Your premise is wrong – while the security of encryption, for example, is as weak as the weakest out of algorithm, key, random numbers used etc., the security o

Your premise is wrong – while the security of encryption, for example, is as weak as the weakest out of algorithm, key, random numbers used etc., the security of a system solely attacked via the SSH daemon is the sum of each layer of defence (or at least the strongest of these layers); that is, an attacker has to pierce each layer individually and successfully attacking one of them (e.g. finding the SSH port or the correct port knocking sequence) is not enough to render the whole defence void.