CBOR Object Signing and Encryption (COSE) and JSON Object Signing and Encryption (JOSE) Registrations for SQIsign
draft-mott-cose-sqisign-06
This document is an Internet-Draft (I-D).
Anyone may submit an I-D to the IETF.
This I-D is not endorsed by the IETF and has no formal standing in the
IETF standards process.
| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Author | Antony R. Mott | ||
| Last updated | 2026-06-04 | ||
| RFC stream | (None) | ||
| Intended RFC status | (None) | ||
| Formats | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | I-D Exists | |
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-mott-cose-sqisign-06
COSE A. R. Mott
Internet-Draft RustyKey®
Intended status: Standards Track 4 June 2026
Expires: 6 December 2026
CBOR Object Signing and Encryption (COSE) and JSON Object Signing and
Encryption (JOSE) Registrations for SQIsign
draft-mott-cose-sqisign-06
Abstract
*NOTE: This document describes a signature scheme based on an
algorithm currently under evaluation in the 3rd round
[NIST-3rd-round-candidates] 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
Mott Expires 6 December 2026 [Page 1]
Internet-Draft cose-sqisign June 2026
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.
About This Document
This note is to be removed before publishing as an RFC.
Status information for this document may be found at
https://datatracker.ietf.org/doc/draft-mott-cose-sqisign/.
Discussion of this document takes place on the COSE Working Group
mailing list (mailto:cose@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/browse/cose/. Subscribe at
https://www.ietf.org/mailman/listinfo/cose/.
Source for this draft and an issue tracker can be found at
https://github.com/https://github.com/antonymott/quantum-resistant-
rustykey.
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 6 December 2026.
Copyright Notice
Copyright (c) 2026 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
Mott Expires 6 December 2026 [Page 2]
Internet-Draft cose-sqisign June 2026
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 . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1. Background and Motivation . . . . . . . . . . . . . . . . 5
1.1.1. Pressing Need for Smaller PQC Signatures . . . . . . 5
1.1.2. Estimated Constrained Device Footprint . . . . . . . 6
1.1.3. Pressing need: Limit or Stop 'Harvest now; decrypt
later' Attacks . . . . . . . . . . . . . . . . . . . 8
1.2. Scope and Status . . . . . . . . . . . . . . . . . . . . 8
1.3. Relationship to Other Work . . . . . . . . . . . . . . . 8
1.4. Constrained Device Applicability . . . . . . . . . . . . 9
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 9
3. Cryptanalytic Resistance: SIDH/SIKE Attacks Do Not Apply . . 9
3.1. SIKE Vulnerability (The "Torsion Point" Attack) of
2022 . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.2. Why SQISign appears unaffected by the SIKE
Vulnerability . . . . . . . . . . . . . . . . . . . . . . 10
4. SQIsign Algorithm Overview . . . . . . . . . . . . . . . . . 10
4.1. Cryptographic Foundation . . . . . . . . . . . . . . . . 10
4.2. Security Levels . . . . . . . . . . . . . . . . . . . . . 11
4.3. Performance Characteristics . . . . . . . . . . . . . . . 11
4.4. SQIsign Variants and the Post-SIKE Landscape . . . . . . 12
4.4.1. Core SQIsign (Dimension 1) . . . . . . . . . . . . . 12
4.4.2. Multi-dimensional variants . . . . . . . . . . . . . 12
5. COSE Integration . . . . . . . . . . . . . . . . . . . . . . 13
5.1. SQIsign Algorithms . . . . . . . . . . . . . . . . . . . 13
5.2. SQIsign Key Types . . . . . . . . . . . . . . . . . . . . 13
5.3. SQIsign Key Parameters . . . . . . . . . . . . . . . . . 13
5.4. SQIsign-Specific Key Parameters . . . . . . . . . . . . . 14
5.5. COSE Key Format Examples . . . . . . . . . . . . . . . . 14
5.5.1. Public Key (COSE_Key) . . . . . . . . . . . . . . . . 14
5.5.2. Private Key (COSE_Key) . . . . . . . . . . . . . . . 14
5.6. COSE Signature Format . . . . . . . . . . . . . . . . . . 14
5.6.1. Protected Headers . . . . . . . . . . . . . . . . . . 15
5.6.2. Example COSE_Sign1 Structure . . . . . . . . . . . . 15
6. JOSE Integration . . . . . . . . . . . . . . . . . . . . . . 15
6.1. JSON Web Signature (JWS) Algorithm Registration . . . . . 15
6.2. JSON Web Key (JWK) Representation . . . . . . . . . . . . 15
6.2.1. Public Key Parameters . . . . . . . . . . . . . . . . 16
