Network Working Group R. Housley Internet-Draft Vigil Security Intended status: Standards Track S. Fluhrer Expires: 2 May 2025 Cisco Systems P. Kampanakis Amazon Web Services B. Westerbaan Cloudflare 29 October 2024 Use of the SLH-DSA Signature Algorithm in the Cryptographic Message Syntax (CMS) draft-ietf-lamps-cms-sphincs-plus-10 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. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 2 May 2025. Copyright Notice Copyright (c) 2024 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights Housley, et al. Expires 2 May 2025 [Page 1] Internet-Draft SLH-DSA Signature Algorithm in CMS October 2024 and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. ASN.1 . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Motivation . . . . . . . . . . . . . . . . . . . . . . . 3 1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 2. SLH-DSA Hash-based Signature Algorithm Overview . . . . . . . 3 3. SLH-DSA Public Key Identifier . . . . . . . . . . . . . . . . 4 4. Signed-data Conventions . . . . . . . . . . . . . . . . . . . 7 5. Security Considerations . . . . . . . . . . . . . . . . . . . 9 6. Operational Considerations . . . . . . . . . . . . . . . . . 10 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 9.1. Normative References . . . . . . . . . . . . . . . . . . 11 9.2. Informative References . . . . . . . . . . . . . . . . . 12 Appendix A. Appendix: ASN.1 Module . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18 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 [RFC8554] and XMSS [RFC8391]. Without the need for state kept by the signer, SLH-DSA is much less fragile. Housley, et al. Expires 2 May 2025 [Page 2] Internet-Draft SLH-DSA Signature Algorithm in CMS October 2024 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) are ever built, they will be able to break many of the public-key cryptosystems currently in use, including RSA, DSA, ECDSA, and EdDSA. A 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. One use of a PQC signature algoritm is the protection of software updates, perhaps using the format described in [RFC4108], to enable deployment of software that implements other new PQC algorithms for key management and confidentiality. 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 Signature Algorithm Overview SLH-DSA is a hash-based signature scheme which consists of a few time signature construction, 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+. 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 of the bottom Merkle subtrees are then signed with WOTS+ and the corresponding WOTS+ public keys form the leaves of the next level up subtree. Housley, et al. Expires 2 May 2025 [Page 3] Internet-Draft SLH-DSA Signature Algorithm in CMS October 2024 Subtree roots are consequently signed by their corresponding subtree layers until we reach the top subtree. The top layer subtree forms the hypertree root which is trusted at the verifier. A 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 SLH-DSA signature is verified by verifying the FORS signature, the WOTS+ 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 reused or the scheme loses it security. Although its security decreases, FORS which is used at the bottom of the SLH-DSA 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+, the number of FORS trees and leaves in each. The parameters for each of the security levels were chosen to 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 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 SHA-256 [FIPS180] or SHAKE256 [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. Housley, et al. Expires 2 May 2025 [Page 4] Internet-Draft SLH-DSA Signature Algorithm in CMS October 2024 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 -- } Housley, et al. Expires 2 May 2025 [Page 5] Internet-Draft SLH-DSA Signature Algorithm in CMS October 2024 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 -- } Housley, et al. Expires 2 May 2025 [Page 6] Internet-Draft SLH-DSA Signature Algorithm in CMS October 2024 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 SLH-DSA-PrivateKey ::= OCTET STRING 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 SLH-DSA public key appears outside of aa 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 the 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 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. Housley, et al. Expires 2 May 2025 [Page 7] Internet-Draft SLH-DSA Signature Algorithm in CMS October 2024 When signed attributes are absent, the SLH-DSA (pure mode) signature is computed over the content. When signed attributes are present, a hash is computed over the content using the same hash function that is used in the 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 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 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. To ensure collision resistance, the identified hash function SHOULD produce a hash value that is at least twice the size of the hash function used in the SLH-DSA tree. The following hash functions defined in [FIPS180] and [FIPS202] are RECOMMENDED for use with the variants of SLH-DSA: Housley, et al. Expires 2 May 2025 [Page 8] Internet-Draft SLH-DSA Signature Algorithm in CMS October 2024 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 output id-slh-dsa-shake-128f: SHAKE128 with 256 bit output id-slh-dsa-shake-192s: SHAKE256 with 256 bit output id-slh-dsa-shake-192f: SHAKE256 with 256 bit output id-slh-dsa-shake-256s: SHAKE256 with 256 bit output id-slh-dsa-shake-256f: SHAKE256 with 256 bit output 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 operation is specified in Section 10.2.1 of [FIPS205] and the SLH- DSA signature verification operation is specified in Section 10.3.1 of [FIPS205]. 