Java tutorial
//package com.java2s; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.PrintStream; import java.io.UnsupportedEncodingException; import java.security.GeneralSecurityException; import javax.crypto.Mac; import javax.crypto.SecretKey; import javax.crypto.spec.SecretKeySpec; public class Main { private static byte[] encryptHMAC(String data, String secret) throws IOException { byte[] bytes = null; try { SecretKey secretKey = new SecretKeySpec(secret.getBytes("UTF-8"), "HmacMD5"); Mac mac = Mac.getInstance(secretKey.getAlgorithm()); mac.init(secretKey); bytes = mac.doFinal(data.getBytes("UTF-8")); } catch (GeneralSecurityException gse) { String msg = getStringFromException(gse); throw new IOException(msg); } return bytes; } private static String getStringFromException(Throwable e) { String result = ""; ByteArrayOutputStream bos = new ByteArrayOutputStream(); PrintStream ps = new PrintStream(bos); e.printStackTrace(ps); try { result = bos.toString("UTF-8"); } catch (UnsupportedEncodingException e1) { // won't happen } return result; } }