大きなファイルのAES暗号化

Question

大きなファイル（〜1GB）を暗号化および復号化する必要があります。私はこの例を使ってみました： http://www.codeproject.com/Articles/769741/Csharp-AES-bits-Encryption-Library-with-Salt しかし、ファイルが非常に大きいので私の問題です、outOfMemory例外が発生します。だから私はメモリストリームをファイルストリームに置き換える必要があります、それを行う方法がわかりません...

（私のコードの追加:)

private static void AES_Encrypt(string srcFile, string encryptedFile,  byte[] passwordBytes)
    {


        // Set your salt here, change it to meet your flavor:
        // The salt bytes must be at least 8 bytes.
        byte[] saltBytes = new byte[] { 1, 2, 3, 4, 5, 6, 7, 8};

        FileStream fsInput = new FileStream(srcFile,
            FileMode.Open,
            FileAccess.Read);

        FileStream fsEncrypted = new FileStream(encryptedFile,
                        FileMode.Create,
                        FileAccess.Write);

        using (RijndaelManaged AES = new RijndaelManaged())
        {
            AES.KeySize = 256;
            AES.BlockSize = 128;

            var key = new Rfc2898DeriveBytes(passwordBytes, saltBytes, 1000);
            AES.Key = key.GetBytes(AES.KeySize / 8);
            AES.IV = key.GetBytes(AES.BlockSize / 8);

            AES.Mode = CipherMode.CBC;

            using (var cs = new CryptoStream(fsEncrypted, AES.CreateEncryptor(), CryptoStreamMode.Write))
            {
                byte[] bytearrayinput = new byte[fsInput.Length - 1];
                fsInput.Read(bytearrayinput, 0, bytearrayinput.Length);
                cs.Write(bytearrayinput, 0, bytearrayinput.Length);
                cs.Close();
                fsInput.Flush();
                fsInput.Close();
                fsEncrypted.Close();
            }

        }


    }

    public static void AES_Decrypt(string encryptedFile, string decryptedFile, byte[] passwordBytes)
    {
        byte[] decryptedBytes = null;

        // Set your salt here, change it to meet your flavor:
        // The salt bytes must be at least 8 bytes.
        byte[] saltBytes = new byte[] { 1, 2, 3, 4, 5, 6, 7, 8};

        FileStream fsread = new FileStream(encryptedFile,
                               FileMode.Open,
                               FileAccess.Read);

        using (RijndaelManaged AES = new RijndaelManaged())
        {
            AES.KeySize = 256;
            AES.BlockSize = 128;

            var key = new Rfc2898DeriveBytes(passwordBytes, saltBytes, 1000);
            AES.Key = key.GetBytes(AES.KeySize / 8);
            AES.IV = key.GetBytes(AES.BlockSize / 8);

            AES.Mode = CipherMode.CBC;

            FileStream fsDecrypted = new FileStream(decryptedFile,
                        FileMode.Create,
                        FileAccess.Write);

            using (var cs = new CryptoStream(fsDecrypted, AES.CreateDecryptor(), CryptoStreamMode.Write))
            {
                byte[] bytearrayinput = new byte[fsread.Length - 1];
                fsread.Read(bytearrayinput, 0, bytearrayinput.Length);
                cs.Write(bytearrayinput, 0, bytearrayinput.Length);
                cs.Close();
                fsread.Close();
                fsDecrypted.Close();
            }

        }
    }

Answer 1

結局、これは私のために働いたコードです：

 private static void AES_Encrypt(string inputFile, string outputFile, byte[] passwordBytes)
 {
        byte[] saltBytes = new byte[] { 1, 2, 3, 4, 5, 6, 7, 8};
        string cryptFile = outputFile;
        FileStream fsCrypt = new FileStream(cryptFile, FileMode.Create);

        RijndaelManaged AES = new RijndaelManaged();

        AES.KeySize = 256;
        AES.BlockSize = 128;


        var key = new Rfc2898DeriveBytes(passwordBytes, saltBytes, 1000);
        AES.Key = key.GetBytes(AES.KeySize / 8);
        AES.IV = key.GetBytes(AES.BlockSize / 8);
        AES.Padding = PaddingMode.Zeros;

        AES.Mode = CipherMode.CBC;

        CryptoStream cs = new CryptoStream(fsCrypt,
             AES.CreateEncryptor(),
            CryptoStreamMode.Write);

        FileStream fsIn = new FileStream(inputFile, FileMode.Open);

        int data;
        while ((data = fsIn.ReadByte()) != -1)
            cs.WriteByte((byte)data);


        fsIn.Close();
        cs.Close();
        fsCrypt.Close();

    }

    private static void AES_Decrypt(string inputFile, string outputFile, byte[] passwordBytes)
    {



        byte[] saltBytes = new byte[] { 1, 2, 3, 4, 5, 6, 7, 8};
        FileStream fsCrypt = new FileStream(inputFile, FileMode.Open);

        RijndaelManaged AES = new RijndaelManaged();

        AES.KeySize = 256;
        AES.BlockSize = 128;


        var key = new Rfc2898DeriveBytes(passwordBytes, saltBytes, 1000);
        AES.Key = key.GetBytes(AES.KeySize / 8);
        AES.IV = key.GetBytes(AES.BlockSize / 8);
        AES.Padding = PaddingMode.Zeros;

        AES.Mode = CipherMode.CBC;

        CryptoStream cs = new CryptoStream(fsCrypt,
            AES.CreateDecryptor(),
            CryptoStreamMode.Read);

