1 millimeter Exchange is a web-based cross-chain DEX that lets anyone swap assets between Ethereum Holesky and the Internet Computer in a single click. 
Powered by 1inch Fusion+ intents, an on-chain ICP ↔ ETH bridge and atomic HTLC escrow, every swap is permissionless, MEV-protected and either completes or fully reverts. 
The frontend is a lightweight React dApp—connect MetaMask, confirm, done.

1 millimeter Exchange – Technical Deep-Dive

Project Goal

Provide a seamless, trust-minimised bridge for value between Ethereum (Holesky) and the Internet Computer. The user experience must resemble a single-chain swap: connect MetaMask, sign once, and watch funds arrive on the other chain without juggling RPCs or bridges.

Tech Stack

| Layer | Technology | Purpose | |-------|------------|---------| | Smart Contracts | Solidity 0.8.x | Escrow, Hash-Time-Lock, Fusion Resolver, ICP Bridge contracts | | | Motoko / Rust canisters | ICP-side resolver & ledger interactions | | Intents | 1inch Fusion+ | MEV-proof limit-order execution on the ETH side | | Relayer | Node 18, ethers.js, @dfinity/agent | Listens for escrow events, forwards proofs cross-chain, triggers ICP canisters | | Frontend | React 18, Vite, TailwindCSS | Single-page dApp with wallet hooks | | | canvas-confetti | Visual confirmation burst on swap completion | | | react-icons | Chain & token glyphs |

Deployment Targets

• Ethereum Holesky test-net (verified source code)
• Internet Computer main network (canister IDs baked into build)

Scripts / Tooling

• generate-config.sh – bootstraps every .env from one prompt
• deploy-holesky.sh – Foundry script deploying all ETH contracts and writing addresses to disk
• verify-deployment.sh – Hardhat + Etherscan API verification helper
• monitor-system.sh – bash script hitting health endpoints (relayer & RPC status)

Key Features

1. Intent-Based Swaps – users post intents executed by off-chain solvers; the Fusion Resolver enforces price and deadline on-chain.
2. HTLC Safety Net – both sides must reveal the same secret within their time-lock window; otherwise funds automatically refund.
3. Progress Overlay – centre-screen modal shows staged messages (sign → swapping → almost done → success tick).
4. Token Lore & Onboarding Panels – gamified educational panels flanking the swap UI.

Challenges & Solutions

| Challenge | Solution | |-----------|----------| | Bridging two execution environments (EVM vs IC) | Lightweight relayer using @dfinity/agent to sign ingress messages and submit proofs back to ETH. | | Preserving UX despite cross-chain latency | 10-second staged overlay keeps the user informed while the relayer completes the remote leg. | | MEV protection on L2 test-net | Leveraged 1inch Fusion+ Dutch-auction intents which are natively resistant to sandwich attacks. | | Handling two wallet paradigms | MetaMask for ETH, Internet Identity for ICP, stitched together with a shared React context so components can query ethConnected / icpConnected. | | Gas optimisation | Foundry benchmarks drove inline assembly in the resolver, achieving < 190 k gas per swap intent fulfilment. |

Future Work

• Multi-hop routing (e.g. Holesky → Base → ICP)
• Zero-knowledge proofs replacing HTLCs for lower latency
• Mobile wallet deep-links & WalletConnect 2.0

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