//**********************************************************************
//
// SimCrypt.NET
// .NET 1.1/2.0  AES 256 bit Encryption Tool
//
// Copyright (C) 2006  JavaScience Consulting
//
//**********************************************************************
//
// SimCryptNet.cs
//
// This C# utility for .NET Framework 1.1/2.0 is a simple GUI application
// to encrypt any local file using 256 bit Rijndael (AES) encryption.
// Uses a new random 16 byte salt data for each invocation.
// Uses 33000 iterations (~15 bits extra computational entropy)
// Writes output file formatted as:
//	byte[] salt
//	byte[] IV
//	byte inputfilenamelength
//	byte[] inputfilename
//	byte[] encryptedinputfilecontents
// All output file data encrypted except salt and IV
//
// Also decrypts any binary DER or b64 encoded CMS/PKCS #7 EnvelopedData file.
// Raw binary output, or base64 encoded (both salt and encrypted content)
//***********************************************************************

using System;
using System.IO;
using System.Diagnostics;
using System.Net;
using System.Text;
using System.Windows.Forms;
using System.Drawing;
using System.Reflection;
using System.Security.Cryptography;
using System.Runtime.InteropServices;
using System.ComponentModel;

namespace JavaScience
{

public class Win32 {
 [DllImport("crypt32.dll", CharSet=CharSet.Auto, SetLastError=true)]
    public static extern IntPtr CertOpenSystemStore(
        IntPtr hCryptProv,
        string storename) ;

 [DllImport("crypt32.dll", SetLastError=true)]
    public static extern bool CertCloseStore(
        IntPtr hCertStore,
        uint dwFlags) ;

 [DllImport("crypt32.dll", SetLastError=true)]
  public static extern bool CryptDecryptMessage(
   ref CRYPT_DECRYPT_MESSAGE_PARA pDecryptPara,
   byte[] pbEncryptedBlob,
   int cbEncryptedBlob,
   [In, Out] byte[] pbDecrypted,
   ref int pcbDecrypted,
   IntPtr ppXchgCert);
}



 [StructLayout(LayoutKind.Sequential)]
  public struct CRYPT_DECRYPT_MESSAGE_PARA
  {
        public int cbSize;
        public uint dwMsgAndCertEncodingType;
        public int cCertStore;
        public IntPtr rghCertStore;
        //public uint dwFlags;
  }
//--Note: CRYPT_DECRYPT_MESSAGE_PARA.dwFlags only for XP+ OS

public class SimCryptNet : Form
{
  const   String	TITLE	=	"SymCrypt.NET";
  const   String	INSTRUCT= "(1) Select a File or URL  (2) Enter Encryption Key  (3) Encrypt, Decrypt or Denvelop ";
  const	  String	ABOUT 	= "AES 256 bit Encryption Tool:    JavaScience 2006";
  const   String	ICONIMAGE = "JavaScience.simcrypt.gif";
  const   int		SALTBYTES = 16;
  const   int		ITERS = 33000;   //roughly 15 bits 

  const  string MY        = "MY";
  const  uint PKCS_7_ASN_ENCODING	= 0x00010000;
  const  uint X509_ASN_ENCODING		= 0x00000001;
  static uint MY_ENCODING_TYPE	= PKCS_7_ASN_ENCODING | X509_ASN_ENCODING ;


  private Label		about;
  private Label		lbl;
  private Label		instr;
  private TextBox	pwbox;
  private TextBox	filepath;
  private Button	selectButton;
  private Button	encryptButton;
  private Button	decryptButton;
  private Button	denvelopButton;

  private PictureBox    imagebox;
  private String	infile;
  private String	DESKPATH;
  private Label		lb64;
  private Label		lbautostart;
  private CheckBox	b64check;
  private CheckBox	autostartcheck;
  private bool		autostartenabled = false;
  private bool 		b64enabled = false;
	
  public SimCryptNet() : base()
  { 
   DESKPATH = Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory);
   InitializeComponent();
   LoadImageIcon();
  }


 private void LoadImageIcon()
 {
  Assembly oass = Assembly.GetExecutingAssembly();
  try
  {
   Stream icostream = oass.GetManifestResourceStream(ICONIMAGE);
   imagebox.Image = (Image) new Bitmap(icostream);
  }
  catch { }
 }

 private void InitializeComponent()
 {
  int x2ndcol = 170;

