diff --git a/Composite-Signatures-2023.asn b/Composite-Signatures-2023.asn new file mode 100644 index 0000000..d24fc97 --- /dev/null +++ b/Composite-Signatures-2023.asn @@ -0,0 +1,349 @@ + + Composite-Signatures-2023 + { joint-iso-itu-t(2) country(16) us(840) organization(1) entrust(114027) + algorithm(80) id-composite-signatures-2023 (TBDMOD) } + +DEFINITIONS IMPLICIT TAGS ::= BEGIN + +EXPORTS ALL; + +IMPORTS + PUBLIC-KEY, SIGNATURE-ALGORITHM, AlgorithmIdentifier{} + FROM AlgorithmInformation-2009 -- RFC 5912 [X509ASN1] + { iso(1) identified-organization(3) dod(6) internet(1) + security(5) mechanisms(5) pkix(7) id-mod(0) + id-mod-algorithmInformation-02(58) } + + SubjectPublicKeyInfo + FROM PKIX1Explicit-2009 + { iso(1) identified-organization(3) dod(6) internet(1) + security(5) mechanisms(5) pkix(7) id-mod(0) + id-mod-pkix1-explicit-02(51) } + + OneAsymmetricKey + FROM AsymmetricKeyPackageModuleV1 + { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) + pkcs-9(9) smime(16) modules(0) + id-mod-asymmetricKeyPkgV1(50) } + + RSAPublicKey, ECPoint + FROM PKIXAlgs-2009 + { iso(1) identified-organization(3) dod(6) + internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) + id-mod-pkix1-algorithms2008-02(56) } + + sa-rsaSSA-PSS + FROM PKIX1-PSS-OAEP-Algorithms-2009 + {iso(1) identified-organization(3) dod(6) internet(1) security(5) + mechanisms(5) pkix(7) id-mod(0) id-mod-pkix1-rsa-pkalgs-02(54)} + +; + +-- +-- Object Identifiers +-- + +-- Defined in ITU-T X.690 +der OBJECT IDENTIFIER ::= + {joint-iso-itu-t asn1(1) ber-derived(2) distinguished-encoding(1)} + + + + +-- +-- Signature Algorithm +-- + + +-- +-- Composite Signature basic structures +-- + +CompositeSignaturePublicKey ::= SEQUENCE SIZE (2) OF BIT STRING + +CompositeSignaturePublicKeyOs ::= OCTET STRING (CONTAINING + CompositeSignaturePublicKey ENCODED BY der) + +CompositeSignaturePublicKeyBs ::= BIT STRING (CONTAINING + CompositeSignaturePublicKey ENCODED BY der) + +CompositeSignaturePrivateKey ::= SEQUENCE SIZE (2) OF OneAsymmetricKey + +CompositeSignatureValue ::= SEQUENCE SIZE (2) OF BIT STRING + +-- Composite Signature Value is just a sequence of OCTET STRINGS + +-- CompositeSignaturePair{FirstSignatureValue, SecondSignatureValue}  ::= +-- SEQUENCE { +-- signaturevalue1 FirstSignatureValue, +-- signaturevalue2 SecondSignatureValue } + + -- An Explicit Compsite Signature is a set of Signatures which + -- are composed of OCTET STRINGS +-- ExplicitCompositeSignatureValue ::= CompositeSignaturePair { +-- OCTET STRING,OCTET STRING} + + +-- +-- Information Object Classes +-- + +pk-CompositeSignature {OBJECT IDENTIFIER:id, + FirstPublicKeyType,SecondPublicKeyType} + PUBLIC-KEY ::= { + IDENTIFIER id + KEY SEQUENCE { + firstPublicKey BIT STRING (CONTAINING FirstPublicKeyType), + secondPublicKey BIT STRING (CONTAINING SecondPublicKeyType) + } + PARAMS ARE absent + CERT-KEY-USAGE { digitalSignature, nonRepudiation, keyCertSign, cRLSign} + } + + +sa-CompositeSignature{OBJECT IDENTIFIER:id, + PUBLIC-KEY:publicKeyType } + SIGNATURE-ALGORITHM ::= { + IDENTIFIER id + VALUE CompositeSignatureValue + PARAMS ARE absent + PUBLIC-KEYS {publicKeyType} + } + +-- TODO: OID to be replaced by IANA +id-MLDSA44-RSA2048-PSS-SHA256 OBJECT IDENTIFIER ::= { + joint-iso-itu-t(2) country(16) us(840) organization(1) + entrust(114027) algorithm(80) composite(8) signature(1) 1 } + +pk-MLDSA44-RSA2048-PSS-SHA256 PUBLIC-KEY ::= + pk-CompositeSignature{ id-MLDSA44-RSA2048-PSS-SHA256, + OCTET STRING, RSAPublicKey} + +sa-MLDSA44-RSA2048-PSS-SHA256 SIGNATURE-ALGORITHM ::= + sa-CompositeSignature{ + id-MLDSA44-RSA2048-PSS-SHA256, + pk-MLDSA44-RSA2048-PSS-SHA256 } + +-- TODO: OID to be replaced by IANA +id-MLDSA44-RSA2048-PKCS15-SHA256 OBJECT IDENTIFIER ::= { + joint-iso-itu-t(2) country(16) us(840) organization(1) + entrust(114027) algorithm(80) composite(8) signature(1) 2 } + +pk-MLDSA44-RSA2048-PKCS15-SHA256 PUBLIC-KEY ::= + pk-CompositeSignature{ id-MLDSA44-RSA2048-PKCS15-SHA256, + OCTET STRING, RSAPublicKey} + +sa-MLDSA44-RSA2048-PKCS15-SHA256 SIGNATURE-ALGORITHM ::= + sa-CompositeSignature{ + id-MLDSA44-RSA2048-PKCS15-SHA256, + pk-MLDSA44-RSA2048-PKCS15-SHA256 } + + +-- TODO: OID to be replaced by IANA +id-MLDSA44-Ed25519-SHA512 OBJECT IDENTIFIER ::= { + joint-iso-itu-t(2) country(16) us(840) organization(1) + entrust(114027) algorithm(80) composite(8) signature(1) 3 } + +pk-MLDSA44-Ed25519-SHA512 PUBLIC-KEY ::= + pk-CompositeSignature{ id-MLDSA44-Ed25519-SHA512, + OCTET STRING, ECPoint} + +sa-MLDSA44-Ed25519-SHA512 SIGNATURE-ALGORITHM ::= + sa-CompositeSignature{ + id-MLDSA44-Ed25519-SHA512, + pk-MLDSA44-Ed25519-SHA512 } + + +-- TODO: OID to be replaced by IANA +id-MLDSA44-ECDSA-P256-SHA256 OBJECT IDENTIFIER ::= { + joint-iso-itu-t(2) country(16) us(840) organization(1) + entrust(114027) algorithm(80) composite(8) signature(1) 4 } + +pk-MLDSA44-ECDSA-P256-SHA256 PUBLIC-KEY ::= + pk-CompositeSignature{ id-MLDSA44-ECDSA-P256-SHA256, + OCTET STRING, ECPoint} + +sa-MLDSA44-ECDSA-P256-SHA256 SIGNATURE-ALGORITHM ::= + sa-CompositeSignature{ + id-MLDSA44-ECDSA-P256-SHA256, + pk-MLDSA44-ECDSA-P256-SHA256 } + + +-- TODO: OID to be replaced by IANA +id-MLDSA44-ECDSA-brainpoolP256r1-SHA256 OBJECT IDENTIFIER ::= { + joint-iso-itu-t(2) country(16) us(840) organization(1) + entrust(114027) algorithm(80) composite(8) signature(1) 5 } + +pk-MLDSA44-ECDSA-brainpoolP256r1-SHA256 PUBLIC-KEY ::= + pk-CompositeSignature{ id-MLDSA44-ECDSA-brainpoolP256r1-SHA256, + OCTET STRING, ECPoint} + +sa-MLDSA44-ECDSA-brainpoolP256r1-SHA256 SIGNATURE-ALGORITHM ::= + sa-CompositeSignature{ + id-MLDSA44-ECDSA-brainpoolP256r1-SHA256, + pk-MLDSA44-ECDSA-brainpoolP256r1-SHA256 } + + +-- TODO: OID to be replaced by IANA +id-MLDSA65-RSA3072-PSS-SHA512 OBJECT IDENTIFIER ::= { + joint-iso-itu-t(2) country(16) us(840) organization(1) + entrust(114027) algorithm(80) composite(8) signature(1) 6 } + +pk-MLDSA65-RSA3072-PSS-SHA512 PUBLIC-KEY ::= + pk-CompositeSignature{ id-MLDSA65-RSA3072-PSS-SHA512, + OCTET STRING, RSAPublicKey} + +sa-MLDSA65-RSA3072-PSS-SHA512 SIGNATURE-ALGORITHM ::= + sa-CompositeSignature{ + id-MLDSA65-RSA3072-PSS-SHA512, + pk-MLDSA65-RSA3072-PSS-SHA512 } + + +-- TODO: OID to be replaced by IANA +id-MLDSA65-RSA3072-PKCS15-SHA512 OBJECT IDENTIFIER ::= { + joint-iso-itu-t(2) country(16) us(840) organization(1) + entrust(114027) algorithm(80) composite(8) signature(1) 7 } + +pk-MLDSA65-RSA3072-PKCS15-SHA512 PUBLIC-KEY ::= + pk-CompositeSignature{ id-MLDSA65-RSA3072-PKCS15-SHA512, + OCTET STRING, RSAPublicKey} + +sa-MLDSA65-RSA3072-PKCS15-SHA512 SIGNATURE-ALGORITHM ::= + sa-CompositeSignature{ + id-MLDSA65-RSA3072-PKCS15-SHA512, + pk-MLDSA65-RSA3072-PKCS15-SHA512 } + + +-- TODO: OID to be replaced by IANA +id-MLDSA65-ECDSA-P256-SHA512 OBJECT IDENTIFIER ::= { + joint-iso-itu-t(2) country(16) us(840) organization(1) + entrust(114027) algorithm(80) composite(8) signature(1) 8 } + +pk-MLDSA65-ECDSA-P256-SHA512 PUBLIC-KEY ::= + pk-CompositeSignature{ id-MLDSA65-ECDSA-P256-SHA512, + OCTET STRING, ECPoint} + +sa-MLDSA65-ECDSA-P256-SHA512 SIGNATURE-ALGORITHM ::= + sa-CompositeSignature{ + id-MLDSA65-ECDSA-P256-SHA512, + pk-MLDSA65-ECDSA-P256-SHA512 } + + +-- TODO: OID to be replaced by IANA +id-MLDSA65-ECDSA-brainpoolP256r1-SHA512 OBJECT IDENTIFIER ::= { + joint-iso-itu-t(2) country(16) us(840) organization(1) + entrust(114027) algorithm(80) composite(8) signature(1) 9 } + +pk-id-MLDSA65-ECDSA-brainpoolP256r1-SHA512 PUBLIC-KEY ::= + pk-CompositeSignature{ id-MLDSA65-ECDSA-brainpoolP256r1-SHA512, + OCTET STRING, ECPoint} + +sa-id-MLDSA65-ECDSA-brainpoolP256r1-SHA512 SIGNATURE-ALGORITHM ::= + sa-CompositeSignature{ + id-MLDSA65-ECDSA-brainpoolP256r1-SHA512, + pk-id-MLDSA65-ECDSA-brainpoolP256r1-SHA512 } + + +-- TODO: OID to be replaced by IANA +id-MLDSA65-Ed25519-SHA512 OBJECT IDENTIFIER ::= { + joint-iso-itu-t(2) country(16) us(840) organization(1) + entrust(114027) algorithm(80) composite(8) signature(1) 10 } + +pk-MLDSA65-Ed25519-SHA512 PUBLIC-KEY ::= + pk-CompositeSignature{ id-MLDSA65-Ed25519-SHA512, + OCTET STRING, ECPoint} + +sa-MLDSA65-Ed25519-SHA512 SIGNATURE-ALGORITHM ::= + sa-CompositeSignature{ + id-MLDSA65-Ed25519-SHA512, + pk-MLDSA65-Ed25519-SHA512 } + + +-- TODO: OID to be replaced by IANA +id-MLDSA87-ECDSA-P384-SHA512 OBJECT IDENTIFIER ::= { + joint-iso-itu-t(2) country(16) us(840) organization(1) + entrust(114027) algorithm(80) composite(8) signature(1) 11 } + +pk-MLDSA87-ECDSA-P384-SHA512 PUBLIC-KEY ::= + pk-CompositeSignature{ id-MLDSA87-ECDSA-P384-SHA512, + OCTET STRING, ECPoint} + +sa-MLDSA87-ECDSA-P384-SHA512 SIGNATURE-ALGORITHM ::= + sa-CompositeSignature{ + id-MLDSA87-ECDSA-P384-SHA512, + pk-MLDSA87-ECDSA-P384-SHA512 } + + +-- TODO: OID to be replaced by IANA +id-MLDSA87-ECDSA-brainpoolP384r1-SHA512 OBJECT IDENTIFIER ::= { + joint-iso-itu-t(2) country(16) us(840) organization(1) + entrust(114027) algorithm(80) composite(8) signature(1) 12 } + +pk-MLDSA87-ECDSA-brainpoolP384r1-SHA512 PUBLIC-KEY ::= + pk-CompositeSignature{ id-MLDSA87-ECDSA-brainpoolP384r1-SHA512, + OCTET STRING, ECPoint} + +sa-MLDSA87-ECDSA-brainpoolP384r1-SHA512 SIGNATURE-ALGORITHM ::= + sa-CompositeSignature{ + id-MLDSA87-ECDSA-brainpoolP384r1-SHA512, + pk-MLDSA87-ECDSA-brainpoolP384r1-SHA512 } + + +-- TODO: OID to be replaced by IANA +id-MLDSA87-Ed448-SHA512 OBJECT IDENTIFIER ::= { + joint-iso-itu-t(2) country(16) us(840) organization(1) + entrust(114027) algorithm(80) composite(8) signature(1) 13 } + +pk-MLDSA87-Ed448-SHA512 PUBLIC-KEY ::= + pk-CompositeSignature{ id-MLDSA87-Ed448-SHA512, + OCTET STRING, ECPoint} + +sa-MLDSA87-Ed448-SHA512 SIGNATURE-ALGORITHM ::= + sa-CompositeSignature{ + id-MLDSA87-Ed448-SHA512, + pk-MLDSA87-Ed448-SHA512 } + +-- TODO: OID to be replaced by IANA +id-Falon512-ECDSA-P256-SHA256 OBJECT IDENTIFIER ::= { + joint-iso-itu-t(2) country(16) us(840) organization(1) + entrust(114027) algorithm(80) composite(8) signature(1) 14 } + +pk-Falon512-ECDSA-P256-SHA256 PUBLIC-KEY ::= + pk-CompositeSignature{ id-Falon512-ECDSA-P256-SHA256, + OCTET STRING, ECPoint} + +sa-Falon512-ECDSA-P256-SHA256 SIGNATURE-ALGORITHM ::= + sa-CompositeSignature{ + id-Falon512-ECDSA-P256-SHA256, + pk-Falon512-ECDSA-P256-SHA256 } + +-- 