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Encrypt/Decrypt text files using Rijndael or TripleDES

Posted By:Deepika Haridas       Posted Date: August 30, 2009    Points: 10    Category: Encryption & Decryption    URL: http://www.dotnetspark.com  

This sample code shows you how to use Rijndael or TripleDES to encrypt and decrypt text files that you can browse for and load into a TextBox.

using System.Security.Cryptography;
private SampleCrypto crpSample;
private bool FormHasLoaded = false;
private string strCurrentKeyFile;
private string strSourcePath;
private string strRijndaelSaltIVFile;
private string strTripleDESSaltIVFile;

This routine handles the "Load" button click event.

private void btnLoad_Click(object sender, System.EventArgs e)
//Open fle dialog control used
odlgSourceFile.InitialDirectory = @"C:\";

// The file could be of any type. The Filter is restricted to Text Format
// files only for demonstration purposes.

odlgSourceFile.Filter = "Text Format (*.txt)|*.txt";
odlgSourceFile.FilterIndex = 1;

// The OpenFileDialog control only has an Open button, not an OK button.
// However, there is no DialogResult.Open enum so use DialogResult.OK.

if (odlgSourceFile.ShowDialog() == DialogResult.OK) {
txtCrypto.Text = ReadFileAsstring(odlgSourceFile.FileName);
strSourcePath = odlgSourceFile.FileName;
catch( ArgumentException exp)
MessageBox.Show(exp.Message, this.Text,MessageBoxButtons.OK, MessageBoxIcon.Warning);

This routine handles the "Encrypt" and "Decrypt" button click events.

private void EncryptDecrypt_Click(object sender, System.EventArgs e)
Button btn = (Button) sender;
crpSample.SourceFileName = strSourcePath;
if (btn.Name == "btnEncrypt")

txtCrypto.Text = ReadFileAsstring(strSourcePath);
catch(CryptographicException expCrypto)
MessageBox.Show("The file could not be decrypted. Make sure you entered " +
"the correct password. " + Environment.NewLine + "This error can also be caused by changing " +
"crypto type between encryption and decryption.",
this.Text,MessageBoxButtons.OK, MessageBoxIcon.Warning);
catch( Exception exp)
MessageBox.Show(exp.Message, this.Text,MessageBoxButtons.OK, MessageBoxIcon.Warning);

This routine encrypts a file.

public void EncryptFile()
// Create a FileStream object to read in the source file.
FileStream fsInput = new FileStream(strSourceFile, FileMode.Open, FileAccess.Read);
// Create a byte array from the FileStream object by reading in the source file.

byte[] abytInput = new byte[Convert.ToInt32(fsInput.Length)];
fsInput.Read(abytInput, 0, Convert.ToInt32(fsInput.Length));

// Create a FileStream object to write to a temp file.

FileStream fsCipherText = new FileStream("temp.dat", FileMode.Create, FileAccess.Write);

// Create a Crypto Stream that transforms the file stream using the chosen
// encryption and writes it to the output FileStream object.

CryptoStream csEncrypted = new CryptoStream(fsCipherText, crpSym.CreateEncryptor(),
csEncrypted.Write(abytInput, 0, abytInput.Length);
// Clean up. There is no need to call fsCipherText.Close() because closing the
// crypto stream automatically encloses the stream that was passed into it.

This routine decrypts a file.

public void DecryptFile()
// Create a FileStream object to read back the encrypted file.
FileStream fsCipherText = new FileStream(strSourceFile, FileMode.Open, FileAccess.Read);
// Create a FileStream object to write to the temp file.
FileStream fsPlainText = new FileStream("temp.dat", FileMode.Create, FileAccess.Write);
// Read in the encrypted file and decrypt.
CryptoStream csDecrypted = new CryptoStream(fsCipherText, crpSym.CreateDecryptor(),
// Create a StreamWriter to write to the temp file.
StreamWriter swWriter = new StreamWriter(fsPlainText);
// Read the decrypted stream into a StreamReader.
StreamReader srReader = new StreamReader(csDecrypted);
// Write out the decrypted stream.
catch( CryptographicException expCrypto)
throw new CryptographicException();
// Close and clean up.


Further Readings:

Author: Admiral Ackbar         Company URL: http://www.dotnetspark.com
Posted Date: November 22, 2013

Thank you for posting an incomplete article

hungarian notation is dead

please do not post anything again

this was useless

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