Sebastien Rousseau
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Unveiling a new Cryptocurrency and Faster Payment Solution

A new cryptocurrency and faster-payments solution for the next-generation of finance.

6 min read
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A very tall building that has a lot of holes in it

Executive Summary / Key Takeaways

  • The core hypothesis. Ethereum smart contracts could replace the correspondent-banking relay race for cross-border payments, settling in seconds rather than days and eliminating the 3–7% fee layer (World Bank, 2018).
  • ERC-223’s specific contribution. The standard fixed the silent-token-loss flaw in ERC-20 by requiring smart contracts to expose a tokenFallback function, making failed transfers revert rather than burn tokens irreversibly (Ethereum EIPs).
  • EXTC’s payment primitives. The token design supported single atomic transfers, time-triggered standing orders, multi-signature corporate disbursements, and instant collateral-backed micro-loans — all without a clearing institution.
  • What the experiment revealed. The technical design was coherent, but Ethereum mainnet in 2018 processed roughly 15 transactions per second. Payment volume at scale required Layer-2 solutions that were not yet production-ready.
  • Legacy. The architectural ideas in EXTC — programmable money, atomic settlement, compliance-embedded token logic — reappeared in later DeFi protocols, CBDC designs, and tokenised deposit frameworks.

The Problem: Cross-Border Payments in 2018 #

International payments in early 2018 were slow, expensive, and opaque by design. A retail transfer from the United Kingdom to Southeast Asia typically involved two to four correspondent banks, each charging a fee and adding a day to the settlement chain. The World Bank’s Remittance Prices Worldwide database recorded a global average cost of 6.9% for a USD 200 remittance in Q1 2018.

Cryptocurrency had already demonstrated that peer-to-peer digital cash was technically feasible. Bitcoin settled transactions globally in roughly ten minutes, and Ethereum’s programmable layer added smart contracts — self-executing code that could encode payment rules directly into the transfer itself. The gap between what was technically possible on-chain and what legacy correspondent banking delivered was the design space EXTC entered.

The Technical Foundation: ERC-20 and Its Flaw #

The ERC-20 standard, formalised in Ethereum Improvement Proposal 20, defined the canonical interface for fungible tokens: balanceOf, transfer, transferFrom, approve, and allowance. By early 2018, ERC-20 was the dominant token standard, with hundreds of tokens deployed on mainnet.

However, ERC-20 had a structural problem. When tokens were sent directly to a smart contract address using the standard transfer function, the contract had no way to detect the incoming transfer or act on it. Tokens sent this way were permanently trapped. The Ethereum community estimated that millions of dollars in ERC-20 tokens had been lost this way by mid-2018.

ERC-223, proposed by Dexaran on the Ethereum GitHub issue tracker, addressed this by adding a tokenFallback(address _from, uint _value, bytes _data) function requirement on receiving contracts. If the receiving contract did not implement tokenFallback, the transfer reverted and the tokens were returned to the sender. This made ERC-223 transfers atomic: either the contract accepted the tokens and executed its logic, or the transaction failed cleanly.

The EXTC Token Design #

The Express Transaction Credits token was designed around five core attributes:

Payment Primitives the Platform Targeted #

EXTC’s architecture was designed to replace four specific payment workflows that legacy systems handled inefficiently:

Single atomic payments — a one-time transfer that settled in a single Ethereum transaction, typically within 15–30 seconds on the 2018 mainnet.

Time-based standing orders — recurring transfers encoded as time-locked smart contract calls, eliminating the need for a bank to receive and re-execute periodic instructions.

Corporate mass disbursements — batch payments to multiple recipients in one transaction, with each individual transfer requiring multi-signature authorisation, reducing cost and counterparty risk.

Collateral-backed instant loans — borrowers locked EXTC tokens as collateral in a smart contract; the contract released loan proceeds automatically upon receipt, without a credit committee or underwriting delay.

What the Experiment Revealed #

The EXTC design was technically coherent. The ERC-223 foundation resolved the most significant safety flaw of the dominant token standard, and the payment primitives mapped directly to real workflows that correspondent banking handled inefficiently.

The practical constraint was Ethereum’s throughput. In Q1 2018, mainnet averaged 15 transactions per second with a gas limit of approximately 8 million per block. A payment network processing even a small fraction of global remittance volume — the World Bank estimated 270 million migrants sending money home in 2017 — would have saturated mainnet within minutes.

Layer-2 scaling solutions, particularly state channels and the early versions of what became rollup technology, were under active research in 2018 but were not production-ready. The Lightning Network had just launched on Bitcoin mainnet in January 2018 with significant caveats. The technical preconditions for a blockchain-based payment network to operate at correspondent-bank scale did not yet exist.

The Ideas That Survived #

Several architectural concepts from EXTC and contemporaneous payment token projects were validated by subsequent development:

Programmable money — encoding payment rules directly in the transfer logic — became a central feature of DeFi lending protocols such as Compound and Aave, launched in 2018 and 2020 respectively.

Atomic settlement without clearing houses — the property that a transfer either succeeds completely or reverts — is now a design requirement in tokenised deposit frameworks and wholesale CBDC architectures explored by central banks including the Bank of England and the European Central Bank.

Compliance-embedded tokens — transfer restrictions and reporting obligations encoded in the token contract itself — appear in regulated token standards such as ERC-1400 (security tokens) and in the compliance layer designs for Project Agorá and similar multi-central-bank tokenisation experiments.

The EXTC experiment did not reach production scale, but the questions it asked — about programmable settlement, atomic transfers, and self-enforcing payment rules — were the right questions for 2018. The infrastructure required to answer them took five more years to mature.

Questions? Answers.

What was ERC-223 and why did EXTC use it instead of ERC-20?

ERC-20 tokens sent directly to smart contract addresses were silently lost because contracts had no way to detect the incoming transfer. ERC-223 fixed this by requiring recipient contracts to implement a tokenFallback function; if the function was absent, the transfer reverted rather than burning the tokens. EXTC adopted ERC-223 to make all on-chain transfers atomic and safe.

Why did early payment token projects not scale to replace correspondent banking?

Ethereum mainnet in 2018 processed roughly 15 transactions per second. Global remittance volumes alone — not counting trade finance or corporate payments — would require tens of thousands of transactions per second. The Layer-2 scaling infrastructure needed to reach that throughput was not production-ready until 2021–2023.

What happened to the ideas behind EXTC?

The core concepts — programmable payment rules, atomic settlement, compliance-embedded token logic — were adopted by DeFi protocols, regulated security token standards (ERC-1400), and central bank digital currency research. Tokenised deposit frameworks now being piloted by commercial banks trace directly to the design questions that early payment token experiments like EXTC first asked.

How does the 2018 EXTC design compare to 2026 tokenised deposit proposals?

The settlement model is similar — tokens representing monetary claims, transferred atomically on a distributed ledger. The key differences are: (1) 2026 tokenised deposits are commercial bank liabilities rather than bearer tokens; (2) they operate on permissioned or hybrid ledgers with regulatory oversight rather than public mainnet; (3) compliance and identity verification are enforced at the protocol layer rather than left to participants.

References #

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