crec

CRE Connect SDK

Build the next generation of verifiable applications with secure, blockchain-agnostic event processing and transaction execution — powered by the Chainlink Runtime Environment and Verifiable Network.

What problem does CRE Connect SDK solve?

Building reliable blockchain applications requires handling:

Event Verification Challenges:

• Ensuring events from the blockchain are authentic and haven't been tampered with
• Decoding complex event data from various smart contracts
• Managing multiple signature verification schemes for trust

Transaction Execution Complexities:

• Batching multiple transactions atomically without gas estimation headaches
• Supporting various signature algorithms beyond traditional ECDSA
• Abstracting away account management while maintaining security

How CRE Connect SDK solves it

CRE Connect SDK is a client library for the Chainlink Runtime Environment (CRE), designed to facilitate the development of applications that interact with onchain data and services.

• Receiving verifiable events from the blockchain with high assurance of authenticity
• Sending operations to the blockchain using account abstraction with gas sponsorship

Key Features

• 🔐 Cryptographically Secure: Multi-signature verification ensures event authenticity
• ⛽ Account Abstraction: Batch transactions, gas sponsorship, and multiple signature support
• 🛠️ Developer-Friendly: Rich helper services for common blockchain operations
• 🧱 Modular Design: Use individual components or combine them for complex use cases

Quick Start

Prerequisites

• Go 1.24 or higher - Check with go version
• Basic Go and blockchain knowledge

Installation

go get github.com/smartcontractkit/crec-sdk

Initialize the Client

import "github.com/smartcontractkit/crec-sdk"

client, err := crec.NewClient(
    "https://api.crec.chainlink.com",
    "your-api-key",
)

Event verification is enabled by default using the production DON public keys. See Event Verification Keys for details.

The unified client provides access to all sub-clients:

client.Channels   // Channel CRUD operations
client.Events     // Event polling and verification
client.Transact   // Operation signing and sending
client.Watchers   // Watcher CRUD operations

Using Individual Sub-Clients

If you only need a subset of the SDK's functionality, create individual sub-clients using NewAPIClient:

import (
    "github.com/smartcontractkit/crec-sdk"
    "github.com/smartcontractkit/crec-sdk/channels"
    "github.com/smartcontractkit/crec-sdk/watchers"
)

// Create an authenticated API client
api, err := crec.NewAPIClient(
    "https://api.crec.chainlink.com",
    "your-api-key",
)

// Create only the sub-clients you need
channelsClient, _ := channels.NewClient(&channels.Options{APIClient: api})
watchersClient, _ := watchers.NewClient(&watchers.Options{
    APIClient:    api,
    PollInterval: 5 * time.Second,
})

Core Workflows

🔍 Receiving and Verifying Events

graph LR
    A[Smart Contract Event] --> B(DON Consensus) --> C(Event Signing) --> D{CREC API} --> E[SDK: Events Client] --> F[Verify Signatures] --> G[Your Logic]

Poll and verify events:

// Poll events from a channel
events, hasMore, _ := client.Events.Poll(ctx, channelID, nil)

for _, event := range events {
    // CRITICAL: Always verify before processing
    verified, _ := client.Events.Verify(&event)
    if verified {
        var decoded map[string]interface{}
        client.Events.Decode(&event, &decoded)
        processEvent(decoded)
    }
}

⚡ Sending Signed Operations (Gas-less)

graph LR
    A[Build Operation] --> B[Sign] --> C[SDK: Transact Client] --> D{CREC API} --> E[Pays Gas & Relays] --> F[Smart Account Executes]

Build and execute an operation:

import (
    "github.com/smartcontractkit/crec-sdk/transact/signer/local"
    "github.com/smartcontractkit/crec-sdk/transact/types"
)

// Build the operation
operation := &types.Operation{
    ID:      big.NewInt(time.Now().Unix()),
    Account: accountAddress,
    Transactions: []types.Transaction{
        {To: target, Value: big.NewInt(0), Data: calldata},
    },
}

// Create signer and execute
signer := local.NewSigner(privateKey)
result, _ := client.Transact.ExecuteOperation(ctx, channelID, signer, operation, chainSelector)

Documentation

API Reference

For complete API documentation, use Go's built-in documentation tools:

go doc github.com/smartcontractkit/crec-sdk
go doc github.com/smartcontractkit/crec-sdk/events
go doc github.com/smartcontractkit/crec-sdk/transact
go doc github.com/smartcontractkit/crec-sdk/channels
go doc github.com/smartcontractkit/crec-sdk/watchers

Or run a local documentation server:

go install golang.org/x/pkgsite/cmd/pkgsite@latest
pkgsite -http :8080
# Navigate to http://localhost:8080/github.com/smartcontractkit/crec-sdk

Complete Example

See the crec-example-payment-processor repository for a full working application.

Extensions

Protocol-specific helpers for common Chainlink systems:

• crec-sdk-ext-ccip - Cross-Chain Interoperability Protocol
• crec-sdk-ext-dvp - Delivery versus Payment
• crec-sdk-ext-dta - Digital Token Assets

Event Verification Keys (Mainnet)

The SDK includes built-in mainnet DON public keys for event verification. No configuration is required — verification is enabled by default.

Default Configuration

• Keys: All Zone A workflow nodes (10 keys)
• Required Signatures: 3 (configurable)

DON Keys Reference

ethereum-mainnet

zone-a

Customizing Verification

Override the defaults if you need custom keys or signature requirements:

// Use custom keys and signature threshold
client, err := crec.NewClient(
    "https://api.crec.chainlink.com",
    "your-api-key",
    crec.WithEventVerification(5, []string{  // Require 5 signatures
        "0xff9b062fccb2f042311343048b9518068370f837",
        "0xe55fcaf921e76c6bbcf9415bba12b1236f07b0c3",
        // ... custom key list ...
    }),
)

// Or disable verification entirely
client, err := crec.NewClient(
    "https://api.crec.chainlink.com",
    "your-api-key",
    crec.WithoutEventVerification(),
)

Note: Keys rarely change. When they do, update the SDK to get the latest defaults.

Glossary