Network Working Group
Internet Engineering Task Force (IETF) R. Housley
Internet-Draft
Request for Comments: 9814 Vigil Security
Intended status:
Category: Standards Track S. Fluhrer
Expires: 17 July 2025
ISSN: 2070-1721 Cisco Systems
P. Kampanakis
Amazon Web Services
B. Westerbaan
Cloudflare
13 January
July 2025
Use of the SLH-DSA Signature Algorithm in the Cryptographic Message
Syntax (CMS)
draft-ietf-lamps-cms-sphincs-plus-19
Abstract
SLH-DSA is a stateless hash-based signature scheme. This document
specifies the conventions for using the SLH-DSA signature algorithm
with the Cryptographic Message Syntax (CMS). In addition, the
algorithm identifier and public key syntax are provided.
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https://www.rfc-editor.org/info/rfc9814.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. ASN.1 . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Motivation . . . . . . . . . . . . . . . . . . . . . . . 3
1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. SLH-DSA Hash-based Hash-Based Signature Algorithm Overview . . . . . . . 3
3. SLH-DSA Public Key Identifier . . . . . . . . . . . . . . . . 4
4. Signed-data Signed-Data Conventions . . . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6. Operational Considerations . . . . . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
8.1. Normative References . . . . . . . . . . . . . . . . . . 11
8.2. Informative References . . . . . . . . . . . . . . . . . 12
Appendix A. ASN.1 Module . . . . . . . . . . . . . . . . . . . . 13
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction
This document specifies the conventions for using the SLH-DSA hash-
based signature algorithm [FIPS205] with the Cryptographic Message
Syntax (CMS) [RFC5652] signed-data content type.
SLH-DSA offers two signature modes: pure mode and pre-hash mode.
SLH-DSA signature operations include a context string as input. The
context string has a maximum length of 255 bytes. By default, the
context string is the empty string. This document only specifies the
use of pure mode with an empty context string for the CMS signed-data
content type.
SLH-DSA offers three security levels. The parameters for each of the
security levels were chosen to provide 128 bits of security, 192 bits
of security, and 256 bits of security. Separate algorithm
identifiers have been assigned for SLH-DSA at each of these security
levels.
SLH-DSA is a stateless hash-based signature algorithm. Other hash-
based signature algorithms are stateful, including HSS/LMS Hierarchical
Signature System (HSS) / Leighton-Micali Signatures (LMS) [RFC8554]
and XMSS eXtended Merkle Signature Scheme (XMSS) [RFC8391]. Without the
need for state kept by the signer, SLH-DSA is much less fragile than
the stateful hash-based signature algorithms.
1.1. ASN.1
CMS values are generated using ASN.1 [X680], using the Basic Encoding
Rules (BER) and the Distinguished Encoding Rules (DER) [X690].
1.2. Motivation
There have been recent advances in cryptanalysis and advances in the
development of quantum computers. Each of these advances pose a
threat to widely deployed digital signature algorithms.
If cryptographically relevant quantum computers (CRQC) Cryptographically Relevant Quantum Computers (CRQCs) are ever
built, they will be able to break many of the public-key public key
cryptosystems currently in use, including RSA, DSA, ECDSA, Elliptic Curve
Digital Signature Algorithm (ECDSA), and EdDSA. Edwards-curve Digital
Signature Algorithm (EdDSA). A post-quantum cryptosystem Post-Quantum Cryptosystem (PQC) is
secure against quantum computers that have more than a trivial number
of quantum bits (qu-bits). It is open to conjecture when it will be
feasible to build such quantum computers; however, it is prudent to
use cryptographic algorithms that remain secure if a CRQC is
invented. SLH-DSA is a PQC signature algorithm.
1.3. 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.
2. SLH-DSA Hash-based Hash-Based Signature Algorithm Overview
SLH-DSA is a hash-based signature scheme. SLH-DSA makes use of a few
time signature construction, constructions, namely Forest of Random Subsets (FORS)
and a hypertree. FORS signs a message with a private key. The
corresponding FORS public keys are the leaves in k binary trees. The
roots of these trees are hashed together to form a FORS root. SLH-
DSA uses a one-time signature scheme called WOTS+. Winternitz One-Time
Signature Plus (WOTS+). The FORS tree roots are signed by a WOTS+
one-time signature private key. The corresponding WOTS+ public keys
form the leaves in d-layers of Merkle subtrees in the SLH-DSA
hypertree. The bottom layer of that hypertree signs the FORS roots
with WOTS+. The root roots of the bottom Merkle subtrees are then signed
with WOTS+ and the corresponding WOTS+ public keys form the leaves of
the next level up next-level-up subtree. Subtree roots are consequently signed by
their corresponding subtree layers until the top subtree is reached.
