DES算法java实现

2015/05/28 35564

DES算法为密码体制中的对称密码体制，又被称为美国数据加密标准，是1972年美国IBM公司研制的对称密码体制加密算法。明文按64位进行分组，密钥长64位，密钥事实上是56位参与DES运算（第8、16、24、32、40、48、56、64位是校验位，使得每个密钥都有奇数个1）分组后的明文组和56位的密钥按位替代或交换的方法形成密文组的加密方法。

DES算法具有极高安全性，到目前为止，除了用穷举搜索法对DES算法进行攻击外，还没有发现更有效的办法。而56位长的密钥的穷举空间为256，这意味着如果一台计算机的速度是每一秒钟检测一百万个密钥，则它搜索完全部密钥就需要将近2285年的时间，可见，这是难以实现的

其入口参数有三个：key、data、mode。key为加密解密使用的密钥，data为加密

解密的数据，mode为其工作模式。当模式为加密模式时，明文按照64位进行分组，形成明文组，key用于对数据加密，当模式为解密模式时，key用于对数据解密。实际运用中，密钥只用到了64位中的56位，这样才具有高的安全性。

1、算法主程序类 SymmetricAlgorithm

package com.gary.test.ws.test;

import java.io.UnsupportedEncodingException;
import java.security.InvalidKeyException;
import java.security.Key;
import java.security.NoSuchAlgorithmException;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.SecretKeySpec;

public class SymmetricAlgorithm {
    private String strKey = "&^%$*#@~";
    private String info;

    public SymmetricAlgorithm(String info) {
        this.info = info;
    }

    public SymmetricAlgorithm(String info, String strKey) {
        this.info = info;
        this.strKey = strKey;
    }

    private Key getKey() {
        byte[] keyBtye = this.strKey.getBytes();

        byte[] _keyByte = new byte[8];

        for (int i = 0; (i < keyBtye.length) && (i < _keyByte.length); i++) {
            _keyByte[i] = keyBtye[i];
        }

        return new SecretKeySpec(_keyByte, "DES");
    }

    public String desEncrypt() {
        return desEncrypt(this.info, "UTF-8");
    }

    public String desEncrypt(String origin, String encoding) {
        if ((origin == null) || (encoding == null))
            return null;
        try {
            return encrypt(origin.getBytes(encoding), "DES");
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        return null;
    }

    public String desDecrypt() {
        return desDecrypt(this.info, "UTF-8");
    }

    public String desDecrypt(String ciperData, String encoding) {
        if ((ciperData == null) || (encoding == null)) {
            return null;
        }
        byte[] b = decrypt(EncryptHelper.hex2byte(ciperData), "DES");
        try {
            return new String(b, encoding);
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        return null;
    }

    private String encrypt(byte[] data, String algorithm) {
        try {
            Key key = getKey();

            Cipher c1 = Cipher.getInstance(algorithm);
            c1.init(1, key);
            byte[] cipherByte = c1.doFinal(data);
            return EncryptHelper.byte2hex(cipherByte);
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (NoSuchPaddingException e) {
            e.printStackTrace();
        } catch (InvalidKeyException e) {
            e.printStackTrace();
        } catch (IllegalBlockSizeException e) {
            e.printStackTrace();
        } catch (BadPaddingException e) {
            e.printStackTrace();
        }
        return null;
    }

    private byte[] decrypt(byte[] data, String algorithm) {
        try {
            Key key = getKey();
            Cipher c1 = Cipher.getInstance(algorithm);
            c1.init(2, key);
            return c1.doFinal(data);
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (NoSuchPaddingException e) {
            e.printStackTrace();
        } catch (InvalidKeyException e) {
            e.printStackTrace();
        } catch (IllegalBlockSizeException e) {
            e.printStackTrace();
        } catch (BadPaddingException e) {
            e.printStackTrace();
        }
        return null;
    }

    public static void main(String[] args) {
        SymmetricAlgorithm s =new SymmetricAlgorithm("gp3adm","&^%$*#@~");//加密
        
        String sa_pwd = s.desEncrypt("gp3adm","UTF-8");
        
        System.out.println("加密后："+sa_pwd);
        String pwd = "84DFA223A4521331";

       String password = (new SymmetricAlgorithm(pwd)).desDecrypt();// 解密
       System.out.println("解密后："+password);

    }
}

2、助手类 EncryptHelper

package com.gary.test.ws.test;

public class EncryptHelper
{
  public static final String DEFAULT_ENCODING = "UTF-8";

  public static String byte2hex(byte[] bytes)
  {
    StringBuffer retString = new StringBuffer();
    for (int i = 0; i < bytes.length; i++) {
      retString.append(Integer.toHexString(256 + (bytes[i] & 0xFF)).substring(1));
    }
    return retString.toString().toUpperCase();
  }

  public static byte[] hex2byte(String hex)
  {
    byte[] bts = new byte[hex.length() / 2];
    for (int i = 0; i < bts.length; i++) {
      bts[i] = (byte)Integer.parseInt(hex.substring(2 * i, 2 * i + 2), 16);
    }
    return bts;
  }
}

代码片段