//File decrypteren
private void btnDecrypt_Click(object sender, EventArgs e)
{
RSAWithRSAParameterKey rsaParams = new RSAWithRSAParameterKey();
HybridEncryption hybrid = new HybridEncryption();
//Session key en IV in string-variabelen zetten + omzetten naar byte-arrays
string encryptedSessionKeyFile = Application.StartupPath + @"\Users\" + username + @"\Cryptodata\Encrypted Session Key";
string ivFile = Application.StartupPath + @"\Users\" + username + @"\CryptoData\IV";
byte[] encryptedSessionKey = null;
byte[] iv = null;
try
{
encryptedSessionKey = File.ReadAllBytes(encryptedSessionKeyFile);
iv = File.ReadAllBytes(ivFile);
//Dialoogvenster openen om een te decrypteren file te openen
openFileDialog.InitialDirectory = myInbox;
openFileDialog.Filter = "Text|*.txt|All|*.*";
if (openFileDialog.ShowDialog() == DialogResult.OK)
{
filenameToDecrypt = openFileDialog.FileName;
byte[] dataToDecrypt = File.ReadAllBytes(filenameToDecrypt); //file omzetten naar byte-array
byte[] decryptedData = hybrid.DecryptData(encryptedSessionKey, dataToDecrypt, iv, rsaParams);
//Filename van gedecrypteerde boodschap maken
string myFolder = Application.StartupPath + @"\Users\" + username + @"\Inbox\";
int startIndex = filenameToDecrypt.LastIndexOf(@"\") + 6; //+6 Zodat de naam begint vanaf de "From"
int indexUnderscore = filenameToDecrypt.LastIndexOf("_") + 1;
string decryptedFilename = myFolder + "Decr_" + filenameToDecrypt.Substring(startIndex);
//Gedecrypteerde data in bestand schrijven
File.WriteAllBytes(decryptedFilename, decryptedData);
MessageBox.Show("You have successfully decrypted the received file!", "Successfully decrypted!");
}
}
catch (FileNotFoundException)
{
MessageBox.Show("You have no files to decrypt yet. You were able to click this button because you appear to have a hidden file in your inbox.", "Warning");
}
catch (System.Security.Cryptography.CryptographicException)
{
MessageBox.Show("You can not decrypt this file.", "Not possible to decrypt!");
return;
}
}