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 (PRNGs) to generate these values can result in little or no security. An attacker may find it Housley, et al. Expires 2 May 2025 [Page 9] Internet-Draft SLH-DSA Signature Algorithm in CMS October 2024 much easier to reproduce the PRNG environment that produced the keys, searching the resulting small set of possibilities, rather than brute force searching the whole key space. The generation of quality random numbers is difficult, and [RFC4086] offers important guidance in this area. When computing signatures, the same hash function SHOULD be used to compute the message digest of the content and the signed attributes, if they are present. When computing signatures, implementations SHOULD include protections against fault injection attacks [CMP2018]. Protections against these attacks include signature verification prior to releasing the signature value to confirm that no error injected and generating the signature a few times to confirm that the same signature value is produced each time. To avoid 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 countermeasures [CMP2018] [Ge2023]. Verifying a signature before releasing the signature value is a typical fault attack countermeasure; however, this countermeasure is not effective for SLH-DSA [Ge2023]. Redundancy by replicating the signature generation process MAY be used as an effective fault attack countermeasure for SLH-DSA [Ge2023]; however, the SLH-DSA signature generation is already considered slow. Likewise, 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 (HSM) or portable cryptographic token, implementations might want to avoid is 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. Housley, et al. Expires 2 May 2025 [Page 10] Internet-Draft SLH-DSA Signature Algorithm in CMS October 2024 Following the approach in the previous paragraph is essentially the same as using SLH-DSA in pre-hash mode, which means that a hash of the content is passed to the SLH-DSA signature operation instead of the full message content. For this reason, this document only specifies the use od SLH-DSA pure mode. 7. IANA Considerations For the ASN.1 Module in the Appendix of this document, IANA is requested to assign an object identifier (OID) for the module identifier (TBD1) with a Description of "id-mod-slh-dsa-2024". The OID for the module should be allocated in the "SMI Security for PKIX Module Identifier" registry (1.3.6.1.5.5.7.0). 8. Acknowledgements Thanks to Mike Ounsworth, Tomas Gustavsson, Daniel Van Geest, Carl Wallace, and Phillip Hallam-Baker for their careful review and constructive comments. 9. References 9.1. Normative References [FIPS180] National Institute of Standards and Technology (NIST), "Secure Hash Standard (SHS)", FIPS PUB 180-4, August 2015. [FIPS202] National Institute of Standards and Technology (NIST), "SHA-3 Standard: Permutation-Based Hash and Extendable- Output Functions", FIPS PUB 202, August 2015. [FIPS205] National Institute of Standards and Technology (NIST), "Stateless Hash-Based Digital Signature Standard", FIPS PUB 205, 13 August 2024, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [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, . Housley, et al. Expires 2 May 2025 [Page 11] Internet-Draft SLH-DSA Signature Algorithm in CMS October 2024 [RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70, RFC 5652, DOI 10.17487/RFC5652, September 2009, . [RFC5958] Turner, S., "Asymmetric Key Packages", RFC 5958, DOI 10.17487/RFC5958, August 2010, . [RFC6211] Schaad, J., "Cryptographic Message Syntax (CMS) Algorithm Identifier Protection Attribute", RFC 6211, DOI 10.17487/RFC6211, April 2011, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [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, . [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, . 9.2. 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, Lecture Notes in Computer Science vol 10786, 2018, . [Ge2023] Genêt, A., "On Protecting SPHINCS+ Against Fault Attacks", TCHES 2023/02, DOI 10.46586/tches.v2023.i2.80-114, 2023, . [RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker, "Randomness Requirements for Security", BCP 106, RFC 4086, DOI 10.17487/RFC4086, June 2005, . Housley, et al. Expires 2 May 2025 [Page 12] Internet-Draft SLH-DSA Signature Algorithm in CMS October 2024 [RFC4108] Housley, R., "Using Cryptographic Message Syntax (CMS) to Protect Firmware Packages", RFC 4108, DOI 10.17487/RFC4108, August 2005, . [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, . [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, . [RFC8554] McGrew, D., Curcio, M., and S. Fluhrer, "Leighton-Micali Hash-Based Signatures", RFC 8554, DOI 10.17487/RFC8554, April 2019, . [SLotH] Saarinen, M.-J., "Accelerating SLH-DSA by Two Orders of Magnitude with a Single Hash Unit", 2024, . Appendix A. Appendix: ASN.1 Module This ASN.1 Module builds upon the conventions established in [RFC5911]. 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) } 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 -- Housley, et al. Expires 2 May 2025 [Page 13] Internet-Draft SLH-DSA Signature Algorithm in CMS October 2024 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 Housley, et al. Expires 2 May 2025 [Page 14] Internet-Draft SLH-DSA Signature Algorithm in CMS October 2024 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 Housley, et al. Expires 2 May 2025 [Page 15] Internet-Draft SLH-DSA Signature Algorithm in CMS October 2024 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 Housley, et al. Expires 2 May 2025 [Page 16] Internet-Draft SLH-DSA Signature Algorithm in CMS October 2024 { 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 SLH-DSA-PrivateKey ::= OCTET STRING Housley, et al. Expires 2 May 2025 [Page 17] Internet-Draft SLH-DSA Signature Algorithm in CMS October 2024 -- -- 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 Authors' Addresses Russ Housley Vigil Security, LLC Email: housley@vigilsec.com Housley, et al. Expires 2 May 2025 [Page 18] Internet-Draft SLH-DSA Signature Algorithm in CMS October 2024 Scott Fluhrer Cisco Systems Email: sfluhrer@cisco.com Panos Kampanakis Amazon Web Services Email: kpanos@amazon.com Bas Westerbaan Cloudflare Email: bas@westerbaan.name Housley, et al. Expires 2 May 2025 [Page 19]