The top layer top-layer subtree forms the hypertree root root, which is trusted at
the verifier.
A
An SLH-DSA signature consists of the randomization string, the FORS
signature, the WOTS+ signature in each layer, and the path to the
root of each subtree until the root of the hypertree is reached.
A
An SLH-DSA signature is verified by verifying using the FORS signature, the WOTS+ signatures
signatures, and the path to the root of each subtree. When reaching
the root of the hypertree, the signature verifies only if it hashes
to the pre-trusted root of the SLH-DSA hypertree.
SLH-DSA is a stateless hash-based signature algorithm. Stateful
hash-based signature schemes require that the WOTS+ private key
(generated by using a state index) is never be reused or the scheme
loses it its security. Although its security decreases, FORS FORS, which is
used at the bottom of the SLH-DSA hypertree hypertree, does not collapse if the
same private key used to sign two or more different messages like in
stateful hash-based signature schemes. Without the need for state
kept by the signer to ensure it is not reused, SLH-DSA is much less
fragile.
SLH-DSA was designed to sign up to 2^64 messages and offers three
security levels. The parameters of the SLH-DSA hypertree include the
security parameter, the hash function, the tree height, the number of
layers of subtrees, the Winternitz parameter of WOTS+, and the number
of FORS trees and leaves in each. The parameters for each of the
security levels were chosen to be at least as secure as a generic
block cipher of 128, 192, or 256 bits.
3. SLH-DSA Public Key Identifier
The AlgorithmIdentifier for a an SLH-DSA public key MUST use one of the
twelve id-slh-dsa object identifiers listed below, based on the
security level used to generate the SLH-DSA hypertree, the small or
fast version of the algorithm, and the use of SHA2 [FIPS180] or SHAKE
[FIPS202]. For example, id-slh-dsa-shake-256s represents the 256-bit
security level, the small version of the algorithm, and the use of
SHAKE256. The parameters field of the AlgorithmIdentifier for the
SLH-DSA public key MUST be absent.
nistAlgorithms OBJECT IDENTIFIER ::= { joint-iso-itu-t(2)
country(16) us(840) organization(1) gov(101) csor(3) 4 }
sigAlgs OBJECT IDENTIFIER ::= { nistAlgorithms 3 }
id-slh-dsa-sha2-128s OBJECT IDENTIFIER ::= { sigAlgs 20 }
id-slh-dsa-sha2-128f OBJECT IDENTIFIER ::= { sigAlgs 21 }
id-slh-dsa-sha2-192s OBJECT IDENTIFIER ::= { sigAlgs 22 }
id-slh-dsa-sha2-192f OBJECT IDENTIFIER ::= { sigAlgs 23 }
id-slh-dsa-sha2-256s OBJECT IDENTIFIER ::= { sigAlgs 24 }
id-slh-dsa-sha2-256f OBJECT IDENTIFIER ::= { sigAlgs 25 }
id-slh-dsa-shake-128s OBJECT IDENTIFIER ::= { sigAlgs 26 }
id-slh-dsa-shake-128f OBJECT IDENTIFIER ::= { sigAlgs 27 }
id-slh-dsa-shake-192s OBJECT IDENTIFIER ::= { sigAlgs 28 }
id-slh-dsa-shake-192f OBJECT IDENTIFIER ::= { sigAlgs 29 }
id-slh-dsa-shake-256s OBJECT IDENTIFIER ::= { sigAlgs 30 }
id-slh-dsa-shake-256f OBJECT IDENTIFIER ::= { sigAlgs 31 }
When this AlgorithmIdentifier appears in the SubjectPublicKeyInfo
field of an X.509 certificate [RFC5280], the certificate key usage
extension MAY contain digitalSignature, nonRepudiation, keyCertSign,
and cRLSign; the certificate key usage extension MUST NOT contain
other values.
