文件加密与解密

前些时间看了一下加密的，接着就写了一个文件加密:
先定义一个加密异常类

/// <summary>
    /// 加密异常类
    /// </summary>
    public class CryptoFileException : ApplicationException
    {
        /// <summary>
        /// 加密异常构造函数
        /// </summary>
        /// <param name="msg">异常信息</param>
        public CryptoFileException(string msg) : base(msg) { }
    }

下面是实现

/// <summary>
    /// 文件加密
    /// </summary>
    public class CrypToFile
    {
        private string password="Grouppower";
        private const ulong FC_TAG = 0xFC010203040506CF;
        private const int BUFFER_SIZE = 128 * 1024;
        private  RandomNumberGenerator rand = new RNGCryptoServiceProvider();//加密文件随机数生成

        /// <summary>
        /// 文件加密构造
        /// </summary>
        /// <param name="password">用于文件加密的密钥</param>
        public CrypToFile(string password)
        {
            this.password = password;
        }

        /// <summary>
        /// 文件加密默认构造
        /// </summary>
        public CrypToFile() { }

        /// <summary>
        /// 返加加密密钥
        /// </summary>
        public string Password
        {
            get
            {
                string result = "";
                if (password == null || password == "Grouppower")
                {
                    result = "";
                }
                else
                {
                    result = password;
                }
                return result;
            }
            set
            {
                if (value == null || value == "")
                {
                    value = "Grouppower";
                }
                password = value;
            }
        }

        /// <summary>
        /// 检验两个Byte数组是否相同
        /// </summary>
        /// <param name="b1">字节数组一</param>
        /// <param name="b2">字节数组二</param>
        /// <returns>结果是否相等</returns>
        private  bool CheckByteArrays(byte[] b1, byte[] b2)
        {
            if (b1.Length == b2.Length)
            {
                for (int i = 0; i < b1.Length; ++i)
                {
                    if (b1[i] != b2[i])
                        return false;
                }
                return true;
            }
            return false;
        }

        /// <summary>
        /// 创建Rijndael SymmetricAlgorithm
        /// </summary>
        /// <param name="password">密码</param>
        /// <param name="salt">密钥的字节数组</param>
        /// <returns>加密对象</returns>
        private  SymmetricAlgorithm CreateRijndael(string password, byte[] salt)
        {
            PasswordDeriveBytes pdb = new PasswordDeriveBytes(password, salt, "SHA256", 1000);
            SymmetricAlgorithm sma = Rijndael.Create();
            sma.KeySize = 256;
            sma.Key = pdb.GetBytes(32);
            sma.Padding = PaddingMode.PKCS7;
            return sma;
        }

        /// <summary>
        /// 生成指定长度的随机Byte数组
        /// </summary>
        /// <param name="count">长度</param>
        /// <returns>随机Byte数组</returns>
        private  byte[] GenerateRandomBytes(int count)
        {
            byte[] bytes = new byte[count];
            rand.GetBytes(bytes);
            return bytes;
        }

        /// <summary>
        /// 加密文件
        /// </summary>
        /// <param name="inFile">原始文件</param>
        /// <param name="outFile">密码文件</param>
        /// <param name="password">密码</param>
        private  void EncryptFile(string inFile, string outFile, string password)
        {
            string fileName = Path.GetFileName(inFile);
            string pFileName = Path.GetFileNameWithoutExtension(inFile);
            if (outFile.EndsWith("\\"))
            {
                outFile = string.Format("{0}{1}.pgd", outFile, pFileName);
            }
            else
            {
                outFile = string.Format("{0}\\{1}.pgd", outFile, pFileName);
            }
            using (FileStream fin = File.OpenRead(inFile),
            fout = File.OpenWrite(outFile))
            {
                long lSize = fin.Length; // 输入文件长度
                int size = (int)lSize;
                byte[] bytes = new byte[BUFFER_SIZE]; // 缓存
                int read = -1; // 输入文件读取数量
                int value = 0;

                // 获取IV和salt
                byte[] IV = GenerateRandomBytes(16);
                byte[] salt = GenerateRandomBytes(16);

                // 创建加密对象
                SymmetricAlgorithm sma = CreateRijndael(password, salt);
                sma.IV = IV;

                // 在输出文件开始部分写入IV和salt
                fout.Write(IV, 0, IV.Length);
                fout.Write(salt, 0, salt.Length);

                // 创建散列加密
                HashAlgorithm hasher = SHA256.Create();
                using (CryptoStream cout = new CryptoStream(fout, sma.CreateEncryptor(), CryptoStreamMode.Write),
                chash = new CryptoStream(Stream.Null, hasher, CryptoStreamMode.Write))
                {
                    BinaryWriter bw = new BinaryWriter(cout);
                    bw.Write(lSize);

                    bw.Write(FC_TAG);

                    // 读写字节块到加密流缓冲区
                    while ((read = fin.Read(bytes, 0, bytes.Length)) != 0)
                    {
                        cout.Write(bytes, 0, read);
                        chash.Write(bytes, 0, read);
                        value += read;
                    }
                    // 关闭加密流
                    chash.Flush();
                    chash.Close();

