Hinkal Private Payments

The Request Network SDK supports Hinkal Private Payments using ERC-20 tokens. Hinkal is a middleware and suite of smart contracts on EVM-compatible chains that leverage zero-knowledge proofs and shielded addresses to facilitate compliant and private transactions.

Each public address has exactly one Hinkal shielded address.

The @requestnetwork/payment-processor package provides functions to:

• Pay a request from a Hinkal shielded address to a public address: such that the payment sender's public address never appears on-chain.

• Deposit to a Hinkal shielded address from a public address: such that the payment recipient's public address never appears on-chain. Callers can choose to deposit to their own shielded address or someone else's shielded address.

Paying a request where the payment recipient address is a Hinkal shielded address is not supported because the Request Network payment proxy smart contracts can only send funds to public addresses. Consider using Declarative Payment instead.

Benefits

• Privacy: Obfuscates payer address when paying a request.

• Compliance: Ensures transactions adhere to regulatory requirements. See Hinkal Compliance for details

Supported Chains

See Hinkal Supported Chains for a list of chains on which Hinkal Private Payments are supported.

Installation

To use Hinkal Private Payments, install the necessary package:

npm install @requestnetwork/payment-processor

Usage

Pay a request from a Hinkal shielded address

To pay a request from a Hinkal shielded address to a public address, where only the payment sender's address is obfuscated, use the `payErc20FeeProxyRequestFromHinkalShieldedAddress()` function. Ensure the payment sender's Hinkal shielded address has a positive balance usingDeposit to a Hinkal shielded address

Strongly consider using Encryption and Decryption to keep the request contents private, including the payer and payee identity addresses, when paying requests from a Hinkal shielded address. Revealing the payer and payee identity addresses increases the likelihood of un-shielding the payment sender's address via on-chain analysis.

import { 
  payErc20FeeProxyRequestFromHinkalShieldedAddress,
} from '@requestnetwork/payment-processor';

// Instantiation of `RequestNetwork` and `Signer` omitted for brevity

const request = await requestClient.fromRequestId('insert request id');
const requestData = request.getData();

const relayerTx = await payErc20FeeProxyRequestFromHinkalShieldedAddress(
  requestData,
  signer,
);

See Quickstart - Browser for how to instantiate a RequestNetwork and Signer

Deposit to a Hinkal shielded address

To deposit funds to a Hinkal shielded address from a public address, where only the payment recipient's address is obfuscated, use the sendToHinkalShieldedAddressFromPublic() function.

• Deposit to own Hinkal shielded address: omit the recipientInfo argument

• Deposit to someone else's Hinkal shielded address: set recipientInfo to the shielded address of the payment recipient.

Hinkal shielded addresses must be shared out-of-band. This SDK doesn't offer functions for sharing Hinkal shielded addresses.

import { 
  sendToHinkalShieldedAddressFromPublic,
} from '@requestnetwork/payment-processor';

// Instantiation of `Signer` omitted for brevity

const recipientShieldedAddress = '142590100039484718476239190022599206250779986428210948946438848754146776167,0x096d6d5d8b2292aa52e57123a58fc4d5f3d66171acd895f22ce1a5b16ac51b9e,0xc025ccc6ef46399da52763a866a3a10d2eade509af27eb8411c5d251eb8cd34d'
const tx = await sendToHinkalShieldedAddressFromPublic({
    signerOrProvider: paymentSender,
    tokenAddress: '0x833589fcd6edb6e08f4c7c32d4f71b54bda02913', // USDC on Base
    amount: '1000000', // 1 USDC
    recipientInfo: recipientShieldedAddress, // omit to deposit to own Hinkal shielded address
})

See Quickstart - Browser for how to instantiate a Signer

Details

For more details, refer to the Pull Request #1482 on GitHub.