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(8) signature(1) 15 } + +pk-Falcon512-ECDSA-brainpoolP256r1-SHA256 PUBLIC-KEY ::= + pk-CompositeSignature{ id-Falcon512-ECDSA-brainpoolP256r1-SHA256, + OCTET STRING, ECPoint} + +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(8) 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 diff --git a/README.md b/README.md deleted file mode 100644 index 2583c57..0000000 --- a/README.md +++ /dev/null @@ -1,18 +0,0 @@ -# Internet-Draft Template Repository - -Use this repository as a template if you want to start working on -[IETF](https://www.ietf.org/) documents. [Click here to create a new repository using the -template](https://github.com/martinthomson/internet-draft-template/generate). -Make sure to check "Include all branches", or you will need to enable GitHub Pages manually. - -[Read the -instructions](https://github.com/martinthomson/i-d-template/blob/main/doc/TEMPLATE.md) -for more information. - -Once you have created your own repository, start work by: - -1. Set "Workflow permissions" to "Read and write permissions" - [in the repository settings](../../settings/actions#actions_default_workflow_permissions_write). - -2. Rename the `draft-todo-yourname-protocol.md` file - [here](../../edit/main/draft-todo-yourname-protocol.md). diff --git a/draft-ounsworth-pq-composite-sigs.md b/draft-ounsworth-pq-composite-sigs.md new file mode 100644 index 0000000..f1e55b6 --- /dev/null +++ b/draft-ounsworth-pq-composite-sigs.md @@ -0,0 +1,915 @@ +--- +title: Composite Signatures For Use In Internet PKI +abbrev: PQ Composite Sigs +# +docname: draft-ounsworth-pq-composite-sigs-12 + +# +ipr: trust200902 +area: Security +wg: LAMPS +kw: Internet-Draft +cat: std + +coding: us-ascii +pi: # can use array (if all yes) or hash here + toc: yes + sortrefs: # defaults to yes + symrefs: yes + +author: + - + ins: M. Ounsworth + name: Mike Ounsworth + org: Entrust Limited + abbrev: Entrust + street: 2500 Solandt Road – Suite 100 + city: Ottawa, Ontario + country: Canada + code: K2K 3G5 + email: mike.ounsworth@entrust.com + + - + ins: J. Gray + name: John Gray + org: Entrust Limited + abbrev: Entrust + street: 2500 Solandt Road – Suite 100 + city: Ottawa, Ontario + country: Canada + code: K2K 3G5 + email: john.gray@entrust.com + + - + ins: M. Pala + name: Massimiliano Pala + org: CableLabs + email: director@openca.org + abbrev: CableLabs + street: 858 Coal Creek Circle + city: Louisville, Colorado + country: United States of America + code: 80027 + + - + ins: J. Klaussner + name: Jan Klaussner + org: D-Trust GmbH + email: jan.klaussner@d-trust.net + street: Kommandantenstr. 15 + code: 10969 + city: Berlin + country: Germany + + +normative: + RFC2119: + RFC2986: + RFC4210: + RFC4211: + RFC5280: + RFC5480: + RFC5639: + RFC5652: + RFC5958: + RFC6090: + RFC6234: + RFC7748: + RFC8032: + RFC8174: + RFC8410: + RFC8411: + X.690: + title: "Information technology - ASN.1 encoding Rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER)" + date: November 2015 + author: + org: ITU-T + seriesinfo: + ISO/IEC: 8825-1:2015 + + +# + +informative: + RFC3279: + RFC7292: + RFC7296: + RFC7299: + RFC8446: + RFC8551: + RFC8017: + I-D.draft-hale-pquip-hybrid-signature-spectrums-01: + I-D.draft-ounsworth-pq-composite-kem-01: + I-D.draft-becker-guthrie-noncomposite-hybrid-auth-00: + I-D.draft-guthrie-ipsecme-ikev2-hybrid-auth-00: + I-D.draft-pala-klaussner-composite-kofn-00: + I-D.draft-driscoll-pqt-hybrid-terminology-01: + I-D.draft-vaira-pquip-pqc-use-cases-00: + I-D.draft-massimo-lamps-pq-sig-certificates-00: + I-D.draft-ietf-lamps-dilithium-certificates-01: + Bindel2017: + title: "Transitioning to a quantum-resistant public key infrastructure" + target: "https://link.springer.com/chapter/10.1007/978-3-319-59879-6_22" + author: + - + ins: N. Bindel + name: Nina Bindel + - + ins: U. Herath + name: Udyani Herath + - + ins: M. McKague + name: Matthew McKague + - + ins: D. Stebila + name: Douglas Stebila + date: 2017 + + +--- 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. + + + + +--- middle + +# Changes in version -12 + +* Fixed the ASN.1 module pk-CompositeSignature Information Object Class so it now compiles + +# Changes in version -11 + +* Remove ambiguity and made it clear that all component signature MUST be verified +* Added language to ensure that component keys MUST not be used in any other context +* Changed the content of the OID artifact to the DER encoded OID +* Reduced number of pre-hashing algorithm by removing SHA384 and SHAKE and replacing those with SHA512 +* Updated the prototype OIDs since the changes in this draft are not compatible with version -10 +* Fixed other nits + + +# Introduction {#sec-intro} + +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: + +- 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 {{sec-backwards-compat}}. + +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}} + +## Terminology {#sec-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. + +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 {{sec-composite-structs}}. + +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. + + +## 