6.2.2. Private Key Parameters . . . . . . . . . . . . . . . 16
6.3. JWK Examples . . . . . . . . . . . . . . . . . . . . . . 16
6.3.1. Public Key (JWK) Example . . . . . . . . . . . . . . 16
6.3.2. Private Key (JWK) Example . . . . . . . . . . . . . . 17
Mott Expires 6 December 2026 [Page 3]
Internet-Draft cose-sqisign June 2026
6.4. JWS Compact Serialization . . . . . . . . . . . . . . . . 17
6.4.1. Example JWS Protected Header . . . . . . . . . . . . 17
6.4.2. Complete JWS Example . . . . . . . . . . . . . . . . 17
7. Implementation Considerations . . . . . . . . . . . . . . . . 17
7.1. Signature and Key Generation . . . . . . . . . . . . . . 17
7.2. Randomness Requirements . . . . . . . . . . . . . . . . . 18
7.3. Side-Channel Protections . . . . . . . . . . . . . . . . 18
7.4. Performance Trade-offs . . . . . . . . . . . . . . . . . 18
7.5. Interoperability Testing . . . . . . . . . . . . . . . . 18
7.6. Performance testing under real-world scenarios . . . . . 18
8. Security Considerations . . . . . . . . . . . . . . . . . . . 19
8.1. Algorithm Security . . . . . . . . . . . . . . . . . . . 19
8.2. Quantum Security . . . . . . . . . . . . . . . . . . . . 19
8.3. Cryptanalysis and Algorithm Maturity . . . . . . . . . . 19
8.4. Implementation Security . . . . . . . . . . . . . . . . . 19
8.4.1. Random Number Generation . . . . . . . . . . . . . . 19
8.4.2. Side-Channel Resistance . . . . . . . . . . . . . . . 19
8.4.3. Key Management . . . . . . . . . . . . . . . . . . . 20
8.5. Cryptographic Agility . . . . . . . . . . . . . . . . . . 20
8.6. Constrained Device Specific Risks . . . . . . . . . . . . 20
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
9.1. Additions to Existing Registries . . . . . . . . . . . . 20
9.1.1. New COSE Algorithms . . . . . . . . . . . . . . . . . 21
9.1.2. New COSE Key Types . . . . . . . . . . . . . . . . . 21
9.1.3. New COSE Key Type Parameters . . . . . . . . . . . . 21
9.1.4. New JWS Algorithms . . . . . . . . . . . . . . . . . 22
9.1.5. New JSON Web Key Types . . . . . . . . . . . . . . . 22
9.1.6. New JSON Web Key Parameters . . . . . . . . . . . . . 23
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 23
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
11.1. Normative References . . . . . . . . . . . . . . . . . . 24
11.2. Informative References . . . . . . . . . . . . . . . . . 24
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
12.1. Normative References . . . . . . . . . . . . . . . . . . 24
12.2. Informative References . . . . . . . . . . . . . . . . . 25
Appendix A. Test Vectors . . . . . . . . . . . . . . . . . . . . 26
A.1. SQIsign-L1 Test Vectors . . . . . . . . . . . . . . . . . 26
A.1.1. Example 1: Simple Message Signing . . . . . . . . . . 26
A.1.2. COSE_Sign1 Complete Example . . . . . . . . . . . . . 27
A.1.3. JWS Complete Example . . . . . . . . . . . . . . . . 27
A.2. SQIsign-L3 Test Vectors . . . . . . . . . . . . . . . . . 27
A.2.1. Example 1: Simple Message Signing . . . . . . . . . . 27
A.2.2. COSE_Sign1 Complete Example . . . . . . . . . . . . . 28
A.2.3. JWS Complete Example . . . . . . . . . . . . . . . . 29
A.3. SQIsign-L5 Test Vectors . . . . . . . . . . . . . . . . . 29
A.3.1. Example 1: Simple Message Signing . . . . . . . . . . 29
A.3.2. COSE_Sign1 Complete Example . . . . . . . . . . . . . 30
A.3.3. JWS Complete Example . . . . . . . . . . . . . . . . 30
Mott Expires 6 December 2026 [Page 4]
Internet-Draft cose-sqisign June 2026
Appendix B. Implementation Status . . . . . . . . . . . . . . . 30
B.1. Open Source Implementations . . . . . . . . . . . . . . . 31
B.1.1. Reference Implementation . . . . . . . . . . . . . . 31
B.1.2. Rust Implementation . . . . . . . . . . . . . . . . . 31
B.2. Commercial Implementations . . . . . . . . . . . . . . . 31
B.3. Interoperability Testing . . . . . . . . . . . . . . . . 31
Appendix C. Design Rationale . . . . . . . . . . . . . . . . . . 31
C.1. Algorithm Identifier Selection . . . . . . . . . . . . . 31
C.2. Key Type Design . . . . . . . . . . . . . . . . . . . . . 32
Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 32
D.1. draft-mott-cose-sqisign-06 . . . . . . . . . . . . . . . 32
D.2. draft-mott-cose-sqisign versions prior to -06 . . . . . . 32
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 33
1. Introduction
This document registers algorithm identifiers and key type parameters
for SQIsign in COSE and JOSE.
