South Korean payments heavyweight Toss has launched a strategic, three-month technology trial with Optimism and Sunnyside Labs to explore whether blockchain infrastructure can underpin won-linked stablecoins and institutional payment systems in Korea.
What they’re testing
- A proof-of-concept (PoC) to see if public-blockchain tech can meet Korea’s regulatory and operational needs for fiat-denominated digital payments.
- Whether financial institutions can directly handle payment and settlement flows while complying with KYC and AML rules.
- Methods to keep sensitive transaction details private on a public ledger while still allowing regulated parties to verify and audit activity.
- The ability of the system to support high transaction volumes typical of mass-market payment services.
Who’s involved and what they bring
- Toss: the South Korean fintech “super app,” with roughly 30 million users and acceptance at more than 500,000 online and offline merchants, will lead experiments across its payment and platform services. Toss says it intends to scale blockchain-based trials gradually if the PoC succeeds.
- Optimism: providing the blockchain foundation via its OP Stack — a modular framework for application-specific chains that rely on Ethereum for security and final settlement. Layer 2s like Optimism process transactions off-chain then post finality to Ethereum, reducing costs and increasing throughput. Toss will test whether an OP Stack-backed, dedicated chain can better serve Korean digital payments than shared public infrastructure.
- Sunnyside Labs: a core Optimism developer, bringing Privacy Boost — a privacy layer designed to hide transaction-level details and wallet balances on public blockchains while preserving verifiability for regulated institutions.
Why privacy and compliance matter
Public blockchains’ transparency is at odds with many financial regulations. Privacy Boost aims to bridge that gap by enabling confidentiality for sensitive data without preventing institutions from performing required compliance checks. That capability is central to the three-month technical assessment.
Context and broader adoption
Optimism’s OP Stack is already powering more than 30 networks — including projects from Sony, World Chain, Uniswap, OKX Layer and Kraken — and has been promoted for institutional deployments. Regulated firms such as Bitpanda have adopted Optimism’s tech for production use. The Toss pilot therefore joins a growing wave of institutional experiments with OP Stack-based solutions.
Timing and recent Optimism work
The partnership follows Optimism’s recent four-week experiment on its OP mainnet that tested stake-based transaction ordering alongside the existing gas-fee model. That pilot explored whether staking incentives could improve transaction prioritisation without changing the everyday user experience, and adds to Optimism’s ongoing infrastructure development.
Bottom line
The Toss–Optimism–Sunnyside PoC is a notable step in testing whether Layer 2 and privacy tools can deliver a regulatory-compliant, high-performance platform for won-linked stablecoins and large-scale payment services in Korea. Results from the next three months will be watched closely by payments firms and regulators considering the practical rollout of currency-linked digital assets.
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