public byte[] DecryptData(byte[] data)
{
var packet = new EncryptedPacket()
{
Iv = data.Take(16).ToArray(),
Hmac = data.Skip(16).Take(32).ToArray(),
EncryptedData = data.Skip(48).ToArray()
};
return(AES.DecryptPacket(packet));
}
internal byte[] DecryptPacket(EncryptedPacket packet)
{
using (var hmac = new HMACSHA256(_sessionKey))
{
var hmacToCheck = hmac.ComputeHash(packet.EncryptedData);
if (!Compare(packet.Hmac, hmacToCheck))
{
throw new CryptographicException("HMAC for decryption does not match encrypted packet, data has been tamperd with");
}
}
return(Decrypt(packet.EncryptedData, _sessionKey, packet.Iv));
}
internal EncryptedPacket EncryptData(byte[] data)
{
//Create new encrypted packet with random Iv
var encryptedpacket = new EncryptedPacket()
{
Iv = GenerateRanomNumber(16)
};
//Encrypt data with AES
encryptedpacket.EncryptedData = Encrypt(data, _sessionKey, encryptedpacket.Iv);
//Generate HMAC using session key for data integrety check
using (var hmac = new HMACSHA256(_sessionKey))
{
encryptedpacket.Hmac = hmac.ComputeHash(encryptedpacket.EncryptedData);
}
return(encryptedpacket);
}