Sebastien Rousseau
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Black and White Portrait of Sebastien Rousseau

Sebastien Rousseau

Securing the future of banking
with agentic AI
and post-quantum cryptography.

Built for the edge. Architected for uncompromising resilience. Powering the next generation of global payments.

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For decision makers

Where this work shows up
on the balance sheet.

The open-source libraries below aren’t research curios. Each one maps to a board-level risk a Tier-1 bank is being asked to evidence under DORA, BCBS 239, Basel III or NIST CSF 2.0 — and shaves real cost off the audit trail that satisfies the regulator.

Compliance

DORA Article 5 & BCBS 239 evidence

Lossless parsing, signed releases and structured ISO 20022 outputs mean the configuration and payment files that move money are auditable end-to-end. Less to defend in your next supervisory exam.

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Cost reduction

Open source over proprietary licensing

Apache-2.0 / MIT replaces six- and seven-figure vendor contracts on pain.001 generation, statement parsing and edge security tooling. Audit-grade quality without the per-seat fee.

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Strategic hedging

Post-quantum cryptography readiness

KyberLib gives your team an inspectable, NIST FIPS 203-aligned implementation of ML-KEM today — ready for the SWIFT structured-address cutover and the longer harvest-now-decrypt-later horizon.

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Authored & maintained

Open source for the
future of finance.

A portfolio of Python, Rust and JavaScript libraries I created and maintain. Open source, free to use, and applied to wholesale payments, cross-border settlement, financial data and quantum-resistant cryptography.

pain001 logo. Open-source ISO 20022 payment file automation by Sebastien Rousseau
Python · Payments

pain001

Problem
Hand-authoring ISO 20022 pain.001 is fragile under SEPA and SWIFT cutovers.
Approach
Schema-driven Python that maps CSV or SQLite into validated payment XML.
Outcome
Ops ship pain.001 in minutes; the audit trail survives the migration.

Impact ISO 20022 · SEPA + SWIFT

Learn about pain001

4116Apache-2.0last commit 2mo ago

pacs008 logo. Open-source ISO 20022 pacs.008 toolkit by Sebastien Rousseau
Python · Cross-border

pacs008

Problem
FI-to-FI credit transfers fail audit when XSD, IBAN and PII rules diverge.
Approach
One library: JSON Schema, XSD, IBAN across 75 countries, GDPR-grade masking.
Outcome
Cross-border credit transfers that pass first-time at the regulator.

Impact 75 countries · IBAN

Learn about pacs008

2Apache-2.0last commit 2mo ago

Bank Statement Parser logo. Open-source finance toolkit by Sebastien Rousseau
Python · Finance

Bank Statement Parser

Problem
Statement formats trap reconciliation teams in manual rekeying.
Approach
One Python toolkit that normalises multi-format statements with audit-grade lineage.
Outcome
Reconciliation runs without bespoke per-bank glue code.

Impact Multi-format · Audit-grade

Learn about Bank Statement Parser

215Apache-2.0last commit 1mo ago

Hash HSH logo. Open-source Rust hash library by Sebastien Rousseau
Rust · Security

Hash (HSH)

Problem
Pre-PQC hashing libraries leave credential stores quantum-exposed.
Approach
Memory-safe Rust hash and digest library with a post-quantum posture.
Outcome
Drop-in secure hashing for services planning PQC migration.

Impact Memory-safe · Rust

Learn about HSH

201Apache-2.0last commit 3mo ago

KyberLib logo. Open-source Rust CRYSTALS-Kyber library by Sebastien Rousseau
Rust · Quantum

KyberLib

Problem
Tier-1 banks carry harvest-now-decrypt-later exposure on every TLS session.
Approach
Pure-Rust CRYSTALS-Kyber (NIST FIPS 203) that plugs into existing auth flows.
Outcome
Post-quantum key exchange in production-grade Rust, independently validated.

