DES 加密

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package com.ningpai.des;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;
import java.security.SecureRandom;

/**
 * DES 加解密帮助类
 *
 * @author Chendaiming
 * @date 16/8/15
 */
public class DESHelper {
    private static final String PASSWORD_CRYPT_KEY = "kEHFx-BAllrzCuBFae-SavDvgqZq";
    private final static String ALGORITHM = "DES";
    //url标识符替换  （加号不能传输，用此字段替换）
    private static final String OMS_URL_FLAG = "OMS_URL_FLAG";


    public final static String decrypt(String data) {
        try {
            data = data.replace(OMS_URL_FLAG, "+");
            return new String(decrypt(hex2byte(data.getBytes()),
                    PASSWORD_CRYPT_KEY.getBytes()));
        } catch (Exception e) {
            e.printStackTrace();
            throw new IllegalArgumentException("decrypt error!");
        }
    }

    public final static String encrypt(String data) {
        try {
            String str = byte2hex(encrypt(data.getBytes(), PASSWORD_CRYPT_KEY
                    .getBytes()));
            str = str.replace("+", OMS_URL_FLAG);
            return str;
        } catch (Exception e) {
            e.printStackTrace();
            throw new IllegalArgumentException("encrypt error!");
        }
    }

    private static byte[] encrypt(byte[] data, byte[] key) throws Exception {
        SecureRandom sr = new SecureRandom();
        DESKeySpec dks = new DESKeySpec(key);
        SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM);
        SecretKey securekey = keyFactory.generateSecret(dks);
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, securekey, sr);
        return cipher.doFinal(data);
    }

    private static byte[] decrypt(byte[] data, byte[] key) throws Exception {
        // DES算法要求有一个可信任的随机数源
        SecureRandom sr = new SecureRandom();
        // 从原始密匙数据创建一个DESKeySpec对象
        DESKeySpec dks = new DESKeySpec(key);
        // 创建一个密匙工厂，然后用它把DESKeySpec对象转换成
        // 一个SecretKey对象
        SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM);
        SecretKey securekey = keyFactory.generateSecret(dks);
        // Cipher对象实际完成解密操作
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        // 用密匙初始化Cipher对象
        cipher.init(Cipher.DECRYPT_MODE, securekey, sr);
        // 现在，获取数据并解密
        // 正式执行解密操作
        return cipher.doFinal(data);
    }
    private static byte[] hex2byte(byte[] b) {
        if ((b.length % 2) != 0)
            throw new IllegalArgumentException("长度不是偶数");
        byte[] b2 = new byte[b.length / 2];
        for (int n = 0; n < b.length; n += 2) {
            String item = new String(b, n, 2);
            b2[n / 2] = (byte) Integer.parseInt(item, 16);
        }
        return b2;
    }
    private static String byte2hex(byte[] b) {
        String hs = "";
        String stmp = "";
        for (int n = 0; n < b.length; n++) {
            stmp = (Integer.toHexString(b[n] & 0XFF));
            if (stmp.length() == 1)
                hs = hs + "0" + stmp;
            else
                hs = hs + stmp;
        }
        return hs.toUpperCase();
    }

}