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 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 signature algorithms without requiring any modification of the protocol to handle multiple keys. + + + +## Composite Signatures {#sec-sigs} + +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. + +### 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 {{sec-composite-pub-keys}} and a composite secret key `sk` is per {{sec-priv-key}}. The component keys MUST be uniquely generated for each component key of a Composite and MUST NOT be used in any other keys or as a standalone key. + + +### Composite Sign {#sec-comp-sig-gen} + +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 {{sec-composite-sig-structs}}. + +The following process is used to generate composite signature values. + +~~~ +Sign (sk, Message) -> (signature) +Input: + K1, K2 Signing private keys for each component. See note below on + composite inputs. + + A1, A2 Component signature algorithms. See note below on + composite inputs. + + Message The Message to be signed, an octet string + + HASH The Message Digest Algorithm used for pre-hashing. See section + on pre-hashing below. + + OID The Composite Signature String Algorithm Name converted + from ASCII to bytes. See section on OID concatenation + below. + +Output: + signature The composite signature, a CompositeSignatureValue + +Signature Generation Process: + + 1. Compute a Hash of the Message + + M' = HASH(Message) + + 2. Generate the n component signatures independently, + according to their algorithm specifications. + + S1 := Sign( K1, A1, DER(OID) || M' ) + S2 := Sign( K2, A2, DER(OID) || M' ) + + 3. Encode each component signature S1 and S2 into a BIT STRING + according to its algorithm specification. + + signature ::= Sequence { S1, S2 } + + 4. Output signature +~~~ +{: #alg-composite-sign title="Composite Sign(sk, Message)"} + +Note on composite inputs: the method of providing the list of component keys and algorithms is flexible and beyond the scope of this pseudo-code. When passed to the Composite Sign(sk, Message) API the sk is a CompositePrivateKey. It is possible to construct a CompositePrivateKey from component keys stored in separate software or hardware keystores. Variations in the process to accommodate particular private key storage mechanisms are considered to be conformant to this document so long as it produces the same output as the process sketched above. + +Since recursive composite public keys are disallowed, no component signature may itself be a composite; ie the signature generation process MUST fail if one of the private keys K1 or K2 is a composite. + +A composite signature MUST produce, and include in the output, a signature value for every component key in the corresponding CompositePublicKey, and they MUST be in the same order; ie in the output, S1 MUST correspond to K1, S2 to K2. + + +### Composite Verify {#sec-comp-sig-verify} + +Verification of a composite signature involves applying each component algorithm's verification process according to its specification. + +Compliant applications MUST output "Valid signature" (true) if and only if all component signatures were successfully validated, and "Invalid signature" (false) otherwise. + +The following process is used to perform this verification. + + +~~~ +Composite Verify(pk, Message, signature) +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. + + 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, DER(OID) || M', S1, A1 ) then + output "Invalid signature" + if not verify( P2, DER(OID) || M', S2, A2 ) then + output "Invalid signature" + + if all succeeded, then + output "Valid signature" +~~~ +{: #alg-composite-verify title="Composite Verify(pk, Message, signature)"} + +Note on composite inputs: the method of providing the list of component keys and algorithms is flexible and beyond the scope of this pseudo-code. When passed to the Composite Verify(pk, Message, signature) API the pk is a CompositePublicKey. It is possible to construct a CompositePublicKey from component keys stored in separate software or hardware keystores. Variations in the process to accommodate particular private key storage mechanisms are considered to be conformant to this document so long as it produces the same output as the process sketched above. + +Since recursive composite public keys are disallowed, no component signature may itself be a composite; ie the signature generation process MUST fail if one of the private keys K1 or K2 is a composite. + +## OID Concatenation {#sec-oid-concat} + +As mentioned above, the OID input value for the Composite Signature Generation and verification process is the DER encoding of the OID represented in Hexidecimal bytes. The following table shows the HEX encoding for each Signature AlgorithmID + +| Composite Signature AlgorithmID | DER Encoding to be prepended to each Message | +| ----------- | ----------- | ----------- | ----------- | +| id-MLDSA44-RSA2048-PSS-SHA256 | 060B6086480186FA6B50080101| +| id-MLDSA44-RSA2048-PKCS15-SHA256 |060B6086480186FA6B50080102| +| id-MLDSA44-Ed25519-SHA512 |060B6086480186FA6B50080103| +| id-MLDSA44-ECDSA-P256-SHA256 |060B6086480186FA6B50080104| +| id-MLDSA44-ECDSA-brainpoolP256r1-SHA256 |060B6086480186FA6B50080105| +| id-MLDSA65-RSA3072-PSS-SHA512 |060B6086480186FA6B50080106| +| id-MLDSA65-RSA3072-PKCS15-SHA512 |060B6086480186FA6B50080107| +| id-MLDSA65-ECDSA-P256-SHA512 |060B6086480186FA6B50080108| +| id-MLDSA65-ECDSA-brainpoolP256r1-SHA512 |060B6086480186FA6B50080109| +| id-MLDSA65-Ed25519-SHA512 |060B6086480186FA6B5008010A| +| id-MLDSA87-ECDSA-P384-SHA512 |060B6086480186FA6B5008010B| +| id-MLDSA87-ECDSA-brainpoolP384r1-SHA512 |060B6086480186FA6B5008010C| +| id-MLDSA87-Ed448-SHA512 |060B6086480186FA6B5008010D| +| id-Falon512-ECDSA-P256-SHA256 |060B6086480186FA6B5008010E| +| id-Falcon512-ECDSA-brainpoolP256r1-SHA256 |060B6086480186FA6B5008010F| +| id-Falcon512-Ed25519-SHA512 |060B6086480186FA6B50080110| +{: #tab-sig-alg-oids title="Composite Signature OID Concatenations"} + +## PreHashing the Message {#sec-prehash} +As noted in the composite signature generation process and composite signature verification process, the Message should be pre-hashed into M' with the digest algorithm specified in the composite signature algorithm identifier. The choice of the digest algorithm was chosen with the following criteria: + +1. For composites paired with RSA or ECDSA, the hashing algorithm SHA256 or SHA512 is used as part of the RSA or ECDSA signature algorithm and is therefore also used as the composite prehashing algorithm. + +1. For ML-DSA signing a digest of the message is allowed as long as the hash function provides at least y bits of classical security strength against both collision and second preimage attacks. For MLDSA44 y is 128 bits, MLDSA65 y is 192 bits and for MLDSA87 y is 256 bits. Therefore SHA256 is paired with RSA and ECDSA with MLDSA44 and SHA512 is paired with RSA and ECDSA with MLDSA65 and MLDSA87 to match the appropriate security strength. + +1. Ed25519 [RFC8032] uses SHA512 internally, therefore SHA512 is used to pre-hash the message when Ed25519 is a component algorithm. + +1. 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. + +1. TODO: For Falcon signing it is expected prehashing digest accomodations will be allowed. + + + + + +## 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. +1. 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. +1. NIST level 1 candidates are provided, matched with 256-bit elliptic curves, intended for constrained use cases. + +If other combinations are needed, a separate specification should be submitted to the IETF LAMPS working group. To ease implementation, these specifications are encouraged to follow the construction pattern of the algorithms specified in this document. + +The composite structures defined in this specification allow only for pairs of algorithms. This also does not preclude future specification from extending these structures to define combinations with three or more components. + + + + +# Composite Signature Structures {#sec-composite-structs} + +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]. + + +## pk-CompositeSignature + +The following ASN.1 Information Object Class is a template to be used in defining all composite Signature public key types. + +~~~ ASN.1 +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} + } +~~~ +{: artwork-name="CompositeKeyObject-asn.1-structures"} + +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 {{sec-asn1-module}}. + +## CompositeSignaturePublicKey {#sec-composite-pub-keys} + +Composite public key data is represented by the following structure: + +~~~ ASN.1 +CompositeSignaturePublicKey ::= SEQUENCE SIZE (2) OF BIT STRING +~~~ +{: artwork-name="CompositeSignaturePublicKey-asn.1-structures"} + +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 {{sec-alg-ids}}. + +Some applications may need to reconstruct the `SubjectPublicKeyInfo` objects corresponding to each component public key. {{tab-sig-algs}} in {{sec-alg-ids}} 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 {{sec-encoding-rules}}. + +Component keys of a CompositeSignaturePublicKey MUST NOT be used in any other type of key or as a standalone key. + +## CompositeSignaturePrivateKey {#sec-priv-key} + +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. + +~~~ ASN.1 +CompositeSignaturePrivateKey ::= SEQUENCE SIZE (2) OF OneAsymmetricKey +~~~ +{: artwork-name="CompositeSignaturePrivateKey-asn.1-structures"} + +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 {{sec-composite-pub-keys}} 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 {{sec-alg-ids}}, the privateKey field SHALL contain the CompositeSignaturePrivateKey, and the publicKey field MUST NOT be present. Associated public key material MAY be present in the CompositeSignaturePrivateKey. + +In some usecases the private keys that comprise a composite key may not be represented in a single structure or even be contained in a single cryptographic module; for example if one component is within the FIPS boundary of a cryptographic module and the other is not; see {sec-fips} for more discussion. The establishment of correspondence