DataTransferSign.java

package controllers;

import java.io.UnsupportedEncodingException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;

public class DataTransferSign
{
	private static String key = "your_key";
	private static String merchId = "your_merchID";

	public static void main(String[] args) throws Exception
	{
		String amount = args[0];
		String ccy = args[1];
		String idno = args[2];

		String str = merchId + amount + ccy + idno;
		System.out.println(hmacDigest(str, key, "HmacMD5"));
	}

	public static byte[] hexStringToByteArray(String s)
	{
		int len = s.length();
		byte[] data = new byte[len / 2];
		for (int i = 0; i < len; i += 2)
		{
			data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4) + Character.digit(s.charAt(i + 1), 16));
		}
		return data;
	}

	public static String hmacDigest(String msg, String keyString, String algo)
	{
		String digest = null;
		try
		{
			byte[] hexStringToByteArray = hexStringToByteArray(keyString);
			SecretKeySpec key = new SecretKeySpec(hexStringToByteArray, algo);
			Mac mac = Mac.getInstance(algo);
			mac.init(key);

			byte[] bytes = mac.doFinal(msg.getBytes("ASCII"));

			StringBuffer hash = new StringBuffer();
			for (int i = 0; i < bytes.length; i++)
			{
				String hex = Integer.toHexString(0xFF & bytes[i]);
				if (hex.length() == 1)
				{
					hash.append('0');
				}
				hash.append(hex);
			}
			digest = hash.toString();
		}
		catch (UnsupportedEncodingException e)
		{
		}
		catch (InvalidKeyException e)
		{
		}
		catch (NoSuchAlgorithmException e)
		{
		}
		return digest;
	}
}