// Decrypt
private void btnDecrypt_Click(object sender, EventArgs e)
{
byte[] RSAdecbytes;
byte[] AESdecbytes;
byte[] KIV;
byte[] Cipher;
byte[] CipherBytes;
string PlainText;
// Make sure there is text to decrypt
if (txtMainText.Text == String.Empty)
{
return;
}
// Set cursor as hourglass
Cursor.Current = Cursors.WaitCursor;
try
{
// Show the Get Password Dialog
password1.Location = new Point(this.Location.X + 10, this.Location.Y + 50);
password1.StartPosition = FormStartPosition.Manual;
password1.ShowDialog();
string password = password1.Password;
if (password == String.Empty)
{
return;
}
// Read Private Keys
string privkey = crypto.RSAReadPrivateKey(keyStorePath + cmbChooseKey.Text + ".prvkey", password);
// Recover RSA and AES ciphers bytes from Base64
try
{
CipherBytes = Convert.FromBase64String(crypto.RemoveWhitespace(txtMainText.Text));
}
catch
{
MessageBox.Show("Cannot Decrypt non-cipher text!", "Cipher Text Error");
// Set cursor as default arrow
Cursor.Current = Cursors.Default;
return;
}
// Split Key and IV bytes from Cipher bytes
KIV = crypto.GetKeyIVfromKeyIVCipher(CipherBytes);
Cipher = crypto.GetCipherfromKeyIVCipher(CipherBytes);
if (KIV == null || Cipher == null)
{
MessageBox.Show("RSA/AES Cipher Split Error!", "RSA/AES Split Error");
// Set cursor as default arrow
Cursor.Current = Cursors.Default;
return;
}
// Decrypt the Key and IV
RSAdecbytes = crypto.RSADecrypt(privkey, KIV);
if (RSAdecbytes == null)
{
MessageBox.Show("RSA Decryption failed!", "RSA Decryption Error");
// Set cursor as default arrow
Cursor.Current = Cursors.Default;
return;
}
// Decrypt AES
AESdecbytes = crypto.AESDecrypt(Cipher, crypto.GetKeyfromKeyIV(RSAdecbytes), crypto.GetIVfromKeyIV(RSAdecbytes));
if (AESdecbytes == null)
{
MessageBox.Show("AES Decryption failed!", "AES Decryption Error");
// Set cursor as default arrow
Cursor.Current = Cursors.Default;
return;
}
// Extract Plain Text
PlainText = Encoding.UTF8.GetString(AESdecbytes);
// Check to see if we have a file to download
if (PlainText[0] == '<')
{
int x = PlainText.IndexOf('>');
string fileName = PlainText.Substring(1, x - 1);
string contents = PlainText.Substring(x + 1);
try
{
File.WriteAllBytes(fileStorePath + fileName, Convert.FromBase64String(contents));
}
catch
{
MessageBox.Show("Failed to download file", "File Error");
// Set cursor as default arrow
Cursor.Current = Cursors.Default;
return;
}
txtMainText.Text = "Downloaded file: " + fileStorePath + fileName;
// Set cursor as default arrow
Cursor.Current = Cursors.Default;
return;
}
// Send to main window
txtMainText.Text = PlainText;
}
catch
{
MessageBox.Show("General Decryption failure!", "Decryption Error");
// Set cursor as default arrow
Cursor.Current = Cursors.Default;
return;
}
// Set cursor as default arrow
Cursor.Current = Cursors.Default;
}