/// <summary>
/// Calculates symetric encryption key with generate keypair's private key and public key received by key exchange. Key should be stored in order to use it for encryption and decryption until next key exchange (persumably once per day)
/// </summary>
/// <returns></returns>
public byte[] CalculateSecureSymetricKey()
{
return(ecKey.GenerateKeyAgreement(ReceivedPublicKey.X, ReceivedPublicKey.Y));
}