c#实现文件加解密

using System;
using System.IO;
using System.Data;
using System.Text;
using System.Windows.Forms;
using System.Collections;
using System.Collections.Generic;
using System.Security.Cryptography;
using System.Threading;
using System.ComponentModel;

namespace aaa
{
     class En_Dn
    {
     
        private Hashtable hs = new Hashtable();
        private RijndaelManaged myRijndael;
        private string Key = "";
        private string IV = "~!#@$%HGF^&%&^hggk)KJKL989#er345(&*(HBh(u%g6HJ($jhWk7&!hg4ui%$hjk";
      
        private string 解密(string files, int a)
        {
            try
            {
                int id = 0;
                hs.Clear();
                hs.Add(id++, files);
                string CPath = Path.GetDirectoryName(files);
                string FileName = Path.GetFileName(files);

                myRijndael = new RijndaelManaged();

                string inFileName = "";
                foreach (System.Collections.DictionaryEntry de in this.hs)
                {
                    inFileName = (string)de.Value;
                }
                FileStream fin = new FileStream(inFileName, FileMode.Open, FileAccess.Read);
                StreamReader sr = new StreamReader(fin);
                char[] infolengthchar = new char[5];//文件的最后五个字符代表加密后的文件信息长度
                fin.Seek(-5, SeekOrigin.End);
                sr.Read(infolengthchar, 0, 5);
                string infolengthstr = new string(infolengthchar);
                int infolength = Convert.ToInt32(infolengthstr);//加密后的文件信息长度
                fin.Seek(-(5 + infolength), SeekOrigin.End);
                char[] Filedatachar = new char[infolength];
                sr.Read(Filedatachar, 0, infolength);
                string Filedatastr = new string(Filedatachar);
                Filedatastr = this.Decrypt(Filedatastr);
                int count = Convert.ToInt32(Filedatastr.Substring(Filedatastr.Length - 5, 5));
                FileInfomation[] FI = new FileInfomation[count];
                for (int i = 0; i < count; i++)
                {
                    FI[i] = new FileInfomation();
                    // FI[i].Filename = Filedatastr.Substring(i * 150, 100).TrimStart(new char[] { ' ' });
                    FI[i].Filename = "~" + Filedatastr.Substring(i * 150, 100).TrimStart(new char[] { ' ' });
                    FI[i].Size = Convert.ToInt32(Filedatastr.Substring(i * 150 + 100, 50).TrimStart(new char[] { ' ' }));
                }
                fin.Close();
                //已得到该文件中包括的文件个数、文件名、长度。开始解密。
                long start = 0, currentlength = 0;

                string outFileName = CPath + "\\" + FI[0].Filename;
                for (int i = 0; i < count; i++)
                {
                    outFileName = CPath + "\\" + FI[i].Filename;
                    File.Delete(outFileName);
                    currentlength = FI[i].Size;

                    fin = new FileStream(inFileName, FileMode.Open, FileAccess.Read);
                    FileStream fout = new FileStream(outFileName, FileMode.OpenOrCreate, FileAccess.Write);
                    fout.SetLength(0);
                    fin.Seek(start, SeekOrigin.Begin);
                    int cut = 100000;
                    byte[] bin = new byte[cut];
                    long rdlen = 0;
                    long totlen = currentlength;
                    int len;
                    myRijndael.Key = GetLegalKey();
                    myRijndael.IV = GetLegalIV();
                    ICryptoTransform encrypto = myRijndael.CreateDecryptor();
                    CryptoStream cs = new CryptoStream(fout, encrypto, CryptoStreamMode.Write);
                    while (rdlen < totlen)
                    {
                        int report = (int)(((double)rdlen / totlen) * 1000);
                        if (totlen - rdlen < cut)
                        {
                            cut = (int)(totlen - rdlen);
                            rdlen = totlen;
                        }
                        len = fin.Read(bin, 0, cut);
                        cs.Write(bin, 0, len);
                        rdlen = rdlen + len;
                    }
                    cs.Close();
                    cs.Dispose();

                    fout.Close();
                    fout.Dispose();

                    fin.Close();
                }

                fin.Dispose();

                return outFileName;
            }
            catch (Exception ex)
            {
                // MessageBox.Show("在文件解密的时候出现错误！错误提示： \n" + ex.Message, "", MessageBoxButtons.OK, MessageBoxIcon.Error);
                return "";
            }
        }
        private string 解密(string files)
        {
            try
            {
                int id = 0;
                hs.Clear();
                hs.Add(id++, files);
                string pw = "";
                string CPath = Path.GetDirectoryName(files);
                //FileName = Path.GetFileNameWithoutExtension(this.files) + "~.tif";
                string FileName = Path.GetFileName(files);

