/// <summary>
/// Taken from https://stackoverflow.com/a/30821908
/// </summary>
/// <param name="privateKey"></param>
/// <param name="stream"></param>
/// <param name="decryptedFileName"></param>
public static void DecryptAES(RSACryptoServiceProvider privateKey, FileStream stream,
string decryptedFileName)
{
try
{
using (RijndaelManaged AES = new RijndaelManaged())
{
var data = ReadFully(stream, privateKey.KeySize / 8);
var AESKey = privateKey.Decrypt(data, false);
AES.Key = AESKey;
var iv = ReadFully(stream, AES.BlockSize / 8);
AES.IV = iv;
using (var cs = new NotClosingCryptoStream(stream, AES.CreateDecryptor(), CryptoStreamMode.Read))
{
using (FileStream fs = new FileStream(decryptedFileName, FileMode.Create, FileAccess.Write))
{
cs.CopyTo(fs);
}
}
}
}
catch (Exception e)
{
MessageBox.Show("Error while decrypting the file or writing to file." + Environment.NewLine + e.Message);
return;
}
finally
{
stream.Seek(0, SeekOrigin.Begin);
}
}
public static void DecryptAndVerify(RSACryptoServiceProvider privateKey, RSACryptoServiceProvider publicKey,
FileStream stream, string decryptedFileName)
{
byte[] sign = null;
try
{
using (RijndaelManaged AES = new RijndaelManaged())
{
var data = ReadFully(stream, privateKey.KeySize / 8);
var AESKey = privateKey.Decrypt(data, false);
AES.Key = AESKey;
var iv = ReadFully(stream, AES.BlockSize / 8);
AES.IV = iv;
using (var cs = new NotClosingCryptoStream(stream, AES.CreateDecryptor(), CryptoStreamMode.Read))
{
sign = ReadFully(cs, publicKey.KeySize / 8);
using (FileStream fs = new FileStream(decryptedFileName, FileMode.Create, FileAccess.Write))
{
cs.CopyTo(fs);
}
}
}
}
catch (Exception e)
{
MessageBox.Show("Error while decrypting the file or writing to file." + Environment.NewLine + e.Message);
return;
}
finally
{
stream.Seek(0, SeekOrigin.Begin);
}
//============//
try
{
using (FileStream decrypted = new FileStream(decryptedFileName, FileMode.Open, FileAccess.Read, FileShare.None))
{
if (publicKey.VerifyData(decrypted, sign, HashAlgorithmName.SHA512, RSASignaturePadding.Pkcs1))
{
MessageBox.Show("File sign is verified");
}
else
{
MessageBox.Show("File is tempered");
}
}
}
catch (Exception e)
{
MessageBox.Show("Error while verifying the signature." + Environment.NewLine + e.Message);
return;
}
}
