Custody Platform Integration

Arc is fully EVM-compatible—same key derivation, same signing curve (secp256k1), same transaction formats. If your custody platform supports custom EVM chains, you can add Arc without code changes. This guide covers what’s different and what to configure.

Arc uses USDC as its native gas token. There is no separate ETH-like token to fund for gas. A single USDC balance covers both transfer value and transaction fees.

What custody engineers need to know

Arc behaves like any EVM chain with three key differences:

Property	Ethereum	Arc
Gas token	ETH (18 decimals)	USDC (6 display decimals, 18 internal decimals)
Finality	Probabilistic (~12 min for safety)	Deterministic, sub-second. 1 confirmation = final.
Gas funding	Requires separate ETH balance	No separate funding—USDC covers everything

Everything else is standard:

Address derivation: BIP-44 path m/44'/60'/0'/0/x
Signing algorithm: secp256k1 (identical to Ethereum)
Transaction types: Legacy (type 0) and EIP-1559 (type 2) both supported
Smart contracts: Solidity, same EVM opcodes
Multi-sig: Standard Ethereum multi-sig contracts (including SAFE) work without modification

Network configuration

Use these parameters when registering Arc as a custom EVM chain:

Parameter	Testnet value
Chain ID	`5042002`
RPC (HTTPS)	`https://rpc.testnet.arc.io`
RPC (WebSocket)	`wss://rpc.testnet.arc.io`
Block explorer	`https://testnet.arcscan.app`
Native currency symbol	`USDC`
Native currency decimals	`18` (internal representation)
Display decimals	`6`
EIP-1559 support	Yes (recommended)
Minimum base fee	20 Gwei

The native currency uses 18 decimals internally (like ETH uses Wei) but represents USDC which has 6 display decimals. Configure your balance display to show 6 decimal places to users while using 18 decimals for transaction construction.

USDC ERC-20 contract

For ERC-20 interactions (approvals, transferFrom, allowance checks), the USDC contract is deployed at a precompile address:

0x3600000000000000000000000000000000000000

Native USDC transfers (simple sends) and ERC-20 transfer() calls both move the same underlying balance. There is no wrapped/unwrapped distinction.

Register Arc in your custody platform

Most custody platforms provide a “custom EVM chain” or “custom network” configuration flow. The following sections provide platform-specific guidance and a generic template.

Provider configuration reference

Provider	Integration method	Notes
Fireblocks	Workspace Settings → Add EVM Network	Use “EVM-based chain” template. Set native asset to USDC.
BitGo	Admin → Coin Management → Custom EVM	Register as custom ERC-20 chain. Configure 1-block finality.
Cactus	Network Management → Add Custom Chain	Standard EVM chain wizard. Set gas token symbol to USDC.
Zodia	Network Configuration → Custom EVM	Use provided chain ID and RPC. No special signing config needed.
SAFE	Add custom network in web interface	Works natively—same contract addresses and factory.
Taurus	TaurusProtect → Network Settings	Register RPC endpoint. Configure display decimals separately.
Copper	ClearLoop → Custom Networks	Standard EVM registration. Set confirmation threshold to 1.
CEFFU	Asset Management → Custom Chain	Follow EVM chain onboarding flow. Specify USDC as fee token.

Generic custom EVM chain template

Use this configuration when your platform has a general-purpose “add custom EVM chain” form:

const arcNetworkConfig = {
  chainId: 5042002,
  name: "Arc Testnet",
  rpcUrl: "https://rpc.testnet.arc.io",
  wsUrl: "wss://rpc.testnet.arc.io",
  blockExplorer: "https://testnet.arcscan.app",
  nativeCurrency: {
    name: "USDC",
    symbol: "USDC",
    decimals: 18, // Internal representation (like Wei for ETH)
  },
  // Display configuration
  displayDecimals: 6, // Show balances with 6 decimal places
  // Finality configuration
  confirmationsRequired: 1, // Deterministic finality—1 block is final
  // Transaction type preference
  eip1559: true,
  // No separate gas token funding address needed
};

Transaction signing

Arc uses standard Ethereum transaction signing. No custom signing schemes or transaction types are required.

Recommended: EIP-1559 (type 2)

import { createWalletClient, http, parseUnits } from "viem";

const arcTestnet = {
  id: 5042002,
  name: "Arc Testnet",
  nativeCurrency: { name: "USDC", symbol: "USDC", decimals: 18 },
  rpcUrls: {
    default: { http: ["https://rpc.testnet.arc.io"] },
  },
};

const client = createWalletClient({
  chain: arcTestnet,
  transport: http(),
});

// Standard EIP-1559 transaction—identical to Ethereum
const txHash = await client.sendTransaction({
  account, // Your custody-managed account
  to: "0x742d35Cc6634C0532925a3b844Bc9e7595f2bD28",
  value: parseUnits("100", 18), // 100 USDC (18 decimals internally)
  maxFeePerGas: parseUnits("30", 9), // 30 Gwei
  maxPriorityFeePerGas: parseUnits("1", 9), // 1 Gwei tip
});

// With deterministic finality, 1 confirmation means the transaction is final

Key signing details

Curve: secp256k1 (same as Ethereum)
Address derivation: Keccak-256 hash of public key, last 20 bytes
HD path: m/44'/60'/0'/0/x (coin type 60, same as Ethereum)
Transaction serialization: RLP encoding, identical to Ethereum
Chain ID in signature: Required (EIP-155). Use 5042002 for testnet.

