]> RustyKey®

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SEC COSE post-quantum cryptography isogeny-based cryptography constrained devices aerospace satellite remote robotic telesurgery IAM IoT security NOTE: This document describes a signature scheme based on an algorithm currently under evaluation in the 3rd round NIST Post-Quantum Cryptography standardization process. Be aware that the underlying primitive may change as a result of that process. This document specifies the algorithm encodings and representations for the SQIsign digital signature scheme within the CBOR Object Signing and Encryption (COSE) and JSON Object Signing and Encryption (JOSE) frameworks. SQIsign is an isogeny-based post-quantum signature scheme that provides the most compact signature and public key sizes of any candidate in the NIST Post-Quantum Cryptography (PQC) standardization and on-ramp-to-standardization processes. The standardization of SQIsign will be helpful to address current infrastructure bottlenecks, specifically the FIDO2 CTAP2 specification used by billions of in-service devices and browser installations. Depending on authenticator implementation, transport (USB/NFC/BLE) and message fragmentation support, some deployments of CTAP2-based authenticators enforce limits near 1024 bytes for external key communication, and some standardized post-quantum signature schemes increase message sizes and may stress constrained authenticators or transports. As a result CBOR-encoded messages may hit 7609-byte limit in some authenticators. SQIsign-L1, L3 and L5 signatures are small enough to enable delivery over constrained networks like 802.15.4 and may be more suitable for constrained networks due to smaller signature sizes. This document clarifies that SQIsign does not expose the auxiliary torsion-point information exploited in the SIDH/SIKE attacks. Consequently, the specific attack techniques of Castryck–Decru do not directly apply. However, the scheme remains subject to ongoing cryptanalysis of isogeny-based constructions. By establishing stable COSE and JOSE identifiers, this document ensures the interoperability required for the seamless integration of post-quantum security into high-density, bandwidth-constrained, and legacy-compatible hardware environments. Status information for this document may be found at . Discussion of this document takes place on the COSE Working Group mailing list (), which is archived at . Subscribe at . Source for this draft and an issue tracker can be found at .

Introduction This document registers algorithm identifiers and key type parameters for SQIsign in COSE and JOSE.

Background and Motivation Post-quantum cryptography readiness is critical for constrained devices. As of 2026, while FIDO2/WebAuthn supports various COSE algorithms, some hardware authenticators and platform authenticators (like TPMs) have strict memory/storage constraints, effectively limiting public keys to 1024 bytes or less, hindering the adoption of large-key post-quantum algorithms.

Pressing Need for Smaller PQC Signatures FN-DSA (Falcon) and ML-DSA (Dilithium) have larger signatures that may not fit in constrained environments. The fundamental differences between ML-DSA, FN-DSA, and SQIsign lie in their underlying hard mathematical problems, implementation complexity, and performance trade-offs. Falcon (NIST secondary) uses NTRU lattices to achieve very small signatures and fast verification, but requires complex floating-point math. Dilithium (NIST primary) is a balanced, high-efficiency lattice scheme using Module-LWE/SIS, easy to implement. SQIsign is a non-lattice, isogeny-based scheme that offers the smallest signature sizes but suffers from significantly slower signature generation where even vI may take seconds to minutes, or longer with WASM implementations for browsers of particular relevance to signatures required for WebAuthn PassKeys . SQIsign is an isogeny-based digital signature scheme participating in NIST's Round 3 Additional Digital Signature Schemes, not yet a NIST standard. Speed: SQIsign is significantly slower at signing (roughly 100x to 1000x) compared to ML-DSA, though the math is changing fast and variants improve this. Table 1 compares representative parameter sets; note that these schemes are at different stages of standardization and evaluation. Algorithm Public Key Size Signature Size PK + Sig Fits < 1024? ML-DSA-44 1,312 bytes 2,420 bytes ❌ ML-DSA-65 1,952 bytes 3,293 bytes ❌ ML-DSA-87 2,592 bytes 4,595 bytes ❌ FN-DSA-512 897 bytes 666 bytes ❌ (1,563 total) FN-DSA-1024 1,793 bytes 1,280 bytes ❌ SQIsign-L1 65 bytes 148 bytes ✅ (213 total) SQIsign-L3 97 bytes 224 bytes ✅ (321 total) SQIsign-L5 129 bytes 292 bytes ✅ (421 total)

Estimated Constrained Device Footprint The total addressable market for SQIsign in constrained devices is estimated at ~6.25 billion units.

Device Category Breakdown

Legacy Hardware Security Keys: ~120 - 150 million Security keys in Service: ~120 - 150 million legacy keys in active circulation (Series 5 and older). Some firmware introduced PQC readiness. Some older keys cannot be updated to increase buffer sizes.

Constrained TPMs and Platform Modules: ~1.1 billion Trusted Platform Modules (TPMs) are integrated into PCs and servers, but their WebAuthn implementation often inherits protocol-level constraints. Estimated ~2.5 billion active chips worldwide. Constrained Subset: We estimate ~1.1 billion of these are in older Windows 10/11 or Linux machines where the OS "virtual authenticator" or TPM driver still enforces the 1024-byte message default to maintain backward compatibility with external CTAP1/2 tools.

Browser and Software Implementations: ~5 billion This category refers to the "User-Agent" layer that mediates between the web and the hardware. Global Browser Agents: There are over 5 billion active browser instances across mobile and desktop (Chrome, Safari, Edge, Firefox). Legacy Protocols: Even on modern hardware, browsers often use the FIDO2 CTAP2 specification which, unless explicitly negotiated for larger messages, maintains a 1024-byte default for external key communication.

