Tuven Chain: A New Solution to the Gas Fee Payment Dilemma and Analysis of Related Security Risks

Almost everyone who has used an on-chain wallet has encountered this problem: a wallet full of tokens, wanting to transfer or interact with a smart contract, but the transaction fails due to insufficient gas fees. In mainstream EVM-compatible public chains, the gas fees for transactions are required to be paid using the native tokens of the chain, which means new users need to acquire native tokens to initiate interactions. Additionally, gas fees fluctuate dynamically with the level of congestion in the blockchain network, making it impossible for users to accurately predict the actual transaction costs before confirmation. This is one of the main obstacles to the widespread adoption of Web3.

This article will analyze the existing mainstream gas fee solutions in the Web3 industry and provide an analysis of the new solution from RWA public chain Tuven Chain from the perspectives of technical implementation logic, architectural innovations, and potential risks, serving as a reference for public chain developers and security auditors.

1. Mainstream Gas Fee Solutions

1.1 ERC-4337 (Account Abstraction) Paymaster Payment Mechanism

Paymaster is a special contract defined in the ERC-4337 framework that allows for gas fees to be paid on behalf of users during the execution of UserOperation. This way, users do not need to hold native coins when sending transactions, thus lowering the entry barrier for new users. The core workflow for gas payment is as follows:

1. User Initiates Operation: The user signs and submits a UserOperation in their smart wallet.
2. Bundling and Verification: The Bundler collects multiple operations and sends them to the Paymaster contract and the Entrypoint contract.
3. Paymaster Intervention: The Paymaster contract verifies whether it agrees to pay the gas for the operation.
4. Fee Settlement: The transaction is executed on-chain, and the Entrypoint deducts the native tokens (e.g., ETH) from the Paymaster's deposit account as gas fees.
5. Post-Compensation: Common payment models include full sponsorship, where the project fully covers 100% of the gas fees for new users or specific activities; token payment, where users without native tokens (e.g., ETH) can pay gas fees using USDT or USDC in their wallets, with the Paymaster automatically converting in the background; and conditional payment, where the project sets rules to only allow payment for users holding specific NFTs, completing specific tasks, or using specific in-app tokens.

The limitation of this solution is that ordinary external accounts (EOA) cannot use it directly; users need to switch or upgrade to an account abstraction wallet.

1.2 Meta Transactions and Relayer Model

This is another solution used in blockchain to lower the entry barrier for users, achieving "gas-free" transactions or paying miner fees on behalf of users. Meta transactions refer to users not directly sending transactions to the blockchain but signing a "meta-data" message containing operation intentions and data off-chain with their private keys. The relayer is responsible for collecting users' off-chain signatures, acting as the actual initiator of the on-chain transaction and paying the gas fees, broadcasting the transaction to the blockchain. The core workflow is as follows:

1. User Signs: The user locally signs their intention (e.g., transfer, contract call) without consuming any on-chain gas.
2. Submit to Off-Chain Service: The user sends the signature and data to the relayer (which can be the DApp's official server or a third-party service).
3. Relayer Bundles: The relayer packages the signature into a real on-chain transaction, signs it with its own wallet account, and pays the gas fees.
4. Smart Contract Verification: The target smart contract receives the transaction, parses and verifies the user's original signature, and executes the corresponding logic if confirmed.

However, this solution has centralization risks and replay attack issues: if the relayer goes down or deliberately rejects certain users' requests, users will be unable to send transactions; and the relayer can see users' transaction intentions, potentially using this information for front-running transactions. If a user's signature is obtained by an attacker and the contract lacks checks for Nonce and ChainID, it may lead to replay attacks.

The above solutions do not directly modify the billing logic at the chain consensus execution layer. Tuven Chain attempts to achieve custom token payments for fixed gas fees by modifying the underlying execution logic without changing ordinary wallets or altering applications.

2. Core Implementation Logic of Tuven Chain

Tuven Chain is a fork of Circle's Arc chain, inheriting the basic ability of stablecoin payments for gas. The core innovation lies in the reverse reuse of the original blacklist verification mechanism. It constructs a SponsorRegistry registry, combining SBT identity credentials to complete user access control, fee deduction, and transaction admission logic.

2.1 Core Component SponsorRegistry.sol / sponsor_registry.rs

SponsorRegistry is a pre-deployed core contract that serves as a global "gas fee package table," storing multiple gas billing configurations. The data storage layout is strictly fixed, and the execution layer's Rust code reads data directly through storage slots.

// SponsorRegistry.sol — The layout is "frozen"; handler reads directly by slot, order cannot change
struct GasPlan {
    address token;
    uint256 feePerTx;
    address feeBeneficiary;
}
address public multisig;                        // slot 0
mapping(uint256 => GasPlan) public plans;       // slot 1: planId → package
mapping(address => uint256) public sourcePlan;  // slot 2: SBT → grantable planId
mapping(address => uint256) public userPlan;    // slot 3: holder → planId (0=not in package)
// Unique write entry: authorized SBT adds/removes from the list
function setSponsored(address who, bool on) external {
    uint256 plan = sourcePlan[msg.sender];      // Caller must be an authorized SBT
    if (plan == 0) revert NotAuthorizedSource();
    userPlan[who] = on ? plan : 0;              // on=add to list; off=clear 0
}

In this, plans[planId] = { token: which currency to use, feePerTx: how much per transaction, feeBeneficiary: who receives it }. During settlement, Tuven Chain first checks which package the user belongs to; if not in a package (userPlan[you]==0), the user pays with the native stablecoin USDX; if in a package, the specified token of the package is used for payment. It is important to note that USDX is a stablecoin contract from Circle, but the minting/freezing/pausing powers lie with the operator, isolating it from real USDC. Its "stability" comes from the operator's strategy, not from reserve support.

