c# - 对大文件使用 Rijndael 加密

Question

我现在需要安全地加密/解密一个长度为 n 的文件，最好使用 Rijndael，但绝对是 256 位加密。

我以前玩过加密，并且非常愉快地加密/解密字符串和字节数组。 但是，因为我不知道文件的大小(而且有问题的文件可能非常大(~2.5gb)是非常可行的)我不能只将它们加载到字节数组中并在其中加密/解密它们像我以前一样的单一界限。

因此，在谷歌上进行了一些阅读之后，我知道答案是分块加密和解密文件，因此我生成了以下代码:

private static void Enc(string decryptedFileName, string encryptedFileName)
{            
   FileStream fsOutput = File.OpenWrite(encryptedFileName);
   FileStream fsInput = File.OpenRead(decryptedFileName);

   byte[] IVBytes = Encoding.ASCII.GetBytes("1234567890123456");

   fsOutput.Write(BitConverter.GetBytes(fsInput.Length), 0, 8);
   fsOutput.Write(IVBytes, 0, 16);

   RijndaelManaged symmetricKey = new RijndaelManaged() { Mode = CipherMode.CBC};
   ICryptoTransform encryptor = symmetricKey.CreateEncryptor(passwordDB.GetBytes(256 / 8), IVBytes);
   CryptoStream cryptoStream = new CryptoStream(fsOutput, encryptor, CryptoStreamMode.Write);

   for (long i = 0; i < fsInput.Length; i += chunkSize)
   {
      byte[] chunkData = new byte[chunkSize];
      fsInput.Read(chunkData, 0, chunkSize);
      cryptoStream.Write(chunkData, 0, chunkData.Length);
   }
   cryptoStream.Close();
   fsInput.Close();
   fsInput.Dispose();
   cryptoStream.Dispose();
}

private static void Dec(string encryptedFileName, string decryptedFileName)
{
    FileStream fsInput = File.OpenRead(encryptedFileName);
    FileStream fsOutput = File.OpenWrite(decryptedFileName);

    byte[] buffer = new byte[8];
    fsInput.Read(buffer, 0, 8);

    long fileLength = BitConverter.ToInt64(buffer, 0);

    byte[] IVBytes = new byte[16];
    fsInput.Read(IVBytes, 0, 16);

    RijndaelManaged symmetricKey = new RijndaelManaged() { Mode = CipherMode.CBC };
    ICryptoTransform decryptor = symmetricKey.CreateDecryptor(passwordDB.GetBytes(256 / 8), IVBytes);
    CryptoStream cryptoStream = new CryptoStream(fsOutput,decryptor,CryptoStreamMode.Write);

    for (long i = 0; i < fsInput.Length; i += chunkSize)
    {
        byte[] chunkData = new byte[chunkSize];
        fsInput.Read(chunkData, 0, chunkSize);
        cryptoStream.Write(chunkData, 0, chunkData.Length);
    }
    cryptoStream.Close();
    cryptoStream.Dispose();
    fsInput.Close();
    fsInput.Dispose();                      
} 

这一切对我来说都“看起来”不错，但遗憾的是看起来似乎是骗人的!

加密工作没有错误，但在解密过程中，“cryptoStream.Close()”方法抛出以下异常:

System.Security.Cryptography.CryptographicException was unhandled Message="Padding is invalid and cannot be removed."
Source="mscorlib" StackTrace: at System.Security.Cryptography.RijndaelManagedTransform.DecryptData(Byte[] inputBuffer, Int32 inputOffset, Int32 inputCount, Byte[]& outputBuffer, Int32 outputOffset, PaddingMode paddingMode, Boolean fLast) at System.Security.Cryptography.RijndaelManagedTransform.TransformFinalBlock(Byte[] inputBuffer, Int32 inputOffset, Int32 inputCount) at System.Security.Cryptography.CryptoStream.FlushFinalBlock() at System.Security.Cryptography.CryptoStream.Dispose(Boolean disposing) at System.IO.Stream.Close()

似乎未加密的文件大小与预期的文件大小不匹配(范围从大约 8 个字节到大约 60 个字节)

我通过更改 RijndaelManaged 对象创建行以包含填充类型来“修复”异常，如下所示:

RijndaelManaged symmetricKey = new RijndaelManaged() { Mode = CipherMode.CBC,Padding=PaddingMode.None };

但是文件大小仍然不匹配，可以预见，新的未加密文件是胡说八道!

