Cryptography & Digital Signatures
Post-Quantum Signing: Software HSM & Crypto-Agility with ML-DSA and SLH-DSA
Modular quantum-resistant digital signature engine based on the newly standardized NIST FIPS 204 and FIPS 205 specifications.
Standards
NIST FIPS 204 & FIPS 205
ML-DSA Throughput
> 1,400 signs/sec on standard CPU
Verification Latency
< 0.4ms per document
NIST Vectors
100% official test vectors passed
01 · The Engineering Challenge
The impact of Q-Day on digital signature trust
The eventual arrival of Cryptographically Relevant Quantum Computers (CRQCs) will break classical asymmetric algorithms (RSA, ECDSA, Ed25519) via Shor’s algorithm. Regulated entities issuing legal contracts and identity certificates must prepare now (Store Now, Decrypt Later). However, post-quantum cryptography introduces significant performance and storage penalties.
Key risks addressed:
- Key and signature size blowup: ML-DSA-44 signatures are 2,420 bytes (compared to Ed25519's 64 bytes), exhausting database columns, HTTP headers, and X.509 envelopes.
- Migration friction: big-bang cutovers break backward compatibility with existing document verifiers.
- Hardcoded cryptography in legacy architectures where algorithms are tightly coupled to business code.
02 · Architecture & System Design
Dual-Engine Cryptographic Abstraction Pattern
A decoupled Provider architecture isolates business signature requests from underlying crypto math. It supports lattice-based signatures (ML-DSA / CRYSTALS-Dilithium) for high throughput and hash-based signatures (SLH-DSA / SPHINCS+) as a conservative zero-lattice backup.
Core modules & responsibilities:
CryptoProvider Dispatcher
Selects appropriate post-quantum or classical engines based on document sensitivity and latency requirements.
ML-DSA WebAssembly Engine
High-performance polynomial arithmetic implementation for lattice operations.
SLH-DSA Engine
Stateless hash-based signature engine providing a conservative fallback independent of lattice mathematics.
CMS / X.509 Packager
Generates ASN.1 envelopes compatible with hybrid certificate chains.
Benchmarking Harness
Measures throughput, verification speeds, and heap allocations under continuous workloads.
03 · Engineering Decisions & Trade-offs
Every technical choice prioritizes reducing operational risk and maintaining system clarity.
WebAssembly for lattice polynomial computation in Node/TypeScript
Rationale: Delivers near-native C throughput for Number Theoretic Transforms (NTT) while maintaining universal TypeScript portability.
Explicit trade-off: Requires linear memory management and explicit buffer copies across the JS/WASM boundary.
Hybrid cryptographic envelope (RSA/ECDSA + ML-DSA concurrently)
Rationale: Ensures signed documents can be verified by today's verifiers while remaining mathematically secure after quantum breakthroughs.
Explicit trade-off: Doubles the signature payload footprint in stored documents.
Strict adherence to finalized NIST FIPS 204 & 205 specifications
Rationale: Avoids technical debt from pre-standardization drafts and guarantees interoperability with federal and international compliance frameworks.
Explicit trade-off: Required rebuilding test vectors and padding logic to match the official 2024-2026 standards.
Engineered Benchmarks & Architecture Roadmap
This work provided the technical blueprint for post-quantum modernization strategies in enterprise digital signature infrastructures, proving that crypto-agility can be deployed without unacceptable latency.
Professional discussion
Does your company handle digital signatures, PKI, or long-term identity?
Let’s plan a concrete crypto-agility and post-quantum migration strategy tailored to your legacy systems and regulatory requirements.