DES、MD5、RSA加密算法

本篇主要是实现标题中的三个加密算法，至于机制大家自行百度吧。

一、DES

实现类：DES.java

package com.kale.des;

import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;
/*
 * DES加密介绍
    DES是一种对称加密算法，所谓对称加密算法即：加密和解密使用相同密钥的算法。
    DES加密算法出自IBM的研究，后来被美国政府正式采用，之后开始广泛流传，但是近些年使用越来越少，
     因为DES使用56位密钥，以现代计算能力，24小时内即可被破解。虽然如此，在某些简单应用中，我们还是可
    以 使用DES加密算法，本文简单讲解DES的JAVA实现。
 */
public class DES{

    /**
     * 加密过程，密钥长度都必须是8的倍数
     * @param datasource
     * @param password
     * @return 加密后的结果
     */
    public static byte[] desLock(byte[] datasource, String password) {
        try{
            SecureRandom random = new SecureRandom();
            DESKeySpec desKey = new DESKeySpec(password.getBytes());
            //创建一个密匙工厂，然后用它把DESKeySpec转换成
            SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
            SecretKey securekey = keyFactory.generateSecret(desKey);
            //Cipher对象实际完成加密操作
            Cipher cipher = Cipher.getInstance("DES");
            //用密匙初始化Cipher对象
            cipher.init(Cipher.ENCRYPT_MODE, securekey, random);
            //现在，获取数据并加密
            //正式执行加密操作
            return cipher.doFinal(datasource);
        }catch(Throwable e){
            e.printStackTrace();
        }
        return null;
    }

    /**
     * 解密过程，密钥长度都必须是8的倍数
     * @param src
     * @param password
     * @return 解密后的内容
     * @throws Exception
     */
    public static byte[] desUnclock(byte[] src, String password) throws Exception {
        // DES算法要求有一个可信任的随机数源
        SecureRandom random = new SecureRandom();
        // 创建一个DESKeySpec对象
        DESKeySpec desKey = new DESKeySpec(password.getBytes());
        // 创建一个密匙工厂
        SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
        // 将DESKeySpec对象转换成SecretKey对象
        SecretKey securekey = keyFactory.generateSecret(desKey);
        // Cipher对象实际完成解密操作
        Cipher cipher = Cipher.getInstance("DES");
        // 用密匙初始化Cipher对象
        cipher.init(Cipher.DECRYPT_MODE, securekey, random);
        // 真正开始解密操作
        return cipher.doFinal(src);
    }

}

测试类：DesTest.java

package com.kale.des;

public class DesTest {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO 自动生成的方法存根
        //待加密内容
        String str = "kale123456789";
        //密码，长度要是8的倍数
        String password = "12345678";
        byte[] result = null;
        try{
            result = DES.desLock(str.getBytes(),password);
            System.out.println("加密后内容为："+new String(result));
        }
        catch(Exception e){
            System.out.println("加密失败！");
        }

        //解密
        try {
            byte[] unLockResult = DES.desUnclock(result, password);
            System.out.println("解密后内容为："+new String(unLockResult));
        }
        catch (Exception e1) {
            //e1.printStackTrace();
            System.out.println("密钥错误，无法解密！");
        }
    }

}

结果：

加密后内容为：S��:�3@d!�A��.
解密后内容为：kale123456789

二、MD5

实现类：MD5.java

package com.kale.md5;

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

public class MD5 {
    /*
       * MD5加密
       */
      public static String getMD5Str(String str) {
          MessageDigest messageDigest = null;     

          try {
              messageDigest = MessageDigest.getInstance("MD5");     

              messageDigest.reset();     

              messageDigest.update(str.getBytes("UTF-8"));
          } catch (NoSuchAlgorithmException e) {
              System.out.println("NoSuchAlgorithmException caught!");
              System.exit(-1);
          } catch (UnsupportedEncodingException e) {
              e.printStackTrace();
          }     

          byte[] byteArray = messageDigest.digest();     

          StringBuffer md5StrBuff = new StringBuffer();     

          for (int i = 0; i < byteArray.length; i++) {
              if (Integer.toHexString(0xFF & byteArray[i]).length() == 1)
                  md5StrBuff.append("0").append(Integer.toHexString(0xFF & byteArray[i]));
              else
                  md5StrBuff.append(Integer.toHexString(0xFF & byteArray[i]));
          }
          //16位加密，从第9位到25位
          return md5StrBuff.substring(8, 24).toString().toUpperCase();
      }
}  