                myRijndael = new RijndaelManaged();
                Key = pw;
                IV = "~!#@$%HGF^&%&^hggk)KJKL989#er345(&*(HBh(u%g6HJ($jhWk7&!hg4ui%$hjk";
                //Directory.CreateDirectory(CPath + "\\已解密的文件");

                string inFileName = "";
                foreach (System.Collections.DictionaryEntry de in this.hs)
                {
                    inFileName = (string)de.Value;
                }
                FileStream fin = new FileStream(inFileName, FileMode.Open, FileAccess.Read);
                StreamReader sr = new StreamReader(fin);
                char[] infolengthchar = new char[5];//文件的最后五个字符代表加密后的文件信息长度
                fin.Seek(-5, SeekOrigin.End);
                sr.Read(infolengthchar, 0, 5);
                string infolengthstr = new string(infolengthchar);
                int infolength = Convert.ToInt32(infolengthstr);//加密后的文件信息长度
                fin.Seek(-(5 + infolength), SeekOrigin.End);
                char[] Filedatachar = new char[infolength];
                sr.Read(Filedatachar, 0, infolength);
                string Filedatastr = new string(Filedatachar);
                Filedatastr = this.Decrypt(Filedatastr);
                int count = Convert.ToInt32(Filedatastr.Substring(Filedatastr.Length - 5, 5));
                FileInfomation[] FI = new FileInfomation[count];
                for (int i = 0; i < count; i++)
                {
                    FI[i] = new FileInfomation();
                    //FI[i].Filename = Filedatastr.Substring(i * 150, 100).TrimStart(new char[] { ' ' });
                    FI[i].Filename = "~" + Filedatastr.Substring(i * 150, 100).TrimStart(new char[] { ' ' });
                    FI[i].Size = Convert.ToInt32(Filedatastr.Substring(i * 150 + 100, 50).TrimStart(new char[] { ' ' }));
                }
                fin.Close();
                //已得到该文件中包括的文件个数、文件名、长度。开始解密。
                long start = 0, currentlength = 0;
                string outFileName = "";
                for (int i = 0; i < count; i++)
                {
                    //string outFileName = CPath + @"\已解密的文件\" + FI[i].Filename;
                    outFileName = CPath + "\\" + FI[i].Filename;
                    File.Delete(outFileName);
                    currentlength = FI[i].Size;

                    fin = new FileStream(inFileName, FileMode.Open, FileAccess.Read);
                    FileStream fout = new FileStream(outFileName, FileMode.OpenOrCreate, FileAccess.Write);
                    fout.SetLength(0);
                    fin.Seek(start, SeekOrigin.Begin);
                    int cut = 100000;
                    byte[] bin = new byte[cut];
                    long rdlen = 0;
                    long totlen = currentlength;
                    int len;
                    myRijndael.Key = GetLegalKey();
                    myRijndael.IV = GetLegalIV();
                    ICryptoTransform encrypto = myRijndael.CreateDecryptor();
                    CryptoStream cs = new CryptoStream(fout, encrypto, CryptoStreamMode.Write);
                    while (rdlen < totlen)
                    {
                        if (totlen - rdlen < cut)
                        {
                            cut = (int)(totlen - rdlen);
                            rdlen = totlen;
                        }
                        len = fin.Read(bin, 0, cut);
                        cs.Write(bin, 0, len);
                        rdlen = rdlen + len;
                    }
                    cs.Close();
                    fout.Close();
                    fin.Close();
                }
                return outFileName;
            }
            catch (Exception ex)
            {
                MessageBox.Show("在文件解密的时候出现错误！错误提示： \n" + ex.Message, "", MessageBoxButtons.OK, MessageBoxIcon.Error);
                return "";
            }
        }

        private void 加密(string files, string newname)
        {
            try
            {
                int id = 0;
                hs.Clear();
                hs.Add(id++, files);
                string pw = "";
                string CPath = Path.GetDirectoryName(files);
                //string FileName = "~" + Path.GetFileName(files);
                myRijndael = new RijndaelManaged();
                Key = pw;
                IV = "~!#@$%HGF^&%&^hggk)KJKL989#er345(&*(HBh(u%g6HJ($jhWk7&!hg4ui%$hjk";
                string outFileName = newname;

                string Filedata = "";//文件名(100字节)长度(50)个数(5)前补空格 加密后 长度(5)
                int count = 0;
                long curlength = -16;//这里是负16,我也不知道是为什么,第一次读fout长度时会少16,以后再读都正常
                foreach (System.Collections.DictionaryEntry de in this.hs)
                {
                    FileStream fout = new FileStream(outFileName, FileMode.Append, FileAccess.Write);
                    FileStream fin = new FileStream((string)de.Value, FileMode.Open, FileAccess.Read);
                    myRijndael.Key = GetLegalKey();
                    myRijndael.IV = GetLegalIV();

                    byte[] bin = new byte[100000];
                    long rdlen = 0;
                    long totlen = fin.Length;
                    int len;