1.1. 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.
1.1.1. 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 [SQIsign-Standard] [SQIsign-Analysis] 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 [WebAuthn-PQC-Signature-size-constraints]. SQIsign is an
Mott Expires 6 December 2026 [Page 5]
Internet-Draft cose-sqisign June 2026
isogeny-based digital signature scheme participating in NIST's Round
3 [NIST-3rd-round-candidates] 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) |
+-------------+-----------------+----------------+--------------+
Table 1
1.1.2. Estimated Constrained Device Footprint
The total addressable market for SQIsign in constrained devices is
estimated at ~6.25 billion units.
1.1.2.1. Device Category Breakdown
Mott Expires 6 December 2026 [Page 6]
Internet-Draft cose-sqisign June 2026
1.1.2.1.1. 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.
1.1.2.1.2. 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.
1.1.2.1.3. 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.
1.1.2.1.4. 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."
[CNSA-2], Page 4.
Mott Expires 6 December 2026 [Page 7]
Internet-Draft cose-sqisign June 2026
1.1.3. 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) [RFC9052] 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.
1.2. Scope and Status
This document is published on the *Standards* track rather than
Informational Track for the following reasons:
1. *Algorithm Maturity*: SQIsign is currently undergoing evaluation
in NIST's on-ramp process
2. *Continued Cryptanalysis*: The algorithm has active ongoing
review by the cryptographic research community, including the
IRTF CFRG
3. *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.
1.3. Relationship to Other Work
This document follows the precedent established by
[I-D.ietf-cose-falcon] and [I-D.ietf-cose-dilithium] 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.
Mott Expires 6 December 2026 [Page 8]
Internet-Draft cose-sqisign June 2026
1.4. 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
2. 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 [RFC2119] [RFC8174] 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 [RFC7049]
* *ECDH*: Elliptic Curve Diffie-Hellman
* *IANA*: Internet Assigned Numbers Authority
3. Cryptanalytic Resistance: SIDH/SIKE Attacks Do Not Apply
Mott Expires 6 December 2026 [Page 9]
Internet-Draft cose-sqisign June 2026
3.1. 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.
3.2. 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.
4. SQIsign Algorithm Overview
4.1. 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:
Mott Expires 6 December 2026 [Page 10]
Internet-Draft cose-sqisign June 2026
* *Smaller key and signature sizes*
* *Algebraic structure* based on elliptic curve isogenies
* *Different security assumptions* (diversification from lattice-
based schemes)
4.2. Security Levels
SQIsign is defined with three parameter sets corresponding to NIST
security levels:
+===============+=======+========+===========+==================+
| Parameter Set | NIST | Public | Signature | Quantum Security |
| | Level | Key | | (estimated) |
+===============+=======+========+===========+==================+
| SQIsign-L1 | I | 65 | 148 bytes | ~128 bits |
| | | bytes | | |
+---------------+-------+--------+-----------+------------------+
| SQIsign-L3 | III | 97 | 224 bytes | ~192 bits |
| | | bytes | | |
+---------------+-------+--------+-----------+------------------+
| SQIsign-L5 | V | 129 | 292 bytes | ~256 bits |
| | | bytes | | |
+---------------+-------+--------+-----------+------------------+
Table 2
4.3. 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
Mott Expires 6 December 2026 [Page 11]
Internet-Draft cose-sqisign June 2026
4.4. 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:
4.4.1. 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.
4.4.2. Multi-dimensional variants
* SQIsignHD [SQIsignHD] dramatically shrunk signature sizes,
simplified verification.