pk-slh-dsa-sha2-128s PUBLIC-KEY ::= {
IDENTIFIER id-slh-dsa-sha2-128s
-- KEY no ASN.1 wrapping --
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
-- PRIVATE-KEY no ASN.1 wrapping -- }
pk-slh-dsa-sha2-128f PUBLIC-KEY ::= {
IDENTIFIER id-slh-dsa-sha2-128f
-- KEY no ASN.1 wrapping --
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
-- PRIVATE-KEY no ASN.1 wrapping -- }
pk-slh-dsa-sha2-192s PUBLIC-KEY ::= {
IDENTIFIER id-slh-dsa-sha2-192s
-- KEY no ASN.1 wrapping --
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
-- PRIVATE-KEY no ASN.1 wrapping -- }
pk-slh-dsa-sha2-192f PUBLIC-KEY ::= {
IDENTIFIER id-slh-dsa-sha2-192f
-- KEY no ASN.1 wrapping --
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
-- PRIVATE-KEY no ASN.1 wrapping -- }
pk-slh-dsa-sha2-256s PUBLIC-KEY ::= {
IDENTIFIER id-slh-dsa-sha2-256s
-- KEY no ASN.1 wrapping --
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
-- PRIVATE-KEY no ASN.1 wrapping -- }
pk-slh-dsa-sha2-256f PUBLIC-KEY ::= {
IDENTIFIER id-slh-dsa-sha2-256f
-- KEY no ASN.1 wrapping --
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
-- PRIVATE-KEY no ASN.1 wrapping -- }
pk-slh-dsa-shake-128s PUBLIC-KEY ::= {
IDENTIFIER id-slh-dsa-shake-128s
-- KEY no ASN.1 wrapping --
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
-- PRIVATE-KEY no ASN.1 wrapping -- }
pk-slh-dsa-shake-128f PUBLIC-KEY ::= {
IDENTIFIER id-slh-dsa-shake-128f
-- KEY no ASN.1 wrapping --
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
-- PRIVATE-KEY no ASN.1 wrapping -- }
pk-slh-dsa-shake-192s PUBLIC-KEY ::= {
IDENTIFIER id-slh-dsa-shake-192s
-- KEY no ASN.1 wrapping --
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
-- PRIVATE-KEY no ASN.1 wrapping -- }
pk-slh-dsa-shake-192f PUBLIC-KEY ::= {
IDENTIFIER id-slh-dsa-shake-192f
-- KEY no ASN.1 wrapping --
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
-- PRIVATE-KEY no ASN.1 wrapping -- }
pk-slh-dsa-shake-256s PUBLIC-KEY ::= {
IDENTIFIER id-slh-dsa-shake-256s
-- KEY no ASN.1 wrapping --
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
-- PRIVATE-KEY no ASN.1 wrapping -- }
pk-slh-dsa-shake-256f PUBLIC-KEY ::= {
IDENTIFIER id-slh-dsa-shake-256f
-- KEY no ASN.1 wrapping --
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
-- PRIVATE-KEY no ASN.1 wrapping -- }
SLH-DSA-PublicKey ::= OCTET STRING (SIZE (32 | 48 | 64))
SLH-DSA-PrivateKey ::= OCTET STRING (SIZE (64 | 96 | 128))
No additional encoding of the SLH-DSA public key is applied in the
SubjectPublicKeyInfo field of an X.509 certificate [RFC5280].
No additional encoding of the SLH-DSA private key is applied in the
PrivateKeyInfo field of the privateKey field of the OneAsymmetricKey
type of an Asymmetric Key Package [RFC5958].
When a an SLH-DSA public key appears outside of a SubjectPublicKeyInfo
type in an environment that uses ASN.1 encoding, the SLH-DSA public
key can be encoded as an OCTET STRING by using the SLH-DSA-PublicKey
type.
When a an SLH-DSA private key appears outside of an Asymmetric Key
Package in an environment that uses ASN.1 encoding, the SLH-DSA
private key can be encoded as an OCTET STRING by using the SLH-DSA-
PrivateKey type.
4. Signed-data Signed-Data Conventions
As specified in CMS [RFC5652], the digital signature is produced from
the message digest and the signer's private key. The signature is
computed over different values depending on whether signed attributes
are absent or present.
When signed attributes are absent, the SLH-DSA (pure mode) signature
is computed over the content. When signed attributes are present, a
hash MUST be computed over the content using the same hash function
that is used in the SLH-DSA tree. The signed attributes MUST include
a content-type attribute and a message-digest attribute. The
message-digest attribute contains the hash value of the content. The
SLH-DSA signature is computed over the DER encoding of the set of
signed attributes. The SLH-DSA signature generation signature-generation operation is
called slh_sign; see Section 10.2.1 of [FIPS205]. In summary:
IF (signed attributes are absent)
THEN slh_sign(content)
ELSE message-digest attribute = Hash(content);
slh_sign(DER(SignedAttributes))
In some implementations, performance may be significantly improved by
signing and verifying DER(SignedAttributes) when the content is
large. That is, passing an entire large message content to the
signing function or the signature validation function can have an
impact on performance. When the signed attributes are present,
Section 5.3 of [RFC5652] requires the inclusion of the content-type
attribute and the message-digest attribute. Other attributes can
also be included.
When using SLH-DSA and signed attributes are present in the
SignerInfo, the digestAlgorithms digestAlgorithm field in the SignedData MUST include
the identifier for the one-way hash function used to compute the
message digest.
