private void button_Click(object sender, RoutedEventArgs e)
{
try
{
if (sender == btnAssignKey)
{
rsaParams.AssignNewKey();
}
else if (sender == btnEncrypt)
{
var encryptBlock = HybridEncryptionAddedIntegrity.EncryptData(txtMessage.Text, rsaParams);
txtEncryptedSessionKey.Text = Convert.ToBase64String(encryptBlock.EncryptedSessionKey);
txtEncryptedData.Text = Convert.ToBase64String(encryptBlock.EncryptedData);
txtIv.Text = Convert.ToBase64String(encryptBlock.Iv);
txtHmac.Text = Convert.ToBase64String(encryptBlock.Hmac);
}
else if (sender == btnDecrypt)
{
var encryptBlock = new EncryptedPacket
{
EncryptedData = Convert.FromBase64String(txtEncryptedData.Text),
EncryptedSessionKey = Convert.FromBase64String(txtEncryptedSessionKey.Text),
Iv = Convert.FromBase64String(txtIv.Text),
Hmac = Convert.FromBase64String(txtHmac.Text)
};
var decrypted = HybridEncryptionAddedIntegrity.DecryptData(encryptBlock, rsaParams);
txtResult.Text = decrypted;
}
}
catch (Exception exc)
{
MessageBox.Show("Error\n" + exc.Message);
}
}
public static string DecryptData(EncryptedPacket encryptedPacket, RSAWithRSAParameterKey rsaParams)
{
var aes = new AesEncryption();
// Decrypt AES key with RSA and then decrypt data with AES.
var decryptedSessionKey = rsaParams.DecryptData(encryptedPacket.EncryptedSessionKey);
using (var hmac = new HMACSHA256(decryptedSessionKey))
{
var hmacToCheck = hmac.ComputeHash(encryptedPacket.EncryptedData);
if (!CompareArrays.Compare(encryptedPacket.Hmac, hmacToCheck))
{
throw new CryptographicException("HMAC for decryption does not match encrypted packet.");
}
}
var decryptedData = aes.Decrypt(encryptedPacket.EncryptedData, decryptedSessionKey, encryptedPacket.Iv);
return(Encoding.UTF8.GetString(decryptedData));
}
public static EncryptedPacket EncryptData(string original, RSAWithRSAParameterKey rsaParams)
{
var aes = new AesEncryption();
var sessionKey = RandomCryptography.Random.GenerateRandomNumber(32);
var encryptedPacket = new EncryptedPacket
{
Iv = RandomCryptography.Random.GenerateRandomNumber(16)
};
// Encrypt data with AES and AES key with RSA.
encryptedPacket.EncryptedData = aes.Encrypt(Encoding.UTF8.GetBytes(original), sessionKey, encryptedPacket.Iv);
encryptedPacket.EncryptedSessionKey = rsaParams.EncryptData(sessionKey);
using (var hmac = new HMACSHA256(sessionKey))
{
encryptedPacket.Hmac = hmac.ComputeHash(encryptedPacket.EncryptedData);
}
return(encryptedPacket);
}