* SQIsign2D-West [SQIsign2D-West] prioritized a rigorous security
proof over raw speed.
* SQIsign2D-East [SQIsign2D-East] fast 2D verification using a
generalized random isogeny algorithm.
* SQIPrime [SQIPrime]: Offers two sub-variants with different
dimension trade-offs:
Mott Expires 6 December 2026 [Page 12]
Internet-Draft cose-sqisign June 2026
- 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.
5. COSE Integration
This section defines the identifiers for SQIsign in COSE [RFC8152].
5.1. 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)
5.2. SQIsign Key Types
A new key type is defined for SQIsign with the name "SQIsign".
5.3. SQIsign Key Parameters
SQIsign keys use the following COSE Key common parameters:
Mott Expires 6 December 2026 [Page 13]
Internet-Draft cose-sqisign June 2026
+===============+============+===========+==========================+
| 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) |
+---------------+------------+-----------+--------------------------+
Table 3
5.4. SQIsign-Specific Key Parameters
+===============+=======+===========+====================+
| Key Parameter | Label | CBOR Type | Description |
+===============+=======+===========+====================+
| pub | -1 | bstr | SQIsign public key |
+---------------+-------+-----------+--------------------+
| priv | -2 | bstr | SQIsign private |
| | | | key (sensitive) |
+---------------+-------+-----------+--------------------+
Table 4
5.5. COSE Key Format Examples
5.5.1. Public Key (COSE_Key)
cbor { 1: IETF, / kty: SQIsign / 3: -61, / alg: SQIsign-L1 / -1:
h'[PUBLIC_KEY]' / pub: SQIsign public key bytes / }
5.5.2. 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 / }
5.6. COSE Signature Format
SQIsign signatures in COSE follow the standard COSE_Sign1 structure
[RFC9052]:
Mott Expires 6 December 2026 [Page 14]
Internet-Draft cose-sqisign June 2026
COSE_Sign1 = [ protected: bstr .cbor header_map, unprotected:
header_map, payload: bstr / nil, signature: bstr ]
The signature field contains the raw SQIsign signature bytes.
5.6.1. Protected Headers
The protected header MUST include:
cbor { 1: -61 / alg: SQIsign-L1, -62 for L3, -63 for L5 / }
5.6.2. Example COSE_Sign1 Structure
cbor 18( / COSE_Sign1 tag / [ h'A10139003C', / protected: {"alg":
-61} / {}, / unprotected /
h'546869732069732074686520636F6E74656E742E', / payload /
h'[SQISIGN_SIGNATURE_BYTES]' / signature / ] )
6. JOSE Integration
6.1. JSON Web Signature (JWS) Algorithm Registration
The following algorithm identifiers are registered for use in the JWS
"alg" header parameter for JSON Web Signatures [RFC7515]:
+================+==============+=============================+
| Algorithm Name | Description | Implementation Requirements |
+================+==============+=============================+
| SQIsign-L1 | SQIsign NIST | Optional |
| | Level I | |
+----------------+--------------+-----------------------------+
| SQIsign-L3 | SQIsign NIST | Optional |
| | Level III | |
+----------------+--------------+-----------------------------+
| SQIsign-L5 | SQIsign NIST | Optional |
| | Level V | |
+----------------+--------------+-----------------------------+
Table 5
6.2. JSON Web Key (JWK) Representation
SQIsign keys are represented in JWK [RFC7517] format as follows:
Mott Expires 6 December 2026 [Page 15]
Internet-Draft cose-sqisign June 2026
6.2.1. 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) |
+-----------+--------+-------------------------------+
Table 6
6.2.2. Private Key Parameters
Private keys include all public key parameters plus:
+===========+========+===============================+
| Parameter | Type | Description |
+===========+========+===============================+
| priv | string | Base64url-encoded private key |
+-----------+--------+-------------------------------+
Table 7
6.3. JWK Examples
6.3.1. 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"] }
Mott Expires 6 December 2026 [Page 16]
Internet-Draft cose-sqisign June 2026
6.3.2. 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"] }
6.4. JWS Compact Serialization
A JWS using SQIsign follows the standard compact serialization:
BASE64URL(UTF8(JWS Protected Header)) || '.' || BASE64URL(JWS
Payload) || '.' || BASE64URL(JWS Signature)
6.4.1. Example JWS Protected Header
json { "alg": "SQIsign-L1", "typ": "JWT" }
Base64url-encoded: eyJhbGciOiJTUUlzaWduLUwxIiwidHlwIjoiSldUIn0
6.4.2. Complete JWS Example
eyJhbGciOiJTUUlzaWduLUwxIiwidHlwIjoiSldUIn0 . [BASE64URL_PAYLOAD] .
