USDCx-Bridge (TorramChain x Circle Integration)

Overview

This repository contains the CosmWasm smart contract for TorramChain’s integration with Circle’s Unified Bridge (CUB).
The contract enables issuance and redemption of USDCx on Cosmos, ensuring every USDCx remains fully backed 1:1 by native USDC held in Circle’s custody, while meeting Circle’s security and audit requirements.

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Phase 1 – Contract Development

Timeline: Weeks 1–2 of the integration roadmap
Deliverable: Auditable CosmWasm USDCx contract aligned with Circle’s token specification

Implemented Features

• Mint with Circle Attestation
  • Entry point: execute_mint
  • Verifies Circle attestation signature (secp256k1) (stubbed in Phase 1)
  • Enforces nonce replay protection
• Burn with BurnIntent
  • Entry point: execute_burn
  • Emits BurnIntent event for Circle relayer submission
• Attester Management
  • Admin-only control via SetAttester
  • Maintains attester allow-list on-chain
• Nonce Replay Protection
  • Each mint/burn requires a unique nonce
  • Used nonces tracked in storage
• Query Endpoints
  • VerifyNonce: check if a nonce has been used
  • IsAttester: check if an address is an authorized attester

Code Structure

• contract.rs – Core entry points (instantiate, execute, query)
• state.rs – Storage for config, attesters, and nonces
• error.rs – Custom errors (Unauthorized, NonceUsed, InvalidAttestation)
• helpers.rs – Wrappers for relayer integration and testing

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Roadmap

Phase	Description	Status
Phase 1	Contract development (mint, burn, attesters, nonces, unit tests)	Complete
Phase 2	Attester infrastructure (secure KMS/HSM keys, rotation)	⏳ Pending
Phase 3	Relayer integration (Circle APIs: /attestation, /withdraw)	⏳ Pending
Phase 4	Monitoring & governance (supply checks, withdrawal limits, pause)	⏳ Pending
Phase 5	External audit & fixes	⏳ Pending
Phase 6	Circle review & production launch	⏳ Pending

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Development

Build Contract

cargo wasm

Run Tests

cargo test

Generate Schemas

cargo schema

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Status

Phase 1 complete: USDCx CosmWasm contract with mint, burn, attester management, nonce replay protection, and attestation verification stub.
Next: Phase 2 – provision secure attester infrastructure and prepare for Circle relayer integration.