2.2 Modification of Fee Deduction Logic at the Execution Layer

// handler.rs — Mimicking "blacklist": performing "non-metered SLOAD" on the package table, deciding which currency to use for payment per transaction
fn charge_sponsored_gas(&self, evm, caller) -> Result<bool> {
    journal.load_account(SPONSOR_REGISTRY_ADDRESS)?;  // Preheat first, otherwise cold read SLOAD will panic
    let plan_id = sload(REG, compute_user_plan_slot(caller))?;
    if plan_id.is_zero() { return Ok(false); }  // Not in package → pay USDX as usual
    let token = sload(REG, compute_plan_slot(plan_id, PLAN_TOKEN_OFFSET))?;
    if token.is_zero() { return Err(GAS_PLAN_UNCONFIGURED); }  // Package not configured → reject, no fallback
    let fee = sload(REG, compute_plan_slot(plan_id, PLAN_FEE_OFFSET))?;
    let bal = sload(token, compute_erc20_balance_slot(caller))?;
    if bal < fee { return Err(INSUFFICIENT_GAS_TOKEN); }  // Insufficient member token → reject
    sstore(token, caller_slot, bal - fee)?;            // Deduct fixed fee: member pays
    sstore(token, benef_slot, benef_bal + fee)?;  // Credit to feeBeneficiary (unrelated to gas)
    Ok(true)  // true = paid with member token, USDX fully exempt
}

Here, users are charged a fixed amount of a specific token per transaction, regardless of the actual computational consumption. This setting raises the base fee across the entire chain, with the increased gas fees being borne by ordinary USDX (non-package) users, effectively shifting the cost to these users.

2.3 Identity Badge SoulboundToken.sol / DeployUserland.s.sol

// SoulboundToken.sol — Non-transferable "identity badge" (ERC-5192)
function issue(address to, uint256 id, string uri) external onlyIssuer {
    _safeMint(to, id);
    registry.setSponsored(to, true);  // Add to package list upon issuance
}
function revoke(uint256 id) external onlyIssuer {
    address owner = ownerOf(id);
    _burn(id);
    registry.setSponsored(owner, false);  // Remove from package list upon revocation
}
// Only allows mint(from=0)/burn(to=0); all other transfers are blocked → cannot be transferred or sold
function _update(...) internal override returns (address) {
    if (from != address(0) && to != address(0)) revert Soulbound(); ...
}
// DeployUserland.s.sol — Deploy to hand over management rights to multisig (1-of-2 is key redundancy, not checks and balances)
registry.setSourcePlan(address(sbt), PLAN_ID);  // Authorize SBT to bind to package 1
registry.setMultisig(address(multisig));  // Admin hands over to management multisig
// Hidden risk: feeSigner defaults to admin signer when not explicitly set (treasury and management share the same private key)

Tuven Chain reuses Arc's existing blacklist mechanism, combining SBT identity credentials to complete user access control. The characteristics of its solution can be summarized as follows:

1. Native Multi-Token Gas Payment Capability: Unlike upper-layer contract payment solutions, the billing logic is pushed down to the consensus execution layer, supporting multiple packages in parallel, allowing different identity users to use different custom tokens to pay transaction fees.
2. Fixed Single Transaction Fee Model: Detaching from the traditional pricing model of "Gas price × computational consumption," achieving predictable transaction fees in advance.
3. High Compatibility with Existing Infrastructure: No need for smart accounts or DApp modifications; ordinary EOA wallets like MetaMask can interact directly.
4. Mechanism Reuse: Reusing the execution path of the chain's original blacklist storage reading, reverse-engineering it into forward identity access control, maximizing the reuse of the existing underlying code framework.

However, the above convenience is built on a large number of new trust assumptions, and there may be risks associated with underlying kernel changes, permission designs, economic models, and cross-chain components. The original semantics of the blacklist have been modified, and the interception logic originally targeted only transfer scenarios has been expanded to cover ordinary contract calls, changing the logical boundaries. The specific package token fee deduction represents a newly developed business logic that requires independent security audits to ensure that storage read/write and balance calculations are free of vulnerabilities, avoiding serious consequences such as transaction anomalies, chain consensus forks, and abnormal asset deductions.

This content is provided for general informational purposes only and doesn't constitute financial, investment, legal, or tax advice. Any events, rewards, online promotions, or related information mentioned herein should not be considered a recommendation, solicitation, or invitation to purchase, sell, trade, or otherwise deal in any crypto assets. Crypto assets are highly volatile and may result in loss. The availability of WEEX services, products, and related events may vary by region. You are responsible for ensuring that your participation is in accordance with applicable local laws and regulations.