Appendix 2

Signature Verification

Java

Step 1 : Import the required packages

import java.security.KeyFactory;
import java.security.PublicKey;
import java.security.Signature;

Step 2 : Create a PublicKey object from the public key bytes

KeyFactory keyFactory = KeyFactory.getInstance("RSA");
PublicKey publicKey = keyFactory.generatePublic(new X509EncodedKeySpec(publicKeyBytes));

Step 3 : Create a Signature object and initialize it with the public key

Signature signature = Signature.getInstance("SHA256withRSA");
signature.initVerify(publicKey);

Step 4 : Convert all parameters into bytes except signedMessage

response.setACQ("FNX");
response.setDeviceBrandModel("SB-001");
response.setDeviceID("SB000000001");
response.setLang("EN");
response.setTrxRefNo("FNX202302170100000000000000001");
response.setTrxCurr("MYR");
response.setTrxAmt("100.00");
response.setTrxDateTms("20230217121212236");
response.setTrxPymtBrand("PN");
response.setMID("000010000010440");
response.setTID("60003614");
Gson gson = new Gson();
String jsonStr = gson.toJson(response);
byte[] messageBytes = jsonStr.getBytes();

Step 5 : Update the signature with the message bytes

signature.update(messageBytes);

Step 6 : Convert signedMessage to bytes and verify

boolean verified = signature.verify(signedMessageBytes);

Node.js

Step 1 : Import the required packages

import forge from "node-forge";

Step 2 : Create a PublicKey object from the public key bytes

const publicKeyPath = "key/public.key";

const fetchPublicKey = async (path) => {
    try {
      const response = await fetch(path);
      const publicKey = await response.text();
      return publicKey;
    } catch (error) {
      //to do ...
    }
};

const publicKey = await fetchPublicKey(publicKeyPath);
const rsaPubicKey = forge.pki.publicKeyFromPem(publicKey);

Step 3 : Put all parameters except signedMessage as string

const response = {
    ACQ: "FNX",
    deviceBrandModel: "SB-001",
    deviceID: "SB000000001",
    lang: "EN",
    trxRefNo: "FNX202302170100000000000000001",
    trxCurr: "MYR",
    trxAmt: "100.00",
    trxDateTms: "20230217121212236",
    trxPymtBrand: "PN",
    MID: "000010000010440",
    TID: "60003614"
};

const json = JSON.stringify(request);
const jsonString = `${json}`;
const signature = "68acc11449277468cb5e619f16bcff62f5448fa3911a462fd52abadaf4bc8f3effb";
function hexToBytes(hex) {
    const bytes = [];
    for (let i = 0; i < hex.length; i += 2) {
        bytes.push(parseInt(hex.substr(i, 2), 16));
    }
    return new Uint8Array(bytes);
}
const byteArray = hexToBytes(signature);

const md = forge.md.sha256.create();
md.update(jsonString, "utf8");
const verified = rsaPubicKey.verify(md.digest().bytes(), byteArray);

Step 4 : Verify the signature

const md = forge.md.sha256.create();
md.update(jsonString, "utf8");
const verified = rsaPubicKey.verify(md.digest().bytes(), byteBuffer);

Python

Step 1 : Import the required packages

import cryptography

Step 2 : Create an RSAPublicKey object from your public key

public_key = cryptography.hazmat.primitives.asymmetric.RSAPublicKey.load_pem_public_key(
    open("public_key.pem").read()
)

Step 3 : Create a PKCS1v15 padding object

padding = cryptography.hazmat.primitives.asymmetric.padding.PKCS1v15()

Step 4 : Create a SHA256 hash object

hasher = cryptography.hazmat.primitives.hashes.SHA256()

