Crypto Gear

Introduction

Crypto Gear application is developed in the concept of Cryptography in WPF C# .NET which is to encrypt files and decrypt files, giving security for data from unauthorized access. In this application the user Interface is much more concentrated on look and feel and ease of access.

Background

This article is very much useful for those interested in UI design and development. Mostly WPF is preferred for developing stunning user interfaces. And we could design controls of our own.

Using the code

Here is the application crypto gear used for file security. It uses namespaces System.IO and System.Security.Cryptography.

We use a ListView in this application. To add items in the ListView, we must have create a property class for binding in the Listview. The ObservableCollection class is used for selecting items in the ListView.

ObservableCollection<FileHandle> Lst = new ObservableCollection<FileHandle>();

private void btAdd_Click(object sender, RoutedEventArgs e)
{
    Microsoft.Win32.OpenFileDialog op = new Microsoft.Win32.OpenFileDialog();
    op.Multiselect = true;
    FileInfo n;
    if (op.ShowDialog() == true)
    {
        foreach (string fil in op.FileNames)
        {
            n = new FileInfo(fil);
            if (n.Extension != ".enc")
		    {
		        s1 = n.Name;
		        s2 = n.FullName;
		        Lst.Add(new FileHandle(s1, s2));
		        LstEnc.ItemsSource = Lst;
		    }
		    else
		    {
		        System.Windows.MessageBox.Show(n.Name + " : File Is Already Encrypted", 
		                "Crypto Gear", MessageBoxButton.OK, MessageBoxImage.Information);
		    }
		}
		RemoveDuplicates();
	}
}

Here is the property class for displaying data in the ListView:

class FileHandle
{
    public System.Drawing.Image filico;
    private string FileName;
    private string FilePath;

    public System.Drawing.Image FileIco
    {
        get
        { 
            return filico; 
        }
        set 
        {
            filico = value; 
        }
    }

    public string FirstCol
    {
        get { return FileName; }
        set { FileName = value; }
    }

    public string LastCol
    {
        get { return FilePath; }
        set { FilePath = value; }
    }

    public FileHandle(string fn,string fp)
    {
        FileName = fn;
        FilePath = fp;
        //filico;
    }
}

Here is the data binding code for the ListView:

<ListView Margin="101,39,297,32" Name="LstEnc" >
    <ListView.View>
        <GridView>
            <GridViewColumn Header="Files To Be Encrypted" Width="500">
                <GridViewColumn.CellTemplate>
                        <DataTemplate>
                            <DockPanel Height="50" Width="Auto">
                                <Image Height="30" Width="40" Name="FileIcons" 
                                       Source="{Binding FileIco}" Stretch="Fill" />
                                <StackPanel>
                                    <TextBlock FontFamily="verdana" FontSize="15" 
                                       FontWeight="Bold" Height="25" HorizontalAlignment="Left" 
                                       Name="FileName" Padding="3" Text="{Binding FirstCol}" 
                                       TextAlignment="Center" VerticalAlignment="Center" 
                                       Width="Auto" Foreground="Black" />
                                    <TextBlock FontFamily="ArialBlack" FontSize="12" 
                                            ForceCursor="False" Height="17" 
                                            HorizontalAlignment="Left" Name="FilePath" 
                                            Padding="3" Text="{Binding LastCol}" 
                                            TextAlignment="Center" TextDecorations="None" 
                                            VerticalAlignment="Center" Width="Auto" Foreground="Black">
                                        <TextBlock.BindingGroup>
                                            <BindingGroup Name="s2" NotifyOnValidationError="True" />
                                        </TextBlock.BindingGroup>
                                    </TextBlock>
                                </StackPanel>
                            </DockPanel>
                        </DataTemplate>
                    </GridViewColumn.CellTemplate>
            </GridViewColumn>
        </GridView>
    </ListView.View>
</ListView>

Encryption Algorithm (Rijindael)

AES is based on a design principle known as a substitution-permutation network. It is fast in both software and hardware.^[6]. Unlike its predecessor, DES, AES does not use a Feistel network.

AES has a fixed block size of 128 bits and a key size of 128, 192, or 256 bits, whereas Rijndael is specified with block and key sizes in any multiple of 32 bits, both with a minimum of 128 and a maximum of 256 bits. AES operates on a 4×4 column-major order matrix of bytes, termed the state (versions of Rijndael with a larger block size have additional columns in the state). Most AES calculations are done in a special finite field.

