using System;using System.IO;using System.Security.Cryptography;namespace ConsoleApp_SymmetricalEncryption{    class PRogram    {        static void Main(string[] args)        {            SymmetricalEncryption ss = new SymmetricalEncryption();            ss.EncryptFile(@"C:/error.txt", @"C:/error_EncryptFile.txt", ss.Key);            Console.WriteLine("加密成功！");            Console.ReadKey();            ss.DecryptFile(@"C:/error_EncryptFile.txt", @"C:/error_DecryptFile.txt", ss.Key);            Console.WriteLine("解密成功！");            Console.ReadKey();        }    }    /// <summary>    /// 對文件使用對稱加密算法    /// </summary>    public class SymmetricalEncryption    {        /* 對稱加密：          * 需要發送者和接收者協定一個密鑰K，K可以是一個密鑰對，但必須是加密密鑰和解密密鑰之間能夠互相推算出來的。         * 常用的對稱加密算法中，加密解密共享一個密鑰。         * 本例中使用的是同一個密鑰；         *          * 非對稱加密：         * 有一個密鑰對，分別為 公鑰、私鑰(公鑰用來加密，私鑰用來解密)         * 私鑰永遠不需要傳遞給對方；         *                  * 優缺點比較：         * 非對稱加密算法復雜，導致加解密速度慢，只適合與數據量小的場合。         * 對稱加密解密效率高，系統開銷小，適合金星大數據量的加解密。(大文件一般適合使用對稱加密)                  */        /// <summary>        /// 隨機產生的密鑰(也可以自己指定)        /// 【注意：對稱加密算法 加密解密用的Key值是相同的(非對稱加密才分：公鑰和私鑰)】        /// </summary>        public string Key = Guid.NewGuid().ToString().Replace("-", "").ToUpper() + Guid.NewGuid().ToString().Replace("-", "").ToUpper();        /// <summary>        /// 緩沖區大小        /// </summary>        private int bufferSize = 128 * 1024;        /// <summary>        /// 密鑰salt        /// </summary>        private byte[] salt = { 134, 216, 7, 36, 88, 164, 91, 227, 174, 76, 191, 197, 192, 154, 200, 248 };        //salt用來防止窮舉暴力破解(salt是在密鑰導出之前在密碼末尾引入的隨機字節，它使得這類攻擊變得非常困難)        /// <summary>        /// 初始化向量        /// </summary>        private byte[] iv = { 134, 216, 7, 36, 88, 164, 91, 227, 174, 76, 191, 197, 192, 154, 200, 248 };        //初始化向量iv起到的也是增強破解難度的作用        /// <summary>        /// 初始化 并返回對稱加密算法        /// </summary>        /// <param name="argKey"></param>        /// <param name="argSalt"></param>        /// <returns></returns>        private SymmetricAlgorithm CreateRijindael(string argKey, byte[] argSalt)        {            PassWordDeriveBytes pdb = new PasswordDeriveBytes(argKey, argSalt, "SHA256", 1000);            SymmetricAlgorithm sma = Rijndael.Create();            sma.KeySize = 256;            sma.Key = pdb.GetBytes(32);            sma.Padding = PaddingMode.PKCS7;            return sma;        }        /// <summary>        /// 加密文件        /// </summary>        /// <param name="argInFile">輸入文件</param>        /// <param name="argOutFile">輸出加密后的文件</param>        /// <param name="argKey">加密用的Key</param>        public void EncryptFile(string argInFile, string argOutFile, string argKey)        {            using (FileStream inFileStream = File.OpenRead(argInFile),                    outFileStream = File.Open(argOutFile, FileMode.OpenOrCreate))            using (SymmetricAlgorithm algorithm = CreateRijindael(argKey, salt))            {                algorithm.IV = iv;                using (CryptoStream cryptoStream = new CryptoStream(outFileStream, algorithm.CreateEncryptor(),                        CryptoStreamMode.Write))                {                    byte[] bytes = new byte[bufferSize];                    int readSize = -1;                    while ((readSize = inFileStream.Read(bytes, 0, bytes.Length)) != 0)                    {                        cryptoStream.Write(bytes, 0, readSize);                    }                    cryptoStream.Flush();                }            }        }        /// <summary>        /// 解密文件        /// </summary>        /// <param name="argInFile">輸入待解密的文件</param>        /// <param name="argOutFile">輸出解密后的文件</param>        /// <param name="argKey">加密用的Key</param>        public void DecryptFile(string argInFile, string argOutFile, string argKey)        {            try            {                using (FileStream inFileStream = File.OpenRead(argInFile), outFileStream = File.OpenWrite(argOutFile))                using (SymmetricAlgorithm algorithm = CreateRijindael(argKey, salt))                {                    algorithm.IV = iv;                    using (CryptoStream cryptoStream = new CryptoStream(inFileStream, algorithm.CreateDecryptor(),                            CryptoStreamMode.Read))                    {                        byte[] bytes = new byte[bufferSize];                        int readSize = -1;                        int numReads = (int)(inFileStream.Length / bufferSize);                        int slack = (int)(inFileStream.Length % bufferSize);                        for (int i = 0; i < numReads; ++i)                        {                            readSize = cryptoStream.Read(bytes, 0, bytes.Length);                            outFileStream.Write(bytes, 0, readSize);                        }                        if (slack > 0)                        {                            readSize = cryptoStream.Read(bytes, 0, (int)slack);                            outFileStream.Write(bytes, 0, readSize);                        }                        outFileStream.Flush();                    }                }            }            catch (Exception ex)            {                 throw new Exception("解密失敗：" + ex.Message);//可能是密鑰輸入的不正確，或者文件被修改過            }        }    }}