I'm a really optimistic type, really. Optimistic to the annoyance of some people. But in the case of security and cryptology there does not exist a choice between optimism and pessimism, but a choice between sharp eyed paranoia and wilful ignorance.

A defence is always only as strong as the weakest link, and an attacker usually has all the time in the world to find and exploit it.

Optimism has no place here.