Impact NIST FIPS 203

Learn about KyberLib

413last commit 3mo ago

noyalib logo. Open-source pure-Rust YAML 1.2 ecosystem by Sebastien Rousseau
Rust · YAML

noyalib

Problem
AI, MCP and config pipelines run on YAML parsers with C-backed UB and silent spec drift.
Approach
Pure-Rust YAML 1.2 across library, CLI, LSP, MCP and WASM — zero unsafe, full spec.
Outcome
YAML pipelines that stop being the supply-chain weak link.

Impact 406 / 406 spec · 0 unsafe

Learn about noyalib

1Apache-2.0last commit 1mo ago

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“Quantum computing threatens the cryptographic foundations of financial services. Payments, from real-time to cross-border settlement, rely on protections that quantum computing will eventually render obsolete.”

Emerging Payments Association Asia (EPAA) · September 2025

Quantum-Safe Payments.

Industry white paper for the Emerging Payments Association Asia. The structural threat quantum computing poses to payment infrastructure, and the case for coordinated action now.

Banner illustration for the EPAA Quantum-Safe Payments white paper

EPAA · September 2025

Why the payments industry must act now.

Regulators are treating harvest-now-decrypt-later as a credible present risk. This paper outlines the structural threat and the urgent case for coordinated action across wholesale payment rails.

Read the white paper

Latest

From the desk.

Recent research and writing on quantum-safe cryptography, ISO 20022 migration and the future of wholesale payments.

Architectural geometry under dramatic light — symbolising NoyaLib's role as the load-bearing safe Rust YAML parser beneath CI, Kubernetes, MCP, and financial-services configuration
Safer Rust YAML Parser · NoyaLib · YAML 1.2

Why YAML Needs a Safer Rust Stack for AI, MCP, and Financial Infrastructure in 2026

NoyaLib is a safer Rust YAML stack — zero unsafe blocks, 406/406 YAML 1.2 spec compliance, lossless Concrete Syntax Tree, JSON-Schema (Draft 2020-12) validation, and MCP/WASM bindings — engineered for AI agents, Kubernetes, CI/CD, and the configuration control plane behind financial infrastructure.

Stage view from the Economist Impact 5th Annual Commercialising Quantum Global 2026 summit in London — symbolising quantum technology's transition from physics research to enterprise-ready workflows
Quantum · Post-Quantum Cryptography · NIST ML-KEM

From Qubits to Profits: Strategic Takeaways from the Economist's 5th Annual Commercialising Quantum Global 2026 Summit

The Economist Impact 5th Annual Commercialising Quantum Global 2026 summit confirmed quantum's pivot to enterprise workflows: $1.3B raised in five months, post-quantum cryptography is a board-level fiduciary issue under SNDL harvesting, quantum sensing is shipping today for GPS-independent navigation, and HSBC's Philip Intallura delivered the directive that waiting for fault-tolerant hardware is an unforced error.

Office worker with voice assistant and laptop — symbolising the structured, machine-readable interbank payment messages that pacs.008 automation makes programmable
Pacs008 · ISO 20022 · Interbank Payments

Building pacs.008 Automation for the ISO 20022 Interbank Era in 2026

pacs008 is an open-source Python toolkit that makes ISO 20022 FI-to-FI customer credit transfer messages programmable — structured addresses, validation, routing, compliance hooks, and the SWIFT November 2026 deadline baked in as defaults.

Aerial view of the City of London at dusk — symbolising the post-quantum migration banks must run from NIST standards into inspectable cryptographic code
KyberLib · Post-Quantum Cryptography · Quantum-Safe Banking

KyberLib and the Post-Quantum Banking Migration in 2026: From Standards to Code

KyberLib turns the post-quantum banking migration from policy paper into inspectable Rust — FIPS 203 ML-KEM key encapsulation, hybrid classical-plus-quantum handshakes, no_std compilation for HSMs, crypto-agile abstraction boundaries, and the DORA Article 5 governance evidence boards now need.

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Experience

Brands along the way.

From global Tier-1 banks to consumer technology. Payments and digital product leadership across HSBC, PayPal, Barclays, Shazam, AKQA and Virgin Group.