Setting up the Particle Omnichain Paymaster

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Particle Network’s Omnichain Paymaster

Particle Network hosts a proprietary Paymaster capable of omnichain gas sponsorships from a single USDT deposit. This allows developers to deposit on one chain and have it automatically converted to the native token of EVM chains in which the request transaction has to be sponsored. In addition to this, Particle’s Omnichain Paymaster allows for complete programmatic customization of sponsorship logic through webhooks. While our AA SDK supports any Paymaster (including Biconomy’s, natively), Particle Network’s Omnichain Paymaster presents a built-in, seamless mechanism for gas sponsorship.

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Funding the Paymaster

To fund your instance of the Paymaster and thus begin sponsoring gas, you’ll need to head over to the Particle Network dashboard and navigate to the “Paymaster” menu. Upon entering this menu, you can deposit USDT on either Ethereum or BNB Chain. The chain you chose does not affect the functionality of the Paymaster, only the origin of your deposit.

Upon sponsorship request, your USDT will be converted into the native token of the chain in question. You’ll need to connect a wallet (or social login through Particle Auth) to deposit, tying the funds directly with your project (specified by your projectId, clientKey, and appId—you’ll need to use these values within Particle’s AA SDK or the Paymaster RPC to authenticate it).

Once you’ve deposited USDT, you’re can define sponsorship conditions and sponsoring transactions on any supported EVM chain (see Network Coverage).

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Configuring webhooks (sponsorship conditions)

To set the conditions for the Paymaster to sponsor transactions, you’ll need to use two different webhooks: before_paymaster_sign and after_paymaster_sign. The combination of these hooks, expressed through a webhook URL, set the sponsorship conditions (true,200 or false, 400) on whether or not a specific UserOperation should be sponsored).

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before_paymaster_sign

before_paymaster_sign is hit before the Paymaster signs a given user operation (qualifies it as sponsored), thus before_paymaster_sign will set the core logic behind whether or not a UserOperation should be signed by the Paymaster. This hook should take, as a request body:

• projectUuid - the project ID associated with your application (retrieved from the Particle dashboard).
• chainId - the specific chain that sponsorship is requested on.
• userOp - a UserOperation object.
  • sender
  • nonce
  • initCode
  • callData
  • callGasLimit
  • paymasterAndData
  • signature
  • verificationGasLimit
  • maxFeePerGas
  • maxPriorityFeePerGas
  • preVerificationGas
• entryPoint - the Entry Point address to be used, this should be 0x5FF137D4b0FDCD49DcA30c7CF57E578a026d2789.
• parsed - the UserOperation deconstructed into a standard transaction object.
  • accountType - the smart account implementation being used, SIMPLE, BICONOMY, or CYBERCONNECT.
  • txs - an array of transaction objects.
    • to
    • value
    • data

Upon receiving this request, logic should be ran and return either 200 for a confirmed sponsorship, or 400 for a rejected sponsorship. See the below snippet for an example of what this request would look like:

POST https://your-domain/hook-before-paymaster-sign

Header
x-particle-signature: WH/6YifcF2dad3qbS4HkjQ7EboDXNTcIfCH4cCW0lfOWJsQR1GPoHZpqtqr3XedAG3bi+RlTUGmetJiaiCqflr1+dWuXFsvrML7LNu2wWNDzlGAEM3iLwrdHl1vIZx6ftlbYyyQD4CHEBpDhbnrDn2IGj64dF8nmho4gc/PNQQUTBJL+Xy0MEHVLSNSDeRMA5/BhwFjiufvDqmW3verX/ynvUAVLnLiAWkVnN2aBF4TncsqV37W8EN3q2SILpdnbG2UWzeawg+0owtw9xgo4QXgqi8PfYrd3ta5PxjoenbUA7OBJtXt4R/TwYs8Vb+mggJ+ZbrJrVd45F8U9hNt7bQ==