between public keys in a CompositeSignaturePublicKey and private keys not represented in a single composite structure is beyond the scope of this document. + +Component keys of a CompositeSignaturePrivateKey MUST NOT be used in any other type of key or as a standalone key. + +## Encoding Rules {#sec-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. + +~~~ ASN.1 +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. + +~~~ ASN.1 +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. + +## 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; +~~~ + +# Composite Signature Structures + +## sa-CompositeSignature {#sec-composite-sig-structs} + +The ASN.1 algorithm object for a composite signature is: + +~~~ asn.1 +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: + +| SIGNATURE-ALGORITHM element | Definition | +| --------- | ---------- | +| IDENTIFIER | The Object ID used to identify the composite Signature Algorithm | +| VALUE | The Sequence of BIT STRINGS for each component signature value | +| PARAMS | Parameters are absent | +| PUBLIC-KEYS | The composite key required to produce the composite signature | + + +## CompositeSignatureValue {#sec-compositeSignatureValue} + +The output of the composite signature algorithm is the DER encoding of the following structure: + +~~~ asn.1 +CompositeSignatureValue ::= SEQUENCE SIZE (2) OF BIT STRING +~~~ +{: artwork-name="composite-sig-asn.1"} + +Where each BIT STRING within the SEQUENCE is a signature value produced by one of the component keys. It MUST contain one signature value produced by each component algorithm, and in the same order as specified in the object identifier. + +The choice of `SEQUENCE SIZE (2) OF BIT STRING`, rather than for example a single BIT STRING containing the concatenated signature values, is to gracefully handle variable-length signature values by taking advantage of ASN.1's built-in length fields. + + +# Algorithm Identifiers {#sec-alg-ids} + +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. + +Some use-cases desire the flexibility for clients to use any combination of supported algorithms, while others desire the rigidity of explicitly-specified combinations of algorithms. + +The following table summarizes the details for each explicit composite signature algorithms: + + +The OID referenced are TBD for prototyping only, and the following prefix is used for each: + +replace <CompSig> with the String "2.16.840.1.114027.80.8.1" + +Therefore <CompSig>.1 is equal to 2.16.840.1.114027.80.8.1.1 + +Signature public key types: + +| Composite Signature AlgorithmID | OID | First Algorithm | Second Algorithm | Pre-Hash | +| ----------- | ----------- | ----------- | ----------- | +| id-MLDSA44-RSA2048-PSS-SHA256 | <CompSig>.1 | MLDSA44 | SHA256WithRSAPSS| SHA256 | +| id-MLDSA44-RSA2048-PKCS15-SHA256 | <CompSig>.2 | MLDSA44 | SHA256WithRSAEncryption| SHA256 | +| id-MLDSA44-Ed25519-SHA512 | <CompSig>.3 | MLDSA44 | Ed25519| SHA512 | +| id-MLDSA44-ECDSA-P256-SHA256 | <CompSig>.4 | MLDSA44 | SHA256withECDSA | SHA256 | +| id-MLDSA44-ECDSA-brainpoolP256r1-SHA256 | <CompSig>.5 | MLDSA44 | SHA256withECDSA| SHA256 | +| id-MLDSA65-RSA3072-PSS-SHA512 | <CompSig>.6 | MLDSA65 | SHA512WithRSAPSS |SHA512 | +| id-MLDSA65-RSA3072-PKCS15-SHA512 | <CompSig>.7 | MLDSA65 | SHA512WithRSAEncryption |SHA512 | +| id-MLDSA65-ECDSA-P256-SHA512 | <CompSig>.8 | MLDSA65 | SHA512withECDSA |SHA512 | +| id-MLDSA65-ECDSA-brainpoolP256r1-SHA512 | <CompSig>.9 | MLDSA65 | SHA512withECDSA |SHA512 | +| id-MLDSA65-Ed25519-SHA512 | <CompSig>.10 | MLDSA65 | Ed25519 |SHA512 | +| id-MLDSA87-ECDSA-P384-SHA512 | <CompSig>.11 | MLDSA87 | SHA512withECDSA |SHA512| +| id-MLDSA87-ECDSA-brainpoolP384r1-SHA512 | <CompSig>.12 | MLDSA87 | SHA512withECDSA | SHA512 | +| id-MLDSA87-Ed448-SHA512 | <CompSig>.13 | MLDSA87 | Ed448 |SHA512 | +| id-Falon512-ECDSA-P256-SHA256 | <CompSig>.14 | Falcon512 | SHA256withECDSA | SHA256 | +| id-Falcon512-ECDSA-brainpoolP256r1-SHA256 | <CompSig>.15 | Falcon512 | SHA256withECDSA |SHA256 | +| id-Falcon512-Ed25519-SHA512 | <CompSig>.16 | Falcon512 | Ed25519| SHA512 | +{: #tab-sig-algs title="Composite Signature Algorithms"} + +The table above contains everything needed to implement the listed explicit composite algorithms. See the ASN.1 module in section {{sec-asn1-module}} 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] + + +## 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 | +{: #rsa-pss-params2048 title="RSA-PSS 2048 Parameters"} + +where: + +* `Mask Generation Function (mgf1)` is defined in [RFC8017] +* `SHA-256` is defined in [RFC6234]. + + +## Notes on id-MLDSA65-RSA3072-PSS-SHA512 + +The RSA component keys MUST be generated at the 3072-bit security level in order to match with ML-DSA-65. + +As with the other composite signature algorithms, when `id-MLDSA65-RSA3072-PSS-SHA512` is used in an AlgorithmIdentifier, the parameters MUST be absent. `id-MLDSA65-RSA3072-PSS-SHA512` SHALL instantiate RSA-PSS with the following parameters: + +| RSA-PSS Parameter | Value | +| -------------------------- | -------------------------- | +| Mask Generation Function | mgf1 | +| Mask Generation params | SHA-512 | +| Message Digest Algorithm | SHA-512 | +{: #rsa-pss-params3072 title="RSA-PSS 3072 Parameters"} + +where: + +* `Mask Generation Function (mgf1)` is defined in [RFC8017] +* `SHA-512` is defined in [RFC6234]. + + + + + +# ASN.1 Module {#sec-asn1-module} + +~~~ asn.1 + + + +{::include Composite-Signatures-2023.asn} + + + +~~~ + + + +# IANA Considerations {#sec-iana} +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. + +## Object Identifier Allocations +EDNOTE to IANA: OIDs will need to be replaced in both the ASN.1 module and in {{tab-sig-algs}}. + +### Module Registration - SMI Security for PKIX Module Identifier +- Decimal: IANA Assigned - **Replace TBDMOD** +- Description: Composite-Signatures-2023 - id-mod-composite-signatures +- References: This Document + +### Object Identifier Registrations - SMI Security for PKIX Algorithms + +- id-MLDSA44-RSA2048-PSS-SHA256 + - Decimal: IANA Assigned + - Description: id-MLDSA44-RSA2048-PSS-SHA256 + - References: This Document + +- id-MLDSA44-RSA2048-PKCS15-SHA256 + - Decimal: IANA Assigned + - Description: id-MLDSA44-RSA2048-PKCS15-SHA256 + - References: This Document + +- id-MLDSA44-Ed25519-SHA512 + - Decimal: IANA Assigned + - Description: id-MLDSA44-Ed25519-SHA512 + - References: This Document + +- id-MLDSA44-ECDSA-P256-SHA256 + - Decimal: IANA Assigned + - Description: id-MLDSA44-ECDSA-P256-SHA256 + - References: This Document + +- id-MLDSA44-ECDSA-brainpoolP256r1-SHA256 + - Decimal: IANA Assigned + - Description: id-MLDSA44-ECDSA-brainpoolP256r1-SHA256 + - References: This Document + +- id-MLDSA65-RSA3072-PSS-SHA512 + - Decimal: IANA Assigned + - Description: id-MLDSA65-RSA3072-PSS-SHA512 + - References: This Document + +- id-MLDSA65-RSA3072-PKCS15-SHA512 + - Decimal: IANA Assigned + - Description: id-MLDSA65-RSA3072-PKCS15-SHA512 + - References: This Document + +- id-MLDSA65-ECDSA-P256-SHA512 + - Decimal: IANA Assigned + - Description: id-MLDSA65-ECDSA-P256-SHA512 + - References: This Document + +- id-MLDSA65-ECDSA-brainpoolP256r1-SHA512 + - Decimal: IANA Assigned + - Description: id-MLDSA65-ECDSA-brainpoolP256r1-SHA512 + - References: This Document + +- id-MLDSA65-Ed25519-SHA512 + - Decimal: IANA Assigned + - Description: id-MLDSA65-Ed25519-SHA512 + - References: This Document + +- id-MLDSA87-ECDSA-P384-SHA512 + - Decimal: IANA Assigned + - Description: id-MLDSA87-ECDSA-P384-SHA512 + - References: This Document + +- id-MLDSA87-ECDSA-brainpoolP384r1-SHA512 + - Decimal: IANA Assigned + - Description: id-MLDSA87-ECDSA-brainpoolP384r1-SHA512 + - References: This Document + +- id-MLDSA87-Ed448-SHA512 + - Decimal: IANA Assigned + - Description: id-MLDSA87-Ed448-SHA512 + - References: This Document + +- 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-SHA512 + - References: This Document + + + + + +# Security Considerations + +## Policy for Deprecated and Acceptable Algorithms + +Traditionally, a public key, certificate, or signature contains a single cryptographic algorithm. If and when an algorithm becomes deprecated (for example, RSA-512, or SHA1), then clients performing signatures or verifications should be updated to adhere to appropriate policies. + +In the composite model this is less obvious since implementers may decide that certain cryptographic algorithms have complementary security properties and are acceptable in combination even though one or both algorithms are deprecated for individual use. As such, a single composite public key or certificate may contain a mixture of deprecated and non-deprecated algorithms. + +Since composite algorithms are registered independently of their component algorithms, their deprecation can be handled indpendently from that of their component algorithms. For example a cryptographic policy might continue to allow `id-MLDSA65-ECDSA-P256-SHA256` even after ECDH-P256 is deprecated. + + + + + + +--- back + + +# Samples {#appdx-samples} + +## Explicit Composite Signature Examples {#appdx-expComposite-examples} + +### MLDSA44-ECDSA-P256-SHA256 Public Key + +{::include examples/MLDSA44-ECDSA-P256-SHA256.pub} + +### MLDSA44-ECDSA-P256 Private Key + +{::include examples/MLDSA44-ECDSA-P256-SHA256.pvt} + + +### MLDSA44-ECDSA-P256 Self-Signed X509 Certificate + +{::include examples/MLDSA44-ECDSA-P256-SHA256.crt} + +# Implementation Considerations {#sec-imp-considers} + +## FIPS certification {#sec-fips} + +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. + + +## Backwards Compatibility {#sec-backwards-compat} + +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. + + +### 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 {{sec-alg-ids}} 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-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. + +### Hybrid Extensions (Keys and Signatures) +The use of Composite Crypto provides the possibility to process multiple algorithms without changing the logic of applications, but updating the cryptographic libraries: one-time change across the whole system. However, when it is not possible to upgrade the crypto engines/libraries, it is possible