it seems that my code adds 6 bytes to the result file after encrypt decrypt is called.. i tries it on a mkv file.. please help

here is my code

class TripleDESCryptoService : IEncryptor, IDecryptor
{
    public void Encrypt(string inputFileName, string outputFileName, string key)
    {
        EncryptFile(inputFileName, outputFileName, key);
    }

    public void Decrypt(string inputFileName, string outputFileName, string key)
    {
        DecryptFile(inputFileName, outputFileName, key);
    }

    static void EncryptFile(string inputFileName, string outputFileName, string sKey)
    {
        var outFile = new FileStream(outputFileName, FileMode.OpenOrCreate, FileAccess.ReadWrite);

        // The chryptographic service provider we're going to use
        var cryptoAlgorithm = new TripleDESCryptoServiceProvider();
        SetKeys(cryptoAlgorithm, sKey);

        // This object links data streams to cryptographic values
        var cryptoStream = new CryptoStream(outFile, cryptoAlgorithm.CreateEncryptor(), CryptoStreamMode.Write);

        // This stream writer will write the new file
        var encryptionStream = new BinaryWriter(cryptoStream);

        // This stream reader will read the file to encrypt
        var inFile = new FileStream(inputFileName, FileMode.Open, FileAccess.Read);
        var readwe = new BinaryReader(inFile);

        // Loop through the file to encrypt, line by line
        var date = readwe.ReadBytes((int)readwe.BaseStream.Length);


        // Write to the encryption stream
        encryptionStream.Write(date);


        // Wrap things up
        inFile.Close();
        encryptionStream.Flush();
        encryptionStream.Close();
    }

    private static void SetKeys(SymmetricAlgorithm algorithm, string key)
    {
        var keyAsBytes = Encoding.ASCII.GetBytes(key);
        algorithm.IV = keyAsBytes.Take(algorithm.IV.Length).ToArray();
        algorithm.Key = keyAsBytes.Take(algorithm.Key.Length).ToArray();
    }

    static void DecryptFile(string inputFilename, string outputFilename, string sKey)
    {
        // The encrypted file
        var inFile = File.OpenRead(inputFilename);

        // The decrypted file
        var outFile = new FileStream(outputFilename, FileMode.OpenOrCreate, FileAccess.ReadWrite);

        // Prepare the encryption algorithm and read the key from the key file
        var cryptAlgorithm = new TripleDESCryptoServiceProvider();

        SetKeys(cryptAlgorithm, sKey);

        // The cryptographic stream takes in the encrypted file
        var encryptionStream = new CryptoStream(inFile, cryptAlgorithm.CreateDecryptor(), CryptoStreamMode.Read);

        // Write the new unecrypted file
        var cleanStreamReader = new BinaryReader(encryptionStream);
        var cleanStreamWriter = new BinaryWriter(outFile);
        cleanStreamWriter.Write(cleanStreamReader.ReadBytes((int)inFile.Length));
        cleanStreamWriter.Close();
        outFile.Close();
        cleanStreamReader.Close();
    }
}