSA87-Ed448
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* References: This Document
* id-Falon512-ECDSA-P256-SHA256
* Decimal: IANA Assigned
* Description: id-Falon512-ECDSA-P256-SHA256
* References: This Document
* id-Falcon512-ECDSA-brainpoolP256r1-SHA256
* Decimal: IANA Assigned
* Description: id-Falcon512-ECDSA-brainpoolP256r1-SHA256
* References: This Document
* id-Falcon512-Ed25519-SHA512
* Decimal: IANA Assigned
* Description: id-Falcon512-Ed25519
* References: This Document
8. Security Considerations
8.1. Policy for Deprecated and Acceptable Algorithms
Traditionally, a public key, certificate, or signature contains a
single cryptographic algorithm. If and when an algorithm becomes
deprecated (for example, RSA-512, or SHA1), then clients performing
signatures or verifications should be updated to adhere to
appropriate policies.
In the composite model this is less obvious since implementers may
decide that certain cryptographic algorithms have complementary
security properties and are acceptable in combination even though one
or both algorithms are deprecated for individual use. As such, a
single composite public key or certificate may contain a mixture of
deprecated and non-deprecated algorithms.
Since composite algorithms are registered independently of their
component algorithms, their deprecation can be handled indpendently
from that of their component algorithms. For example a cryptographic
policy might continue to allow id-MLDSA65-ECDSA-P256-SHA256 even
after ECDH-P256 is deprecated.
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9. References
9.1. 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>.
[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>.
[RFC5958] Turner, S., "Asymmetric Key Packages", RFC 5958,
DOI 10.17487/RFC5958, August 2010,
<https://www.rfc-editor.org/info/rfc5958>.
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[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>.
[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.
9.2. Informative References
[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>.
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[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>.
[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.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>.
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[I-D.pala-klaussner-composite-kofn]
Pala, M. and J. Klaußner, "K-threshold Composite
Signatures for the Internet PKI", Work in Progress,
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/api/v1/doc/document/draft-
vaira-pquip-pqc-use-cases/>.
[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>.
[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. Samples
A.1. Explicit Composite Signature Examples
A.1.1. MLDSA44-ECDSA-P256-SHA256 Public Key
-----BEGIN PUBLIC KEY-----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 -----END PUBLIC KEY-----
A.1.2. MLDSA44-ECDSA-P256 Private Key
-----BEGIN PRIVATE KEY----- MIIPmQIBADANBgtghkgBhvprUAcBBASCD4Mwgg9/
BIIPAD4utSoZ1LlFJjMVZ8YS Y1JmGI0Xu9b6VPKhQRKa7WJa8O4O357Umw24m9Pd/
Jg06IDz9AmosfLTjayQT5j9
tRaYa9SlMtuRa++YF0vtPF5KCc2GSbvH8nHNJaKc8to8JSCAYIKyJNtEchq1gIoG
ZYDCZKIQkSDFaSRDKSKQcRmIYVkUSlsAAdoiKcTEZJQoLQGyTIgQAViyaWAkERwR
DSNHYRhACcwWJhMRJROHLFoWScIGMpFIkQIBUEGEUIEyShPGCJPIjaPECZoYSACn
jYNIToxGSIKgEViAkEgIQRDDhFsGbQwxjuJIMUumDBNIgRqnkQIxJQpDiknIaeJG
ZcLGSQITclFEcJIojNMwQVsEDUA2ShsWiFlCAFA2Ssy4gNGiTQHISRMWglG4EEgi
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ShFHCSDDYYQiTdgQcIgYLCMyERskMpIUMsM0aRJIgaAmhmCIBVlEQBSZSAEZcFoG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Ounsworth, et al. Expires 25 April 2024 [Page 38]
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9UUnIzx58SRKIJ3DJg== -----END PRIVATE KEY-----
A.1.3. MLDSA44-ECDSA-P256 Self-Signed X509 Certificate
-----BEGIN CERTIFICATE-----
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HT9NXmx/l7DQ3P8aHjU+coPCxyA0P0tPVFWgprC3xM/7CFNUXWRwcoPN7fP3AAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAOFiQwA0gAMEUCIBZgPd/De2z8
KVaX4IdLzKwgoTxOvQbM2VFO79bQmwhVAiEAw7plaHGiHrVngE1TDaTjNpVZKpMh
6VjbIrd6yvAdXUA= -----END CERTIFICATE-----
Appendix B. Implementation Considerations
B.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 algorith with zero security, and the overall composite
should be considered full strength and thus FIPS-approved.
The authors wish to note that this gives composite algorithms great
future utility both for future cryptographic migrations as well as
bridging across jurisdictions; for example defining composite
algorithms which combine FIPS cryptography with cryptography from a
different national standards body.
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B.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.
B.2.1. Parallel PKIs
We present the term "Parallel PKI" to refer to the setup where a PKI
end entity possesses two or more distinct public keys or certificates
for the same identity (name), but containing keys for different
cryptographic algorithms. One could imagine a set of parallel PKIs
where an existing PKI using legacy algorithms (RSA, ECC) is left
operational during the post-quantum migration but is shadowed by one
or more parallel PKIs using pure post quantum algorithms or composite
algorithms (legacy and post-quantum).
Equipped with a set of parallel public keys in this way, a client
would have the flexibility to choose which public key(s) or
certificate(s) to use in a given signature operation.
For negotiated protocols, the client could choose which public key(s)
or certificate(s) to use based on the negotiated algorithms, or could
combine two of the public keys for example in a non-composite hybrid
method such as [I-D.becker-guthrie-noncomposite-hybrid-auth] or
[I-D.guthrie-ipsecme-ikev2-hybrid-auth]. Note that it is possible to
use the signature algorithms defined in Section 5 as a way to carry
the multiple signature values generated by one of the non-composite
public mechanism in protocols where it is easier to support the
composite signature algorithms than to implement such a mechanism in
the protocol itself. There is also nothing precluding a composite
public key from being one of the components used within a non-
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composite authentication operation; this may lead to greater
convenience in setting up parallel PKI hierarchies that need to
service a range of clients implementing different styles of post-
quantum migration strategies.
For non-negotiated protocols, the details for obtaining backwards
compatibility will vary by protocol, but for example in CMS
[RFC5652], the inclusion of multiple SignerInfo objects is often
already treated as an OR relationship, so including one for each of
the signer's parallel PKI public keys would, in many cases, have the
desired effect of allowing the receiver to choose one they are
compatible with and ignore the others, thus achieving full backwards
compatibility.
B.2.2. 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 C. Intellectual Property Considerations
The following IPR Disclosure relates to this draft:
https://datatracker.ietf.org/ipr/3588/
Appendix D. 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 year in pursuit of
this document:
Serge Mister (Entrust), Scott Fluhrer (Cisco Systems), Panos
Kampanakis (Cisco Systems), Daniel Van Geest (ISARA), Tim Hollebeek
(Digicert), and Francois Rousseau.
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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].
D.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/EntrustCorporation/draft-ounsworth-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
Massimiliano Pala
CableLabs
858 Coal Creek Circle
Louisville, Colorado, 80027
United States of America
Email: director@openca.org
Jan Klaussner
D-Trust GmbH
Kommandantenstr. 15
10969 Berlin
Germany
Email: jan.klaussner@d-trust.net
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