🏦 Bank / QRIS Bridge Integration

PAY.ID can act as a policy oracle for traditional fiat payment rails like QRIS, SWIFT, SEPA, and ACH — without ever custodying funds or executing settlements.

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Architecture Overview

End User → Bank App → PAY.ID Engine → Decision Proof → Bank Settlement
                  │
                  ▼
         Rule Authority (on-chain)

1. User scans QRIS → Bank app reads payload
2. Bank app constructs PAY.ID context with fiat fields
3. PAY.ID evaluates merchant rules off-chain
4. PAY.ID returns DecisionProof (EIP-712 signed)
5. Bank verifies proof → executes or rejects payment

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Extended Context Schema

Fiat payments extend the standard RuleContext with additional tx fields:

interface FiatContext {
  tx: {
    // Standard fields
    sender: string;      // wallet or bank account hash
    receiver: string;    // merchant identifier
    asset: string;       // "IDR" | "USD" | "ETH"
    amount: string;      // smallest unit
    chainId?: number;    // optional for crypto-fiat hybrid

    // Fiat extension
    currency: string;     // ISO-4217: "IDR", "USD", "EUR"
    rail: string;       // "QRIS" | "SWIFT" | "SEPA" | "ACH" | "CARD"
    merchantId: string;   // MID
    psp: string;         // PSP code, e.g. "BANK_ABC"
    terminalId?: string; // POS terminal
    mcc?: string;        // Merchant Category Code
  };
  payId: { id: string; owner: string };
  env: { timestamp: number };
  oracle?: { kycLevel?: number; country?: string };
  risk?: { score?: number };
}

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Rule Examples

PSP Allowlist

{
  "id": "psp_allowlist",
  "if": {
    "field": "tx.psp",
    "op": "in",
    "value": ["BANK_ABC", "BANK_XYZ"]
  }
}

MCC Blocklist

{
  "id": "mcc_blocklist",
  "if": {
    "field": "tx.mcc",
    "op": "not_in",
    "value": ["7995", "7994"]
  }
}

Combined Fiat Policy

{
  "version": "1",
  "logic": "and",
  "rules": [
    { "id": "psp", "if": { "field": "tx.psp", "op": "in", "value": ["BANK_ABC"] } },
    { "id": "min", "if": { "field": "tx.amount", "op": ">=", "value": "10000" } },
    { "id": "mcc", "if": { "field": "tx.mcc", "op": "not_in", "value": ["7995"] } }
  ]
}

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Fiat Adapter

import { createPayIDClient } from 'payid';
import type { RuleContext, DecisionProof } from 'payid';

interface QRISPayload {
  amount: string;
  currency: string;
  merchantId: string;
  pspCode: string;
  terminalId?: string;
  mcc?: string;
}

export class FiatAdapter {
  private client = createPayIDClient();

  async evaluatePayment(
    payload: QRISPayload,
    merchantRuleURI: string,
    signer: any
  ) {
    const context: RuleContext = {
      tx: {
        amount: payload.amount,
        currency: payload.currency,
        rail: 'QRIS',
        merchantId: payload.merchantId,
        psp: payload.pspCode,
        terminalId: payload.terminalId,
        mcc: payload.mcc,
        sender: 'bank:user:anon',
        receiver: payload.merchantId,
        asset: payload.currency,
      },
      payId: {
        id: `pay.id/${payload.merchantId}`,
        owner: payload.merchantId,
      },
      env: { timestamp: Math.floor(Date.now() / 1000) },
    };

    return this.client.evaluateAndProve({
      context,
      authorityRule: { uri: merchantRuleURI },
      payId: `pay.id/${payload.merchantId}`,
      payer: 'bank:user:anon',
      receiver: payload.merchantId,
      asset: payload.currency,
      amount: BigInt(payload.amount),
      signer,
      verifyingContract: '0x...',
      ruleAuthority: '0x...',
      chainId: 31337,
      blockTimestamp: context.env.timestamp,
    });
  }
}

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Failure Semantics

Scenario	Result
Rule REJECT	Bank MUST reject
Evaluation error / timeout	Bank MUST reject (fail-closed)
Invalid proof signature	Bank MUST reject
Expired proof	Bank MUST reject

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Regulatory Notes

• PAY.ID does not replace bank KYC — it complements it with programmable transaction-level policy
• No fiat custody → no banking license required for PAY.ID
• Context sender can be pseudonymized
• Evidence stored off-chain (IPFS/Arweave), only hashes on-chain

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Deployment Roadmap

Phase	Milestone
Phase 1	QRIS MVP with single PSP (testnet)
Phase 2	Multi-PSP support
Phase 3	VRAN integration (merchant reputation)
Phase 4	SWIFT / SEPA cross-border
Phase 5	CBDC programmable policy pilot