Glossary
Every load-bearing term used across sebastienrousseau.com is defined here against its canonical standards-body or central-bank source. Each entry carries a sameAs link in the JSON-LD pointing to the primary specification — NIST FIPS publications for the cryptographic terms, the ISO catalogue for messaging standards, EUR-Lex for EU regulation, BIS / CPMI / ECB / Federal Reserve documents for payment-systems vocabulary.
The list is short by design. Terms graduate to this page only once they appear in at least three articles and carry a primary-source citation. Acronyms that show up once in passing are defined inline in the article, not here.
If a term you expected to find is missing, email contact@sebastienrousseau.com with the article context and we will add it.
Post-quantum cryptography
ML-KEM — Module-Lattice-Based Key-Encapsulation Mechanism
NIST-standardised post-quantum key-encapsulation mechanism, published as FIPS 203 in August 2024. Based on the CRYSTALS-Kyber lattice scheme that won the third round of the NIST post-quantum standardisation competition. Replaces RSA / ECDH key agreement in TLS, IKE, and SWIFT messaging where quantum resistance is required.
Parameter sets: ML-KEM-512 (Category 1, ~AES-128), ML-KEM-768 (Category 3, ~AES-192), ML-KEM-1024 (Category 5, ~AES-256). Public-key sizes are 800 / 1184 / 1568 bytes respectively — substantially larger than ECDH P-256's 65 bytes but practical at TLS handshake scale.
ML-DSA — Module-Lattice-Based Digital Signature Algorithm
NIST-standardised post-quantum digital signature scheme, published as FIPS 204 in August 2024. Based on CRYSTALS-Dilithium. Replaces RSA / ECDSA signatures in code-signing, TLS certificates, payment authorisation, and document signing where quantum resistance is required.
Parameter sets: ML-DSA-44 (Category 2), ML-DSA-65 (Category 3), ML-DSA-87 (Category 5). Signature sizes range from 2420 to 4595 bytes — large enough to affect packet fragmentation strategies for certificate chains, manageable for code-signing and payment-message use.
Messaging standards
ISO 20022 — Universal financial industry message scheme
ISO standard for electronic data interchange between financial institutions. Defines an XML / JSON message syntax — pacs.008 (customer credit transfer), pain.001 (initiation), camt.054 (notification), and several hundred others — carrying structured remittance, party, and regulatory data.
Mandatory for SWIFT cross-border payments from November 2022, with full adoption by November 2025. T2 (the eurozone RTGS) migrated in March 2023, the Fedwire Funds Service in March 2025, CHAPS in stages through 2024. ISO 20022 is the data layer underneath every modern wholesale-payments programme.
Catalogue: iso.org/standard/76074.
SWIFT gpi — Global Payments Innovation
SWIFT's cross-border-payments service introduced in 2017, providing same-day settlement, end-to-end tracking via a UETR (Unique End-to-end Transaction Reference), and full transparency on fees and FX. Carries 90%+ of cross-border value across SWIFT today. Fully on ISO 20022 from November 2025.
Specification: swift.com/our-solutions/swift-gpi.
Settlement infrastructure
RTGS — Real-Time Gross Settlement
An interbank payment system that settles each transfer individually and irrevocably in central-bank money at the moment it is processed, with no netting. The settlement layer for wholesale payments above retail thresholds. Examples: Fedwire (US), CHAPS (UK), T2 (eurozone), CHATS (Hong Kong), CNAPS (mainland China).
The canonical reference is BIS CPMI's Principles for Financial Market Infrastructures (PFMI), 2012.
FedNow
Federal Reserve instant-payment rail launched July 2023. 24/7/365 settlement in central-bank money, ISO 20022 messaging end-to-end, transaction cap raised from $100,000 to $500,000 in February 2024. Sits alongside The Clearing House's RTP rail (live since November 2017) for US instant payments — the two rails are interoperable at the participant tier but settle separately.
Reference: federalreserve.gov/paymentsystems/fednow_about.htm.
Digital money
CBDC — Central Bank Digital Currency
A central-bank-issued digital liability, denominated in the sovereign unit of account, available either retail (to households) or wholesale (to financial institutions). Distinct from commercial-bank money (a claim on the issuing bank), from e-money (a claim on a non-bank issuer), and from crypto-assets (no issuer at all).
Live or actively piloted across 130+ jurisdictions per the BIS survey. Notable production-grade examples: Bahamas Sand Dollar (2020), Jamaica JAM-DEX (2022), Nigeria eNaira (2021). Notable wholesale pilots: Project Agorá (BIS), Project Mariana (BIS / Banque de France / MAS / SNB), Project mBridge.
Tokenised deposits
Commercial-bank deposits issued as transferable tokens on a programmable ledger, preserving the depositor's claim on the issuing bank. Distinct from stablecoins (non-bank issuers, often money-market-fund-backed) and from CBDC (central-bank liability). Programmable, atomic-settlement-capable, and — crucially — inside the deposit-insurance perimeter (FDIC, FSCS, ESM coverage).
Reference: BIS Working Paper 1101, The tokenisation continuum, April 2023.
Regulation
DORA — Digital Operational Resilience Act
EU Regulation 2022/2554 establishing uniform ICT risk-management, incident-reporting, resilience-testing, and third-party-risk requirements for financial entities. In force from 17 January 2025.
Applies to banks, insurers, investment firms, crypto-asset service providers, trade repositories, central counterparties, and — for the first time in EU financial regulation — directly to critical ICT third-party providers (CTPPs) through a designation regime operated by the European Supervisory Authorities.
PSD3 — Third Payment Services Directive
EU proposal succeeding PSD2 (Directive 2015/2366), tightening fraud-prevention, strong-customer-authentication, and open-banking access regimes. Paired with the Payment Services Regulation (PSR) for directly-applicable rules across the EU.
Commission proposal: COM/2023/366, 28 June 2023. Political agreement expected during 2026; member-state transposition runs through 2027–2028.
Revision history
- 2026-06-02 — Initial publication. Seeded with 10 terms across post-quantum cryptography, messaging standards, settlement infrastructure, digital money, and regulation. Quarterly review.