测试类：Md5Test.java

package com.kale.md5;

public class Md5Test {

    /**
     * @param args
     */
    public static void main(String[] args) {
        String password = "123456789";
        String result = MD5.getMD5Str(password);
        System.out.println(result.toLowerCase());
    }

}

结果：323b453885f5181f

三、RSA

实现类：RSA.java

package com.kale.rsa;

import java.math.BigInteger;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.RSAPrivateKeySpec;
import java.security.spec.RSAPublicKeySpec;
import java.util.HashMap;

import javax.crypto.Cipher;

public class RSA{

    /**
     * 生成公钥和私钥
     * @throws NoSuchAlgorithmException
     *
     */
    public static HashMap<String, Object> getKeys() throws NoSuchAlgorithmException{
        HashMap<String, Object> map = new HashMap<String, Object>();
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
        keyPairGen.initialize(1024);
        KeyPair keyPair = keyPairGen.generateKeyPair();
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
        map.put("public", publicKey);
        map.put("private", privateKey);
        return map;
    }
    /**
     * 使用模和指数生成RSA公钥
     * 注意：【此代码用了默认补位方式，为RSA/None/PKCS1Padding，不同JDK默认的补位方式可能不同，如Android默认是RSA
     * /None/NoPadding】
     *
     * @param modulus
     *            模
     * @param exponent
     *            指数
     * @return
     */
    public static RSAPublicKey getPublicKey(String modulus, String exponent) {
        try {
            BigInteger b1 = new BigInteger(modulus);
            BigInteger b2 = new BigInteger(exponent);
            KeyFactory keyFactory = KeyFactory.getInstance("RSA");
            RSAPublicKeySpec keySpec = new RSAPublicKeySpec(b1, b2);
            return (RSAPublicKey) keyFactory.generatePublic(keySpec);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    /**
     * 使用模和指数生成RSA私钥
     * 注意：【此代码用了默认补位方式，为RSA/None/PKCS1Padding，不同JDK默认的补位方式可能不同，如Android默认是RSA
     * /None/NoPadding】
     *
     * @param modulus
     *            模
     * @param exponent
     *            指数
     * @return
     */
    public static RSAPrivateKey getPrivateKey(String modulus, String exponent) {
        try {
            BigInteger b1 = new BigInteger(modulus);
            BigInteger b2 = new BigInteger(exponent);
            KeyFactory keyFactory = KeyFactory.getInstance("RSA");
            RSAPrivateKeySpec keySpec = new RSAPrivateKeySpec(b1, b2);
            return (RSAPrivateKey) keyFactory.generatePrivate(keySpec);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    /**
     * 公钥加密
     *
     * @param data
     * @param publicKey
     * @return
     * @throws Exception
     */
    public static String encryptByPublicKey(String data, RSAPublicKey publicKey)
            throws Exception {
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        // 模长
        int key_len = publicKey.getModulus().bitLength() / 8;
        // 加密数据长度 <= 模长-11
        String[] datas = splitString(data, key_len - 11);
        String mi = "";
        //如果明文长度大于模长-11则要分组加密
        for (String s : datas) {
            mi += bcd2Str(cipher.doFinal(s.getBytes()));
        }
        return mi;
    }

    /**
     * 私钥解密
     *
     * @param data
     * @param privateKey
     * @return
     * @throws Exception
     */
    public static String decryptByPrivateKey(String data, RSAPrivateKey privateKey)
            throws Exception {
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        //模长
        int key_len = privateKey.getModulus().bitLength() / 8;
        byte[] bytes = data.getBytes();
        byte[] bcd = ASCII_To_BCD(bytes, bytes.length);
        System.err.println(bcd.length);
        //如果密文长度大于模长则要分组解密
        String ming = "";
        byte[][] arrays = splitArray(bcd, key_len);
        for(byte[] arr : arrays){
            ming += new String(cipher.doFinal(arr));
        }
        return ming;
    }
    /**
     * ASCII码转BCD码
     *
     */
    public static byte[] ASCII_To_BCD(byte[] ascii, int asc_len) {
        byte[] bcd = new byte[asc_len / 2];
        int j = 0;
        for (int i = 0; i < (asc_len + 1) / 2; i++) {
            bcd[i] = asc_to_bcd(ascii[j++]);
            bcd[i] = (byte) (((j >= asc_len) ? 0x00 : asc_to_bcd(ascii[j++])) + (bcd[i] << 4));
        }
        return bcd;
    }
    public static byte asc_to_bcd(byte asc) {
        byte bcd;

