Signature Authentication

Overview

All API requests must be authenticated and signed to ensure request security and integrity.

Authentication Method

Header Authentication

Each request must include the following fields in the request header:

x-access-keystringRequired

Merchant access identifier assigned by the platform

signaturestringRequired

Request signature

Example

POST /api/v2/pay/submit
Content-Type: application/json
x-access-key: MERCHANT_001
signature: a1b2c3d4e5f6...

Signature Algorithm

Signature Calculation Steps

Step 1: Prepare Parameters

Collect all body parameters and exclude:

• The signature field itself
• Parameters with null or empty string values

Request Parameter Example

{
  "timestamp": "1742205605123",
  "orderAmount": "12000",
  "merchantOrderNo": "BDC202604170001",
  "payMethod": "BKASH",
  "customerName": "Rahim",
  "customerPhone": "01712345678",
  "customerEmail": "pkbuyer@gmail.com",
  "callbackUrl": "https://merchant.example.com/payments/notify"
}

Step 2: Sort Parameters

Sort all parameters alphabetically by parameter name (a-z).

Example

After sorting:
callbackUrl, customerEmail, customerName, customerPhone, merchantOrderNo, orderAmount, payMethod, timestamp

Step 3: Concatenate String

Concatenate the sorted parameters in key=value format, joined by &. Use the original string values from the request when building the signing string.

Example

callbackUrl=https://merchant.example.com/payments/notify&customerEmail=pkbuyer@gmail.com&customerName=Rahim&customerPhone=01712345678&merchantOrderNo=BDC202604170001&orderAmount=12000&payMethod=BKASH&timestamp=1742205605123

Step 4: Append Secret Key

Append the merchant's Secret Key to the end of the concatenated string.

Example

callbackUrl=https://merchant.example.com/payments/notify&customerEmail=pkbuyer@gmail.com&customerName=Rahim&customerPhone=01712345678&merchantOrderNo=BDC202604170001&orderAmount=12000&payMethod=BKASH&timestamp=1742205605123{SECRET_KEY}

Step 5: Calculate Hash

Use the SHA256 algorithm to calculate the hash value.

Step 6: Convert to Lowercase

Convert the hash result to a lowercase hexadecimal string.

Final Signature

If the example above uses demo_secret_key_bd as the secret key, the signature result is:

acfc0c9a2b8538fbad46bb6b09aa902f3378579487a6b95fb7fcdac1fdbd2bc0

Async callback signature verification follows the same rule above. The callback signature field is also named signature, and the signature field itself must be excluded during verification.

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Signature Example Code

Java

import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Map;
import java.util.TreeMap;

public class SignUtil {

    public static String sign(Map<String, Object> params, String secretKey) throws NoSuchAlgorithmException {
        // 1. Use TreeMap for alphabetical sorting, filter empty values and signature field
        TreeMap<String, String> sortedParams = new TreeMap<>();
        for (Map.Entry<String, Object> entry : params.entrySet()) {
            String key = entry.getKey();
            Object value = entry.getValue();
            if (value != null && !"".equals(value) && !"signature".equals(key)) {
                sortedParams.put(key, value.toString());
            }
        }

        // 2. Concatenate parameters in key=value&key=value format
        StringBuilder sb = new StringBuilder();
        for (Map.Entry<String, String> entry : sortedParams.entrySet()) {
            if (sb.length() > 0) {
                sb.append("&");
            }
            sb.append(entry.getKey()).append("=").append(entry.getValue());
        }

        // 3. Append secret key
        sb.append(secretKey);

        // 4. Calculate SHA256
        MessageDigest md = MessageDigest.getInstance("SHA-256");
        byte[] hash = md.digest(sb.toString().getBytes(StandardCharsets.UTF_8));

        // 5. Convert to lowercase hexadecimal
        StringBuilder hexString = new StringBuilder();
        for (byte b : hash) {
            String hex = Integer.toHexString(b & 0xff);
            if (hex.length() == 1) {
                hexString.append('0');
            }
            hexString.append(hex);
        }

        return hexString.toString().toLowerCase();
    }
}

Node.js

const crypto = require('crypto');

function generateSignature(params, secretKey) {
  // 1. Filter empty values and signature field
  const filteredParams = {};
  for (const [key, value] of Object.entries(params)) {
    if (value !== null && value !== '' && key !== 'signature') {
      filteredParams[key] = value;
    }
  }

  // 2. Sort alphabetically
  const sortedKeys = Object.keys(filteredParams).sort();

  // 3. Concatenate parameters
  const signStr = sortedKeys
    .map(key => `${key}=${filteredParams[key]}`)
    .join('&');

  // 4. Append secret key and calculate SHA256
  const finalStr = signStr + secretKey;
  return crypto.createHash('sha256').update(finalStr).digest('hex').toLowerCase();
}

Java Usage Example

Map<String, Object> params = new HashMap<>();
params.put("timestamp", "1742205605123");
params.put("orderAmount", "12000");
params.put("merchantOrderNo", "BDC202604170001");
params.put("payMethod", "BKASH");
params.put("customerName", "Rahim");
params.put("customerPhone", "01712345678");
params.put("customerEmail", "pkbuyer@gmail.com");
params.put("callbackUrl", "https://merchant.example.com/payments/notify");

String signature = SignUtil.sign(params, "demo_secret_key_bd");
System.out.println(signature);
// acfc0c9a2b8538fbad46bb6b09aa902f3378579487a6b95fb7fcdac1fdbd2bc0

Node.js Usage Example

const params = {
  timestamp: '1742205605123',
  orderAmount: '12000',
  merchantOrderNo: 'BDC202604170001',
  payMethod: 'BKASH',
  customerName: 'Rahim',
  customerPhone: '01712345678',
  customerEmail: 'pkbuyer@gmail.com',
  callbackUrl: 'https://merchant.example.com/payments/notify',
};

const signature = generateSignature(params, 'demo_secret_key_bd');
console.log(signature);
// acfc0c9a2b8538fbad46bb6b09aa902f3378579487a6b95fb7fcdac1fdbd2bc0