BODY
{
    "type": "before_paymaster_sign",
    "chainId": 80001,
    "projectUuid": "ef6c29f5-ad2b-545c-ad0c-54441068b71d",
    "userOp": {
        "sender": "0x2e9661BDA6201F97430dcc1541A1579b83980DD1",
        "nonce": "0x05",
        "initCode": "0x",
        "callData": "0xb61d27f6000000000000000000000000ac6a87c681a5ed4cb58bc4fa7bf81a83b928c83c00000000000000000000000000000000000000000000000000005af3107a400000000000000000000000000000000000000000000000000000000000000000600000000000000000000000000000000000000000000000000000000000000000",
        "callGasLimit": "0x9acc",
        "paymasterAndData": "0x",
        "signature": "0x",
        "verificationGasLimit": "0x0186a0",
        "maxFeePerGas": "0xa79dd02a",
        "maxPriorityFeePerGas": "0xa79dd015",
        "preVerificationGas": "0xc5dc"
    },
    "entryPoint": "0x5FF137D4b0FDCD49DcA30c7CF57E578a026d2789",
    "parsed": {
        "accountType": "SIMPLE",
        "txs": [
            {
                "to": "0xaC6A87c681A5Ed4cb58bC4fa7bF81a83b928C83C",
                "value": "0x5af3107a4000",
                "data": "0x"
            }
        ]
    }
}

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after_paymaster_sign

after_paymaster_sign will be hit after a signature occurs post-qualification from before_paymaster_sign, allowing you to define logic to be executed after a confirmed sponsorship. after_paymaster_sign takes the same parameters as before_paymaster_sign; a request to an after_paymaster_sign hook will look similar to the example included below:

POST https://your-domain/hook-after-paymaster-sign

Header
x-particle-signature: WH/6YifcF2dad3qbS4HkjQ7EboDXNTcIfCH4cCW0lfOWJsQR1GPoHZpqtqr3XedAG3bi+RlTUGmetJiaiCqflr1+dWuXFsvrML7LNu2wWNDzlGAEM3iLwrdHl1vIZx6ftlbYyyQD4CHEBpDhbnrDn2IGj64dF8nmho4gc/PNQQUTBJL+Xy0MEHVLSNSDeRMA5/BhwFjiufvDqmW3verX/ynvUAVLnLiAWkVnN2aBF4TncsqV37W8EN3q2SILpdnbG2UWzeawg+0owtw9xgo4QXgqi8PfYrd3ta5PxjoenbUA7OBJtXt4R/TwYs8Vb+mggJ+ZbrJrVd45F8U9hNt7bQ==

BODY
{
    "type": "after_paymaster_sign",
    "chainId": 80001,
    "projectUuid": "ef6c29f5-ad2b-545c-ad0c-54441068b71d",
    "userOp": {
        "sender": "0x2e9661BDA6201F97430dcc1541A1579b83980DD1",
        "nonce": "0x05",
        "initCode": "0x",
        "callData": "0xb61d27f6000000000000000000000000ac6a87c681a5ed4cb58bc4fa7bf81a83b928c83c00000000000000000000000000000000000000000000000000005af3107a400000000000000000000000000000000000000000000000000000000000000000600000000000000000000000000000000000000000000000000000000000000000",
        "callGasLimit": "0x9acc",
        "paymasterAndData": "0xc89b723809598d0ebf821e89087dc8e1a6ee04990000000000000000000000000000000000000000000000000000000065520368000000000000000000000000000000000000000000000000000000000000000053264ff4c95bfc05d0635b8745f698911a103d11e4995f2d532e931807800aa0313d269ef5824ea5d122af0b08e70c0777898add80e70fffbd81154760eac0991b",
        "signature": "0x",
        "verificationGasLimit": "0x0186a0",
        "maxFeePerGas": "0xa79dd02a",
        "maxPriorityFeePerGas": "0xa79dd015",
        "preVerificationGas": "0xc5dc"
    },
    "entryPoint": "0x5FF137D4b0FDCD49DcA30c7CF57E578a026d2789",
    "userOpHash": "0x45d4f5bb4114907a09426000e152eea5511576924d58700f7f2561f32a552476",
    "parsed": {
        "accountType": "SIMPLE",
        "txs": [
            {
                "to": "0xaC6A87c681A5Ed4cb58bC4fa7bF81a83b928C83C",
                "value": "0x5af3107a4000",
                "data": "0x"
            }
        ]
    }
}

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Request verification

To ensure you can validate where the source of the request is coming from (to make sure it’s from Particle Network and not a third party), Particle Network generates a signature for the hook request body that can be verified to ensure the request originated from Particle. This is done through a unique RSA-2048 public and private key combination generated and used for each project, which you can download through the Particle dashboard.