Here is the code sample:

private void Encrypt(string strInputFile, string strOutputFile, byte[] bytKey, byte[] bytIV)
{
    RemoveDuplicates();
    System.Windows.Forms.Application.DoEvents();
    s2 = "In Progress";            
    FileInfo FileO = new FileInfo(strOutputFile);
    if (FileO.Exists)
    {
        if (MessageBox.Show("Encrypted File Already Exist, want to replace?", 
            FileO.Name, MessageBoxButton.YesNo, MessageBoxImage.Exclamation) == MessageBoxResult.Yes)
        {
            FileO.Delete();
        }
        else
        {
            s2 = "Skipped";
            cl = new CryptFile(FileO.Name, s2, 100, "r");
            LstView.Items[FileListIndex] = cl;
            goto Exit;
        }
    }
    FileInfo FileI = new FileInfo(strInputFile);
    cl = new CryptFile(FileI.Name,s2,0,"");
    LstView.Items[FileListIndex] = cl;
    System.Windows.Forms.Application.DoEvents();          
    try
    {
        FileStream fsInput;
        FileStream fsOutput;
        //Setup file streams to handle input and output.
        fsInput = new FileStream(strInputFile, FileMode.Open, FileAccess.Read);
        fsOutput = new FileStream(strOutputFile, FileMode.OpenOrCreate, FileAccess.Write);
        //fsOutput.Write(GetHash(this.Password), 0, GetHash(this.Password).Length);
        fsOutput.SetLength(0);
        //make sure fsOutput is empty
        //Declare variables for encrypt/decrypt process.
        byte[] bytBuffer = new byte[4097];
        //holds a block of bytes for processing
        long lngBytesProcessed = 0;
        //running count of bytes processed
        long lngFileLength = fsInput.Length;
        //the input file's length
        int intBytesInCurrentBlock = 0;
        //current bytes being processed
        CryptoStream csCryptoStream = default(CryptoStream);
        //Declare your CryptoServiceProvider.
        RijndaelManaged cspRijndael = new RijndaelManaged();
        //Setup Progress Bar
        csCryptoStream = new CryptoStream(fsOutput, 
           cspRijndael.CreateEncryptor(bytKey, bytIV), CryptoStreamMode.Write);
        //Use While to loop until all of the file is processed.
        while (lngBytesProcessed < lngFileLength)
        {
            if (IsPaused != true)
            {
                if (IsCancelled == false)
                {
                    //Read file with the input filestream.
                    intBytesInCurrentBlock = fsInput.Read(bytBuffer, 0, 4096);
                    //Write output file with the cryptostream.
                    csCryptoStream.Write(bytBuffer, 0, intBytesInCurrentBlock);
                    //Update lngBytesProcessed
                    lngBytesProcessed = lngBytesProcessed + Convert.ToInt32(intBytesInCurrentBlock);
                    double prg = Convert.ToDouble(Convert.ToDouble(lngBytesProcessed) / 
                                    Convert.ToDouble(lngFileLength) * 100);
                    cl = new CryptFile(FileI.Name, s2,prg,"");
                    LstView.Items[FileListIndex] = cl;
                }
                else
                {
                    csCryptoStream.Close();
                    fsInput.Close();
                    fsOutput.Close();
                    FileInfo Del = new FileInfo(strOutputFile);
                    Del.Delete();
                    break;
                }
            }
            //System.Windows.Forms.Application.DoEvents();
            Dispatcher.CurrentDispatcher.Invoke(DispatcherPriority.Background, new EmptyDelegate(delegate { }));
        }
        //File.SetAttributes(strOutputFile, File.GetAttributes(strOutputFile) | FileAttributes.Hidden);
        csCryptoStream.Close();
        fsInput.Close();
        fsOutput.Close();
        FilesTODelete.Add(strInputFile);
        s2 = "Encrypted";
        cl = new CryptFile(FileI.Name, s2, 100, "a");
        LstView.Items[FileListIndex] = cl;
    }
    catch
    {
        MessageBox.Show("Encryption Failed", "Crypto Gear", 
                        MessageBoxButton.OK, MessageBoxImage.Error);
        s2 = "Error, Skipped";
        cl = new CryptFile(FileI.Name, s2, 100, "r");
        LstView.Items[FileListIndex] = cl;
    }
    Exit: FileO = null;FileListIndex++;
}