  this.Size = new Size(510, 240);
  this.Text = TITLE;
  this.StartPosition = FormStartPosition.Manual;
  this.SetDesktopLocation(250,250) ;
  this.BackColor = Color.FromArgb(0xE0, 0xE0, 0xE0) ;

  imagebox = new PictureBox();
  imagebox.Location = new Point(05, 10);
  imagebox.SizeMode = PictureBoxSizeMode.AutoSize ;

  about = new Label();
  about.AutoSize = true;
  about.Text = ABOUT ;
  about.Location = new Point(x2ndcol, 10);


  selectButton = new Button();
  selectButton.Text = "SelectFile";
  selectButton.BackColor = Color.Yellow;
  selectButton.ForeColor = Color.Blue;
  selectButton.Location = new Point(20, 50);
  selectButton.Click += new EventHandler(this.select_Clicked);

  lbl = new Label();
  lbl.Text = "Encryption Key:";
  lbl.Font = new Font(lbl.Font.FontFamily, 11, lbl.Font.Style);
  lbl.Location = new Point(x2ndcol, 50);
  lbl.AutoSize = true;

  pwbox = new TextBox();
  pwbox.Location = new Point(x2ndcol + lbl.Width+10,50);
  pwbox.Width = 150;
  pwbox.Text = "";
  pwbox.PasswordChar = '*';


  encryptButton = new Button();
  encryptButton.Text = "Encrypt";
  encryptButton.BackColor = Color.Red;
  encryptButton.Location = new Point(20, 90);
  encryptButton.Click += new EventHandler(this.encrypt_Clicked);

  decryptButton = new Button();
  decryptButton.Text = "Decrypt";
  decryptButton.BackColor = Color.LightGreen;
  decryptButton.Location = new Point(x2ndcol, 75); 
  decryptButton.Click += new EventHandler(this.decrypt_Clicked);



  denvelopButton = new Button();
  denvelopButton.Text = "Denvelop";
  denvelopButton.BackColor = Color.LightGreen;
  denvelopButton.Location = new Point(x2ndcol, 105); 
  denvelopButton.Click += new EventHandler(this.denvelop_Clicked);




  lb64 = new Label();
  lb64.Text = "B64:";
  lb64.TextAlign = ContentAlignment.BottomLeft; 
  lb64.Location = new Point(pwbox.Left, 75);
  lb64.AutoSize = true;

  b64check = new CheckBox();
  b64check.Location = new Point(lb64.Right + 40, 75) ;
  b64check.CheckedChanged += new EventHandler(this.b64Check_Clicked);

  lbautostart = new Label();
  lbautostart.Text = "AutoStart:";
  lbautostart.TextAlign = ContentAlignment.BottomLeft; 
  lbautostart.Location = new Point(pwbox.Left, 100);
  lbautostart.AutoSize = true;

  autostartcheck = new CheckBox();
  autostartcheck.Location = new Point(lb64.Right + 40, 100) ;
  autostartcheck.CheckedChanged += new EventHandler(this.autostartCheck_Clicked);







  filepath = new TextBox();
  filepath.Width = this.Width - 40;
  filepath.Location = new Point(20, 135); 

  instr = new Label();
  instr.Text = INSTRUCT;
  instr.AutoSize = true;
  instr.Location = new Point(05, 175);

  this.Controls.Add(imagebox);
  this.Controls.Add(about);
  this.Controls.Add(selectButton);
  this.Controls.Add(lbl);
  this.Controls.Add(pwbox);
  this.Controls.Add(encryptButton);
  this.Controls.Add(decryptButton);
  this.Controls.Add(denvelopButton);
  this.Controls.Add(filepath);
  this.Controls.Add(instr) ;
  this.Controls.Add(lb64);
  this.Controls.Add(b64check) ;
  this.Controls.Add(lbautostart);
  this.Controls.Add(autostartcheck);
 }




 private void select_Clicked(object sender, EventArgs e)
	{
	String getfile = getInFileDialogName(DESKPATH);
	if(getfile !=null){
		infile = getfile;	//update instance variable
		filepath.Text = infile; //update display
	}
		
   }


 private void b64Check_Clicked(object sender, EventArgs e)
	{
	 b64enabled = b64check.Checked ;
	}
		

 private void autostartCheck_Clicked(object sender, EventArgs e)
	{
	 autostartenabled = autostartcheck.Checked ;
	}



 private void encrypt_Clicked(object sender, EventArgs e)
  {
	if(!File.Exists(filepath.Text))
	{
	 MessageBox.Show("File '" + filepath.Text + "' NOT FOUND ", TITLE, MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
	 return;
	}
	if(pwbox.Text.Equals(""))
	{
	 MessageBox.Show("No Encryption Key provided ", TITLE, MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
	 return;
	}