                    ICryptoTransform encrypto = myRijndael.CreateEncryptor();
                    CryptoStream cs = new CryptoStream(fout, encrypto, CryptoStreamMode.Write);
                    while (rdlen < totlen)
                    {
                        len = fin.Read(bin, 0, 100000);
                        cs.Write(bin, 0, len);
                        rdlen = rdlen + len;
                    }
                    long foutlenth = fout.Length;
                    Filedata += Path.GetFileName((string)de.Value).PadLeft(100, ' ') + (foutlenth - curlength).ToString().PadLeft(50, ' ');
                    curlength = foutlenth;
                    count++;
                    cs.Close();
                    fout.Close();
                    fin.Close();
                }
                Filedata += count.ToString().PadLeft(5, '0');
                Filedata = this.Encrypt(Filedata);
                Filedata += Filedata.Length.ToString().PadLeft(5, '0');
                FileStream f = new FileStream(outFileName, FileMode.Append, FileAccess.Write);
                StreamWriter sw = new StreamWriter(f);
                sw.Write(Filedata);
                sw.Close();
                f.Close();

                File.Delete(files);
            }
            catch (Exception ex)
            {
                MessageBox.Show("在文件加密的时候出现错误！错误提示： \n" + ex.Message, "", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }


        /**//// <summary>
        /// 获得密钥
        /// </summary>
        /// <returns>密钥</returns>
        private byte[] GetLegalKey()
        {
            string sTemp = Key;
            myRijndael.GenerateKey();
            byte[] bytTemp = myRijndael.Key;
            int KeyLength = bytTemp.Length;
            if (sTemp.Length > KeyLength)
                sTemp = sTemp.Substring(0, KeyLength);
            else if (sTemp.Length < KeyLength)
                sTemp = sTemp.PadRight(KeyLength, ' ');
            return System.Text.ASCIIEncoding.ASCII.GetBytes(sTemp);
        }
        /**//// <summary>
        /// 获得初始向量IV
        /// </summary>
        /// <returns>初试向量IV</returns>
        private byte[] GetLegalIV()
        {
            string sTemp = IV;
            myRijndael.GenerateIV();
            byte[] bytTemp = myRijndael.IV;
            int IVLength = bytTemp.Length;
            if (sTemp.Length > IVLength)
                sTemp = sTemp.Substring(0, IVLength);
            else if (sTemp.Length < IVLength)
                sTemp = sTemp.PadRight(IVLength, ' ');
            return System.Text.ASCIIEncoding.ASCII.GetBytes(sTemp);
        }
        /**//// <summary>
        /// 加密方法
        /// </summary>
        /// <param name="Source">待加密的串</param>
        /// <returns>经过加密的串</returns>
        public string Encrypt(string Source)
        {
            try
            {
                byte[] bytIn = System.Text.UTF8Encoding.UTF8.GetBytes(Source);
                MemoryStream ms = new MemoryStream();
                myRijndael.Key = GetLegalKey();
                myRijndael.IV = GetLegalIV();
                ICryptoTransform encrypto = myRijndael.CreateEncryptor();
                CryptoStream cs = new CryptoStream(ms, encrypto, CryptoStreamMode.Write);
                cs.Write(bytIn, 0, bytIn.Length);
                cs.FlushFinalBlock();
                ms.Close();
                byte[] bytOut = ms.ToArray();
                return Convert.ToBase64String(bytOut);
            }
            catch (Exception ex)
            {
                throw new Exception("在文件加密的时候出现错误！错误提示： \n" + ex.Message);
            }
        }
        /**//// <summary>
        /// 解密方法
        /// </summary>
        /// <param name="Source">待解密的串</param>
        /// <returns>经过解密的串</returns>
        public string Decrypt(string Source)
        {
            try
            {
                byte[] bytIn = Convert.FromBase64String(Source);
                MemoryStream ms = new MemoryStream(bytIn, 0, bytIn.Length);
                myRijndael.Key = GetLegalKey();
                myRijndael.IV = GetLegalIV();
                ICryptoTransform encrypto = myRijndael.CreateDecryptor();
                CryptoStream cs = new CryptoStream(ms, encrypto, CryptoStreamMode.Read);
                StreamReader sr = new StreamReader(cs);
                return sr.ReadToEnd();
            }
            catch (Exception ex)
            {
                throw new Exception("在文件解密的时候出现错误！错误提示： \n" + ex.Message);
            }
        }
     
    }
}