When using SLH-DSA, the fields in the SignerInfo are used as follows:
digestAlgorithm:
The digestAlgorithm MUST identify a one-way hash function. When
signed attributes are absent, the digestAlgorithm identifier MUST
match the hash function used in the SLH-DSA tree (as shown in the
list below). When signed attributes are present, to ensure
collision resistance, the identified hash function MUST produce a
hash value that is at least twice the size of the hash function
used in the SLH-DSA tree. The hash functions defined in [FIPS180]
and [FIPS202] MUST be supported for use with the variants of SLH-
DSA as shown below:
id-slh-dsa-sha2-128s: SHA-256
id-slh-dsa-sha2-128f: SHA-256
id-slh-dsa-sha2-192s: SHA-512
id-slh-dsa-sha2-192f: SHA-512
id-slh-dsa-sha2-256s: SHA-512
id-slh-dsa-sha2-256f: SHA-512
id-slh-dsa-shake-128s: SHAKE128 with 256 bit 256-bit output
id-slh-dsa-shake-128f: SHAKE128 with 256 bit 256-bit output
id-slh-dsa-shake-192s: SHAKE256 with 512 bit 512-bit output
id-slh-dsa-shake-192f: SHAKE256 with 512 bit 512-bit output
id-slh-dsa-shake-256s: SHAKE256 with 512 bit 512-bit output
id-slh-dsa-shake-256f: SHAKE256 with 512 bit 512-bit output
The object identifiers for SHA-256 and SHA-512 are included in
[RFC5754]. The object identifiers for SHAKE128 and SHAKE256 are
included in [RFC8702]. In all four cases, the AlgorithmIdentifier
SHOULD NOT include parameters.
signatureAlgorithm:
The signatureAlgorithm MUST contain one of the the SLH-DSA algorithm
identifiers, and the algorithm parameters field MUST be absent.
The algorithm identifier MUST be one of the following:
id-slh-dsa-sha2-128s, id-slh-dsa-sha2-128f,
id-slh-dsa-sha2-192s, id-slh-dsa-sha2-192f,
id-slh-dsa-sha2-256s, id-slh-dsa-sha2-256f,
id-slh-dsa-shake-128s, id-slh-dsa-shake-128f,
id-slh-dsa-shake-192s, id-slh-dsa-shake-192f,
id-slh-dsa-shake-256s, id-slh-dsa-shake-256f.
signature:
The signature contains the signature value resulting from the SLH-
DSA signing operation with the parameters associated with the
selected signatureAlgorithm. The SLH-DSA signature generation signature-generation
operation is specified in Section 10.2.1 of [FIPS205], and the
SLH-DSA signature verification operation is specified in
Section 10.3 of [FIPS205]. Signature verification MUST include
checking that the signatureAlgorithm field identifies SLH-DSA
parameters that are consistent with public key used to validate
the signature.
5. Security Considerations
Implementations MUST protect the private keys. Compromise of the
private keys may result in the ability to forge signatures.
When generating an SLH-DSA key pair, an implementation MUST generate
each key pair independently of all other key pairs in the SLH-DSA
hypertree.
A SLH-DSA tree MUST NOT be used for more than 2^64 signing
operations.
The generation of private keys relies on random numbers. The use of
inadequate pseudo-random number generators Pseudorandom Number Generators (PRNGs) to generate these
values can result in little or no security. An attacker may find it
much easier to reproduce the PRNG environment that produced the keys,
searching the resulting small set of possibilities, rather than brute
force
brute-force searching the whole key space. The generation of quality
random numbers is difficult, and [RFC4086] offers important guidance
in this area.
To avoid algorithm substitution algorithm-substitution attacks, the CMSAlgorithmProtection
attribute defined in [RFC6211] SHOULD be included in signed
attributes.
Implementers should consider their particular use cases and may
choose to implement optional fault attack fault-attack countermeasures [CMP2018]
[Ge2023]. Verifying a signature before releasing the signature value
is a typical fault attack fault-attack countermeasure; however, this
countermeasure is not effective for SLH-DSA [Ge2023]. Redundancy by
replicating the signature generation signature-generation process MAY be used as an
effective fault attack fault-attack countermeasure for SLH-DSA [Ge2023]; however,
the SLH-DSA signature generation is already considered slow.
Likewise, Implementers implementers should consider their particular use cases and
may choose to implement protections against passive power and
emissions side-channel attacks [SLotH].
6. Operational Considerations
If slh_sign is implemented in a hardware device such as hardware
security module Hardware
Security Module (HSM) or portable cryptographic token,
implementations can avoid sending the full content to the device. By
including signed attributes, which necessarily include the message-
digest attribute and the content-type attribute as described in
Section 5.3 of [RFC5652], the much smaller set of signed attributes
are sent to the device for signing.