	String outfile = getOutFileDialogName(DESKPATH, "_simencrypted", "Save encrypted file to ...");
	if(outfile == null)
	{
	 MessageBox.Show("No output file specified ", TITLE, MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
	 return;
	}
	if(EncryptAES(filepath.Text, outfile, pwbox.Text, b64enabled))
	 MessageBox.Show("Created AES encrypted file '" + outfile + "'  ", TITLE, MessageBoxButtons.OK, MessageBoxIcon.Information);
	else
	 MessageBox.Show("FAILED to encrypt file  ", TITLE, MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
  }


 private void decrypt_Clicked(object sender, EventArgs e)
  {
   String filetodecrypt = null;  //for local file
   String dnldfile	= null;  //for URL
   bool isurl = false;

	if(pwbox.Text.Equals(""))
	{
	 MessageBox.Show("No Encryption Key provided ", TITLE, MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
	 return;
	}

	if(File.Exists(filepath.Text)){
		filetodecrypt = filepath.Text;
	}
	else if(GetUrlFile(filepath.Text, ref dnldfile)) {   //if URL file valid and saved
		isurl = true;
		filetodecrypt = dnldfile;
	}
	else
	{
	 MessageBox.Show("File '" + filepath.Text + "' FILE or URL not found  ", TITLE, MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
	 return;
	}

	String outfile = null;
	if(DecryptAES(filetodecrypt, ref outfile, pwbox.Text, b64enabled)){
	if(isurl)
	 MessageBox.Show("Downloaded url and saved to file:\n" + dnldfile + "\n\n" +
		"Decrypted AES encrypted file to:\n" + outfile, TITLE, MessageBoxButtons.OK, MessageBoxIcon.Information);
	else
	 MessageBox.Show("Decrypted AES encrypted file to:\n" + outfile, TITLE, MessageBoxButtons.OK, MessageBoxIcon.Information);
	 if(autostartenabled)
		LaunchProcess(outfile);
	 }
	else {
	 if(isurl)
	  MessageBox.Show("Downloaded url and saved to file:\n" + dnldfile + "\n\n" + "FAILED to decrypt file ", TITLE, MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
	 else
	  MessageBox.Show("FAILED to decrypt file ", TITLE, MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
	}

  }


 private void denvelop_Clicked(object sender, EventArgs e)
  {
   String filetodecrypt = null;  //for local file
   String dnldfile	= null;  //for URL
   bool isurl = false;

	if(File.Exists(filepath.Text)){
		filetodecrypt = filepath.Text;
	}
	else if(GetUrlFile(filepath.Text, ref dnldfile)) {   //if URL file valid and saved
		isurl = true;
		filetodecrypt = dnldfile;
	}
	else
	{
	 MessageBox.Show("File '" + filepath.Text + "' FILE or URL not found  ", TITLE, MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
	 return;
	}

	String outfile = null;
	if(DenvelopCMS(filetodecrypt, ref outfile))
	{
	if(isurl)
	 MessageBox.Show("Downloaded url and saved to file:\n" + dnldfile + "\n\n" +
		"Denveloped file to:\n" + outfile, TITLE, MessageBoxButtons.OK, MessageBoxIcon.Information);
	else
	 MessageBox.Show("Denveloped file to:\n" + outfile, TITLE, MessageBoxButtons.OK, MessageBoxIcon.Information);
	 if(autostartenabled)
		LaunchProcess(outfile);
	 }
	else 
	{
	 if(isurl)
	  MessageBox.Show("Downloaded url and saved to file:\n" + dnldfile + "\n\n" + "FAILED to denvelop file ", TITLE, MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
	 else
	  MessageBox.Show("FAILED to denvelop file ", TITLE, MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
	}

  }


 private bool GetUrlFile(String url, ref String savefile)
 {
   const int bufferLen = 1000;
   String DESKPATH = Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory);
	try
	{
	 Uri myUri =new Uri(url);
	 String localpath = myUri.LocalPath;
	 String filename = Path.GetFileName(localpath);
	 if( filename == String.Empty)
	  savefile = DESKPATH + "\\_simcrypturl";
	 else
	  savefile = DESKPATH + "\\" + filename;
 