Critical Infrastructure: ~300 Million includes Energy (electric, nuclear, oil, gas), Water & Wastewater, Transportation Systems, Communications, Government, Emergency Services, Healthcare and Financial Services Industrial/Government: Agencies like the U.S. Department of Defense rely on high-security FIPS-certified keys that are notoriously slow to upgrade. We estimate ~50 million "frozen" government keys. IoT Security: Of the ~21 billion connected IoT devices in 2026, only a fraction use WebAuthn. However, for those that do (smart locks, secure gateways), approximately 250 million are estimated to use older, non-upgradable secure elements limited to 1024-byte payloads. Recent government-level initiatives highlight the necessity to "...effectively deprecate the use of RSA, Diffie-Hellman (DH), and elliptic curve cryptography (ECDH and ECDSA) when mandated." , Page 4.

Pressing need: Limit or Stop 'Harvest now; decrypt later' Attacks Adversaries are collecting encrypted data today to decrypt when quantum computers become available. The transition to post-quantum cryptography (PQC) is critical for ensuring long-term security of digital communications against adversaries equipped with large-scale quantum computers. The National Institute of Standards and Technology (NIST) has been leading standardization efforts, having selected initial PQC algorithms and continuing to evaluate additional candidates. CBOR Object Signing and Encryption (COSE) is specifically designed for constrained node networks and IoT environments where bandwidth, storage, and computational resources are limited. The compact nature of SQIsign makes it an ideal candidate for COSE deployments.

Scope and Status This document is published on the Standards track rather than Informational Track for the following reasons: Algorithm Maturity: SQIsign is currently undergoing evaluation in NIST's on-ramp process Continued Cryptanalysis: The algorithm has active ongoing review by the cryptographic research community, including the IRTF CFRG High anticipated demand: This specification enables experimentation and early deployment to gather implementation experience This document does not represent Working Group consensus on algorithm innovation. The COSE and JOSE working groups focus on algorithm integration and encoding, not cryptographic algorithm design. The cryptographic properties of SQIsign are being evaluated through NIST's process and academic peer review.

Relationship to Other Work This document follows the precedent established by and for integrating NIST PQC candidate algorithms into COSE and JOSE. The structure and approach are intentionally aligned to provide consistency across post-quantum signature scheme integrations.

Constrained Device Applicability SQIsign is particularly attractive for: IoT sensors with limited flash memory Firmware updates over low-bandwidth networks (LoRaWAN, NB-IoT) Embedded certificates in constrained devices Blockchain and DLT where transaction size affects fees Satellite communications with bandwidth constraints

Conventions and Definitions 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 when, and only when, they appear in all capitals, as shown here. This document uses the following terms: PQC: Post-Quantum Cryptography COSE: CBOR Object Signing and Encryption JOSE: JSON Object Signing and Encryption JWS: JSON Web Signature JWK: JSON Web Key CBOR: Concise Binary Object Representation ECDH: Elliptic Curve Diffie-Hellman IANA: Internet Assigned Numbers Authority

Cryptanalytic Resistance: SIDH/SIKE Attacks Do Not Apply

SIKE Vulnerability (The "Torsion Point" Attack) of 2022 SIKE (Supersingular Isogeny Key Encapsulation) was a key exchange, more specifically, a Key Encapsulation Mechanism (KEM). In the SIKE protocol, users had to share more than just the target elliptic curve. To make the math work for key exchange, they shared the images of specific points (called torsion points) under the secret isogeny. The Info: If the secret isogeny is 𝜙, SIKE gave away 𝜙(𝑃) and 𝜙(𝑄) for specific basis points 𝑃 and 𝑄. The Break: In 2022, Castryck and Decru showed that this auxiliary information allowed an attacker to allowed an attacker to construct a higher-dimensional abelian variety linking the public data. In this setting, the secret isogeny can be recovered efficiently using techniques based on Kani’s results on isogenies between products of elliptic curves. The Oversight: For years, cryptanalysts thought this extra info was harmless. Related techniques existed in the algebraic geometry literature but had not previously been applied in this cryptographic context.

Why SQISign appears unaffected by the SIKE Vulnerability SQIsign is a signature scheme in which the prover demonstrates knowledge of an isogeny through a zero-knowledge protocol. Unlike SIDH/SIKE, it does not publish images of torsion basis points under secret isogenies. The Castryck–Decru attack relies critically on this auxiliary torsion-point information to construct additional structure (e.g., via abelian surfaces) that enables efficient recovery of the secret isogeny. Because SQIsign does not provide such auxiliary data, these techniques do not directly apply. Attacks would instead need to solve instances of the isogeny path problem or related problems in the endomorphism ring, for which no comparable shortcut is currently known.

SQIsign Algorithm Overview

Cryptographic Foundation SQIsign is based on the hardness of finding isogenies between supersingular elliptic curves over finite fields. The security assumption relies primarily on the difficulty of the Isogeny Path Problem Unlike lattice-based schemes, isogeny-based cryptography offers: Smaller key and signature sizes Algebraic structure based on elliptic curve isogenies Different security assumptions (diversification from lattice-based schemes)

Security Levels SQIsign is defined with three parameter sets corresponding to NIST security levels: Parameter Set NIST Level Public Key Signature Quantum Security (estimated) SQIsign-L1 I 65 bytes 148 bytes ~128 bits SQIsign-L3 III 97 bytes 224 bytes ~192 bits SQIsign-L5 V 129 bytes 292 bytes ~256 bits

Performance Characteristics Signing: Computationally intensive (slower than lattice schemes) Verification: Moderate computational cost Key Generation: Intensive computation required Size: Exceptional efficiency: substantially smaller than many lattice-based alternatives at comparable security levels Recommended Use Cases: - Sign-once, verify-many scenarios (firmware, certificates) - Bandwidth-constrained environments - Storage-limited devices - Applications where signature/key size dominates performance considerations

