GXVault Bridge

The GXVault bridge connects GX Chain to external networks, enabling USDC and USDT deposits and withdrawals. The bridge is secured by a multi-validator quorum with a time-locked withdrawal process.

Overview

GXVault is a Solidity smart contract deployed on Arbitrum One that serves as the primary deposit and withdrawal gateway for GX Exchange. Users deposit collateral into GXVault, and GX Chain validators credit the corresponding balance on the L1 chain.

Parameter	Value
Contract Address	`0x55edC6b11c35b5F12358Aa3Fa140B185390Acc71`
Chain	Arbitrum One (Chain ID: 42161)
Accepted Tokens	USDC, USDT
Security Model	Multi-validator quorum (2/3 signatures required)
Withdrawal Timelock	24 hours
Contract Type	Non-upgradeable, pausable, reentrancy-guarded

Deposit Flow

1. User connects wallet to GX Exchange (MetaMask on Arbitrum One)
2. User approves USDC/USDT spending for the GXVault contract
3. User calls GXVault.deposit(token, amount)
4. GXVault emits a Deposited event on Arbitrum
5. GX Chain validators watch for Deposited events
6. Validators credit the user's GX Chain balance
7. Funds are available for trading on GX Core

Deposit Details

Confirmation time: Deposits are credited within seconds of the Arbitrum block confirmation
Minimum deposit: No protocol-enforced minimum (subject to gas costs)
Fee: No bridge fee; users pay only Arbitrum gas for the deposit transaction
Key compatibility: The same Ethereum address is used on both Arbitrum and GX Chain

Withdrawal Flow

1. User submits a withdrawal request via POST /v1/withdraw (EIP-712 signed)
2. A 24-hour timelock begins
3. GX Chain validators review and co-sign the withdrawal
4. 2/3 of validator signatures are required (guardian quorum)
5. GXVault.executeWithdrawal() is called on Arbitrum
6. USDC/USDT is returned to the user's wallet on Arbitrum One

Withdrawal Details

Timelock: 24 hours from request to execution
Quorum: Two-thirds of active validators must sign the withdrawal
Dispute period: During the 24-hour timelock, validators can flag suspicious withdrawals
Cancellation: Users can cancel a pending withdrawal during the timelock period
Fee: No bridge fee; users pay only Arbitrum gas for the withdrawal execution

Security Model

Multi-Validator Quorum

Withdrawals are not controlled by a single private key. Instead, a quorum of GX Chain validators must co-sign every withdrawal transaction. This prevents any single compromised validator from draining the vault.

Security Property	Implementation
Quorum threshold	2/3 of active validators
Signer rotation	Validator set updates propagate to the bridge
Timelock	24-hour delay between request and execution
Pausability	Contract can be paused by guardian multisig in emergencies
Reentrancy protection	OpenZeppelin ReentrancyGuard on all state-changing functions
Non-upgradeable	No proxy pattern; contract code is immutable after deployment

Dispute Resolution

During the 24-hour timelock window, any validator can flag a withdrawal as suspicious. Flagged withdrawals require additional review before execution. This provides a safety net against:

Compromised user keys attempting unauthorized withdrawals
Coordinated attacks on the validator quorum
Smart contract exploits discovered after the withdrawal request

Contract Architecture

GXVault.sol

The core vault contract handles deposits, withdrawal requests, and withdrawal execution:

Function	Description
`deposit(token, amount)`	Accept USDC/USDT deposit, emit Deposited event
`requestWithdrawal(token, amount)`	Initiate withdrawal with 24h timelock
`executeWithdrawal(withdrawalId, signatures)`	Execute withdrawal with validator signatures
`cancelWithdrawal(withdrawalId)`	Cancel pending withdrawal during timelock
`pause()` / `unpause()`	Emergency pause (guardian-only)

Supported Tokens

Token	Address (Arbitrum One)
USDC	`0xaf88d065e77c8cC2239327C5EDb3A432268e5831`
USDT	`0xFd086bC7CD5C481DCC9C85ebE478A1C0b69FCbb9`

Validator Bridge Watchers

Each GX Chain validator runs an EVM watcher module that:

Monitors the GXVault contract on Arbitrum for Deposited events
Verifies the deposit transaction on Arbitrum (block confirmations)
Proposes a deposit credit transaction on GX Chain
Participates in BFT consensus to finalize the credit
Co-signs withdrawal transactions when quorum is reached

The watcher module is built into the validator binary — no separate service is required.

Bridge Fees

Operation	Bridge Fee	Network Gas
Deposit	None	Arbitrum gas (~$0.01-0.10)
Withdrawal	None	Arbitrum gas (~$0.01-0.10)

GX Exchange does not charge any fee for bridging. Users pay only the underlying Arbitrum network gas fees.

Future Expansion

The bridge architecture is designed to support additional networks:

Ethereum mainnet — Direct L1 deposits for users who prefer not to use Arbitrum
Base — Coinbase L2 integration
Other L2s — Optimism, zkSync, and others based on user demand

Additional bridge deployments will follow the same multi-validator quorum security model.

Overview API Servers