	 WebRequest myRequest= WebRequest.Create(myUri);
	 myRequest.Timeout=7000;   //7 second timeout

	 HttpWebResponse myResponse = (HttpWebResponse) myRequest.GetResponse();
	 long contentsize = myResponse.ContentLength;
	 //Console.WriteLine("ContentLength: {0}", myResponse.ContentLength) ;
	 FileStream fOut = new FileStream(savefile, FileMode.Create, FileAccess.Write);
 
	 Stream instr = myResponse.GetResponseStream();
	 byte[] buff = new byte[bufferLen];
	 int bytesread	= 0; 
	 while((bytesread = instr.Read(buff, 0, bufferLen))>0)
		fOut.Write(buff, 0, bytesread); 

	 fOut.Flush();
	 fOut.Close();
	 instr.Close();
	 myResponse.Close();
	 return true;
	 }
	catch(Exception)
	{
	 return false ;
	}
 }



/* EncryptAES()
   Write encrypted output file formatted as:
	byte[] salt
	byte[] IV
	byte inputfilenamelength
	byte[] inputfilename
	byte[] encryptedinputfilecontents
  All output encrypted except salt and IV
*/

  private bool EncryptAES(String fileIn, String fileOut, String pswd, bool b64enabled) 
	{ 
	  String fileInName = null;

	  if(!File.Exists(fileIn))
		return false;
	  try{ fileInName = Path.GetFileName(fileIn);} //ensure valid filename characters
	    catch { return false; }
	  byte[] finname = Encoding.ASCII.GetBytes(fileInName);
	  int fnamelen = finname.Length ;
	  if(fnamelen >255)   //filename must be <256 characters long (length encoded into 1 byte)
		return false;

		try{

		CryptoStream cstream = null;
		CryptoStream b64str = null;

		FileStream fSIn  = new FileStream(fileIn, FileMode.Open, FileAccess.Read); 
		FileStream fSOut = new FileStream(fileOut, FileMode.Create, FileAccess.Write); 

		byte[] ransalt = new byte[SALTBYTES];  //salt can be any size
		RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();
		rng.GetBytes(ransalt) ;

		PasswordDeriveBytes pdb = new PasswordDeriveBytes(pswd, ransalt, "SHA1", ITERS); 

		Rijndael algor = Rijndael.Create();   //instantiages with random key and IV
		algor.Key = pdb.GetBytes(32);    //32 byte (256 bit) key is derived from password

		if(b64enabled)  //if b64 requested, wrap output stream with B64 encoder stream
		{
		 b64str  = new CryptoStream(fSOut, new ToBase64Transform(), CryptoStreamMode.Write);
		 b64str.Write(ransalt, 0, ransalt.Length);     //write out the random salt to file as b64
		 b64str.Write(algor.IV, 0, algor.IV.Length);  //write out the random IV to file as b64
		 cstream = new CryptoStream(b64str, algor.CreateEncryptor(), CryptoStreamMode.Write); 
		}
		else
		{
		 fSOut.Write(ransalt, 0, ransalt.Length);    //write out the random salt to file as binary
		 fSOut.Write(algor.IV, 0,algor.IV.Length);  //write out the random IV to file as binary
		 cstream = new CryptoStream(fSOut, algor.CreateEncryptor(), CryptoStreamMode.Write); 
		}

		int bufferLen	= 1024; 
		byte[] buff	= new byte[bufferLen]; 
		int bytesread	= 0; 

		//----- Encrypt the original filename information  ------------
		cstream.WriteByte((byte)fnamelen);    //write encrypted byte with original filename length
		cstream.Write(finname, 0, fnamelen); //write encrypted ASCII encoded original filename 

		while((bytesread = fSIn.Read(buff, 0, bufferLen))>0)  //write encrypted file contents
		  cstream.Write(buff, 0, bytesread); 
		cstream.FlushFinalBlock();

		fSIn.Close(); 
		fSOut.Close();
		cstream.Close();

		cstream.Clear();
		if(b64str !=null)
		 b64str.Clear();
		Array.Clear(buff, 0, buff.Length) ;
		return true;
	}
	catch(Exception exc)
	{
	 MessageBox.Show("Problem encrypting file\n" + exc.Message, TITLE, MessageBoxButtons.OK, MessageBoxIcon.Exclamation);   
	 return false;
	}
  } 


 
  private bool DecryptAES(String fileIn, ref String fileOut, String pswd, bool b64enabled) 
	{ 
	  if(!File.Exists(fileIn) || (new FileInfo(fileIn)).Length<SALTBYTES ) // filesize must be at least SALTBYTES long
		return false;