By including signed attributes in the SignerInfo, one can obtain
similar interface characteristics to SLH-DSA in pre-hash mode. With
pre-hash mode, the hash of the content is passed to the SLH-DSA
signature operation instead of the full message content. By
including signed attributes in the SignerInfo, a relatively small to-
be-signed value is passed to the SLH-DSA signature operation. For
this reason, SLH-DSA pre-hash mode is not specified for use with the
CMS SignedData. Note SLH-DSA pre-hash mode always yields a different
signature value than SLH-DSA pure mode, even if the to-be-signed
content is the same.
When using SLH-DSA in pure mode, it is not possible to single-pass
process the content to verify a SignedData message that does not
contain signed attributes. To assist recipients that might make use
of stream-based APIs, implementers SHOULD include signed attributes
within any SignerInfo that uses SLH-DSA as signature algorithm.
Doing so allows the recipient implementation to avoid keeping the
signed content in memory. Recall that when signed attributes are
present, they MUST contain a content-type attribute and a message-
digest attribute, and they SHOULD contain a CMSAlgorithmProtection
attribute.
7. IANA Considerations
For the ASN.1 Module in the Appendix of this document, A, IANA is
requested to assign has assigned an object identifier Object
Identifier (OID) for the module identifier (TBD1) (81) with a Description of
"id-mod-slh-dsa-2024". The OID for the module should be has been allocated in
the "SMI Security for S/
MIME S/MIME Module Identifier" (1.2.840.113549.1.9.16.0). Identifier
(1.2.840.113549.1.9.16.0)" registry.
8. References
8.1. Normative References
[FIPS180] National Institute of Standards and Technology (NIST),
"Secure Hash Standard (SHS)", NIST FIPS PUB 180-4,
DOI 10.6028/NIST.FIPS.180-4, August 2015. 2015,
<https://doi.org/10.6028/NIST.FIPS.180-4>.
[FIPS202] National Institute of Standards and Technology (NIST),
"SHA-3 Standard: Permutation-Based Hash and Extendable-
Output Functions", NIST FIPS PUB 202,
DOI 10.6028/NIST.FIPS.202, August 2015. 2015,
<https://doi.org/10.6028/NIST.FIPS.202>.
[FIPS205] National Institute of Standards and Technology (NIST),
"Stateless Hash-Based Digital Signature Standard", NIST
FIPS
PUB 205, DOI 10.6028/NIST.FIPS.205, 13 August 2024,
<https://doi.org/10.6028/NIST.FIPS.205>.
[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/rfc/rfc2119>.
<https://www.rfc-editor.org/info/rfc2119>.
[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/rfc/rfc5280>.
<https://www.rfc-editor.org/info/rfc5280>.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC5652, September 2009,
<https://www.rfc-editor.org/rfc/rfc5652>.
<https://www.rfc-editor.org/info/rfc5652>.
[RFC5754] Turner, S., "Using SHA2 Algorithms with Cryptographic
Message Syntax", RFC 5754, DOI 10.17487/RFC5754, January
2010, <https://www.rfc-editor.org/rfc/rfc5754>. <https://www.rfc-editor.org/info/rfc5754>.
[RFC5958] Turner, S., "Asymmetric Key Packages", RFC 5958,
DOI 10.17487/RFC5958, August 2010,
<https://www.rfc-editor.org/rfc/rfc5958>.
<https://www.rfc-editor.org/info/rfc5958>.
[RFC6211] Schaad, J., "Cryptographic Message Syntax (CMS) Algorithm
Identifier Protection Attribute", RFC 6211,
DOI 10.17487/RFC6211, April 2011,
<https://www.rfc-editor.org/rfc/rfc6211>.
<https://www.rfc-editor.org/info/rfc6211>.
[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/rfc/rfc8174>. <https://www.rfc-editor.org/info/rfc8174>.
[RFC8702] Kampanakis, P. and Q. Dang, "Use of the SHAKE One-Way Hash
Functions in the Cryptographic Message Syntax (CMS)",
RFC 8702, DOI 10.17487/RFC8702, January 2020,
<https://www.rfc-editor.org/rfc/rfc8702>.
<https://www.rfc-editor.org/info/rfc8702>.
[X680] ITU-T, "Information technology -- Abstract Syntax Notation
One (ASN.1): Specification of basic notation", ITU-T
Recommendation X.680, ISO/IEC 8824-1:2021, February 2021,
<https://www.itu.int/rec/T-REC-X.680>.
[X690] ITU-T, "Information technology -- ASN.1 encoding rules:
Specification of Basic Encoding Rules (BER), Canonical
Encoding Rules (CER) and Distinguished Encoding Rules
(DER)", ITU-T Recommendation X.690, ISO/IEC 8825-1-2021,
February 2021, <https://www.itu.int/rec/T-REC-X.690>.