[BASE64URL_SQISIGN_SIGNATURE]
7. Implementation Considerations
7.1. Signature and Key Generation
Implementations MUST follow the SQIsign specification
[SQIsign-Standard] for:
* Key pair generation
* Signature generation
* Signature verification
Mott Expires 6 December 2026 [Page 17]
Internet-Draft cose-sqisign June 2026
7.2. Randomness Requirements
SQIsign signature generation requires high-quality randomness.
Implementations MUST use a cryptographically secure random number
generator (CSRNG) compliant with [RFC4086] or equivalent.
7.3. Side-Channel Protections
Implementations SHOULD implement protections against:
* Timing attacks
* Power analysis
* Fault injection attacks
Particularly for constrained devices deployed in physically
accessible environments.
7.4. 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
7.5. 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
7.6. Performance testing under real-world scenarios
* public metrics, interoperability and performance testing of the
proposed WASM versions can be evaluated on a live testbed
[PQC-Testbed].
Mott Expires 6 December 2026 [Page 18]
Internet-Draft cose-sqisign June 2026
8. Security Considerations
8.1. 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.
8.2. 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.
8.3. Cryptanalysis and Algorithm Maturity
As of this writing, SQIsign is undergoing active cryptanalytic
review:
* *NIST Round 3 evaluation*: [NIST-3rd-round-candidates]
* *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
8.4. Implementation Security
8.4.1. Random Number Generation
Poor randomness can completely compromise SQIsign security.
Implementations MUST use robust CSRNGs, especially on constrained
devices with limited entropy sources.
8.4.2. Side-Channel Resistance
Constrained devices may be physically accessible to attackers.
Implementations SHOULD:
Mott Expires 6 December 2026 [Page 19]
Internet-Draft cose-sqisign June 2026
* Use constant-time algorithms where possible
* Implement countermeasures against DPA/SPA
* Consider fault attack mitigations
8.4.3. 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
8.5. 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
8.6. 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
9. IANA Considerations
9.1. 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 [RFC9053] and [RFC9054].
Mott Expires 6 December 2026 [Page 20]
Internet-Draft cose-sqisign June 2026
9.1.1. New COSE Algorithms
IANA is requested to register the following entries in the "COSE
Algorithms" registry:
+==========+=====+===========+==============+======+========+=====+
|Name |Value|Description| Capabilities |Change|Ref |Rec'd|
| | | | |Cont | | |
+==========+=====+===========+==============+======+========+=====+
|SQIsign-L1|-61 |SQIsign | kty |IETF |THIS-RFC|No |
| | |NIST L I | | | | |
+----------+-----+-----------+--------------+------+--------+-----+
|SQIsign-L3|-62 |SQIsign | kty |IETF |THIS-RFC|No |
| | |NIST L III | | | | |
+----------+-----+-----------+--------------+------+--------+-----+
|SQIsign-L5|-63 |SQIsign | kty |IETF |THIS-RFC|No |
| | |NIST L V | | | | |
+----------+-----+-----------+--------------+------+--------+-----+
Table 8
9.1.2. New COSE Key Types
IANA is requested to register the following entry in the "COSE Key
Types" registry:
+=========+=======+=============+==============+========+==========+
| Name | Value | Description | Capabilities | Change | Ref |
| | | | | Cont | |
+=========+=======+=============+==============+========+==========+
| SQIsign | IETF | SQIsign pub | sign, verify | IETF | THIS-RFC |
| | | key | | | |
+---------+-------+-------------+--------------+--------+----------+
Table 9
9.1.3. New COSE Key Type Parameters
IANA is requested to register the following entries in the "COSE Key
Type Parameters" registry:
Mott Expires 6 December 2026 [Page 21]
Internet-Draft cose-sqisign June 2026
+==========+======+=======+======+=========+========+===========+
| Key Type | Name | Label | CBOR | Desc | Change | Reference |
| | | | Type | | Cont | |
+==========+======+=======+======+=========+========+===========+
| SQIsign | pub | -1 | bstr | Public | IETF | THIS-RFC |
| | | | | key | | |