to leverage X.509 extensions to encode the additional keys and signatures. When the custom extensions are not marked critical, although this approach provides the most +backward-compatible approach where clients can simply ignore the post-quantum (or extra) keys and signatures, it also requires +all applications to be updated for correctly processing multiple algorithms together. + + + + + + +# Intellectual Property Considerations + +The following IPR Disclosure relates to this draft: + +https://datatracker.ietf.org/ipr/3588/ + + + +# Contributors and Acknowledgements +This document incorporates contributions and comments from a large group of experts. The Editors would especially like to acknowledge the expertise and tireless dedication of the following people, who attended many long meetings and generated millions of bytes of electronic mail and VOIP traffic over the past year in pursuit of this document: + +Scott Fluhrer (Cisco Systems), +Daniel Van Geest (ISARA), +Britta Hale, +Tim Hollebeek (Digicert), +Panos Kampanakis (Cisco Systems), +Richard Kisley (IBM), +Serge Mister (Entrust), +François Rousseau, +Falko Strenzke and +Felipe Ventura (Entrust) + +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]. + +## 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 + + diff --git a/draft-todo-yourname-protocol.md b/draft-todo-yourname-protocol.md deleted file mode 100644 index fa51372..0000000 --- a/draft-todo-yourname-protocol.md +++ /dev/null @@ -1,89 +0,0 @@ ---- -### -# Internet-Draft Markdown Template -# -# Rename this file from draft-todo-yourname-protocol.md to get started. -# Draft name format is "draft---.md". -# -# For initial setup, you only need to edit the first block of fields. -# Only "title" needs to be changed; delete "abbrev" if your title is short. -# Any other content can be edited, but be careful not to introduce errors. -# Some fields will be set automatically during setup if they are unchanged. -# -# Don't include "-00" or "-latest" in the filename. -# Labels in the form draft----latest are used by -# the tools to refer to the current version; see "docname" for example. -# -# This template uses kramdown-rfc: https://github.com/cabo/kramdown-rfc -# You can replace the entire file if you prefer a different format. -# Change the file extension to match the format (.xml for XML, etc...) -# -### -title: "TODO - Your title" -abbrev: "TODO - Abbreviation" -category: info - -docname: draft-todo-yourname-protocol-latest -submissiontype: IETF # also: "independent", "editorial", "IAB", or "IRTF" -number: -date: -consensus: true -v: 3 -area: AREA -workgroup: WG Working Group -keyword: - - next generation - - unicorn - - sparkling distributed ledger -venue: - group: WG - type: Working Group - mail: WG@example.com - arch: https://example.com/WG - github: USER/REPO - latest: https://example.com/LATEST - -author: - - - fullname: Your Name Here - organization: Your Organization Here - email: your.email@example.com - -normative: - -informative: - - ---- abstract - -TODO Abstract - - ---- middle - -# Introduction - -TODO Introduction - - -# Conventions and Definitions - -{::boilerplate bcp14-tagged} - - -# Security Considerations - -TODO Security - - -# IANA Considerations - -This document has no IANA actions. - - ---- back - -# Acknowledgments -{:numbered="false"} - -TODO acknowledge. diff --git a/license.txt b/license.txt new file mode 100644 index 0000000..56d0992 --- /dev/null +++ b/license.txt @@ -0,0 +1,12 @@ + Copyright (c) 2022 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 Simplified BSD License text as described in Section 4.e of + the Trust Legal Provisions and are provided without warranty as + described in the Simplified BSD License. diff --git a/readme.md b/readme.md new file mode 100755 index 0000000..fdfee7f --- /dev/null +++ b/readme.md @@ -0,0 +1,39 @@ +# Composite Keys and Signatures Internet-Draft + +NOTE: the name of this repo should be changed to "draft-xxxxx-pq-composite-sigs" to better reflect the contents. + +## Setting up a build environment + +There may be a way to do this in cygwin, but I cut losses and did it in ubuntu: + + $ sudo apt-get install ruby-full + $ sudo gem install kramdown-rfc2629 + $ sudo apt-get install xml2rfc + + +## Using the makefile + +We have provided a makefile to build the draft in either pure TXT, or fancy HTML formats: + + $ make txt + or + $ make html + +The default target will build both: + + $ make + +## Building the document from markdown + + // to build straight to an RFC-style .txt: + $ kdrfc draft-xxxxx-pq-composite-sigs-x509.mkd + + // to produce the intermediary .xml for use with other IETF tools: + $ kramdown-rfc2629 draft-xxxxx-pq-composite-sigs-x509.mkd > draft-xxxxx-pq-composite-sigs-x509.xml + + // to produce HTML (which has links in the ToC!) use this: + $ xml2rfc draft-xxxxx-pq-composite-certs-x509.xml --basename draft-xxxxx-pq-composite-certs-x509 --html + +## Editing Etiquette + +When checking in changes to the document source (`.mkd`), please also check in the modified `.txt` for those who wish to review changes (diffs) in their browser.