		CryptoStream cstream	= null;
		CryptoStream b64str	= null;
		FileStream fSIn		= null;
		FileStream fSOut	= null;

		try{
		Rijndael algor = Rijndael.Create();
		byte[] ransalt = new byte[SALTBYTES];    //read SALT from start of encrypted file
		byte[]  IV = new byte[algor.IV.Length] ;

		fSIn  = new FileStream(fileIn, FileMode.Open, FileAccess.Read); 

		if(b64enabled)  //if b64 requested, wrap decryption stream around b64 decoder stream
		{
		 b64str  = new CryptoStream(fSIn, new FromBase64Transform(), CryptoStreamMode.Read);
		 b64str.Read(ransalt, 0, ransalt.Length);	//read the random salt from file after b64 decoding
		 b64str.Read(IV, 0, IV.Length); 		 //read the random IV from file after b64 decoding
		}
		else
		{
		 fSIn.Read(ransalt, 0, ransalt.Length);	//read the random salt from file as binary
		 fSIn.Read(IV, 0,IV.Length) ;		//read the random IV from file as binary
		}

		PasswordDeriveBytes pdb = new PasswordDeriveBytes(pswd, ransalt, "SHA1", ITERS); 

		// initialize AES object with Key and IV values
		algor.Key = pdb.GetBytes(32);		//256 bit (32 byte) key
		algor.IV    = IV;			//block size is 16 bytes

		if(b64enabled)
		  cstream = new CryptoStream(b64str, algor.CreateDecryptor(), CryptoStreamMode.Read); 
		else
		  cstream = new CryptoStream(fSIn, algor.CreateDecryptor(), CryptoStreamMode.Read); 
	
		int bufferLen	= 1024; 
		byte[] buff	= new byte[bufferLen]; 
		int bytesread	= 0; 

		//----- Recover the original filename information; set as default in FileDialog ------------
		int fnamelen = cstream.ReadByte();   //read decrypted original filename length
	  	byte[] finname = new byte[fnamelen];
		cstream.Read(finname, 0, fnamelen);  //read decrypted original filename
		String fileInName = Encoding.ASCII.GetString(finname) ;		
		fileInName = Path.GetFileName(fileInName) ;  //validate characters in filename
		fileOut = getOutFileDialogName(DESKPATH, fileInName, "Save decrypted file to ...");

		if(fileOut == null)  //cancelled file output dialog
		{
		 fSIn.Close();
		 //cstream.Close();
		 cstream.Clear();
		 if(b64str !=null)
		  b64str.Clear();
		 return false;
		}

		 fSOut = new FileStream(fileOut, FileMode.Create, FileAccess.Write); 
		 while((bytesread = cstream.Read(buff, 0, bufferLen))>0)
		   fSOut.Write(buff, 0, bytesread); 
		 fSOut.Close();
		 fSIn.Close();
		 cstream.Close();
		 cstream.Clear();
		if(b64str !=null)
		 b64str.Clear();
		Array.Clear(buff, 0, buff.Length) ;
		return true;
	}
	catch(Exception exc)
	 {
	  MessageBox.Show("Problem decrypting file\n" + exc.Message, TITLE, MessageBoxButtons.OK, MessageBoxIcon.Exclamation);   
	   return false;
	}
	finally
	 {
	  try {
	  if(fSIn !=null)
		fSIn.Close();
	  if(fSOut !=null)
		fSOut.Close();
	  }
	  catch(Exception) {;}
	 }
     
  } 



//------ Denvelop CMS/PKCS #7 file using Pinvoke; does NOT use streaming  -----
 private bool DenvelopCMS(String fileIn, ref String fileOut)
 {
   String sysstore	= MY;
   IntPtr hSysStore	= IntPtr.Zero;
   IntPtr hCertCntxt	= IntPtr.Zero;
   IntPtr pProvInfo	= IntPtr.Zero;
   IntPtr pexcKey	= IntPtr.Zero;
   const long MAXFILESIZE	= 10000000;  //max size 10 Mb

      //------ Validate input ----------
	if(!File.Exists(fileIn))
		return false;
	if( (new FileInfo(fileIn)).Length > MAXFILESIZE)
		return false;

