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The b402 Relayer is the on-chain smart contract that enables gasless BEP-20 payments on the BNB Chain. It works in tandem with the Facilitator service, verifying off-chain signatures and executing authorized token transfers on behalf of users. Beyond gasless execution, the Relayer supports multiple tokens within the BNB Chain ecosystem, allowing agents and applications to send and receive payments in custom BEP-20 assets.
The b402 Relayer contract is currently unaudited and not intended for production use. It should only be deployed in testing or development environments.

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Key Capabilities

The b402 Relayer serves as a meta-transaction executor for tokens that do not natively implement EIP-3009 or permit() functionality. It allows a facilitator to submit a signed authorization from a user and pay the associated gas cost to execute the transfer on-chain. This design enables off-chain payment authorization, ideal for agents, automated clients, or users without BNB for gas. Features:
  • Executes gasless BEP-20 or ERC-20 transfers (e.g., USDT, USDC, BUSD)
  • Verifies EIP-712 signatures for authenticity
  • Prevents replay attacks using nonces
  • Enforces validity windows (validAfter, validBefore)
  • Supports token whitelisting for enhanced security
  • Compatible with all standard EVM tokens on BNB Chain

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How It Works

  1. User signs off-chain authorization
    The user (or agent) signs an EIP-712 message authorizing a specific token transfer.
    Example message:
    “I authorize the transfer of 1 USDT from my address to the recipient.”
  2. Facilitator verifies and relays on-chain
    The facilitator validates the user’s signature locally.
    If valid, it calls the transferWithAuthorization() function on the Relayer contract and pays the gas for execution.
  3. Contract executes the transfer
    The Relayer verifies the signature, ensures nonce and time constraints are met, and then calls the token contract’s transferFrom() function on behalf of the user.