SQIsign Variants and the Post-SIKE Landscape While the SQIsign team initially focused on improving the core algorithm, the 2022 SIKE vulnerability catalyzed broader research into higher-dimensional algebraic geometry, particularly investigating improvements to key and signature generation speed—widely viewed as implementation bottlenecks. This interest has sparked an evolution of SQIsign variants, all still based on the baseline algorithm currently competing in NIST's Round 3. Remarkably, two independent groups published dimension-2 variants on the same day (May 13, 2024), with a third appearing the following day—demonstrating the rapid, simultaneous evolution of the field following the 2022 SIKE breakthrough. Given this dynamic environment, readers interested in SQIsign's future will benefit from this summary, which we intend to update with each revision of this standards-track submission. The key takeaway is that researchers have repurposed the higher-dimensional techniques from the SIKE cryptanalysis to optimize SQIsign variants with faster signing and potentially smaller sizes, while each group attempts to maintain equivalent post-quantum security levels. Variants can be classified primarily by the geometric dimensions they employ:

Core SQIsign (Dimension 1) The baseline algorithm currently competing in NIST's Round 3. The SQIsign team, in cooperation with IBM researchers, actively maintains and tunes this version. Recent updates focus on reducing memory footprints and accelerating core algebraic operations for practical implementation. However, NIST's current process permits only minor "tweaks" rather than substantial algorithmic changes.

Multi-dimensional variants SQIsignHD dramatically shrunk signature sizes, simplified verification. SQIsign2D-West prioritized a rigorous security proof over raw speed. SQIsign2D-East fast 2D verification using a generalized random isogeny algorithm. SQIPrime : Offers two sub-variants with different dimension trade-offs: SQIPrime2D: Uses only dimension 2 non-smooth challenge isogenies, avoiding the dimension 4 computations required by SQIsignHD. More efficient while remaining highly compact compared to non-isogeny PQC schemes. SQIPrime4D: Uses dimension 4 isogenies for response representation, prioritizing maximum compactness at the cost of exponentially higher runtime. Despite the paper's title, this sub-variant represents the authors' exploration before settling on the 2D approach.

COSE Integration This section defines the identifiers for SQIsign in COSE .

SQIsign Algorithms The algorithms defined in this document are: SQIsign-L1: SQIsign NIST Level I (suggested value -61) SQIsign-L3: SQIsign NIST Level III (suggested value -62) SQIsign-L5: SQIsign NIST Level V (suggested value -63)

SQIsign Key Types A new key type is defined for SQIsign with the name "SQIsign".

SQIsign Key Parameters SQIsign keys use the following COSE Key common parameters: Key Parameter COSE Label CBOR Type Description kty 1 int Key type: IETF (SQIsign) kid 2 bstr Key ID (optional) alg 3 int Algorithm identifier (-61, -62, or -63) key_ops 4 array Key operations (sign, verify)

SQIsign-Specific Key Parameters Key Parameter Label CBOR Type Description pub -1 bstr SQIsign public key priv -2 bstr SQIsign private key (sensitive)

COSE Key Format Examples

Public Key (COSE_Key) cbor { 1: IETF, / kty: SQIsign / 3: -61, / alg: SQIsign-L1 / -1: h'[PUBLIC_KEY]' / pub: SQIsign public key bytes / }

Private Key (COSE_Key) cbor { 1: IETF, / kty: SQIsign / 3: -61, / alg: SQIsign-L1 / -1: h'[PUBLIC_KEY]', / pub: SQIsign public key bytes / -2: h'[PRIVATE_KEY]' / priv: SQIsign private key bytes / }

COSE Signature Format SQIsign signatures in COSE follow the standard COSE_Sign1 structure : COSE_Sign1 = [ protected: bstr .cbor header_map, unprotected: header_map, payload: bstr / nil, signature: bstr ] The signature field contains the raw SQIsign signature bytes.

Protected Headers The protected header MUST include: cbor { 1: -61 / alg: SQIsign-L1, -62 for L3, -63 for L5 / }

Example COSE_Sign1 Structure cbor 18( / COSE_Sign1 tag / [ h'A10139003C', / protected: {"alg": -61} / {}, / unprotected / h'546869732069732074686520636F6E74656E742E', / payload / h'[SQISIGN_SIGNATURE_BYTES]' / signature / ] )

JOSE Integration

JSON Web Signature (JWS) Algorithm Registration The following algorithm identifiers are registered for use in the JWS "alg" header parameter for JSON Web Signatures : Algorithm Name Description Implementation Requirements SQIsign-L1 SQIsign NIST Level I Optional SQIsign-L3 SQIsign NIST Level III Optional SQIsign-L5 SQIsign NIST Level V Optional

JSON Web Key (JWK) Representation SQIsign keys are represented in JWK format as follows:

Public Key Parameters Parameter Type Description kty string Key type: "SQIsign" alg string Algorithm: "SQIsign-L1", "SQIsign-L3", or "SQIsign-L5" pub string Base64url-encoded public key kid string Key ID (optional) use string Public key use: "sig" (optional) key_ops array Key operations: [verify] (optional)

Private Key Parameters Private keys include all public key parameters plus: Parameter Type Description priv string Base64url-encoded private key

JWK Examples

Public Key (JWK) Example json { "kty": "SQIsign", "alg": "SQIsign-L1", "pub": "KxtQx8s8RcBEU67wr57K37fdPEztN4M8NUC_\ 5xZuqgMwkaeJhM94YHi_-2UsQllbnmm-W4XFSLm2hUwiMylrAh0", "kid": "2027-01-device-key", "use": "sig", "key_ops": ["verify"] }