8.2. Informative References
[CMP2018] Castelnovi, L., Martinelli, A., and T. Prest, "Grafting
Trees: A Fault Attack Against the SPHINCS Framework",
Post-Quantum Cryptography pp. 165-184, PQCrypto 2018, (PQCrypto 2018), Lecture Notes
in Computer Science vol Science, vol. 10786, pp. 165-184,
DOI 10.1007/978-3-319-79063-3_8, 2018,
<https://link.springer.com/
chapter/10.1007/978-3-319-79063-3_8>.
[Ge2023] Genêt, A., "On Protecting SPHINCS+ Against Fault Attacks",
TCHES 2023/02,
IACR Transactions on Cryptographic Hardware and Embedded
Systems, vol. 2023, no. 2, pp. 80-114,
DOI 10.46586/tches.v2023.i2.80-114, 2023,
<https://tches.iacr.org/index.php/TCHES/article/
view/10278/9726>.
[RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC 4086,
DOI 10.17487/RFC4086, June 2005,
<https://www.rfc-editor.org/rfc/rfc4086>.
<https://www.rfc-editor.org/info/rfc4086>.
[RFC5911] Hoffman, P. and J. Schaad, "New ASN.1 Modules for
Cryptographic Message Syntax (CMS) and S/MIME", RFC 5911,
DOI 10.17487/RFC5911, June 2010,
<https://www.rfc-editor.org/rfc/rfc5911>.
<https://www.rfc-editor.org/info/rfc5911>.
[RFC8391] Huelsing, A., Butin, D., Gazdag, S., Rijneveld, J., and A.
Mohaisen, "XMSS: eXtended Merkle Signature Scheme",
RFC 8391, DOI 10.17487/RFC8391, May 2018,
<https://www.rfc-editor.org/rfc/rfc8391>.
<https://www.rfc-editor.org/info/rfc8391>.
[RFC8554] McGrew, D., Curcio, M., and S. Fluhrer, "Leighton-Micali
Hash-Based Signatures", RFC 8554, DOI 10.17487/RFC8554,
April 2019, <https://www.rfc-editor.org/rfc/rfc8554>. <https://www.rfc-editor.org/info/rfc8554>.
[SLotH] Saarinen, M.-J., "Accelerating SLH-DSA by Two Orders of
Magnitude with a Single Hash Unit", Cryptology ePrint
Archive, Paper 2024/367, 2024,
<https://eprint.iacr.org/2024/367.pdf>.
Appendix A. ASN.1 Module
This ASN.1 Module builds upon the conventions established in
[RFC5911].
<CODE BEGINS>
SLH-DSA-Module-2024
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
id-smime(16) id-mod(0) id-mod-slh-dsa-2024(TBD1) id-mod-slh-dsa-2024(81) }
DEFINITIONS IMPLICIT TAGS ::= BEGIN
EXPORTS ALL;
IMPORTS
PUBLIC-KEY, SIGNATURE-ALGORITHM, SMIME-CAPS
FROM AlgorithmInformation-2009 -- in [RFC5911]
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-algorithmInformation-02(58) } ;
--
-- Object Identifiers
--
nistAlgorithms OBJECT IDENTIFIER ::= { joint-iso-itu-t(2)
country(16) us(840) organization(1) gov(101) csor(3) 4 }
sigAlgs OBJECT IDENTIFIER ::= { nistAlgorithms 3 }
id-slh-dsa-sha2-128s OBJECT IDENTIFIER ::= { sigAlgs 20 }
id-slh-dsa-sha2-128f OBJECT IDENTIFIER ::= { sigAlgs 21 }
id-slh-dsa-sha2-192s OBJECT IDENTIFIER ::= { sigAlgs 22 }
id-slh-dsa-sha2-192f OBJECT IDENTIFIER ::= { sigAlgs 23 }
id-slh-dsa-sha2-256s OBJECT IDENTIFIER ::= { sigAlgs 24 }
id-slh-dsa-sha2-256f OBJECT IDENTIFIER ::= { sigAlgs 25 }
id-slh-dsa-shake-128s OBJECT IDENTIFIER ::= { sigAlgs 26 }
id-slh-dsa-shake-128f OBJECT IDENTIFIER ::= { sigAlgs 27 }
id-slh-dsa-shake-192s OBJECT IDENTIFIER ::= { sigAlgs 28 }
id-slh-dsa-shake-192f OBJECT IDENTIFIER ::= { sigAlgs 29 }
id-slh-dsa-shake-256s OBJECT IDENTIFIER ::= { sigAlgs 30 }