//------- Get encoded enveloped data from file -----
 byte[] envdata = GetFileBytes(fileIn);
 byte[] denvbytes;
 bool retstatus = false;
 int decbytes = 0;

 hSysStore = Win32.CertOpenSystemStore(IntPtr.Zero, sysstore) ;
 if(hSysStore == IntPtr.Zero) {
  return false;
 }

  CRYPT_DECRYPT_MESSAGE_PARA messpara = new CRYPT_DECRYPT_MESSAGE_PARA();
  messpara.cbSize = Marshal.SizeOf(messpara);
  messpara.dwMsgAndCertEncodingType = MY_ENCODING_TYPE;
  messpara.cCertStore = 1;
  messpara.rghCertStore = Marshal.AllocHGlobal(IntPtr.Size); //one cert store pointer
  Marshal.WriteIntPtr(messpara.rghCertStore, hSysStore);


try {
  //---- if fails, then might be b64 encoded file; try b64 decoding -----
 if(!Win32.CryptDecryptMessage(ref messpara, envdata, envdata.Length, null, ref decbytes, IntPtr.Zero))
  {
 	ASCIIEncoding ascii = new ASCIIEncoding();
 	String datastr = ascii.GetString(envdata);
	envdata = Convert.FromBase64String(datastr);  //try to b64 decode; throws NumberFormatException
 }
 
 if(Win32.CryptDecryptMessage(ref messpara, envdata, envdata.Length, null, ref decbytes, IntPtr.Zero))
  {
    denvbytes = new byte[decbytes];
   if(Win32.CryptDecryptMessage(ref messpara, envdata, envdata.Length, denvbytes, ref decbytes, IntPtr.Zero))
    {
	fileOut = getOutFileDialogName(DESKPATH, "_simdenveloped", "Save denveloped file to ...");
	if(fileOut != null)	//if filedialog not cancelled
	{
	 FileStream fSOut = new FileStream(fileOut, FileMode.Create, FileAccess.Write); 
	 fSOut.Write(denvbytes, 0, decbytes); 
	 fSOut.Close();
	 retstatus = true;
	}
    }
  }
  return retstatus;
 }  //end try

  catch(Exception exc)
  {
	MessageBox.Show("Problem denveloping file\n" + exc.Message, TITLE, MessageBoxButtons.OK, MessageBoxIcon.Exclamation);   
	return retstatus;
  }
  finally
  {
	Marshal.FreeHGlobal(messpara.rghCertStore);
	if(hSysStore != IntPtr.Zero)
         Win32.CertCloseStore(hSysStore, 0) ;
  }

 } 



 private static String getInFileDialogName(String mydir)
 {
    OpenFileDialog openFileDialog1 = new OpenFileDialog();
    openFileDialog1.Title = "Open File to Encrypt/Decrypt .." ;
    openFileDialog1.InitialDirectory = mydir ;
    openFileDialog1.RestoreDirectory = true ;
    if(openFileDialog1.ShowDialog() == DialogResult.OK)
	return openFileDialog1.FileName ;
    else
	return null;
}



 private static String getOutFileDialogName(String mydir, String fname, String title)
 {
    SaveFileDialog saveFileDialog1 = new SaveFileDialog();
    saveFileDialog1.Title = title ;
    saveFileDialog1.InitialDirectory = mydir ;
    saveFileDialog1.RestoreDirectory = true ;
    saveFileDialog1.FileName = fname ;
    if(saveFileDialog1.ShowDialog() == DialogResult.OK)
	return saveFileDialog1.FileName ;
    else
	return null;
}


 private static byte[] GetFileBytes(String filename){
        if(!File.Exists(filename))
         return null;
        Stream stream=new FileStream(filename,FileMode.Open);
        int datalen = (int)stream.Length;
        byte[] filebytes =new byte[datalen];
        stream.Seek(0,SeekOrigin.Begin);
        stream.Read(filebytes,0,datalen);
        stream.Close();
        return filebytes;
  }


 private void LaunchProcess(String applic) {
	if(!File.Exists(applic))
	 return;
	Process p = new Process();
	p.StartInfo.FileName = applic;
	//allow file-extension mapping
	p.StartInfo.UseShellExecute = true; 
	try{
	 p.Start();
	}
	catch {;}
 }



 [STAThread]
 public static void Main()
  {
   SimCryptNet app = new SimCryptNet();
   Application.Run(app);
  }

 }
}