        if ((asc >= '0') && (asc <= '9'))
            bcd = (byte) (asc - '0');
        else if ((asc >= 'A') && (asc <= 'F'))
            bcd = (byte) (asc - 'A' + 10);
        else if ((asc >= 'a') && (asc <= 'f'))
            bcd = (byte) (asc - 'a' + 10);
        else
            bcd = (byte) (asc - 48);
        return bcd;
    }
    /**
     * BCD转字符串
     */
    public static String bcd2Str(byte[] bytes) {
        char temp[] = new char[bytes.length * 2], val;

        for (int i = 0; i < bytes.length; i++) {
            val = (char) (((bytes[i] & 0xf0) >> 4) & 0x0f);
            temp[i * 2] = (char) (val > 9 ? val + 'A' - 10 : val + '0');

            val = (char) (bytes[i] & 0x0f);
            temp[i * 2 + 1] = (char) (val > 9 ? val + 'A' - 10 : val + '0');
        }
        return new String(temp);
    }
    /**
     * 拆分字符串
     */
    public static String[] splitString(String string, int len) {
        int x = string.length() / len;
        int y = string.length() % len;
        int z = 0;
        if (y != 0) {
            z = 1;
        }
        String[] strings = new String[x + z];
        String str = "";
        for (int i=0; i<x+z; i++) {
            if (i==x+z-1 && y!=0) {
                str = string.substring(i*len, i*len+y);
            }else{
                str = string.substring(i*len, i*len+len);
            }
            strings[i] = str;
        }
        return strings;
    }
    /**
     *拆分数组
     */
    public static byte[][] splitArray(byte[] data,int len){
        int x = data.length / len;
        int y = data.length % len;
        int z = 0;
        if(y!=0){
            z = 1;
        }
        byte[][] arrays = new byte[x+z][];
        byte[] arr;
        for(int i=0; i<x+z; i++){
            arr = new byte[len];
            if(i==x+z-1 && y!=0){
                System.arraycopy(data, i*len, arr, 0, y);
            }else{
                System.arraycopy(data, i*len, arr, 0, len);
            }
            arrays[i] = arr;
        }
        return arrays;
    }
}

测试类：RsaTest.java

package com.kale.rsa;

import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.util.HashMap;

public class RsaTest {

    public static void main(String[] args) throws Exception {
        // TODO Auto-generated method stub
        HashMap<String, Object> map = RSA.getKeys();
        //生成公钥和私钥
        RSAPublicKey publicKey = (RSAPublicKey) map.get("public");
        RSAPrivateKey privateKey = (RSAPrivateKey) map.get("private");

        //模
        String modulus = publicKey.getModulus().toString();
        //公钥指数
        String public_exponent = publicKey.getPublicExponent().toString();
        //私钥指数
        String private_exponent = privateKey.getPrivateExponent().toString();
        //明文
        String ming = "kale123456789";
        //使用模和指数生成公钥和私钥
        RSAPublicKey pubKey = RSA.getPublicKey(modulus, public_exponent);
        RSAPrivateKey priKey = RSA.getPrivateKey(modulus, private_exponent);
        //加密后的密文
        String mi = RSA.encryptByPublicKey(ming, pubKey);
        System.out.println(mi);
        //解密后的明文
        ming = RSA.decryptByPrivateKey(mi, priKey);
        System.out.println(ming);
    }
}

结果：

81169AA3AF3CEC80AAA685B0500A2BF058AB13BDEBA62A3D38AD382C444F66EC3DCA3C7E0225DF73C529EB94DDB978B761A87FB26518DEAC7FF85678BFB2B117B765E32E8E7A23864D2D69E9E351AA8FAA26F02F9964DA6275744833D7C8ABF2552DA83DBE66E682CE0592D3595220FAD9E4D56D849867135DE0CD3BDDFDCAF2
128
kale123456789

源码下载：http://download.csdn.net/detail/shark0017/8075485