Step 5 : Put all parameter except signedMessage as string

request_data = OrderedDict()
request_data["ACQ"] = "FNX"
request_data["deviceBrandModel"] = "SB-001"
request_data["deviceID"] = "SB000000001"
request_data["lang"] = "EN"
request_data["trxRefNo"] = "FNX202302170100000000000000001"
request_data["trxCurr"] = "MYR"
request_data["trxAmt"] = "100.00"
request_data["trxDateTms"] = "20230217121212236"
request_data["trxPymtBrand"] = "PN"
request_data["MID"] = "000010000010440"
request_data["TID"] = "60003614"
json_string = json.dumps(request_data, separators=(",", ":"))
message = f"{json_string}"
signature = "68acc11449277468cb5e619f16bcff62f5448fa3911a462fd52abadaf4bc8f3effb"

Step 6 : Use the verify() method to verify the signature

verified = public_key.verify(
    signature,
    hasher.update(message).digest(),
    padding=padding,
)

.Net

Step 1 : Import the required packages

using System.Security.Cryptography;

Step 2 : Create a PublicKey object from the public key bytes

var reader = System.IO.File.ReadAllText(@"E:\xxx\xxx\public.key");
RSA rsa = RSA.Create();
byte[] pubKey = Convert.FromBase64String(reader.Replace("-----BEGIN PUBLIC KEY-----", string.Empty)
    .Replace("-----END PUBLIC KEY-----", string.Empty)
    .Trim());
rsa.ImportSubjectPublicKeyInfo(pubKey, out _);

Step 3 : Put all parameter except signedMessage as string

request.ACQ = "FNX";
request.deviceBrandModel = "SB-001";
request.deviceID = "SB000000001";
request.lang = "EN";
request.trxRefNo = "FNX202302170100000000000000001";
request.trxCurr = "MYR";
request.trxAmt = "100.00";
request.trxDateTms = "20230217121212236";
request.trxPymtBrand = "PN";
request.MID = "000010000010440";
request.TID = "60003614";

string json = JsonConvert.SerializeObject(request);
string jsonString = json;
string signature = "68acc11449277468cb5e619f16bcff62f5448fa3911a462fd52abadaf4bc8f3effb";

Step 4 : Verify the signature

static byte[] HexStringToBytes(string hexString)
    {
        int numberChars = hexString.Length;
        byte[] bytes = new byte[numberChars / 2];
        for (int i = 0; i < numberChars; i += 2)
        {
            bytes[i / 2] = Convert.ToByte(hexString.Substring(i, 2), 16);
        }
        return bytes;
    }
bool verify = rsa.VerifyData(Encoding.UTF8.GetBytes(jsonString), HexStringToBytes(signature), HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1);

PHP

Step 1 : Import the OpenSSL extension

require_once 'vendor/autoload.php';

Step 2 : Create a new OpenSSL public key

$publicKeyFNXLocation = file_get_contents('key/xxx/xxx/public.key');
$publicKeyFNX = openssl_pkey_get_public($publicKeyFNXLocation);
$publicKeyDetailsFNX = openssl_pkey_get_details($publicKeyFNX);
$publicKeyPEM = $publicKeyDetailsFNX['key'];

Step 3 : Put all parameters except signedMessage as string

$request->ACQ = "FNX";
$request->deviceBrandModel = "SB-001";
$request->deviceID = "SB000000001";
$request->lang = "EN";
$request->trxRefNo = "FNX202302170100000000000000001";
$request->trxCurr = "MYR";
$request->trxAmt = "100.00";
$request->trxDateTms = "20230217121212236";
$request->trxPymtBrand = "PN";
$request->MID = "000010000010440";
$request->TID = "60003614";
$jsonStringResponse = json_encode($paymentResponse);
$jsonResponse = json_decode($jsonStringResponse);
$updateJsonResponse = json_encode($jsonResponse);
$minifiedJsonResponse = json_encode(json_decode($updateJsonResponse));
$dataResponse = $minifiedJsonResponse;
$minifiedJson = json_encode(json_decode($updateJson));

$decodedSignedMessage = '68acc11449277468cb5e619f16bcff62f5448fa3911a462fd52abadaf4bc8f3effb';
$decodedSignature = hex2bin($decodedUrl);

Step 4 : Verify the signature

$verifyResponse = openssl_verify($dataResponse, $decodedSignature, $publicKeyPEM, OPENSSL_ALGO_SHA256);