消息摘要-mac

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摘要分类：MD SHA MAC 常用于验证数据的完整性，是数据签名算法的核心算法

可以说MAC是在SHA MD基础上发展而来,现也称HMAC算法，兼容了MD和SHA算法的特性，HMAC 摘要长度等同SHA1算法的摘要长度，160位的二进制数！区别就是有无密钥

例子:jdk Hmac实现与Bouncy castle实现

package com.example.encryption;import org.apache.commons.codec.DecoderException;import org.apache.commons.codec.binary.Hex;import org.bouncycastle.crypto.digests.MD5Digest;import org.bouncycastle.crypto.macs.HMac;import org.bouncycastle.crypto.params.KeyParameter;import java.security.InvalidKeyException;import java.security.NoSuchAlgorithmException;import javax.crypto.KeyGenerator;import javax.crypto.Mac;import javax.crypto.SecretKey;import javax.crypto.spec.SecretKeySpec;/** * @author xuanyouwu * @email xuanyouwu@163.com * @time 2016-05-14 20:05 */public class MacTest {    private static String SrcData = "xuanyouwu";    public static void log(String s) {        System.out.println("------>" + s);    }    public static void main(String[] args) throws Exception {        log("jdk Hmac:" + jdkHmacMd5(SrcData));        log("jdk Hmac mykey:" + jdkHmacMd5WithMyKey(SrcData));        log("bc Hmac:" + bcHmacMD5(SrcData));    }    //JDK 方式实现 默认密钥    private static String jdkHmacMd5(String src) {        try {            //初始化KeyGenerator            KeyGenerator keyGenerator = KeyGenerator.getInstance("HmacMD5");//名称请参考图            //产生密钥            SecretKey secretKey = keyGenerator.generateKey();            //获取密钥            byte[] key = secretKey.getEncoded();            //还原密钥            SecretKey restoreKey = new SecretKeySpec(key, "HmacMD5");            //实例化MAC            Mac mac = Mac.getInstance(restoreKey.getAlgorithm());            //初始化mac            mac.init(restoreKey);            //执行摘要            byte[] hamcMD5bytes = mac.doFinal(src.getBytes());            return Hex.encodeHexString(hamcMD5bytes);        } catch (NoSuchAlgorithmException e) {            e.printStackTrace();        } catch (InvalidKeyException e) {            e.printStackTrace();        }        return "";    }    //JDK 方式实现 自定义密钥    private static String jdkHmacMd5WithMyKey(String src) {        try {            //使用自定义密钥            byte[] key = Hex.decodeHex(new char[]{'a', 'b'});// 必须是16进制的字符，长度必须是2的倍数            //还原密钥            SecretKey restoreKey = new SecretKeySpec(key, "HmacMD5");            //实例化MAC            Mac mac = Mac.getInstance(restoreKey.getAlgorithm());            //初始化mac            mac.init(restoreKey);            //执行摘要            byte[] hamcMD5bytes = mac.doFinal(src.getBytes());            return Hex.encodeHexString(hamcMD5bytes);        } catch (NoSuchAlgorithmException e) {            e.printStackTrace();        } catch (InvalidKeyException e) {            e.printStackTrace();        } catch (DecoderException e) {            e.printStackTrace();        }        return "";    }    // bouncy castle实现方式    private static String bcHmacMD5(String src) {        HMac hMac = new HMac(new MD5Digest());        hMac.init(new KeyParameter(org.bouncycastle.util.encoders.Hex.decode("ab")));// 必须是16进制的字符，长度必须是2的倍数        hMac.update(src.getBytes(), 0, src.getBytes().length);        byte[] bytes = new byte[hMac.getMacSize()];        hMac.doFinal(bytes, 0);        return org.bouncycastle.util.encoders.Hex.toHexString(bytes);    }}

运行结果:

------>jdk Hmac:6cd35433ba176fcf6fba69e43567242a
------>jdk Hmac mykey:6eceb961c0aaf966888a2d935d3b78dd
------>bc Hmac:6eceb961c0aaf966888a2d935d3b78dd

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