using System;
using System.Security.Cryptography;
using System.Text;

namespace ConsoleApplication1
{
    class EncryptHelper
    {
        /// <summary>
        /// MD5加密
        /// </summary>
        /// <param name="plaintext">明文</param>
        /// <param name="bytesEncoding">编码</param>
        /// <returns></returns>
        public static string MD5Encrypt(string plaintext, Encoding bytesEncoding)
        {
            byte[] sourceBytes = bytesEncoding.GetBytes(plaintext);
            MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider();
            byte[] hashedBytes = md5.ComputeHash(sourceBytes);
            return BitConverter.ToString(hashedBytes).Replace("-", "");
        }
        /// <summary>
        /// 以UTF8编码做MD5加密
        /// </summary>
        /// <param name="plaintext">明文</param>
        /// <returns></returns>
        public static string MD5Encrypt(string plaintext)
        {
            return MD5Encrypt(plaintext, Encoding.UTF8);
        }

        private const string DefaultDESKey = "loogn789";
        /// <summary>
        /// 利用DES加密算法加密字符串（可解密）
        /// </summary>
        /// <param name="plaintext">被加密的字符串</param>
        /// <param name="key">密钥（只支持8个字节的密钥）</param>
        /// <returns>加密后的字符串</returns>
        public static string EncryptString(string plaintext, string key = DefaultDESKey)
        {
            DES des = new DESCryptoServiceProvider();
            des.Key = Encoding.UTF8.GetBytes(key);
            des.IV = Encoding.UTF8.GetBytes(key);
            byte[] bytes = Encoding.UTF8.GetBytes(plaintext);
            , bytes.Length);
            return Convert.ToBase64String(resultBytes);
        }

        /// <summary>
        /// 利用DES解密算法解密密文（可解密）
        /// </summary>
        /// <param name="ciphertext">被解密的字符串</param>
        /// <param name="key">密钥（只支持8个字节的密钥，同前面的加密密钥相同）</param>
        /// <returns>返回被解密的字符串</returns>
        public static string DecryptString(string ciphertext, string key = DefaultDESKey)
        {
            DES des = new DESCryptoServiceProvider();
            des.Key = Encoding.UTF8.GetBytes(key);
            des.IV = Encoding.UTF8.GetBytes(key);
            byte[] bytes = Convert.FromBase64String(ciphertext);
            , bytes.Length);
            return Encoding.UTF8.GetString(resultBytes);
        }
    }
}

package net.loogn.utils;

import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;

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

import java.security.MessageDigest;

/**
 * Created by loogn on 2016/8/31 0031.
 */
public class EncryptHelper {
    public final static String md5(String s) {
        char hexDigits[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};
        try {
            byte[] btInput = s.getBytes();
            // 获得MD5摘要算法的 MessageDigest 对象
            MessageDigest mdInst = MessageDigest.getInstance("MD5");
            // 使用指定的字节更新摘要
            mdInst.update(btInput);
            // 获得密文
            byte[] md = mdInst.digest();
            // 把密文转换成十六进制的字符串形式
            int j = md.length;
            char str[] = new char[j * 2];
            int k = 0;
            for (int i = 0; i < j; i++) {
                byte byte0 = md[i];
                str[k++] = hexDigits[byte0 >>> 4 & 0xf];
                str[k++] = hexDigits[byte0 & 0xf];
            }
            return new String(str);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    public static String encryptString(String plaintext, String key) throws Exception {
        Cipher cipher = Cipher.getInstance("DES/CBC/PKCS5Padding");

        DESKeySpec desKeySpec = new DESKeySpec(key.getBytes("UTF-8"));

        SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
        SecretKey secretKey = keyFactory.generateSecret(desKeySpec);
        IvParameterSpec iv = new IvParameterSpec(key.getBytes("UTF-8"));
        cipher.init(Cipher.ENCRYPT_MODE, secretKey, iv);

        byte[] bt = cipher.doFinal(plaintext.getBytes("UTF-8"));
        String strs = new BASE64Encoder().encode(bt);
        return strs;
    }

    public static String decryptString(String ciphertext, String key) throws Exception {
        Cipher cipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
        DESKeySpec desKeySpec = new DESKeySpec(key.getBytes("UTF-8"));
        SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
        SecretKey secretKey = keyFactory.generateSecret(desKeySpec);
        IvParameterSpec iv = new IvParameterSpec(key.getBytes("UTF-8"));
        cipher.init(Cipher.DECRYPT_MODE, secretKey, iv);
        byte[] bt = cipher.doFinal(new BASE64Decoder().decodeBuffer(ciphertext));
        String strs = new String(bt);
        return strs;
    }
}