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curl -X POST https://api.payonproof.com/api/generate-proof \
  -H "Content-Type: application/json" \
  -d '{
    "transactionId": "POP-1709467200-A3F9B2",
    "stellarTxHash": "3389e9f0f1a65f19736cacf544c2e825313e8447f569233bb8db39aa607c8889",
    "route": "MoneyGram → Philippines Anchor",
    "originAmount": 100,
    "originCurrency": "USD",
    "destinationAmount": 5450,
    "destinationCurrency": "PHP",
    "exchangeRate": 54.5,
    "totalFees": 2.5
  }'

​
POST /api/generate-proof

Generates a cryptographic proof of payment after verifying the transaction exists on the Stellar blockchain via Horizon. This endpoint:
  1. Verifies the transaction exists on Horizon
  2. Generates a proof payload with transaction metadata
  3. Returns a verifiable proof object

​
Request body

​
transactionId
string
required
PayOnProof transaction ID (e.g., “POP-1709467200-A3F9B2”)
​
stellarTxHash
string
required
Stellar transaction hash (64-character hex string)
​
route
string
Human-readable route description (e.g., “MoneyGram → Philippines Anchor”)
​
originAmount
number
Amount sent in origin currency
​
originCurrency
string
Origin currency code (e.g., “USD”)
​
destinationAmount
number
Amount received in destination currency
​
destinationCurrency
string
Destination currency code (e.g., “PHP”)
​
exchangeRate
number
Exchange rate applied (destination/origin)
​
totalFees
number
Total fees charged in origin currency

​
Response

​
proof
object
Proof of payment object

​
Response example

{
  "proof": {
    "id": "POP-PROOF-1709467200",
    "transactionId": "POP-1709467200-A3F9B2",
    "timestamp": "2026-03-03T10:15:00.000Z",
    "sender": "Wallet Holder",
    "receiver": "Anchor Settlement",
    "originAmount": 100,
    "originCurrency": "USD",
    "destinationAmount": 5450,
    "destinationCurrency": "PHP",
    "exchangeRate": 54.5,
    "totalFees": 2.5,
    "route": "MoneyGram → Philippines Anchor",
    "stellarTxHash": "3389e9f0f1a65f19736cacf544c2e825313e8447f569233bb8db39aa607c8889",
    "status": "verified",
    "verificationUrl": "https://stellar.expert/explorer/public/tx/3389e9f0f1a65f19736cacf544c2e825313e8447f569233bb8db39aa607c8889"
  }
}

​
Error responses

400 Bad Request - Missing field 
{
  "error": "Missing field: stellarTxHash"
}
405 Method Not Allowed 
{
  "error": "Method not allowed"
}
502 Bad Gateway - Horizon verification failed 
{
  "error": "Transaction not found on Horizon (404): {\"type\":\"https://stellar.org/horizon-errors/not_found\",\"title\":\"Resource Missing\"}"
}
502 Bad Gateway - Network error 
{
  "error": "Horizon request failed (https://horizon.stellar.org/transactions/...): fetch failed"
}

​
Verification process

The endpoint verifies transactions by:
  1. Querying Horizon: GET https://horizon.stellar.org/transactions/{hash}
  2. Checking response: Must return 200 OK
  3. Generating proof: Creates proof payload with verified data

​
Horizon verification example

curl https://horizon.stellar.org/transactions/3389e9f0f1a65f19736cacf544c2e825313e8447f569233bb8db39aa607c8889
If transaction exists: 
{
  "id": "3389e9f0f1a65f19736cacf544c2e825313e8447f569233bb8db39aa607c8889",
  "successful": true,
  "ledger": 12345678,
  ...
}

​
Use cases

​
Generate proof after transfer completion

// After status polling shows completed=true
const statusResponse = await fetch('/api/execute-transfer', {
  method: 'POST',
  body: JSON.stringify({
    phase: 'status',
    transactionId,
    statusRef
  })
});

const { stellarTxHash, completed } = await statusResponse.json();

if (completed && stellarTxHash) {
  const proofResponse = await fetch('/api/generate-proof', {
    method: 'POST',
    body: JSON.stringify({
      transactionId,
      stellarTxHash,
      originAmount: 100,
      originCurrency: 'USD',
      destinationAmount: 5450,
      destinationCurrency: 'PHP',
      exchangeRate: 54.5,
      totalFees: 2.5,
      route: 'MoneyGram → Philippines Anchor'
    })
  });
  
  const { proof } = await proofResponse.json();
  console.log('Proof generated:', proof.id);
  console.log('Verify at:', proof.verificationUrl);
}

​
Display proof certificate

function ProofCertificate({ proof }) {
  return (
    <div className="proof-certificate">
      <h2>Payment Verified</h2>
      <p>Proof ID: {proof.id}</p>
      <p>Amount: {proof.originAmount} {proof.originCurrency} → {proof.destinationAmount} {proof.destinationCurrency}</p>
      <p>Exchange Rate: {proof.exchangeRate}</p>
      <p>Fees: {proof.totalFees} {proof.originCurrency}</p>
      <p>Status: {proof.status}</p>
      <a href={proof.verificationUrl} target="_blank">Verify on Blockchain</a>
    </div>
  );
}

​
Implementation notes

  • Proof generation requires successful Horizon verification
  • Transaction hash must be valid 64-character hex string
  • Optional fields default to sensible values (0, “USDC”, etc.)
  • Verification URL points to StellarExpert for easy blockchain verification
  • Horizon timeout is 5 seconds (inherited from internal config)

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