private void Decrypt(string strInputFile, string strOutputFile, byte[] bytKey, byte[] bytIV)
{
    RemoveDuplicates();
    System.Windows.Forms.Application.DoEvents();
    s2 = "In Progress";
    FileInfo FileO = new FileInfo(strOutputFile);
    if (FileO.Exists)
    {
        if (MessageBox.Show("File Already Exist, want to replace?", FileO.Name, 
            MessageBoxButton.YesNo, MessageBoxImage.Exclamation) == MessageBoxResult.Yes)
        {
            FileO.Delete();
        }
        else
        {
            s2 = "Skipped";
            cl = new CryptFile(FileO.Name, s2, 100, "r");
            LstView.Items[FileListIndex] = cl;
            goto Exit;
        }
    }
    FileInfo FileI = new FileInfo(strInputFile);
    cl = new CryptFile(FileI.Name, s2,0,"");
    LstView.Items[FileListIndex] = cl;
    FileStream fsInput;
    FileStream fsOutput;
    try
    {
        //Setup file streams to handle input and output.
        fsInput = new FileStream(strInputFile, FileMode.Open, FileAccess.Read);
        fsOutput = new FileStream(strOutputFile, FileMode.OpenOrCreate, FileAccess.Write);
        fsOutput.SetLength(0);
        //Declare variables for encrypt/decrypt process.
        byte[] bytBuffer = new byte[4097];
        //holds a block of bytes for processing
        long lngBytesProcessed = 0;
        //running count of bytes processed
        long lngFileLength = fsInput.Length;
        //the input file's length
        int intBytesInCurrentBlock = 0;
        //current bytes being processed
        CryptoStream csCryptoStream = default(CryptoStream);
        //Declare your CryptoServiceProvider.
        RijndaelManaged cspRijndael = new RijndaelManaged();
        //Setup Progress Bar
        csCryptoStream = new CryptoStream(fsOutput, cspRijndael.CreateDecryptor(bytKey, bytIV), CryptoStreamMode.Write);
        //Use While to loop until all of the file is processed.
        //csCryptoStream.
        while (lngBytesProcessed < lngFileLength)
        {
            if (IsPaused != true)
            {
                if (IsCancelled == false)
                {
                    //Read file with the input filestream.
                    intBytesInCurrentBlock = fsInput.Read(bytBuffer, 0, 4096);
                    //Write output file with the cryptostream.
                    csCryptoStream.Write(bytBuffer, 0, intBytesInCurrentBlock);
                    //Update lngBytesProcessed
                    lngBytesProcessed = lngBytesProcessed + Convert.ToInt64(intBytesInCurrentBlock);
                    double prg = Convert.ToDouble(Convert.ToDouble(lngBytesProcessed) / Convert.ToDouble(lngFileLength) * 100);
                    cl = new CryptFile(FileI.Name, s2,prg,"");
                    LstView.Items[FileListIndex] = cl;                           
                }
                else
                {
                    csCryptoStream.Close();
                    fsInput.Close();
                    fsOutput.Close();
                    FileInfo Del = new FileInfo(strOutputFile);
                    Del.Delete();
                    break;
                }
            }
            //System.Windows.Forms.Application.DoEvents();
            Dispatcher.CurrentDispatcher.Invoke(DispatcherPriority.Background, new EmptyDelegate(delegate { }));
        }
        try
        {
            csCryptoStream.Close();
            FilesTODelete.Add(strInputFile);
            s2 = "Decrypted";
            cl = new CryptFile(FileI.Name, s2, 100, "a");
            LstView.Items[FileListIndex] = cl;
        }
        catch
        {
            FileInfo Del = new FileInfo(strOutputFile);
            s2 = "Wrong Password!";
            cl = new CryptFile(FileI.Name, s2, 100, "r");
            LstView.Items[FileListIndex] = cl;
            //MessageBox.Show("Wrong Password!" + Environment.NewLine + 
            //  "File: " + Del.Name, "Crypto Gear", MessageBoxButton.OK, MessageBoxImage.Error);
            //File.SetAttributes(strOutputFile, File.GetAttributes(strOutputFile) | FileAttributes.Normal);
            fsInput.Close();
            fsOutput.Close();
            Del.Delete();
        }
        fsInput.Close();
        fsOutput.Close();

    }
    catch
    {
        s2 = "Error, Skipped";
        MessageBox.Show("Decryption Failed", "Crypto Gear", MessageBoxButton.OK, MessageBoxImage.Error);
        FileInfo Del = new FileInfo(strOutputFile);
        cl = new CryptFile(FileI.Name, s2, 100, "r");
        LstView.Items[FileListIndex] = cl;
        //Del.Delete();
    }
    Exit: FileO = null; FileListIndex++;
}

• http://en.wikipedia.org/wiki/Advanced_Encryption_Standard.