Private Key (JWK) Example json { "kty": "SQIsign", "alg": "SQIsign-L1", "pub": "KxtQx8s8RcBEU67wr57K37fdPEztN4M8NUC_\ 5xZuqgMwkaeJhM94YHi_-2UsQllbnmm-W4XFSLm2hUwiMylrAh0", "priv": "KxtQx8s8RcBEU67wr57K37fdPEztN4M8NUC_5xZuqgMwkaeJhM94YHi_\ -2UsQllbnmm-W4XFSLm2hUwiMylrAh1VwP9vNkBZH0Bjj2wc-\ p7sUgQAAAAAAAAAAAAAAAAAAN68tviJbcCpQ84fh-4IJB4-\ ____________________P38m3fKOhfhMspQU9GmA4CD5___\ _______________________________________________\ ___________wAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\ AAAAAAA5cP9aha40v-8mFd_bdAgpR93Ug2iPhu4_NxG97C7\ 8wBvVMGOrQTCli7NxrR2KlPZR1AC5VddGf4p-ZjCzrWfAJv\ xhEh4uOKXq1MmuS9TwZGuz1YIYMIguu1wqjdmfaQAfOmK2g\ WWO3vcld5s7GR2AcrTv65ocK_pVUWY8eJDcQA", "kid": "2027-01-device-key", "use": "sig", "key_ops": ["sign"] }

JWS Compact Serialization A JWS using SQIsign follows the standard compact serialization: BASE64URL(UTF8(JWS Protected Header)) || '.' || BASE64URL(JWS Payload) || '.' || BASE64URL(JWS Signature)

Example JWS Protected Header json { "alg": "SQIsign-L1", "typ": "JWT" } Base64url-encoded: eyJhbGciOiJTUUlzaWduLUwxIiwidHlwIjoiSldUIn0

Complete JWS Example eyJhbGciOiJTUUlzaWduLUwxIiwidHlwIjoiSldUIn0 . [BASE64URL_PAYLOAD] . [BASE64URL_SQISIGN_SIGNATURE]

Implementation Considerations

Signature and Key Generation Implementations MUST follow the SQIsign specification for: Key pair generation Signature generation Signature verification

Randomness Requirements SQIsign signature generation requires high-quality randomness. Implementations MUST use a cryptographically secure random number generator (CSRNG) compliant with or equivalent.

Side-Channel Protections Implementations SHOULD implement protections against: Timing attacks Power analysis Fault injection attacks Particularly for constrained devices deployed in physically accessible environments.

Performance Trade-offs Implementers should be aware: Signing is computationally expensive: Consider pre-signing or batch operations Verification is moderate: Suitable for resource-constrained verifiers Size is exceptional: Minimizes bandwidth and storage

Interoperability Testing Early implementations SHOULD participate in interoperability testing to ensure: Consistent signature generation and verification Proper encoding in COSE and JOSE formats Cross-platform compatibility

Performance testing under real-world scenarios public metrics, interoperability and performance testing of the proposed WASM versions can be evaluated on a live testbed .

Security Considerations

Algorithm Security The security of SQIsign relies primarily on the hardness of finding isogenies between supersingular elliptic curves. These assumptions are different from lattice-based schemes, providing cryptographic diversity in the post-quantum landscape.

Quantum Security SQIsign is designed to resist attacks by large-scale quantum computers. The three parameter sets provide security equivalent to AES-128, AES-192, and AES-256 against both classical and quantum adversaries.

Cryptanalysis and Algorithm Maturity As of this writing, SQIsign is undergoing active cryptanalytic review: NIST Round 3 evaluation: Academic research: Ongoing analysis of isogeny-based cryptography Known attacks: No attacks are currently known that recover private keys for the standardized parameter sets within their claimed security levels. However, the scheme and its underlying assumptions remain under active study. Implementers are advised: - Monitor NIST announcements and updates - Follow academic literature on isogeny cryptanalysis - Be prepared to deprecate or update as cryptanalysis evolves

Implementation Security

Random Number Generation Poor randomness can completely compromise SQIsign security. Implementations MUST use robust CSRNGs, especially on constrained devices with limited entropy sources.

Side-Channel Resistance Constrained devices may be physically accessible to attackers. Implementations SHOULD: Use constant-time algorithms where possible Implement countermeasures against DPA/SPA Consider fault attack mitigations

Key Management Private keys MUST be protected with appropriate access controls Consider hardware security modules (HSMs) or secure elements for key storage Implement key rotation policies appropriate to the deployment

Cryptographic Agility Organizations deploying SQIsign SHOULD: Maintain hybrid deployments with classical algorithms during transition Plan for algorithm migration if cryptanalysis reveals weaknesses Monitor NIST and IRTF guidance on PQC deployment

Constrained Device Specific Risks IoT devices face unique challenges: Physical access: Devices may be deployed in hostile environments Limited update capability: Firmware updates may be infrequent or impossible Long deployment lifetimes: Devices may operate for 10+ years Design systems with: - Defense in depth (multiple security layers) - Remote update capability when possible - Graceful degradation if algorithm is compromised

IANA Considerations

Additions to Existing Registries IANA is requested to add the following entries to the COSE and JOSE registries. The following completed registration actions are provided as described in and .

