MAC (Message Authentication Code，消息认证码算法）

需要将密钥发送到对方，对方用该密钥进行摘要处理，进行摘要验证。

//初始化KeyGenerator

KeyGenerator keyGenerator= KeyGenerator.getInstance("HmacMd5");

//出生密钥

SecretKey secretKey=KeyGenerator.generator();

//获得密钥

byte[] key=secretKey.getEncoded();

//还原，获得密钥

SecretKey seretKey= new SecretKeySpec(key, "HmacMD5");

//做消息摘要

Mac mc=Mac.getInstance(secretKey.getAlgorithm());

//初始化MAC

mac.init(secretKey);

//执行消息摘要

byte[] data=mac.doFinal(data);

---

public class MACode
{

        //产生密钥

        public static byte[]
initHmacMD5Key() throws Exception{

              KeyGenerator keyGenerator=KeyGenerator. getInstance("HmacMD5");

//            KeyGenerator keyGenerator=KeyGenerator.getInstance("HmacSHA1");

//            KeyGenerator keyGenerator=KeyGenerator.getInstance("HmacSHA256");

//            KeyGenerator keyGenerator=KeyGenerator.getInstance("HmacSHA384");

//            KeyGenerator keyGenerator=KeyGenerator.getInstance("HmacSHA512");

              

              SecretKey secretKey=keyGenerator.generateKey();

               return secretKey.getEncoded();

       }

       

        //进行消息摘要

        public static byte[]
encodeHmacMD5(byte[] data, byte[]
key) throws Exception{

               //还原密钥

              SecretKey secretKey= new SecretKeySpec(key,"HmacMD5" );

//            SecretKey secretKey=new SecretKeySpec(key,"HmacSHA1");

//            SecretKey secretKey=new SecretKeySpec(key,"HmacSHA256");

//            SecretKey secretKey=new SecretKeySpec(key,"HmacSHA384");

//            SecretKey secretKey=new SecretKeySpec(key,"HmacSHA512");

              

               //实例化mac

              Mac mac=Mac. getInstance(secretKey.getAlgorithm());

               //初始化mac

              mac.init(secretKey);

               //返回消息摘要

               return mac.doFinal(data);

       }

        public static final void main(String[]
args) throws Exception{

              String str= "MAC消息摘要" ;

               //初始化密钥

               byte[]
b=initHmacMD5Key();

               //获取消息摘要

               byte[]
data=encodeHmacMD5(str.getBytes(), b);

              System. out.println(new String(Hex.encode(data))); //进行十六进制处理

       }

}