+----------+------+-------+------+---------+--------+-----------+
| SQIsign | priv | -2 | bstr | Private | IETF | THIS-RFC |
| | | | | key | | |
+----------+------+-------+------+---------+--------+-----------+
Table 10
9.1.4. New JWS Algorithms
IANA is requested to register the following entries in the "JSON Web
Signature and Encryption Algorithms" registry:
+============+==========+==========+======+==========+=============+
| Algorithm | Desc | Impl Req |Change| Ref | Recommended |
| Name | | |Cont | | |
+============+==========+==========+======+==========+=============+
| SQIsign-L1 | SQIsign | Optional |IETF | THIS-RFC | No |
| | NIST L I | | | | |
+------------+----------+----------+------+----------+-------------+
| SQIsign-L3 | SQIsign | Optional |IETF | THIS-RFC | No |
| | NIST L | | | | |
| | III | | | | |
+------------+----------+----------+------+----------+-------------+
| SQIsign-L5 | SQIsign | Optional |IETF | THIS-RFC | No |
| | NIST L V | | | | |
+------------+----------+----------+------+----------+-------------+
Table 11
9.1.5. 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 |
+-------------------+--------------------+-------------+-----------+
Table 12
Mott Expires 6 December 2026 [Page 22]
Internet-Draft cose-sqisign June 2026
9.1.6. 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 | Reference |
| | | | Cont | |
+============+=========+=====================+========+===========+
| pub | Public | SQIsign | IETF | THIS-RFC |
| | key | | | |
+------------+---------+---------------------+--------+-----------+
| priv | Private | SQIsign | IETF | THIS-RFC |
| | key | | | |
+------------+---------+---------------------+--------+-----------+
Table 13
10. 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
[I-D.ietf-cose-falcon] and similar PQC integration efforts.
Mott Expires 6 December 2026 [Page 23]
Internet-Draft cose-sqisign June 2026
11. References
11.1. Normative References
_Populated automatically from metadata_
11.2. Informative References
_Populated automatically from metadata_
12. References
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <https://www.rfc-editor.org/rfc/rfc7515>.
[RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015,
<https://www.rfc-editor.org/rfc/rfc7517>.
[RFC8152] Schaad, J., "CBOR Object Signing and Encryption (COSE)",
RFC 8152, DOI 10.17487/RFC8152, July 2017,
<https://www.rfc-editor.org/rfc/rfc8152>.
[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>.
[RFC9052] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Structures and Process", STD 96, RFC 9052,
DOI 10.17487/RFC9052, August 2022,
<https://www.rfc-editor.org/rfc/rfc9052>.
[RFC9053] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Initial Algorithms", RFC 9053, DOI 10.17487/RFC9053,
August 2022, <https://www.rfc-editor.org/rfc/rfc9053>.
[RFC9054] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Hash Algorithms", RFC 9054, DOI 10.17487/RFC9054, August
2022, <https://www.rfc-editor.org/rfc/rfc9054>.
Mott Expires 6 December 2026 [Page 24]
Internet-Draft cose-sqisign June 2026
12.2. Informative References
[CNSA-2] National Security Agency, "Commercial National Security
Algorithm Suite 2.0", May 2025,
<https://media.defense.gov/2025/May/30/2003728741/-1/-1/0/
CSA_CNSA_2.0_ALGORITHMS.PDF>.
[I-D.ietf-cose-dilithium]
Prorock, M. and O. Steele, "ML-DSA for JOSE and COSE",
Work in Progress, Internet-Draft, draft-ietf-cose-
dilithium-11, 15 November 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-cose-
dilithium-11>.
[I-D.ietf-cose-falcon]
Prorock, M., Steele, O., and H. Tschofenig, "FN-DSA for
JOSE and COSE", Work in Progress, Internet-Draft, draft-
ietf-cose-falcon-04, 15 March 2026,
<https://datatracker.ietf.org/doc/html/draft-ietf-cose-
falcon-04>.
[NIST-3rd-round-candidates]
NIST, "Nine Candidates Advance to the Third Round of the
Additional Digital Signatures for the PQC Standardization
Process", May 2026, <https://csrc.nist.gov/News/2026/nist-
advances-9-candidates-to-the-3rd-round-of-pqc>.
[PQC-Testbed]
RustyKey®, "PQC RustyKey® Testbed", June 2026,
<https://pqc.rustykey.me>.
[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>.
[RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
October 2013, <https://www.rfc-editor.org/rfc/rfc7049>.