New COSE Algorithms IANA is requested to register the following entries in the "COSE Algorithms" registry: Name Value Description Capabilities Change Cont Ref Rec'd SQIsign-L1 -61 SQIsign NIST L I kty IETF THIS-RFC No SQIsign-L3 -62 SQIsign NIST L III kty IETF THIS-RFC No SQIsign-L5 -63 SQIsign NIST L V kty IETF THIS-RFC No

New COSE Key Types IANA is requested to register the following entry in the "COSE Key Types" registry: Name Value Description Capabilities Change Cont Ref SQIsign IETF SQIsign pub key sign, verify IETF THIS-RFC

New COSE Key Type Parameters IANA is requested to register the following entries in the "COSE Key Type Parameters" registry: Key Type Name Label CBOR Type Desc Change Cont Reference SQIsign pub -1 bstr Public key IETF THIS-RFC SQIsign priv -2 bstr Private key IETF THIS-RFC

New JWS Algorithms IANA is requested to register the following entries in the "JSON Web Signature and Encryption Algorithms" registry: Algorithm Name Desc Impl Req Change Cont Ref Recommended SQIsign-L1 SQIsign NIST L I Optional IETF THIS-RFC No SQIsign-L3 SQIsign NIST L III Optional IETF THIS-RFC No SQIsign-L5 SQIsign NIST L V Optional IETF THIS-RFC No

New JSON Web Key Types IANA is requested to register the following entry in the "JSON Web Key Types" registry: "kty" Param Value Key Type Desc Change Cont Reference SQIsign SQIsign public key IETF THIS-RFC

New JSON Web Key Parameters IANA is requested to register the following entries in the "JSON Web Key Parameters" registry: Param Name Desc Used with "kty" Val Change Cont Reference pub Public key SQIsign IETF THIS-RFC priv Private key SQIsign IETF THIS-RFC

Acknowledgments The authors would like to thank: Luca DeFeo for reviewing draft-00 and providing valuable feedback. Any remaining errors are solely the responsibility of the authors. The SQIsign design team for groundbreaking work on isogeny-based signatures The NIST PQC team for managing the standardization process The COSE and JOSE working groups for guidance on integration The IRTF Crypto Forum Research Group for ongoing cryptanalytic review Aerospace and constrained-telemetry engineers/contractors who suggested the idea for pqc.rustykey.me, a public testbed devoted to anyone wishing to testout, evaluate and critique actual working WASM implemented code of all three levels. Early implementers who provide valuable feedback This work builds upon the template established by and similar PQC integration efforts.

References

Normative References Populated automatically from metadata

Informative References Populated automatically from metadata

JSON Web Signature (JWS) represents content secured with digital signatures or Message Authentication Codes (MACs) using JSON-based data structures. Cryptographic algorithms and identifiers for use with this specification are described in the separate JSON Web Algorithms (JWA) specification and an IANA registry defined by that specification. Related encryption capabilities are described in the separate JSON Web Encryption (JWE) specification. A JSON Web Key (JWK) is a JavaScript Object Notation (JSON) data structure that represents a cryptographic key. This specification also defines a JWK Set JSON data structure that represents a set of JWKs. Cryptographic algorithms and identifiers for use with this specification are described in the separate JSON Web Algorithms (JWA) specification and IANA registries established by that specification. Concise Binary Object Representation (CBOR) is a data format designed for small code size and small message size. There is a need for the ability to have basic security services defined for this data format. This document defines the CBOR Object Signing and Encryption (COSE) protocol. This specification describes how to create and process signatures, message authentication codes, and encryption using CBOR for serialization. This specification additionally describes how to represent cryptographic keys using CBOR. Concise Binary Object Representation (CBOR) is a data format designed for small code size and small message size. There is a need to be able to define basic security services for this data format. This document defines the CBOR Object Signing and Encryption (COSE) protocol. This specification describes how to create and process signatures, message authentication codes, and encryption using CBOR for serialization. This specification additionally describes how to represent cryptographic keys using CBOR. This document, along with RFC 9053, obsoletes RFC 8152. Concise Binary Object Representation (CBOR) is a data format designed for small code size and small message size. There is a need to be able to define basic security services for this data format. This document defines a set of algorithms that can be used with the CBOR Object Signing and Encryption (COSE) protocol (RFC 9052). This document, along with RFC 9052, obsoletes RFC 8152. The CBOR Object Signing and Encryption (COSE) syntax (see RFC 9052) does not define any direct methods for using hash algorithms. There are, however, circumstances where hash algorithms are used, such as indirect signatures, where the hash of one or more contents are signed, and identification of an X.509 certificate or other object by the use of a fingerprint. This document defines hash algorithms that are identified by COSE algorithm identifiers. In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. Security systems are built on strong cryptographic algorithms that foil pattern analysis attempts. However, the security of these systems is dependent on generating secret quantities for passwords, cryptographic keys, and similar quantities. The use of pseudo-random processes to generate secret quantities can result in pseudo-security. A sophisticated attacker may find it easier to reproduce the environment that produced the secret quantities and to search the resulting small set of possibilities than to locate the quantities in the whole of the potential number space. Choosing random quantities to foil a resourceful and motivated adversary is surprisingly difficult. This document points out many pitfalls in using poor entropy sources or traditional pseudo-random number generation techniques for generating such quantities. It recommends the use of truly random hardware techniques and shows that the existing hardware on many systems can be used for this purpose. It provides suggestions to ameliorate the problem when a hardware solution is not available, and it gives examples of how large such quantities need to be for some applications. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. The Concise Binary Object Representation (CBOR) is a data format whose design goals include the possibility of extremely small code size, fairly small message size, and extensibility without the need for version negotiation. These design goals make it different from earlier binary serializations such as ASN.1 and MessagePack. mesur.io Tradeverifyd University of the Bundeswehr Munich This document specifies JSON Object Signing and Encryption (JOSE) and CBOR Object Signing and Encryption (COSE) serializations for FFT (fast-Fourier transform) over NTRU-Lattice-Based Digital Signature Algorithm (FN-DSA), a Post-Quantum Cryptography (PQC) digital signature scheme defined in US NIST FIPS 206 (expected to be published in late 2026 early 2027). It does not define new cryptographic primitives; rather, it specifies how existing FN-DSA mechanisms are serialized for use in JOSE and COSE. This document registers signature algorithms for JOSE and COSE, specifically FN-DSA-512 and FN-DSA-1024. Tradeverifyd Tradeverifyd This document specifies JSON Object Signing and Encryption (JOSE) and CBOR Object Signing and Encryption (COSE) serializations for Module- Lattice-Based Digital Signature Standard (ML-DSA), a Post-Quantum Cryptography (PQC) digital signature scheme defined in US NIST FIPS 204. NIST SQIsign team IACR ePrint Archive National Security Agency RustyKey® University of Quantum Science

