public byte[] DecryptData(EncryptedPacket encryptedPacket, RsaWithRsaParameterKey rsaParams, DigitalSignature digitalSignature)
{
//Decrypt AES Key with RSA.
var decryptedSessionKey = rsaParams.DecryptData(encryptedPacket.EncryptedSessionKey);
using (var hmac = new HMACSHA256(decryptedSessionKey))
{
var hmacToCheck = hmac.ComputeHash(encryptedPacket.EncryptedData);
if (!Compare(encryptedPacket.Hmac, hmacToCheck))
{
throw new CryptographicException(
"HMAC for decryption does not match encrypted package");
}
if (!digitalSignature.VerifySignature(encryptedPacket.Hmac, encryptedPacket.Signature))
{
throw new CryptographicException(
"Digital Signature can not be verified");
}
}
var decryptedData = _aes.Decrypt(encryptedPacket.EncryptedData, decryptedSessionKey, encryptedPacket.Iv);
return(decryptedData);
}
public EncryptedPacket EncryptData(byte[] original, RsaWithRsaParameterKey rsaParams, DigitalSignature digitalSignature)
{
var sessionKey = _aes.GenerateRandomNumber(32);
var encryptedPacket = new EncryptedPacket {
Iv = _aes.GenerateRandomNumber(16)
};
encryptedPacket.EncryptedData = _aes.Encrypt(original, sessionKey, encryptedPacket.Iv);
encryptedPacket.EncryptedSessionKey = rsaParams.EncryptData(sessionKey);
using (var hmac = new HMACSHA256(sessionKey))
{
encryptedPacket.Hmac = hmac.ComputeHash(encryptedPacket.EncryptedData);
}
encryptedPacket.Signature = digitalSignature.SignData(encryptedPacket.Hmac);
return(encryptedPacket);
}
static void Main()
{
const string original = "Petras";
//Testavimas
var hybrid = new HybridEncryption();
var rsaParams = new RsaWithRsaParameterKey();
rsaParams.AssignNewKey();
var digitalSignature = new DigitalSignature();
digitalSignature.AssignNewKey();
Console.WriteLine("Hybrid Encryption");
Console.WriteLine();
try
{
var encryptedBlock = hybrid.EncryptData(Encoding.UTF8.GetBytes(original),
rsaParams, digitalSignature);
var decrypted = hybrid.DecryptData(encryptedBlock, rsaParams, digitalSignature);
Console.WriteLine("Original Message = " + original);
Console.WriteLine();
Console.WriteLine("Message After Decryption = " + Encoding.UTF8.GetString(decrypted));
}
catch (CryptographicException ex)
{
Console.WriteLine("Error : " + ex.Message);
}
Console.ReadKey();
}