我承认我现在在加密/解密方面超出了我的舒适区，这可能是一个菜鸟错误 - 但我无法发现它!

如能提供解决此问题的任何帮助，我们将不胜感激!

Answer 1

问题是我正在使用:

passwordDB.GetBytes(256 / 8)

在加密和解密方法中的 RijndaelManaged 对象的构造函数中，我没有在尝试解密之前重新初始化 passwordDB 对象。

解决方案是简单地将 passwordDB 对象的构造包含在 Enc 和 Dec 方法的第一行中，如下所示:

        private static void Enc(string decryptedFileName, string encryptedFileName)
        {
            PasswordDeriveBytes passwordDB = new PasswordDeriveBytes("ThisIsMyPassword", Encoding.ASCII.GetBytes("thisIsMysalt!"), "MD5", 2);
            byte[] passwordBytes = passwordDB.GetBytes(128 / 8);

            using (FileStream fsOutput = File.OpenWrite(encryptedFileName))
            {
                using(FileStream fsInput = File.OpenRead(decryptedFileName))
                {
                    byte[] IVBytes = Encoding.ASCII.GetBytes("1234567890123456");

                    fsOutput.Write(BitConverter.GetBytes(fsInput.Length), 0, 8);
                    fsOutput.Write(IVBytes, 0, 16);

                    RijndaelManaged symmetricKey = new RijndaelManaged() { Mode = CipherMode.CBC,Padding=PaddingMode.ANSIX923};
                    ICryptoTransform encryptor = symmetricKey.CreateEncryptor(passwordBytes, IVBytes);                   

                    using (CryptoStream cryptoStream = new CryptoStream(fsOutput, encryptor, CryptoStreamMode.Write))
                    {
                        for (long i = 0; i < fsInput.Length; i += chunkSize)
                        {
                            byte[] chunkData = new byte[chunkSize];
                            int bytesRead = 0;
                            while ((bytesRead = fsInput.Read(chunkData, 0, chunkSize)) > 0)
                            {
                                if (bytesRead != 16)
                                {
                                    for (int x = bytesRead - 1; x < chunkSize; x++)
                                    {
                                        chunkData[x] = 0;
                                    }
                                }
                                cryptoStream.Write(chunkData, 0, chunkSize);
                            }
                        }
                        cryptoStream.FlushFinalBlock();
                    }
                }
            }            
        }

        private static void Dec(string encryptedFileName, string decryptedFileName)
        {
            PasswordDeriveBytes passwordDB = new PasswordDeriveBytes("ThisIsMyPassword", Encoding.ASCII.GetBytes("thisIsMysalt!"), "MD5", 2);
            byte[] passwordBytes = passwordDB.GetBytes(128 / 8);

            using (FileStream fsInput = File.OpenRead(encryptedFileName))
            {
                using (FileStream fsOutput = File.OpenWrite(decryptedFileName))
                {
                    byte[] buffer = new byte[8];
                    fsInput.Read(buffer, 0, 8);

                    long fileLength = BitConverter.ToInt64(buffer, 0);

                    byte[] IVBytes = new byte[16];
                    fsInput.Read(IVBytes, 0, 16);


                    RijndaelManaged symmetricKey = new RijndaelManaged() { Mode = CipherMode.CBC,Padding=PaddingMode.ANSIX923};
                    ICryptoTransform decryptor = symmetricKey.CreateDecryptor(passwordBytes, IVBytes);

                    using (CryptoStream cryptoStream = new CryptoStream(fsOutput, decryptor, CryptoStreamMode.Write))
                    {
                        for (long i = 0; i < fsInput.Length; i += chunkSize)
                        {
                            byte[] chunkData = new byte[chunkSize];
                            int bytesRead = 0;
                            while ((bytesRead = fsInput.Read(chunkData, 0, chunkSize)) > 0)
                            {
                                cryptoStream.Write(chunkData, 0, bytesRead);
                            }
                        }
                    }
                }
            }
        }

知道这一定是一个小学生的错误:P