id-slh-dsa-shake-256f OBJECT IDENTIFIER ::= { sigAlgs 31 }
--
-- Signature Algorithm, Public Key, and Private Key
--
sa-slh-dsa-sha2-128s SIGNATURE-ALGORITHM ::= {
IDENTIFIER id-slh-dsa-sha2-128s
PARAMS ARE absent
PUBLIC-KEYS { pk-slh-dsa-sha2-128s }
SMIME-CAPS { IDENTIFIED BY id-slh-dsa-sha2-128s } }
sa-slh-dsa-sha2-128f SIGNATURE-ALGORITHM ::= {
IDENTIFIER id-slh-dsa-sha2-128f
PARAMS ARE absent
PUBLIC-KEYS { pk-slh-dsa-sha2-128f }
SMIME-CAPS { IDENTIFIED BY id-slh-dsa-sha2-128f } }
sa-slh-dsa-sha2-192s SIGNATURE-ALGORITHM ::= {
IDENTIFIER id-slh-dsa-sha2-192s
PARAMS ARE absent
PUBLIC-KEYS { pk-slh-dsa-sha2-192s }
SMIME-CAPS { IDENTIFIED BY id-slh-dsa-sha2-192s } }
sa-slh-dsa-sha2-192f SIGNATURE-ALGORITHM ::= {
IDENTIFIER id-slh-dsa-sha2-192f
PARAMS ARE absent
PUBLIC-KEYS { pk-slh-dsa-sha2-192f }
SMIME-CAPS { IDENTIFIED BY id-slh-dsa-sha2-192f } }
sa-slh-dsa-sha2-256s SIGNATURE-ALGORITHM ::= {
IDENTIFIER id-slh-dsa-sha2-256s
PARAMS ARE absent
PUBLIC-KEYS { pk-slh-dsa-sha2-256s }
SMIME-CAPS { IDENTIFIED BY id-slh-dsa-sha2-256s } }
sa-slh-dsa-sha2-256f SIGNATURE-ALGORITHM ::= {
IDENTIFIER id-slh-dsa-sha2-256f
PARAMS ARE absent
PUBLIC-KEYS { pk-slh-dsa-sha2-256f }
SMIME-CAPS { IDENTIFIED BY id-slh-dsa-sha2-256f } }
sa-slh-dsa-shake-128s SIGNATURE-ALGORITHM ::= {
IDENTIFIER id-slh-dsa-shake-128s
PARAMS ARE absent
PUBLIC-KEYS { pk-slh-dsa-shake-128s }
SMIME-CAPS { IDENTIFIED BY id-slh-dsa-shake-128s } }
sa-slh-dsa-shake-128f SIGNATURE-ALGORITHM ::= {
IDENTIFIER id-slh-dsa-shake-128f
PARAMS ARE absent
PUBLIC-KEYS { pk-slh-dsa-shake-128f }
SMIME-CAPS { IDENTIFIED BY id-slh-dsa-shake-128f } }
sa-slh-dsa-shake-192s SIGNATURE-ALGORITHM ::= {
IDENTIFIER id-slh-dsa-shake-192s
PARAMS ARE absent
PUBLIC-KEYS { pk-slh-dsa-shake-192s }
SMIME-CAPS { IDENTIFIED BY id-slh-dsa-shake-192s } }
sa-slh-dsa-shake-192f SIGNATURE-ALGORITHM ::= {
IDENTIFIER id-slh-dsa-shake-192f
PARAMS ARE absent
PUBLIC-KEYS { pk-slh-dsa-shake-192f }
SMIME-CAPS { IDENTIFIED BY id-slh-dsa-shake-192f } }
sa-slh-dsa-shake-256s SIGNATURE-ALGORITHM ::= {
IDENTIFIER id-slh-dsa-shake-256s
PARAMS ARE absent
PUBLIC-KEYS { pk-slh-dsa-shake-256s }
SMIME-CAPS { IDENTIFIED BY id-slh-dsa-shake-256s } }
sa-slh-dsa-shake-256f SIGNATURE-ALGORITHM ::= {
IDENTIFIER id-slh-dsa-shake-256f
PARAMS ARE absent
PUBLIC-KEYS { pk-slh-dsa-shake-256f }
SMIME-CAPS { IDENTIFIED BY id-slh-dsa-shake-256f } }
pk-slh-dsa-sha2-128s PUBLIC-KEY ::= {
IDENTIFIER id-slh-dsa-sha2-128s
-- KEY no ASN.1 wrapping --
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
-- PRIVATE-KEY no ASN.1 wrapping -- }
pk-slh-dsa-sha2-128f PUBLIC-KEY ::= {
IDENTIFIER id-slh-dsa-sha2-128f
-- KEY no ASN.1 wrapping --
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
-- PRIVATE-KEY no ASN.1 wrapping -- }
pk-slh-dsa-sha2-192s PUBLIC-KEY ::= {
IDENTIFIER id-slh-dsa-sha2-192s
-- KEY no ASN.1 wrapping --
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
-- PRIVATE-KEY no ASN.1 wrapping -- }
pk-slh-dsa-sha2-192f PUBLIC-KEY ::= {
IDENTIFIER id-slh-dsa-sha2-192f
-- KEY no ASN.1 wrapping --
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