        FileStream fsOut = new FileStream(outputFile, FileMode.Create);

        int data;
        while ((data = cs.ReadByte()) != -1)
            fsOut.WriteByte((byte)data);

        fsOut.Close();
        cs.Close();
        fsCrypt.Close();

    }
}

Answer 2

だから私はかなり高速で低メモリ消費のバージョンを作成しました：
「一時バッファ」を使用し、「ランダムなソルトを使用して、暗号文とともに保存します」。
暗号化するには：

private void AES_Encrypt(string inputFile, string password)
    {
        //http://stackoverflow.com/questions/27645527/aes-encryption-on-large-files

        //generate random salt
        byte[] salt = GenerateRandomSalt();

        //create output file name
        FileStream fsCrypt = new FileStream(inputFile + ".aes", FileMode.Create);

        //convert password string to byte arrray
        byte[] passwordBytes = System.Text.Encoding.UTF8.GetBytes(password);

        //Set Rijndael symmetric encryption algorithm
        RijndaelManaged AES = new RijndaelManaged();
        AES.KeySize = 256;
        AES.BlockSize = 128;
        AES.Padding = PaddingMode.PKCS7;

        //http://stackoverflow.com/questions/2659214/why-do-i-need-to-use-the-rfc2898derivebytes-class-in-net-instead-of-directly
        //"What it does is repeatedly hash the user password along with the salt." High iteration counts.
        var key = new Rfc2898DeriveBytes(passwordBytes, salt, 50000);
        AES.Key = key.GetBytes(AES.KeySize / 8);
        AES.IV = key.GetBytes(AES.BlockSize / 8);

        //Cipher modes: http://security.stackexchange.com/questions/52665/which-is-the-best-cipher-mode-and-padding-mode-for-aes-encryption
        AES.Mode = CipherMode.CFB;

        //write salt to the begining of the output file, so in this case can be random every time
        fsCrypt.Write(salt, 0, salt.Length);

        CryptoStream cs = new CryptoStream(fsCrypt, AES.CreateEncryptor(), CryptoStreamMode.Write);

        FileStream fsIn = new FileStream(inputFile, FileMode.Open);

        //create a buffer (1mb) so only this amount will allocate in the memory and not the whole file
        byte[] buffer = new byte[1048576];
        int read;

        try
        {
            while ((read = fsIn.Read(buffer, 0, buffer.Length)) > 0)
            {
                Application.DoEvents(); // -> for responsive GUI, using Task will be better!
                cs.Write(buffer, 0, read);
            }

            //close up
            fsIn.Close();

        }
        catch (Exception ex)
        {
            Debug.WriteLine("Error: " + ex.Message);
        }
        finally
        {
            cs.Close();
            fsCrypt.Close();
        }
    }

復号化するには：

private void AES_Decrypt(string inputFile, string password)
    {
        //todo:
        // - create error message on wrong password
        // - on cancel: close and delete file
        // - on wrong password: close and delete file!
        // - create a better filen name
        // - could be check md5 hash on the files but it make this slow

        byte[] passwordBytes = System.Text.Encoding.UTF8.GetBytes(password);
        byte[] salt = new byte[32];

        FileStream fsCrypt = new FileStream(inputFile, FileMode.Open);
        fsCrypt.Read(salt, 0, salt.Length);

        RijndaelManaged AES = new RijndaelManaged();
        AES.KeySize = 256;
        AES.BlockSize = 128;
        var key = new Rfc2898DeriveBytes(passwordBytes, salt, 50000);
        AES.Key = key.GetBytes(AES.KeySize / 8);
        AES.IV = key.GetBytes(AES.BlockSize / 8);
        AES.Padding = PaddingMode.PKCS7;
        AES.Mode = CipherMode.CFB;

        CryptoStream cs = new CryptoStream(fsCrypt, AES.CreateDecryptor(), CryptoStreamMode.Read);

        FileStream fsOut = new FileStream(inputFile + ".decrypted", FileMode.Create);

        int read;
        byte[] buffer = new byte[1048576];

        try
        {
            while ((read = cs.Read(buffer, 0, buffer.Length)) > 0)
            {
                Application.DoEvents();
                fsOut.Write(buffer, 0, read);
            }
        }
        catch (System.Security.Cryptography.CryptographicException ex_CryptographicException)
        {
            Debug.WriteLine("CryptographicException error: " + ex_CryptographicException.Message);
        }
        catch (Exception ex)
        {
            Debug.WriteLine("Error: " + ex.Message);
        }

        try
        {
            cs.Close();
        }
        catch (Exception ex)
        {
            Debug.WriteLine("Error by closing CryptoStream: " + ex.Message);
        }
        finally
        {
            fsOut.Close();
            fsCrypt.Close();
        }
    }

ランダムなソルトを生成するには：

        public static byte[] GenerateRandomSalt()
    {
        //Source: http://www.dotnetperls.com/rngcryptoserviceprovider
        byte[] data = new byte[32];

        using (RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider())
        {
            // Ten iterations.
            for (int i = 0; i < 10; i++)
            {
                // Fill buffer.
                rng.GetBytes(data);
            }
        }
        return data;
    }

Answer 3

ファイルから読み取り、ファイルに書き込むため、メモリストリームをIOStreamまたはFileStreamに置き換えるだけです。

プロシージャを少しリファクタリングして、バイト配列を期待したり返したりしないようにする必要があります。