【.NET】对文件的对称加密

8/10/2015来源:ASP.NET技巧人气:2231

【.NET】对文件的对称加密
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>    /// 对文件使用对称加密算法    /// </summary>    public class SymmetricalEncryption    {        /* 对称加密:          * 需要发送者和接收者协定一个密钥K,K可以是一个密钥对,但必须是加密密钥和解密密钥之间能够互相推算出来的。         * 常用的对称加密算法中,加密解密共享一个密钥。         * 本例中使用的是同一个密钥;         *          * 非对称加密:         * 有一个密钥对,分别为 公钥、私钥(公钥用来加密,私钥用来解密)         * 私钥永远不需要传递给对方;         *                  * 优缺点比较:         * 非对称加密算法复杂,导致加解密速度慢,只适合与数据量小的场合。         * 对称加密解密效率高,系统开销小,适合金星大数据量的加解密。(大文件一般适合使用对称加密)                  */        /// <summary>        /// 随机产生的密钥(也可以自己指定)        /// 【注意:对称加密算法 加密解密用的Key值是相同的(非对称加密才分:公钥和私钥)】        /// </summary>        public string Key = Guid.NewGuid().ToString().Replace("-", "").ToUpper() + Guid.NewGuid().ToString().Replace("-", "").ToUpper();        /// <summary>        /// 缓冲区大小        /// </summary>        private int bufferSize = 128 * 1024;        /// <summary>        /// 密钥salt        /// </summary>        private byte[] salt = { 134, 216, 7, 36, 88, 164, 91, 227, 174, 76, 191, 197, 192, 154, 200, 248 };        //salt用来防止穷举暴力破解(salt是在密钥导出之前在密码末尾引入的随机字节,它使得这类攻击变得非常困难)        /// <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起到的也是增强破解难度的作用        /// <summary>        /// 初始化 并返回对称加密算法        /// </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">输入文件</param>        /// <param name="argOutFile">输出加密后的文件</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">输入待解密的文件</param>        /// <param name="argOutFile">输出解密后的文件</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("解密失败:" + ex.Message);//可能是密钥输入的不正确,或者文件被修改过            }        }    }}