- COTI solved Yao’s ‘Millionaires Problem’ on Ethereum’s Sepolia testnet using Garbled Circuits with no trusted intermediaries.
- The solution was developed with Soda Labs, is live on mainnet, and is compatible with the EVM environment and Solidity.
- Vitalik Buterin had publicly identified Garbled Circuits as the path toward purely cryptographic guarantees in multiparty computation.
COTI solved Yao’s ‘Millionaires Problem’ on Ethereum’s Sepolia testnet using Garbled Circuits, with no trusted intermediaries and end-to-end encryption. The demonstration was published this week. It is the first practical solution to this foundational challenge of secure multiparty computation —known as MPC— on Ethereum’s public infrastructure.
The problem was formulated in 1982 by scientist Andrew Yao: how can two parties determine which one holds more wealth without either revealing their actual value? For more than four decades, that question served as the ultimate benchmark for any system aspiring to execute verifiable private computation. COTI had already solved this challenge on its own network in February 2025. The transition to Sepolia extends that capability into the Ethereum ecosystem.
COTI Injects Garbled Circuits Into the Heart of Ethereum
In the demonstration, two parties enter private values representing their wealth. Neither exposes their actual data to the counterparty or to the network. The computation operates over encrypted data and produces a verifiable result —who holds more— without any plaintext value being recorded on-chain. The entire process operates with no centralized trust setup or privileged actor of any kind.
The implementation was developed in collaboration with Soda Labs and has been live on COTI’s mainnet since March 2025. The gcEVM engine, compatible with EVM, allows developers to write confidential smart contracts in Solidity using standard tools like Hardhat, incorporating privacy parameters to leverage MPC capabilities.
Privacy-on-Demand
The deployment on Sepolia anticipates the arrival of Privacy-on-Demand, COTI’s initiative to extend Garbled Circuits as a service layer to Ethereum and other chains. The proposal targets specific use cases: protection of execution parameters in DeFi protocols, handling of private data in institutional applications, and governance voting systems in decentralized settings without exposure of individual inputs.
Vitalik Buterin, co-founder of Ethereum, publicly stated that Garbled Circuits are the path toward purely cryptographic security guarantees in multiparty computation. At ETH Tokyo 2025, Buterin also highlighted their speed compared to more complex forms of MPC and the range of cases where the technology delivers real value. COTI is the only project that responded directly to that call.