-- PRIVATE-KEY no ASN.1 wrapping -- }
pk-slh-dsa-sha2-256s PUBLIC-KEY ::= {
IDENTIFIER id-slh-dsa-sha2-256s
-- KEY no ASN.1 wrapping --
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
-- PRIVATE-KEY no ASN.1 wrapping -- }
pk-slh-dsa-sha2-256f PUBLIC-KEY ::= {
IDENTIFIER id-slh-dsa-sha2-256f
-- KEY no ASN.1 wrapping --
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
-- PRIVATE-KEY no ASN.1 wrapping -- }
pk-slh-dsa-shake-128s PUBLIC-KEY ::= {
IDENTIFIER id-slh-dsa-shake-128s
-- KEY no ASN.1 wrapping --
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
-- PRIVATE-KEY no ASN.1 wrapping -- }
pk-slh-dsa-shake-128f PUBLIC-KEY ::= {
IDENTIFIER id-slh-dsa-shake-128f
-- KEY no ASN.1 wrapping --
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
-- PRIVATE-KEY no ASN.1 wrapping -- }
pk-slh-dsa-shake-192s PUBLIC-KEY ::= {
IDENTIFIER id-slh-dsa-shake-192s
-- KEY no ASN.1 wrapping --
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
-- PRIVATE-KEY no ASN.1 wrapping -- }
pk-slh-dsa-shake-192f PUBLIC-KEY ::= {
IDENTIFIER id-slh-dsa-shake-192f
-- KEY no ASN.1 wrapping --
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
-- PRIVATE-KEY no ASN.1 wrapping -- }
pk-slh-dsa-shake-256s PUBLIC-KEY ::= {
IDENTIFIER id-slh-dsa-shake-256s
-- KEY no ASN.1 wrapping --
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
-- PRIVATE-KEY no ASN.1 wrapping -- }
pk-slh-dsa-shake-256f PUBLIC-KEY ::= {
IDENTIFIER id-slh-dsa-shake-256f
-- KEY no ASN.1 wrapping --
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
-- PRIVATE-KEY no ASN.1 wrapping -- }
SLH-DSA-PublicKey ::= OCTET STRING (SIZE (32 | 48 | 64))
SLH-DSA-PrivateKey ::= OCTET STRING (SIZE (64 | 96 | 128))
--
-- Expand the signature algorithm set used by CMS [RFC5911]
--
SignatureAlgorithmSet SIGNATURE-ALGORITHM ::=
{ sa-slh-dsa-sha2-128s |
sa-slh-dsa-sha2-128f |
sa-slh-dsa-sha2-192s |
sa-slh-dsa-sha2-192f |
sa-slh-dsa-sha2-256s |
sa-slh-dsa-sha2-256f |
sa-slh-dsa-shake-128s |
sa-slh-dsa-shake-128f |
sa-slh-dsa-shake-192s |
sa-slh-dsa-shake-192f |
sa-slh-dsa-shake-256s |
sa-slh-dsa-shake-256f,
... }
--
-- Expand the S/MIME capabilities set used by CMS [RFC5911]
--
SMimeCaps SMIME-CAPS ::=
{ sa-slh-dsa-sha2-128s.&smimeCaps |
sa-slh-dsa-sha2-128f.&smimeCaps |
sa-slh-dsa-sha2-192s.&smimeCaps |
sa-slh-dsa-sha2-192f.&smimeCaps |
sa-slh-dsa-sha2-256s.&smimeCaps |
sa-slh-dsa-sha2-256f.&smimeCaps |
sa-slh-dsa-shake-128s.&smimeCaps |
sa-slh-dsa-shake-128f.&smimeCaps |
sa-slh-dsa-shake-192s.&smimeCaps |
sa-slh-dsa-shake-192f.&smimeCaps |
sa-slh-dsa-shake-256s.&smimeCaps |
sa-slh-dsa-shake-256f.&smimeCaps,
... }
END
<CODE ENDS>
Acknowledgements
Thanks to Mike Ounsworth, Tomas Gustavsson, Daniel Van Geest, Carl
Wallace, Phillip Hallam-Baker, Dieter Bratko, Vijay Gurbani, Paul
Wouters, and Roman Danyliw for their careful review and constructive
comments.
Authors' Addresses
Russ Housley
Vigil Security, LLC
Email: housley@vigilsec.com
Scott Fluhrer
Cisco Systems
Email: sfluhrer@cisco.com
Panos Kampanakis
Amazon Web Services
Email: kpanos@amazon.com
Bas Westerbaan
Cloudflare
Email: bas@westerbaan.name