Test Vectors Vectors use NIST KAT count = 0 from upstream SQIsign response files (PQCsignKAT_*_SQIsign_lvl*.rsp). The same 32-byte message appears at each security level so implementers can compare keys and signatures. Algorithm identifiers -61, -62, and -63 map to SQIsign-L1, SQIsign-L3, and SQIsign-L5 respectively.

SQIsign-L1 Test Vectors

Example 1: Simple Message Signing The following test vector exhibits a SQIsign Level I signature over a short message. Message (hex): d81c4d8d734fcbfbeade3d3f8a039faa2a2c9957e835ad55b2 \ 2e75bf57bb556ac8 Message (ASCII): MsO=?*,W5U.uWUj Public Key (hex): 07CCD21425136F6E865E497D2D4D208F0054AD81372066E \ 817480787AAF7B2029550C89E892D618CE3230F23510BFBE68FCCDDAEA51DB1436 \ B462ADFAF008A010B Public Key (Base64url): B8zSFCUTb26GXkl9LU0gjwBUrYE3IGboF0gHh6r3s \ gKVUMieiS1hjOMjDyNRC_vmj8zdrqUdsUNrRirfrwCKAQs Signature (hex): 84228651f271b0f39f2f19f2e8718f31ed3365ac9e5cb303 \ afe663d0cfc11f0455d891b0ca6c7e653f9ba2667730bb77befe1b1a3182840428 \ 4af8fd7baacc010001d974b5ca671ff65708d8b462a5a84a1443ee9b5fed721876 \ 7c9d85ceed04db0a69a2f6ec3be835b3b2624b9a0df68837ad00bcacc27d1ec806 \ a44840267471d86eff3447018adb0a6551ee8322ab30010202 Signature (Base64url): hCKGUfJxsPOfLxny6HGPMe0zZayeXLMDr-Zj0M_BHw \ RV2JGwymx-ZT-bomZ3MLt3vv4bGjGChAQoSvj9e6rMAQAB2XS1ymcf9lcI2LRipahK \ FEPum1_tchh2fJ2Fzu0E2wppovbsO-g1s7JiS5oN9og3rQC8rMJ9HsgGpEhAJnRx2G \ 7_NEcBitsKZVHugyKrMAECAg

COSE_Sign1 Complete Example cbor 18( [ h'a10139003c', / protected: {"alg": -61} / {}, / unprotected / h'd81c4d8d734fcbfbeade3d3f8a039faa2a2c9957e835ad55b22e75bf57bb \ 556ac8', / payload / h'84228651f271b0f39f2f19f2e8718f31ed3365ac9e5cb303afe663d0cfc1 \ 1f0455d891b0ca6c7e653f9ba2667730bb77befe1b1a31828404284af8fd7b \ aacc010001d974b5ca671ff65708d8b462a5a84a1443ee9b5fed7218767c9d \ 85ceed04db0a69a2f6ec3be835b3b2624b9a0df68837ad00bcacc27d1ec806 \ a44840267471d86eff3447018adb0a6551ee8322ab30010202' ] )

JWS Complete Example eyJhbGciOiJTUUlzaWduLUwxIiwidHlwIjoiSldUIn0 . 2BxNjXNPy_vq3j0_igOfqiosmVfoNa1Vsi51v1e7VWrI . hCKGUfJxsPOfLxny6HGPMe0zZayeXLMDr-Zj0M_BHwRV2JGwymx-ZT-bomZ3MLt3vv \ 4bGjGChAQoSvj9e6rMAQAB2XS1ymcf9lcI2LRipahKFEPum1_tchh2fJ2Fzu0E2wpp \ ovbsO-g1s7JiS5oN9og3rQC8rMJ9HsgGpEhAJnRx2G7_NEcBitsKZVHugyKrMAECAg