MPC and multi-sig considerations

MPC wallets

MPC (multi-party computation) signing works identically to Ethereum:

Key shares are generated for the secp256k1 curve
Threshold signing produces a standard ECDSA signature
The resulting address is a standard Ethereum address
No Arc-specific MPC protocol modifications are needed

Multi-sig wallets (SAFE)

SAFE multi-sig contracts deploy and operate on Arc without modification:

Same factory contract addresses
Same proxy pattern
Same signature verification logic
Transaction confirmation follows the same flow—but only 1 onchain confirmation is needed due to deterministic finality

Operational differences

Balance management

Because USDC is both the transfer currency and the gas token, custody operations are simpler:

No gas station network: You don’t need a separate process to fund addresses with gas tokens.
Unified balance: A single eth_getBalance call returns the USDC balance available for both transfers and fees.
Threshold alerts: Set a single low-balance threshold instead of monitoring separate gas and transfer balances.

import { createPublicClient, http, formatUnits } from "viem";

const client = createPublicClient({
  transport: http("https://rpc.testnet.arc.io"),
});

const balance = await client.getBalance({
  address: "0xYourCustodyAddress",
});

// Display with 6 decimals (USDC precision)
const displayBalance = formatUnits(balance, 18);
// For user-facing display, round to 6 decimal places
const usdcDisplay = parseFloat(displayBalance).toFixed(6);

Finality and confirmation tracking

Arc provides deterministic finality. Once a transaction is included in a block, it is final—no reorgs, no uncle blocks, no chain reorganizations. This means:

Set confirmation requirements to 1 in your custody platform
Remove pending-state tracking logic (no need to wait for additional confirmations)
Transaction receipts are immediately authoritative
No need to handle “dropped and replaced” scenarios

If your platform requires a minimum confirmation count greater than 1, setting it to 1 is still safe on Arc. There is no security benefit to waiting for additional blocks.

Blocklist enforcement

Arc enforces a protocol-level blocklist. Transactions from blocklisted sender addresses are rejected at the pre-mempool stage—they never appear onchain. For custody operations:

Check the blocklist before attempting to sign and broadcast
If a send fails with a blocklist rejection, it was not broadcast—no gas is consumed
Monitor compliance status of custody-managed addresses

Fee estimation

Gas estimation works identically to Ethereum:

// Use standard eth_estimateGas and eth_gasPrice / eth_maxPriorityFeePerGas
const gasEstimate = await client.estimateGas({
  account: "0xYourCustodyAddress",
  to: "0xRecipientAddress",
  value: parseUnits("1000", 18), // 1000 USDC
});

const feeData = await client.estimateFeesPerGas();

// Total fee in USDC (18 decimals internal)
const maxFee = gasEstimate * feeData.maxFeePerGas;

The minimum base fee is 20 Gwei. Set your gas price floor accordingly to avoid underpriced transaction rejections.

Verification and testing

After configuring Arc in your custody platform:

Generate a test address using your standard HD derivation path and verify it matches what you’d get on Ethereum for the same seed.
Fund the address with testnet USDC through the Arc faucet.
Send a transaction and confirm it appears on the block explorer within seconds.
Verify the receipt shows status: 1 (success) with a single block confirmation.
Test balance display to ensure your platform shows the correct USDC amount (6 decimal places).

The same address and private key work on both Arc and Ethereum. If your platform already derives Ethereum addresses for a given seed, those same addresses are valid on Arc.

Exchanges

On/off-ramps

Wallets

DeFi

Relayers and paymasters

Infrastructure

Run a node

Custody Platform Integration

What custody engineers need to know

Network configuration

USDC ERC-20 contract

Register Arc in your custody platform

Provider configuration reference

Generic custom EVM chain template

Transaction signing

Recommended: EIP-1559 (type 2)

Key signing details

MPC and multi-sig considerations

MPC wallets

Multi-sig wallets (SAFE)

Operational differences

Balance management

Finality and confirmation tracking

Blocklist enforcement

Fee estimation

Verification and testing

​What custody engineers need to know

​Network configuration

​USDC ERC-20 contract

​Register Arc in your custody platform

​Provider configuration reference

​Generic custom EVM chain template

​Transaction signing

​Recommended: EIP-1559 (type 2)

​Key signing details

​MPC and multi-sig considerations

​MPC wallets

​Multi-sig wallets (SAFE)

​Operational differences

​Balance management

​Finality and confirmation tracking

​Blocklist enforcement

​Fee estimation

​Verification and testing

What custody engineers need to know

Network configuration

USDC ERC-20 contract

Register Arc in your custody platform

Provider configuration reference

Generic custom EVM chain template

Transaction signing

Recommended: EIP-1559 (type 2)

Key signing details

MPC and multi-sig considerations

MPC wallets

Multi-sig wallets (SAFE)

Operational differences

Balance management

Finality and confirmation tracking

Blocklist enforcement

Fee estimation

Verification and testing