/*
 * DES 使用一个 56 位的密钥以及附加的 8 位奇偶校验位，产生最大 64 位的分组大小。
 * 这是一个迭代的分组密码，使用称为 Feistel 的技术，其中将加密的文本块分成两半。
 * 使用子密钥对其中一半应用循环功能，然后将输出与另一半进行"异或"运算;
 * 接着交换这两半，这一过程会继续下去，但最后一个循环不交换。
 * DES 使用 16 个循环，使用异或，置换，代换，移位操作四种基本运算。
 */

using System;
using System.Text;
using System.Security.Cryptography;//这个是处理文字编码的前提
using System.IO;

namespace GTech.Solution.Api.Common
{
    public  static class DESEncrytion
    {
        #region 1、加密向量自定义
        /// <summary>
        /// DES加密方法
        /// </summary>
        /// <param name="strPlain">明文</param>
        /// <param name="strDESKey">密钥</param>
        /// <param name="strDESIV">向量</param>
        /// <returns>密文</returns>
        public static string DESEncrypt(string strPlain, string strDESKey, string strDESIV)
        {
            //把密钥转换成字节数组
            byte[] bytesDESKey = ASCIIEncoding.ASCII.GetBytes(strDESKey);
            //把向量转换成字节数组
            byte[] bytesDESIV = ASCIIEncoding.ASCII.GetBytes(strDESIV);
            //声明1个新的DES对象
            DESCryptoServiceProvider desEncrypt = new DESCryptoServiceProvider();
            //开辟一块内存流
            MemoryStream msEncrypt = new MemoryStream();
            //把内存流对象包装成加密流对象
            CryptoStream csEncrypt = new CryptoStream(msEncrypt, desEncrypt.CreateEncryptor(bytesDESKey, bytesDESIV), CryptoStreamMode.Write);
            //把加密流对象包装成写入流对象
            StreamWriter swEncrypt = new StreamWriter(csEncrypt);
            //写入流对象写入明文
            swEncrypt.WriteLine(strPlain);
            //写入流关闭
            swEncrypt.Close();
            //加密流关闭
            csEncrypt.Close();
            //把内存流转换成字节数组，内存流现在已经是密文了
            byte[] bytesCipher = msEncrypt.ToArray();
            //内存流关闭
            msEncrypt.Close();
            //把密文字节数组转换为字符串，并返回
            return UnicodeEncoding.Unicode.GetString(bytesCipher);
        }
        /// <summary>
        /// DES解密方法
        /// </summary>
        /// <param name="strCipher">密文</param>
        /// <param name="strDESKey">密钥</param>
        /// <param name="strDESIV">向量</param>
        /// <returns>明文</returns>
        public static string DESDecrypt(string strCipher, string strDESKey, string strDESIV)
        {
            //把密钥转换成字节数组
            byte[] bytesDESKey = ASCIIEncoding.ASCII.GetBytes(strDESKey);
            //把向量转换成字节数组
            byte[] bytesDESIV = ASCIIEncoding.ASCII.GetBytes(strDESIV);
            //把密文转换成字节数组
            byte[] bytesCipher = UnicodeEncoding.Unicode.GetBytes(strCipher);
            //声明1个新的DES对象
            DESCryptoServiceProvider desDecrypt = new DESCryptoServiceProvider();
            //开辟一块内存流，并存放密文字节数组
            MemoryStream msDecrypt = new MemoryStream(bytesCipher);
            //把内存流对象包装成解密流对象
            CryptoStream csDecrypt = new CryptoStream(msDecrypt, desDecrypt.CreateDecryptor(bytesDESKey, bytesDESIV), CryptoStreamMode.Read);
            //把解密流对象包装成读出流对象
            StreamReader srDecrypt = new StreamReader(csDecrypt);
            //明文=读出流的读出内容
            string strPlainText = srDecrypt.ReadLine();
            //读出流关闭
            srDecrypt.Close();
            //解密流关闭
            csDecrypt.Close();
            //内存流关闭
            msDecrypt.Close();
            //返回明文
            return strPlainText;
        }
        
        #endregion
      
        #region 2、加密向量默认值

        //默认密钥向量 
        private static byte[] Keys = { 0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF };
        /// <summary> 
        /// DES加密字符串 
        /// </summary> 
        /// <param name="encryptString">待加密的字符串</param> 
        /// <param name="encryptKey">加密密钥,要求为8位</param> 
        /// <returns>加密成功返回加密后的字符串，失败返回源串</returns> 
        public static string EncryptDES(string encryptString, string encryptKey)
        {
            try
            {
                byte[] rgbKey = Encoding.UTF8.GetBytes(encryptKey.Substring(0, 8));
                byte[] rgbIV = Keys;
                byte[] inputByteArray = Encoding.UTF8.GetBytes(encryptString);
                DESCryptoServiceProvider dCSP = new DESCryptoServiceProvider();
                MemoryStream mStream = new MemoryStream();
                CryptoStream cStream = new CryptoStream(mStream, dCSP.CreateEncryptor(rgbKey, rgbIV), CryptoStreamMode.Write);
                cStream.Write(inputByteArray, 0, inputByteArray.Length);
                cStream.FlushFinalBlock();
                return Convert.ToBase64String(mStream.ToArray());
            }
            catch
            {
                return encryptString;
            }
        }

        /// <summary> 
        /// DES解密字符串 
        /// </summary> 
        /// <param name="decryptString">待解密的字符串</param> 
        /// <param name="decryptKey">解密密钥,要求为8位,和加密密钥相同</param> 
        /// <returns>解密成功返回解密后的字符串，失败返源串</returns> 
        public static string DecryptDES(string decryptString, string decryptKey)
        {
            try
            {
                byte[] rgbKey = Encoding.UTF8.GetBytes(decryptKey);
                byte[] rgbIV = Keys;
                byte[] inputByteArray = Convert.FromBase64String(decryptString);
                DESCryptoServiceProvider DCSP = new DESCryptoServiceProvider();
                MemoryStream mStream = new MemoryStream();
                CryptoStream cStream = new CryptoStream(mStream, DCSP.CreateDecryptor(rgbKey, rgbIV), CryptoStreamMode.Write);
                cStream.Write(inputByteArray, 0, inputByteArray.Length);
                cStream.FlushFinalBlock();
                return Encoding.UTF8.GetString(mStream.ToArray());
            }
            catch
            {
                return decryptString;
            }
        } 
        #endregion
    }
}