An example of c#-symmetric encryption

Encryption using System;
Using System.Drawing;
Using System.Collections;
Using System.ComponentModel;
Using System.Windows.Forms;
Using System.Data;
Using System.Security.Cryptography;
Using System.IO;

namespace symmetric encryption Application
{
///
Summary description of the Form1.
///
public class Form1:System.Windows.Forms.Form
{
Private System.Windows.Forms.TextBox TextBox1;
Private System.Windows.Forms.TextBox TextBox2;
Private System.Windows.Forms.Button button1;
Private System.Windows.Forms.Button button2;
///
The required designer variable.

Private System.Windows.Forms.TextBox TextBox3;
Private System.Windows.Forms.OpenFileDialog OpenFile;
Private System.Windows.Forms.Button Button3;
Private System.Windows.Forms.SaveFileDialog SaveFile;
Private System.Windows.Forms.Button Button4;
Private System.Windows.Forms.Label Label1;
Private System.Windows.Forms.Label Label2;
Private System.Windows.Forms.CheckBox CheckBox1;

Create an instance
RijndaelManaged Rij = new RijndaelManaged ();//
global variable, tag file extension
private static string Ext=null;
Mark encryption successful or not
private static bool Enresult = FALSE;
tag that marks the success of a decryption
private static bool Deresult = FALSE;

///
Private System.ComponentModel.Container components = null;

Public Form1 ()
{
//
Required for Windows Forms Designer support
//
InitializeComponent ();

//
TODO: Add any constructor code after the InitializeComponent call
//
}

///
Clean up all resources that are in use.
///
protected override void Dispose (bool disposing)
{
if (disposing)
{
if (Components!= null)
{
Components. Dispose ();
}
}
Base. Dispose (disposing);
}

Code generated #region the Windows forms Designer
///
Designer supports required methods-do not use the Code editor to modify
The contents of this method.
///
private void InitializeComponent ()
{
This.textbox1 = new System.Windows.Forms.TextBox ();
This.textbox2 = new System.Windows.Forms.TextBox ();
This.button1 = new System.Windows.Forms.Button ();
This.button2 = new System.Windows.Forms.Button ();
This.textbox3 = new System.Windows.Forms.TextBox ();
This.openfile = new System.Windows.Forms.OpenFileDialog ();
This.button3 = new System.Windows.Forms.Button ();
This.savefile = new System.Windows.Forms.SaveFileDialog ();
This.button4 = new System.Windows.Forms.Button ();
This.label1 = new System.Windows.Forms.Label ();
This.label2 = new System.Windows.Forms.Label ();
This.checkbox1 = new System.Windows.Forms.CheckBox ();
This. SuspendLayout ();
//
TextBox1
//
This.textBox1.Location = new System.Drawing.Point (88, 96);
This.textBox1.Name = "TextBox1";
This.textBox1.Size = new System.Drawing.Size (168, 21);
This.textBox1.TabIndex = 0;
This.textBox1.Text = "";
//
TextBox2
//
This.textBox2.Location = new System.Drawing.Point (88, 136);
This.textBox2.Name = "TextBox2";
This.textBox2.Size = new System.Drawing.Size (168, 21);
This.textBox2.TabIndex = 1;
This.textBox2.Text = "";
//
Button1
//
This.button1.Location = new System.Drawing.Point (88, 200);
This.button1.Name = "Button1";
This.button1.TabIndex = 2;
This.button1.Text = "Encrypt";
This.button1.Click + = new System.EventHandler (This.button1_click);
//
Button2
//
This.button2.Location = new System.Drawing.Point (192, 200);
This.button2.Name = "Button2";
This.button2.TabIndex = 3;
This.button2.Text = "decryption";
This.button2.Click + = new System.EventHandler (This.button2_click);
//
TextBox3
//
This.textBox3.HideSelection = false;
This.textBox3.Location = new System.Drawing.Point (88, 48);
This.textBox3.MaxLength = 17;
This.textBox3.Name = "TextBox3";
This.textBox3.PasswordChar = ' $ ';
This.textBox3.TabIndex = 4;
This.textBox3.Text = "";
This.textBox3.TextAlign = System.Windows.Forms.HorizontalAlignment.Center;
//
Button3
//
This.button3.Location = new System.Drawing.Point (280, 96);
This.button3.Name = "Button3";
This.button3.Size = new System.Drawing.Size (40, 23);
This.button3.TabIndex = 5;
This.button3.Text = "Open";
This.button3.Click + = new System.EventHandler (This.button3_click);
//
Button4
//
This.button4.Location = new System.Drawing.Point (280, 136);
This.button4.Name = "Button4";
This.button4.Size = new System.Drawing.Size (40, 23);
This.button4.TabIndex = 6;
This.button4.Text = "Save";
This.button4.Click + = new System.EventHandler (This.button4_click);
//
Label1
//
This.label1.Location = new System.Drawing.Point (88, 24);
This.label1.Name = "Label1";
This.label1.Size = new System.Drawing.Size (136, 23);
This.label1.TabIndex = 7;
This.label1.Text = "Please enter your password:";
//
Label2
//
This.label2.Location = new System.Drawing.Point (216, 48);
This.label2.Name = "Label2";
This.label2.Size = new System.Drawing.Size (184, 23);
This.label2.TabIndex = 8;
This.label2.Text = "(Password size 8 to 16 characters)";
//
CheckBox1
//
This.checkBox1.Location = new System.Drawing.Point (88, 168);
This.checkBox1.Name = "CheckBox1";
This.checkBox1.Size = new System.Drawing.Size (216, 24);
This.checkBox1.TabIndex = 9;
This.checkBox1.Text = "Delete source file";
//
Form1
//
This. AutoScaleBaseSize = new System.Drawing.Size (6, 14);
This. ClientSize = new System.Drawing.Size (456, 278);
This. Controls.Add (This.checkbox1);
This. Controls.Add (THIS.LABEL2);
This. Controls.Add (THIS.LABEL1);
This. Controls.Add (THIS.BUTTON4);
This. Controls.Add (This.button3);
This. Controls.Add (THIS.TEXTBOX3);
This. Controls.Add (This.button2);
This. Controls.Add (This.button1);
This. Controls.Add (THIS.TEXTBOX2);
This. Controls.Add (This.textbox1);
This. Name = "Form1";
This. Text = "Form1";
This. ResumeLayout (FALSE);