SQIsign-L3 Test Vectors

Example 1: Simple Message Signing The following test vector exhibits a SQIsign Level III signature over a short message (NIST KAT count = 0; COSE/JOSE algorithm -62). Message (hex): D81C4D8D734FCBFBEADE3D3F8A039FAA2A2C9957E835AD55B22E75BF \ 57BB556AC8 Message (ASCII): MsO=?*,W5U.uWUj Public Key (hex): C32377D6F6D70729884A7F6877EF4791E35D21F751A3E96DE23F9 \ A7A3C01BCD8A5F146DC19E4E2AC63007457F97D8A40EE84AEE7564CA9A7FBE6200FD3E5 \ E55901BFC60EB25C50D39F5C91C96510556BAA22028DF76360841721A601D65E8D0F06 Public Key (Base64url): wyN31vbXBymISn9od-9HkeNdIfdRo-lt4j-aejwBvNil8Ub \ cGeTirGMAdFf5fYpA7oSu51ZMqaf75iAP0-XlWQG_xg6yXFDTn1yRyWUQVWuqIgKN92NghB \ chpgHWXo0PBg Signature (hex): 0868CFBF275B8E7B19BF597D658D62CC913B9B2933E30A297288FB \ E687F6F6B8AC8AF7AA007F191386BB1A203CDDBC2BDB42792D05DA69A4507073D12B0BD \ C47E2B36BC4BA45C68791918281E578F2DC14294504726DCD4CA4C4565FBB89A1280004 \ 8C7B84746A2CBD8247248E248B70B51AE91994957857692A028D8F5CABABFC91E4BF1C5 \ D350219A0189C57DE4A7710D29E0364C79B2188449EC0397359430D594C7B5980CC6755 \ 1933A902D3C11F0FBD6DC39711D3E1F501159EE7FB85CE81B4CE24E1016006567DF4693 \ 15D513E73F69F6301664E6449AF9DCEB4000D15 Signature (Base64url): CGjPvydbjnsZv1l9ZY1izJE7mykz4wopcoj75of29risiveq \ AH8ZE4a7GiA83bwr20J5LQXaaaRQcHPRKwvcR-Kza8S6RcaHkZGCgeV48twUKUUEcm3NTKT \ EVl-7iaEoAASMe4R0aiy9gkckjiSLcLUa6RmUlXhXaSoCjY9cq6v8keS_HF01AhmgGJxX3k \ p3ENKeA2THmyGIRJ7AOXNZQw1ZTHtZgMxnVRkzqQLTwR8PvW3DlxHT4fUBFZ7n-4XOgbTOJ \ OEBYAZWffRpMV1RPnP2n2MBZk5kSa-dzrQADRU

COSE_Sign1 Complete Example cbor 18( [ h'a10139003d', / protected: {"alg": -62} / {}, / unprotected / h'd81c4d8d734fcbfbeade3d3f8a039faa2a2c995 \ 7e835ad55b22e75bf57bb556ac8', / payload / h'0868cfbf275b8e7b19bf597d658d62cc913b9b2 \ 933e30a297288fbe687f6f6b8ac8af7aa007f191386bb1a203cddbc2bdb42792 \ d05da69a4507073d12b0bdc47e2b36bc4ba45c68791918281e578f2dc1429450 \ 4726dcd4ca4c4565fbb89a12800048c7b84746a2cbd8247248e248b70b51ae91 \ 994957857692a028d8f5cababfc91e4bf1c5d350219a0189c57de4a7710d29e0 \ 364c79b2188449ec0397359430d594c7b5980cc67551933a902d3c11f0fbd6dc \ 39711d3e1f501159ee7fb85ce81b4ce24e1016006567df469315d513e73f69f6 \ 301664e6449af9dceb4000d15', / signature / ] )

JWS Complete Example eyJhbGciOiJTUUlzaWduLUwzIiwidHlwIjoiSldUIn0 . 2BxNjXNPy_vq3j0_igOfqiosmVfoNa1Vsi51v1e7VWrI . CGjPvydbjnsZv1l9ZY1izJE7mykz4wopcoj75of29risiveqAH8ZE4a7GiA83bwr20J5LQXa \ aaRQcHPRKwvcR-Kza8S6RcaHkZGCgeV48twUKUUEcm3NTKTEVl-7iaEoAASMe4R0aiy9gkck \ jiSLcLUa6RmUlXhXaSoCjY9cq6v8keS_HF01AhmgGJxX3kp3ENKeA2THmyGIRJ7AOXNZQw1Z \ THtZgMxnVRkzqQLTwR8PvW3DlxHT4fUBFZ7n-4XOgbTOJOEBYAZWffRpMV1RPnP2n2MBZk5k \ Sa-dzrQADRU

SQIsign-L5 Test Vectors

Example 1: Simple Message Signing The following test vector exhibits a SQIsign Level V signature over a short message (NIST KAT count = 0; COSE/JOSE algorithm -63). Message (hex): D81C4D8D734FCBFBEADE3D3F8A039FAA2A2C9957E835AD55B22E75BF \ 57BB556AC8 Message (ASCII): MsO=?*,W5U.uWUj Public Key (hex): 86FFA3B0F73D55A64D13C6F89F28D75FD17C5E2368E1D451127C1 \ 6D1A97CDB440E20333A233AD2F8E4D70187C8AE31602049ADE949A87F95E79DA4C456F5 \ D400B2485A96D04708A2F30046812B8D65A3BFBFDED0DD6563462F9E2BCE760CD753CAE \ 8471BEC7049EF28FFEFE859C15DAC49DB959AEE99842D97A380A70DD7330106 Public Key (Base64url): hv-jsPc9VaZNE8b4nyjXX9F8XiNo4dRREnwW0al820QOIDM \ 6IzrS-OTXAYfIrjFgIEmt6Umof5XnnaTEVvXUALJIWpbQRwii8wBGgSuNZaO_v97Q3WVjRi \ -eK852DNdTyuhHG-xwSe8o_-_oWcFdrEnblZrumYQtl6OApw3XMwEG Signature (hex): 6B8EF5D7689A1EA1CFCE9C6F7495E309E9D1D1B03E61CD97088E67 \ 9C4901D0B6B6D38217F4AED6C44949B41F9AF80B43E84D0C91BDB1D00E06957BEBF30A5 \ 8012AD01E52CF7906CE197AD06696F7FCF756908EA980549E7C215D089BDE7117799F62 \ 8817A1B9C8FB7FEBFF7E9D9B776142460CFAAFC97D48A57E09E0DA378401000229CC8E1 \ B94E1F2F8AFDC42066BEACE076E3E70DD01F90C4D01DAC17BEC58743532848D438A87A5 \ 74D9DB940C17236AE3566281E27A99EFE5EE26E05B88A1D610A80B3AF38267D845C7FE3 \ 30F199B43794A9B2E14846924127366B8F6A1F0F24D3C4B54D79DBB61B098BF32D98EA8 \ 819F7BE4A5FFBA29E88B1A996C6CDFD32B048BC2ACFFA28870181447FCC8B6F97B63C47 \ CB013C6F3D84CBD07619A5C355B000911 Signature (Base64url): a47112iaHqHPzpxvdJXjCenR0bA-Yc2XCI5nnEkB0La204IX \ 9K7WxElJtB-a-AtD6E0Mkb2x0A4GlXvr8wpYASrQHlLPeQbOGXrQZpb3_PdWkI6pgFSefCF \ dCJvecRd5n2KIF6G5yPt_6_9-nZt3YUJGDPqvyX1IpX4J4No3hAEAAinMjhuU4fL4r9xCBm \ vqzgduPnDdAfkMTQHawXvsWHQ1MoSNQ4qHpXTZ25QMFyNq41ZigeJ6me_l7ibgW4ih1hCoC \ zrzgmfYRcf-Mw8Zm0N5SpsuFIRpJBJzZrj2ofDyTTxLVNedu2GwmL8y2Y6ogZ975KX_uino \ ixqZbGzf0ysEi8Ks_6KIcBgUR_zItvl7Y8R8sBPG89hMvQdhmlw1WwAJEQ