                    // 读取散列
                    byte[] hash = hasher.Hash;

                    // 输入文件写入散列
                    cout.Write(hash, 0, hash.Length);
                    bytes = Encoding.Default.GetBytes(fileName);
                    cout.Write(bytes,0,bytes.Length);

                    // 关闭文件流
                    cout.Flush();
                    cout.Close();
                }
            }
        }

        /// <summary>
        /// 解密文件
        /// </summary>
        /// <param name="inFile">密码文件</param>
        /// <param name="outFile">原始文件</param>
        /// <param name="password">密码</param>
        private  void DecryptFile(string inFile, string outFile, string password)
        {
            string tarDir = outFile;
            string fileName=Path.GetFileNameWithoutExtension(inFile);
            // 创建打开文件流
            if (outFile.EndsWith("\\"))
            {
                outFile = string.Format("{0}{1}", outFile,fileName);
            }
            else
            {
                tarDir+="\\";
                outFile = string.Format("{0}\\{1}", outFile,fileName);
            }
            using (FileStream fin = File.OpenRead(inFile),
            fout = File.OpenWrite(outFile))
            {
                int size = (int)fin.Length;
                byte[] bytes = new byte[BUFFER_SIZE];
                int read = -1;
                int value = 0;
                int outValue = 0;

                byte[] IV = new byte[16];
                fin.Read(IV, 0, 16);
                byte[] salt = new byte[16];
                fin.Read(salt, 0, 16);

                SymmetricAlgorithm sma = CreateRijndael(password, salt);
                sma.IV = IV;

                value = 32;
                long lSize = -1;

                // 创建散列对象, 校验文件
                HashAlgorithm hasher = SHA256.Create();

                using (CryptoStream cin = new CryptoStream(fin, sma.CreateDecryptor(), CryptoStreamMode.Read),
                chash = new CryptoStream(Stream.Null, hasher, CryptoStreamMode.Write))
                {
                    // 读取文件长度
                    BinaryReader br = new BinaryReader(cin);
                    lSize = br.ReadInt64();
                    ulong tag = br.ReadUInt64();

                    if (FC_TAG != tag)
                        throw new CryptoFileException("文件被破坏");

                    long numReads = lSize / BUFFER_SIZE;

                    long slack = (long)lSize % BUFFER_SIZE;

                    for (int i = 0; i < numReads; ++i)
                    {
                        read = cin.Read(bytes, 0, bytes.Length);
                        fout.Write(bytes, 0, read);
                        chash.Write(bytes, 0, read);
                        value += read;
                        outValue += read;
                    }

                    if (slack > 0)
                    {
                        read = cin.Read(bytes, 0, (int)slack);
                        fout.Write(bytes, 0, read);
                        chash.Write(bytes, 0, read);
                        value += read;
                        outValue += read;
                    }

                    chash.Flush();
                    chash.Close();

                    fout.Flush();
                    fout.Close();

                    byte[] curHash = hasher.Hash;

                    // 获取比较和旧的散列对象
                    byte[] oldHash = new byte[hasher.HashSize / 8];
                    read = cin.Read(oldHash, 0, oldHash.Length);
                    if ((oldHash.Length != read) || (!CheckByteArrays(oldHash, curHash)))
                        throw new CryptoFileException("文件被破坏");

                    if (outValue != lSize)
                        throw new CryptoFileException("文件大小不匹配");

                    try
                    {
                        byte[] fileBytes = new byte[256];
                        StringBuilder resultBuilder = new StringBuilder();
                        while ((read = cin.Read(fileBytes, 0, fileBytes.Length)) > 0)
                        {
                            resultBuilder.Append(Encoding.Default.GetString(fileBytes, 0, fileBytes.Length));
                        }
                        fileName = resultBuilder.ToString();
                        if (fileName != null && fileName != "")
                        {
                            string tarFileName = string.Format("{0}{1}", tarDir, fileName).Trim(new char[] { '\0' });
                            File.Move(outFile, tarFileName);
                        }
                    }
                    catch
                    {
                        throw new CryptoFileException("密钥不正确");
                    }
                }
            }
        }

        /// <summary>
        /// 加密文件
        /// </summary>
        /// <param name="inFile">待加密的文件</param>
        /// <param name="outFile">加密后的文件</param>
        public void EncryFile(string inFile,string outFile)
        {
            if (File.Exists(inFile) && Directory.Exists(outFile))
            {
                EncryptFile(inFile, outFile, password);
            }
            else
            {
                throw new FileNotFoundException("文件或文件夹不存在");
            }
        }

        /// <summary>
        /// 解密文件
        /// </summary>
        /// <param name="inFile">待解密的文件</param>
        /// <param name="outFile">解密后的文件</param>
        public void DecryFile(string inFile, string outFile)
        {
            if (File.Exists(inFile) && Directory.Exists(outFile))
            {
                DecryptFile(inFile, outFile, password);
            }
            else
            {
                throw new FileNotFoundException("文件或文件夹不存在");
            }
            
        }
    }