[SQIPrime] Max Duparc, Tako Boris Fouotsa, "SQIPrime: A dimension 2
variant of SQISignHD with non-smooth challenge isogenies",
May 2024, <https://eprint.iacr.org/2024/773>.
[SQIsign-Analysis]
IACR ePrint Archive, ""SQIsign: Compact Post-Quantum
Signatures from Quaternions and Isogenies"", January 2021,
<https://eprint.iacr.org/2020/1240>.
Mott Expires 6 December 2026 [Page 25]
Internet-Draft cose-sqisign June 2026
[SQIsign-Standard]
SQIsign team, "Algorithmspecifications andsupporting
documentation Version 2.0.1", July 2025,
<https://sqisign.org/spec/sqisign-20250707.pdf>.
[SQIsign2D-East]
Kohei Nakagawa, Hiroshi Onuki, "SQIsign2D-East: A New
Signature Scheme Using 2-dimensional Isogenies", May 2024,
<https://eprint.iacr.org/2024/771>.
[SQIsign2D-West]
Andrea Basso, Luca De Feo, Pierrick Dartois, Antonin
Leroux, Luciano Maino, Giacomo Pope, Damien Robert,
Benjamin Wesolowski, "SQIsign2D-West: The Fast, the Small,
and the Safer", May 2024,
<https://eprint.iacr.org/2024/760>.
[SQIsignHD]
Pierrick Dartois, Antonin Leroux, Damien Robert, Benjamin
Wesolowski, "SQISignHD: New Dimensions in Cryptography",
May 2023, <https://eprint.iacr.org/2023/436>.
[WebAuthn-PQC-Signature-size-constraints]
University of Quantum Science, "WebAuthn PQC Signature
size constraints", June 2026,
<https://www.npmjs.com/package/quantum-resistant-
rustykey>.
Appendix A. 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.
A.1. SQIsign-L1 Test Vectors
A.1.1. 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
Mott Expires 6 December 2026 [Page 26]
Internet-Draft cose-sqisign June 2026
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
A.1.2. COSE_Sign1 Complete Example
cbor 18( [ h'a10139003c', / protected: {"alg": -61} / {}, /
unprotected /
h'd81c4d8d734fcbfbeade3d3f8a039faa2a2c9957e835ad55b22e75bf57bb \
556ac8', / payload /
h'84228651f271b0f39f2f19f2e8718f31ed3365ac9e5cb303afe663d0cfc1 \
1f0455d891b0ca6c7e653f9ba2667730bb77befe1b1a31828404284af8fd7b \
aacc010001d974b5ca671ff65708d8b462a5a84a1443ee9b5fed7218767c9d \
85ceed04db0a69a2f6ec3be835b3b2624b9a0df68837ad00bcacc27d1ec806 \
a44840267471d86eff3447018adb0a6551ee8322ab30010202' ] )
A.1.3. JWS Complete Example
eyJhbGciOiJTUUlzaWduLUwxIiwidHlwIjoiSldUIn0 .
2BxNjXNPy_vq3j0_igOfqiosmVfoNa1Vsi51v1e7VWrI .
hCKGUfJxsPOfLxny6HGPMe0zZayeXLMDr-Zj0M_BHwRV2JGwymx-ZT-bomZ3MLt3vv \
4bGjGChAQoSvj9e6rMAQAB2XS1ymcf9lcI2LRipahKFEPum1_tchh2fJ2Fzu0E2wpp \
ovbsO-g1s7JiS5oN9og3rQC8rMJ9HsgGpEhAJnRx2G7_NEcBitsKZVHugyKrMAECAg
A.2. SQIsign-L3 Test Vectors
A.2.1. 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
Mott Expires 6 December 2026 [Page 27]
Internet-Draft cose-sqisign June 2026
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
A.2.2. 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 / ] )
Mott Expires 6 December 2026 [Page 28]
Internet-Draft cose-sqisign June 2026
A.2.3. JWS Complete Example
eyJhbGciOiJTUUlzaWduLUwzIiwidHlwIjoiSldUIn0 .
2BxNjXNPy_vq3j0_igOfqiosmVfoNa1Vsi51v1e7VWrI .