COSE_Sign1 Complete Example cbor 18( [ h'a10139003e', / protected: {"alg": -63} / {}, / unprotected / h'd81c4d8d734fcbfbeade3d3f8a039faa2a2c995 \ 7e835ad55b22e75bf57bb556ac8', / payload / h'6b8ef5d7689a1ea1cfce9c6f7495e309e9d1d1b \ 03e61cd97088e679c4901d0b6b6d38217f4aed6c44949b41f9af80b43e84d0c9 \ 1bdb1d00e06957bebf30a58012ad01e52cf7906ce197ad06696f7fcf756908ea \ 980549e7c215d089bde7117799f628817a1b9c8fb7febff7e9d9b776142460cf \ aafc97d48a57e09e0da378401000229cc8e1b94e1f2f8afdc42066beace076e3 \ e70dd01f90c4d01dac17bec58743532848d438a87a574d9db940c17236ae3566 \ 281e27a99efe5ee26e05b88a1d610a80b3af38267d845c7fe330f199b43794a9 \ b2e14846924127366b8f6a1f0f24d3c4b54d79dbb61b098bf32d98ea8819f7be \ 4a5ffba29e88b1a996c6cdfd32b048bc2acffa28870181447fcc8b6f97b63c47 \ cb013c6f3d84cbd07619a5c355b000911', / signature / ] )

JWS Complete Example eyJhbGciOiJTUUlzaWduLUw1IiwidHlwIjoiSldUIn0 . 2BxNjXNPy_vq3j0_igOfqiosmVfoNa1Vsi51v1e7VWrI . a47112iaHqHPzpxvdJXjCenR0bA-Yc2XCI5nnEkB0La204IX9K7WxElJtB-a-AtD6E0Mkb2x \ 0A4GlXvr8wpYASrQHlLPeQbOGXrQZpb3_PdWkI6pgFSefCFdCJvecRd5n2KIF6G5yPt_6_9- \ nZt3YUJGDPqvyX1IpX4J4No3hAEAAinMjhuU4fL4r9xCBmvqzgduPnDdAfkMTQHawXvsWHQ1 \ MoSNQ4qHpXTZ25QMFyNq41ZigeJ6me_l7ibgW4ih1hCoCzrzgmfYRcf-Mw8Zm0N5SpsuFIRp \ JBJzZrj2ofDyTTxLVNedu2GwmL8y2Y6ogZ975KX_uinoixqZbGzf0ysEi8Ks_6KIcBgUR_zI \ tvl7Y8R8sBPG89hMvQdhmlw1WwAJEQ

Implementation Status [RFC Editor: Please remove this section before publication] This section records the status of known implementations at the time of writing.

Open Source Implementations

Reference Implementation Organization: SQIsign team Repository: https://github.com/SQISign/the-sqisign Language: C License: MIT Status: Active development COSE/JOSE Support: Not yet integrated

Rust Implementation Organization: IETF - Community implementation Repository: IETF Language: Rust License: IETF COSE Support: Planned Status: Development

Commercial Implementations [RFC EDITOR: To be populated as vendors implement]

Interoperability Testing Test Suite Location: IETF Participating Organizations: IETF

Design Rationale

Algorithm Identifier Selection The requested algorithm identifiers (-61, -62, -63) are: In the Standards Action range (-255 to -1) per RFC 9053 Sequential for the three parameter sets Not conflicting with existing registrations (verified against IANA COSE registry) Consistent with the approach used for other PQC algorithms

Key Type Design The SQIsign key type is intentionally simple: Only two parameters (pub, priv) following minimalist design Binary encoding (bstr) for efficiency No algorithm-specific encoding—raw bytes from SQIsign spec This approach: - Minimizes CBOR encoding overhead (critical for constrained devices) - Simplifies implementation - Provides future flexibility for parameter set evolution

Change Log [RFC Editor Note:** Please remove this section before publication]

draft-mott-cose-sqisign-06 fixed typos

draft-mott-cose-sqisign versions prior to -06 added section "SQIsign Variants and the Post-SIKE Landscape" Incorporated technical corrections and feedback from Luca De Feo Updated the Abstract and Introduction to utilize more neutral, objective language Removed vendor-specific branding in favor of generic cryptographic terminology fixed various formatting issues Added SQIsign-L3 and SQIsign-L5 COSE_Sign1 and JWS test vectors (algorithms -62 and -63) Documented NIST KAT count = 0 byte values for cross-implementation checks added informational resource for interactive working code public testbed updated after SQISign advances to NIST round 3 with 8 other candidates