对称加密（Des）

package com.library.app.instrument;

import android.annotation.SuppressLint;
import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;

/**
 * DES算法加密解密
 * 
 * @date 2014-7-16 上午11:19:22
 * @see MD5
 */
public class DesUtil {

    private static final String PASSWORD_CRYPT_KEY = "e8c385c92b815edde652b1eeb4cbac7a";
    private final static String DES = "DES";

    /**
     * 加密
     * 
     * @param src
     *            数据源
     * @param key
     *            密钥，长度必须是8的倍数
     * @return 返回加密后的数据
     * @throws Exception
     */
    public static byte[] encrypt(byte[] src, 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DESKeySpec对象
        DESKeySpec dks = new DESKeySpec(key);
        // 创建一个密匙工厂，然后用它把DESKeySpec转换成
        // 一个SecretKey对象
        SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(DES);
        SecretKey securekey = keyFactory.generateSecret(dks);
        // 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, sr);
        // 现在，获取数据并加密
        // 正式执行加密操作
        return cipher.doFinal(src);
    }

    /**
     * 解密
     * 
     * @param src
     *            数据源
     * @param key
     *            密钥，长度必须是8的倍数
     * @return 返回解密后的原始数据
     * @throws Exception
     */
    public static byte[] decrypt(byte[] src, 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(DES);
        SecretKey securekey = keyFactory.generateSecret(dks);
        // 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, sr);
        // 现在，获取数据并解密
        // 正式执行解密操作
        return cipher.doFinal(src);
    }

    /**
     * 解密
     * 
     * @param data
     * @return
     * @throws Exception
     */
    public final static String decrypt(String data) {
        return decrypt(data, PASSWORD_CRYPT_KEY);
    }

    /**
     * 解密
     * 
     * @param data
     * @return
     * @throws Exception
     */
    public final static String decrypt(String data, String key) {
        try {
            return new String(decrypt(hex2byte(data.getBytes()), key.getBytes()));
        } catch (Exception e) {
        }
        return null;
    }

    /**
     * 加密
     * 
     * @param password
     * @return
     * @throws Exception
     */
    public final static String encrypt(String password) {
        return encrypt(password, PASSWORD_CRYPT_KEY);
    }

    /**
     * 加密
     * 
     * @param password
     * @return
     * @throws Exception
     */
    public final static String encrypt(String password, String key) {
        try {
            return byte2hex(encrypt(password.getBytes(), key.getBytes()));
        } catch (Exception e) {
        }
        return null;
    }

    public static void main(String[] args) {
        System.out.println(encrypt("20352"));
    }

    /**
     * 
     * 二行制转字符串
     * 
     * @param b
     * 
     * @return
     */

    @SuppressLint("DefaultLocale")
    public static String byte2hex(byte[] b) {

        String hs = "";

        String stmp = "";

        for (int n = 0; n < b.length; n++) {

            stmp = (java.lang.Integer.toHexString(b[n] & 0XFF));

            if (stmp.length() == 1)

                hs = hs + "0" + stmp;

            else

                hs = hs + stmp;

        }

        return hs.toUpperCase();

    }

    public static int changeCode(int code) {
        if (code > 127) {
            code -= 95;
        } else if (code < 32) {
            code += 95;
        }
        return code;
    }

    public 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;
    }

}