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Overview

The cctp-go SDK provides a comprehensive Go implementation for Cross-Chain Transfer Protocol (CCTP) V2 integration. It offers high-level abstractions for cross-chain USDC transfers with built-in chain configurations, contract bindings, and transfer orchestration.

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Package Structure

The SDK is organized into several key packages: 
cctp/
├── chains.go                  # Chain configurations and lookup functions
├── client.go                  # Iris API client for attestations
├── transfer.go                # Transfer orchestration and workflow
├── tokenmessenger/            # TokenMessengerV2 contract bindings
│   └── tokenmessenger.go
├── messagetransmitter/        # MessageTransmitterV2 contract bindings
│   └── messagetransmitter.go
└── internal/
    ├── wallet/                # Wallet management utilities
    └── util/                  # Helper functions

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Core Components

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Chain Configuration

Chain Type

The Chain struct contains all necessary configuration for interacting with CCTP-enabled chains:
  • Chain metadata (name, ID, domain)
  • Contract addresses (TokenMessengerV2, MessageTransmitterV2, USDC)
  • RPC endpoints and explorer URLs
  • Finality characteristics
chains.go:24
type Chain struct {
    Name                 string
    ChainID              *big.Int
    Domain               uint32
    RPC                  string
    TokenMessengerV2     string
    MessageTransmitterV2 string
    USDC                 string
    Explorer             string
    IsTestnet            bool
    InstantFinality      bool
}

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Iris Client

IrisClient

Handles communication with Circle’s Iris attestation service for:
  • Fetching attestations for completed burns
  • Polling for attestation availability
  • Querying transfer fees
client.go:79
type IrisClient struct {
    baseURL    string
    httpClient *http.Client
}

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Transfer Orchestrator

TransferOrchestrator

Coordinates the complete transfer workflow:
  • Balance and allowance checks
  • Token approval if needed
  • Burn transaction on source chain
  • Attestation polling
  • Mint transaction on destination chain
transfer.go:83
type TransferOrchestrator struct {
    wallet       *wallet.Wallet
    irisClient   *IrisClient
    sourceClient *ethclient.Client
    destClient   *ethclient.Client
    params       *TransferParams
}

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Contract Bindings

V2 Bindings

Auto-generated Go bindings for CCTP V2 contracts:
  • TokenMessengerV2: Handles burn operations
  • MessageTransmitterV2: Handles message reception and minting
  • IERC20: Standard ERC-20 interface for approvals

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Design Principles

1

Type Safety

Uses Go’s type system to prevent common errors. Contract addresses, chain IDs, and domains are validated at compile time.
2

Abigen V2

Built on Ethereum’s abigen v2 library for improved contract interaction patterns and better error handling.
3

Configurability

Allows RPC endpoint customization while providing sensible defaults for all supported chains.
4

Error Handling

Provides detailed error messages and context for debugging failed transfers.

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Usage Pattern

A typical integration follows this flow: 
// 1. Get chain configurations
sourceChain, _ := cctp.GetChainByName("Ethereum", false)
destChain, _ := cctp.GetChainByName("Avalanche", false)

// 2. Create wallet from private key
wallet, _ := wallet.NewWallet(privateKey)

// 3. Set up transfer parameters
params := &cctp.TransferParams{
    SourceChain:      sourceChain,
    DestChain:        destChain,
    Amount:           amount,
    RecipientAddress: recipient,
    TransferType:     cctp.TransferTypeAuto,
}

// 4. Create orchestrator
orchestrator, _ := cctp.NewTransferOrchestrator(
    wallet,
    params,
    "https://iris-api.circle.com",
)

// 5. Execute transfer
updates := make(chan cctp.TransferUpdate)
go orchestrator.Execute(ctx, updates)

// 6. Monitor progress
for update := range updates {
    fmt.Printf("Step: %s - %s\n", update.Step, update.Message)
}

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Next Steps

Chain Configuration

Explore chain lookup functions and configuration

Iris Client

Learn about attestation polling and retrieval

Transfer Orchestrator

Deep dive into transfer workflow execution

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