}
#endregion

///
The main entry point for the application.
///
[STAThread]
static void Main ()
{
Application.Run (New Form1 ());
}

button to encrypt files
private void Button1_Click (object sender, System.EventArgs e)
{
if (TextBox1.Text!= null | | | TextBox2.Text!= NULL)
Encryption (Textbox3.text,textbox1.text,textbox2.text);
if (checkbox1.checked==true && enresult==true)
DeleteFile (TextBox1.Text);
}
Functions used for encryption
public void encryption (string textbox,string readfile,string WriteFile)
{
Try
{
if (textbox.length >=8 && textbox.length<=16)//The size of the character that determines the password
{

byte [] key = System.Text.Encoding.Default.GetBytes (TextBox);
byte [] IV = RIJ.IV;
Rijndael crypt = Rijndael.create ();
ICryptoTransform transform = crypt. CreateEncryptor (key, iv);
Write in File
FileStream fswrite = new FileStream (writefile,filemode.create);
CryptoStream cs = new CryptoStream (fswrite, transform, cryptostreammode.write);
Open File
FileStream fsread = new FileStream (Readfile,filemode.open);
int length;
while (length = Fsread. ReadByte ())!=-1)
Cs. WriteByte ((byte) length);

Fsread. Close ();
Cs. Close ();
Fswrite. Close ();
Enresult = true;//Successful encryption
MessageBox.Show ("The encryption task has been successfully completed!") ");
}
Else
{
MessageBox.Show ("The minimum length of the password is 8 characters and the maximum length is 16 characters!") ");
return;
}
}
catch (Exception e)
{
MessageBox.Show (E.tostring ());
}
}
Functions for decrypting
public void decryption (string textbox,string readfile,string WriteFile)
{
Try
{
if (textbox.length >=8 && textbox.length<=16)
{
byte [] key = System.Text.Encoding.Default.GetBytes (TextBox);
byte [] IV = RIJ.IV;
Rijndael crypt = Rijndael.create ();
ICryptoTransform transform = crypt. CreateDecryptor (KEY,IV);
Read the Encrypted file
FileStream Fsopen = new FileStream (Readfile,filemode.open);
CryptoStream cs = new CryptoStream (Fsopen, transform, cryptostreammode.read);
Write the decrypted results into the file
FileStream fswrite = new FileStream (writefile,filemode.openorcreate);
int length;
while (length = cs. ReadByte ())!=-1)
Fswrite. WriteByte ((byte) length);

Fswrite. Close ();
Cs. Close ();
Fsopen. Close ();
Deresult=true; Successfully decrypted
MessageBox.Show ("The decryption task has been successfully completed!") ");
}
Else
{
MessageBox.Show ("The minimum length of the password is 8 characters and the maximum length is 16 characters!") ");
return;
}
}
catch (Exception e)
{
MessageBox.Show (E.tostring ());
}
}
Decrypting files
private void Button2_Click (object sender, System.EventArgs e)
{
Decryption (Textbox3.text,textbox1.text,textbox2.text);
if (checkbox1.checked==true && deresult==true)
DeleteFile (TextBox1.Text);
}
button to open a file
private void Button3_Click (object sender, System.EventArgs e)
{
OpenFile = new OpenFileDialog (); OpenFile. Filter = "All Files (*.*) |*.*";
OpenFile. ShowDialog ();
TextBox1.Text = OpenFile. FileName;
ext = Getfileext (openfile. FileName);
}

private void Button4_Click (object sender, System.EventArgs e)
{
SaveFile = new SaveFileDialog ();
SaveFile. Filter =ext + "files" + "(*.") +ext+ ") |*." + ext + "| All Files (*.*) |*.* ";
SaveFile. ShowDialog ();
TextBox2.Text = SaveFile. FileName;
}
Get the file name extension
private string Getfileext (string filename)
{
Try
{
char [] point = new char[] {'. '};
string [] filename2 = filename. Split (point);
return filename2[1];
}
Catch
{
return null;
}
}
function to delete a file
public void DeleteFile (string filename)
{
Try
{
File.delete (filename);
}
catch (Exception e)
{
MessageBox.Show (E.tostring ());
}
}


}
}