CGjPvydbjnsZv1l9ZY1izJE7mykz4wopcoj75of29risiveqAH8ZE4a7GiA83bwr20J5LQXa
\ aaRQcHPRKwvcR-Kza8S6RcaHkZGCgeV48twUKUUEcm3NTKTEVl-
7iaEoAASMe4R0aiy9gkck \
jiSLcLUa6RmUlXhXaSoCjY9cq6v8keS_HF01AhmgGJxX3kp3ENKeA2THmyGIRJ7AOXNZQw1Z
\ THtZgMxnVRkzqQLTwR8PvW3DlxHT4fUBFZ7n-
4XOgbTOJOEBYAZWffRpMV1RPnP2n2MBZk5k \ Sa-dzrQADRU
A.3. SQIsign-L5 Test Vectors
A.3.1. 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
Mott Expires 6 December 2026 [Page 29]
Internet-Draft cose-sqisign June 2026
\ CB013C6F3D84CBD07619A5C355B000911 Signature (Base64url):
a47112iaHqHPzpxvdJXjCenR0bA-Yc2XCI5nnEkB0La204IX \ 9K7WxElJtB-
a-AtD6E0Mkb2x0A4GlXvr8wpYASrQHlLPeQbOGXrQZpb3_PdWkI6pgFSefCF \
dCJvecRd5n2KIF6G5yPt_6_9-nZt3YUJGDPqvyX1IpX4J4No3hAEAAinMjhuU4fL4r9xCBm
\
vqzgduPnDdAfkMTQHawXvsWHQ1MoSNQ4qHpXTZ25QMFyNq41ZigeJ6me_l7ibgW4ih1hCoC
\ zrzgmfYRcf-
Mw8Zm0N5SpsuFIRpJBJzZrj2ofDyTTxLVNedu2GwmL8y2Y6ogZ975KX_uino \
ixqZbGzf0ysEi8Ks_6KIcBgUR_zItvl7Y8R8sBPG89hMvQdhmlw1WwAJEQ
A.3.2. 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 / ] )
A.3.3. JWS Complete Example
eyJhbGciOiJTUUlzaWduLUw1IiwidHlwIjoiSldUIn0 .
2BxNjXNPy_vq3j0_igOfqiosmVfoNa1Vsi51v1e7VWrI .
a47112iaHqHPzpxvdJXjCenR0bA-Yc2XCI5nnEkB0La204IX9K7WxElJtB-
a-AtD6E0Mkb2x \
0A4GlXvr8wpYASrQHlLPeQbOGXrQZpb3_PdWkI6pgFSefCFdCJvecRd5n2KIF6G5yPt_6_9-
\
nZt3YUJGDPqvyX1IpX4J4No3hAEAAinMjhuU4fL4r9xCBmvqzgduPnDdAfkMTQHawXvsWHQ1
\ MoSNQ4qHpXTZ25QMFyNq41ZigeJ6me_l7ibgW4ih1hCoCzrzgmfYRcf-
Mw8Zm0N5SpsuFIRp \
JBJzZrj2ofDyTTxLVNedu2GwmL8y2Y6ogZ975KX_uinoixqZbGzf0ysEi8Ks_6KIcBgUR_zI
\ tvl7Y8R8sBPG89hMvQdhmlw1WwAJEQ
Appendix B. Implementation Status
[RFC Editor: Please remove this section before publication]
This section records the status of known implementations at the time
of writing.
Mott Expires 6 December 2026 [Page 30]
Internet-Draft cose-sqisign June 2026
B.1. Open Source Implementations
B.1.1. 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
B.1.2. Rust Implementation
* *Organization*: IETF - Community implementation
* *Repository*: IETF
* *Language*: Rust
* *License*: IETF
* *COSE Support*: Planned
* *Status*: Development
B.2. Commercial Implementations
[RFC EDITOR: To be populated as vendors implement]
B.3. Interoperability Testing
* *Test Suite Location*: IETF
* *Participating Organizations*: IETF
Appendix C. Design Rationale
C.1. Algorithm Identifier Selection
The requested algorithm identifiers (-61, -62, -63) are:
* In the Standards Action range (-255 to -1) per RFC 9053
Mott Expires 6 December 2026 [Page 31]
Internet-Draft cose-sqisign June 2026
* 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
C.2. 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
Appendix D. Change Log
[RFC Editor Note:** Please remove this section before publication]
D.1. draft-mott-cose-sqisign-06
* fixed typos
D.2. 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
Mott Expires 6 December 2026 [Page 32]
Internet-Draft cose-sqisign June 2026
* added informational resource for interactive working code public
testbed
* updated after SQISign advances to NIST round 3 with 8 other
candidates
Author's Address
Antony R. Mott
RustyKey®
United States of America
Email: antony@rustykey.io
Mott Expires 6 December 2026 [Page 33]